1

PLANT COMMUNICATION SYSTEM (PCS) is a
microprocessor controlled, software programmable, central

exchange based paging system with talk back facility.
The system comprises of page channel and party channels for
two-way communication facility between the control room and
the field.
Page Channel provides loud speaking facility and is used for
broadcasting messages or issue instructions or to locate field
operators in the plant. The announcements made by the users are
heard over the field loudspeakers.
Party Channel is used for carrying prolonged conversations in
private mode, which is not heard over the loudspeakers. The
system possess multiple party channels i.e. one dedicated
channel for each field handset station. Thus each field operator
can carry his separate, independent and simultaneous
conversation.
The field call stations and loudspeakers are installed at various

locations throughout the facility. The person can communicate
from any field call station of the system.
The loudspeakers and field call stations are indoor type for
indoor areas, weatherproof type for outdoor safe (i.e. nonhazardous) areas and explosion proof type for hazardous areas.
The loudspeakers are available in different wattages & sound
pressure levels and in different sizes & constructions to meet all
types of the requirements.
The system provides excellent reproduction of sound, clear
audible announcements and high intelligibility of speech, even in
high noisy areas.
Key Features:
Paging + Alarm broadcasting facility
Master-Slave Configuration with facility to connect multiple master
control desks
Direct Communication between the field operators and the control
room operator
Direct communication between the two field operators (i.e. without
routing any calls through central control room)
Communication between the two field operators with the help of Master
Control Station (MCS)
Individual zone, Multiple zone and All zone selection for
announcements
Facility of connecting emergency siren over the paging channel
Digital display at MCS for identification of field call station number /
area name
Call holding, call waiting, page priority, override and central monitoring
facility at MCS
No requirement of AC mains for operating any field equipment

Access to features can be restricted (by software programming) for few call stations
No correlation between the field handset stations and the loudspeakers. Their quantity, location and
their functioning are 100% independent
Open system to facilitate its integration with EPABX, Fire alarm etc.
Easy and quickly expandable by adding the relevant card in central equipment
Host of various unique and useful features
Key Advantages:
State of the art technology
Software programmable for communication options, features and system access
Simple and economical field cabling
Cost effective design and hardware
Trouble free system
Modular architecture, offering the flexibility to build the system block by block
Centralized monitoring for system operation, performance and equipment healthiness
Reduced and easy maintenance
High flexibility and adaptability
100% non-blocking communication facility to all users
Minimum downtime, easy system operation and maximum safety
Easy and Quick to expand
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Plant Communication System

Explosion Proof Telephone
Weatherproof Telephone
Weatherproof Telephone With
External Ringer
Integrated PA & Intercom
System
Industrial Communication
System
It is a centralized amplifier based system thats been designed to provide voice

paging and to broadcast alarm tone during emergencies.
The system can transmit alarm tone and routine voice messages, from a central
location, to all or selected areas of the facility, in a reliable and safe manner, by the
use of loudspeakers.
The entire operational area / facility can be divided into one or more zones, which
can be accessed independently either for announcements or for alarm broadcasting.
The loudspeakers are installed in these zones.
There are no limitations to number of zones in the system or number of

loudspeakers in each zone. Each loudspeaker is connected to the central equipment
for amplification and other control functions.
Depending on the surrounding environment, either flameproof loudspeakers (for
hazardous atmospheres) or weatherproof loudspeakers (for safe & non-hazardous
atmospheres) or indoor loudspeakers (for indoor areas) are installed in each zone.
The loudspeakers are available in different wattage, sizes, types and constructions.
The system is designed to offer clear reproduction of sound and intelligibility of
speech even in high noisy areas.
Multiple control desks can be installed in the same system, for paging access (with
priority) from more locations.
The system uses high reliability amplifiers with built in over load protection
circuitry, short circuit protection, open circuit protection and thermal protection.
Key Advantages :

Simple, reduced and economical field cabling
Trouble free system
Flexibility to connect the loudspeakers at longer distance.
Modular architecture
Flexibility to build the system for the present need with

enough provision for future expansion.
Connectivity of p. a. system with the EPABX System
Monitoring the healthiness of all associated equipment in the

PA System
Call attention chime tome prior to all announcements

Facility of connecting emergency siren over the paging
channel
No use of AC Power source in the field

Highest priority for control desk paging
Bass and Treble control to custom-tailor the frequency

response, for poor acoustic or highly noisy environments
LED Bar graph in dB scale to read the relative power

Distribution of audio signal through buffered O/P
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Weatherproof Telephone | Integrated PA & Intercom System | Industrial Communication System
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P.A. System (Public Address System)

P.A System can be a set up to work as an independent system or can be integrated with your phone system for
convenience. P.A. Systems are ideal for any type of business that has large open areas,
schools, airports, anywhere that requires some sort of announcement to be made.
Uses for P.A. System include:
* Public Announcement, Paging
* Siren Alarm
* Evacuation Tone
* Music Broadcast
P.A. Systems can be custom made to the environment and use required. Contact Absolute Phone & Data for further
information.
PA/Emergency Voice Alarm Communications System (EVACS)

1. The PA system may also integrate some subsystems of the EVACS to deliver
important information in case of emergency, directing customers to safety. Refer
to Safety and Security Section (Section 4.2.3.6). The National Fire Protection
Association (NFPA) document NFPA 72 recommends that EVACS meet the
speech intelligibility requirements, as defined by International Electrotechnical
Commission (IEC) 60849: 1998 - Sound Systems for Emergency Purposes. The
design of the station PA/EVAC systems should take account of these
requirements. For PA systems that are used for EVACS, the IEC standard
requirement for speech intelligibility is a minimum level of 0.7 on the Common
Intelligibility Scale for all areas of coverage, unless otherwise stated. According
to the standard, this relates to a Speech Transmission Index (STI) value of 0.5.
2. The relationship between STI value and subjective speech quality is suggested
in the STI Rating Table below. It is recommended that STI form the basis of the
PA system acoustic design targets.
3. A STI value of 0.61 is the minimum acceptable standard for a safe system
Table1 of 4.8.4: STI Rating Table
Rating STI Value
Bad 0.20 . 0.25
Poor 0.26 0.44
Fair 0.45 0.50
Good 0.51 0.60
Very Good 0.61 0.70
General Recommendations
1. It is essential to achieve good speech intelligibility and enable passengers to
understand train announcements and voice alarms.
2. Controlling the reverberant buildup of noise on the station platforms also greatly
depends upon the level of noise emission from the various noise sources. The
dominant source is train noise, which includes wheel/rail noise from trains
entering and leaving the platforms, train horn noise, noise emission from train
ventilation fans, and noise from the train motors.
3. Selection of the appropriate finishes providing effective sound absorption can
control the level of reverberance and provide a comfortable acoustic
environment. Under these aural conditions, standard speakers can be used to

achieve a good level of speech intelligibility.
Acoustic considerations should be made to achieve the following objectives:
a) Provide intelligible speech communication (face-to-face,
telephone, public address, intercoms, portable radio)
b) Comply with acoustical criteria
c) Control patron-generated noise in enclosed areas and/or noise
from exterior sources
4.8.5.1 Station Reverberance
1. Acoustical calculations should be carried out for each station design in order to
determine the amount and type of acoustical treatment required to meet the RT
and Speech Intelligibility criteria.
2. Consideration should be given to whether the station is naturally ventilated,
mechanically ventilated or fully air-tempered and the resultant effect on the
reverberant noise buildup within the station.
3. The RT within a station should not typically exceed 1.4 to 1.6 seconds over the
frequency range of 250 Hz to 4 kHz. In addition, the frequency range should
include the 125 Hz, 250 Hz and 4 kHz octave-bands.
4.8.5.2 Structural Noise
1. Structure borne noise from rail sources is generally low frequency in nature (31
Hz to 250 Hz); whereas the information in speech occurs in the frequency range
of 500 Hz to 4000 Hz. Therefore, a high level of structure borne noise must be
generated before interference with speech communication occurs.
2. Typical criterion used on other railway projects for the allowable level of structure
borne noise in the stations public areas is NC 60 (roughly equivalent to 65 dB
(A)).
4.8.5.3 Train Noise
The following shall minimize train Noise in stations:
1. Use of continuous welded rail (CWR) instead of jointed track
2. Locating crossovers and switches away from station waiting areas, as
these elements can result in significant noise and vibration.
3. Inclusion of rubber/electromagnetic pads below rails/sleepers and noise
dampers on the platform walls.
Manual of Standards and Specifications for Railway Stations
Section 4 Station Design Acoustics
117
4.8.5.4 Services Noise

The target noise levels for different programmed services are listed below. Services
noise should include the contributions from all station and tunnel ventilation equipment,
including escalator and elevator equipment.
Table 1 of 4.8.5: Background Services Noise Criteria for Typical Spaces
The following issues shall be addressed in the design of the ventilation systems in
regard to acoustics:
1. Noise levels on platforms during emergency situations from ventilation
equipment should be assessed separately from the ventilation plant
under normal operation.
2. To ensure the ventilation noise meets the noise criteria, the ventilation
design should consider the use of in-duct sound attenuators, plenums,
and lined ductwork to attenuate the fan noise to help reduce the level of
regenerated noise within the system.
3. Regenerated noise at dampers, grilles, louvers, etc. should be taken into
account in the design of the ventilation system design. Air velocities

should be limited.
4.8.5.5 PA Speech Intelligibility
The criteria for speech intelligibility performance of the PA audio systems are as follows:
1. PA system to achieve minimum STI: 0.61
2. PA system to achieve level in range: 65 dB (A) < Lp < 85 dB (A)
The criteria should be measured with all ventilation equipment running at normal
operation, and in the absence of any other noise, such as train noise or noise from
station users.
4.8.5.6. PA system
1. Input
a) The type(s) of microphone used by the person initiating or
recording a PA message.
b) The vocal character (male/female), talking level, and diction of the
PA operator.
c) The acoustic environment in which the message is made,
including the local ambient noise level and the reverberance of
the local area.
2. Device Location
a) Mounting locations for maintenance accessibility
b) Easier architectural integration
Area Target Noise Criteria
Platforms NC 4550
Concessions NC 4050
Toilets NC 4045
Platforms (during emergency) NC 7080
Manual of Standards and Specifications for Railway Stations
Section 4 Station Design Acoustics
118
c) Mounting locations to provide optimal sound coverage to passenger

areas.
3. Design
Coordinate locations with light fixtures and other interchangeable modular elements, but
consideration of locations in relation to these elements shall not override intended
function of the loudspeakers.
a) Use of any special maintenance equipment other than ladders to gain
access to loudspeakers may mean station closure to perform repair.
b) Typical loudspeaker heights for maintenance should be limited to 4.268 m
above a finished floor.
c) Standard loudspeaker dispersion patterns also require a minimum
mounting height to provide adequate coverage. Greater mounting heights
increase the potential for spill and an increase in detrimental reflected
sound energy.
d) With respect to the control of reflected sound energy, it is very important
that the location and coverage of the PA loudspeakers should take into
account the location of any sound-absorptive finishes and vice versa. If
early reflections from the PA system are left to reverberate through the
station, they effectively become noise, limiting the PA signal to noise ratio
and the achievable level of speech intelligibility.
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Understanding Distributed Speaker Systems
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Distributed speaker systems are also known as "100 volt line" or "70 volt line"
speaker systems. They are used extensively where multiple speakers are required.
Distributed speaker systems are commonly used in airports, shopping centers,
schools, churches, clubs, car-parks, sports grounds and anywhere multiple speakers
are required. They can also be used in homes for background music systems.
Advantages of Distributed Speaker Systems
The main advantages of distributed speaker systems are:
No need for complicated calculations of total speaker impedance - simply add
together each speaker's wattage (see below for more details)
Many speakers can be connected to an amplifier.
Extra speakers can normally be added to the system
The volume of each speaker can be adjusted independent of the main volume (so
the toilet speakers are not as loud as the foyer speakers).
Smaller cables can be used. Distributed speaker systems use much less current
through the speaker cables
Longer speaker cables are possible with minimal line loss. Cables runs can be 100's
of metres or 1000's of feet.
Disadvantages of Distributed Speaker Systems
The main disadvantages of distributed speaker systems are:
Each speaker requires a step-down transformer
The transformers afect the quality of the sound - typically the lower frequencies are
not transferred as well as a speaker system without transformers.
Without using expensive transformers, use is often limited to paging, voice and low
level (background) music installations.
Distributed Speaker Systems Overview
The basis of distributed speaker systems is similar to the way electricity is
distributed. Power stations use step up transformers to distribute power as high
voltage, which means low current, and therefore low line losses and thinner cables.
Each town and/or street then converts this high voltage/low current down to low
voltage/high current (through step down transformers) for use in your home.
Distributed speaker systems use a similar principle. The amplifier normally has a
step-up transformer built into it, producing a high voltage/low current output. Then
each speaker has its own step down transformer to convert the signal back to low
voltage/high current. This allows the cable to be very long without having any
significant line losses.
<img class="size-full
wp-image-3226 aligncenter" src="http://geofthegreygeek.com/wpcontent/uploads/100-volt-with-1-spkr.png" alt="distributed speaker systems
overview" width="441" height="125" /> 100 Volt Line Speaker System
The most common "high" voltage used in distributed speaker systems is 100 Volts.
In many countries distributed speaker systems are known as "100 Volt line" speaker
system. In a 100 Volt line speaker system the output of the amplifier is marked "100
volt". Indeed at full output, the amplifier puts out 100 volts RMS. Each speaker then
has a transformer to reduce the 100 volt line level down to normal speaker level.
70 Volt Line Speaker System
In North America the most common "high" voltage for distributed speaker systems
is 70 Volts. This is because years ago, some states had laws stating that any cable
with a maximum voltage greater than 100 Volts peak had to be installed in conduit.
This was time consuming and costly to install. So they developed a system where
the output voltage of the amplifier was a maximum of 100 Volts peak. This equates
to 70.71 Volts RMS. This is commonly known as a "70 Volt line" speaker system. The
principle is the same as for 100 volt line systems, but uses a maximum output
voltage of 70 Volts. While 70 volt line systems are still the most common in the USA,
some 100 volt lines systems are being used.
50 Volt Line and 25 Volt Line Speaker Systems
Less common, but still seen on some amplifiers are 50 volt line or 25 volt line
outputs. The principles are the same for all voltages, but the lower the voltage, the
more current, therefore the shorter the maximum cable length without significant
line losses.
<img class="alignright wpimage-3223" style="border: 0px none;" src="http://geofthegreygeek.com/wpcontent/uploads/100-volt-terminal-300x129.jpg" alt="distributed speaker systems
terminals" width="300" height="139" />
In practice, many commercial amplifiers have multiple outlets. They may have 100
and 70 Volts, or 70 and 25 Volts, as well as 4 ohm and 8 ohm outputs for normal
speakers (without transformers). Normally you should only use one output of a
amplifier, that is, either the 100 volt line output, or the 70 volt line output or the 8
ohm output, not all at the same time.
Transformers
Every speaker in distributed speaker systems needs to be connected to a step down
transformer. This converts the high voltage level down to normal speaker level.
<img class="wp-image-3235 alignleft"

src="http://geofthegreygeek.com/wp-content/uploads/transformer-300x219.png"
alt="transformer for distributed speaker systems" width="234"
height="177" />One side of the transformer normally has a common (or "0 volts")
and a 4 ohm and 8 ohms connection. An 8 ohm speaker would be connected to the
common and 8 ohm taps, while a 4 ohm speaker would be connected to the
common and 4 ohm tap.
Most transformers have a selection of input taps. The example in this picture has
taps for 20 Watts, 15 Watts, 10 Watts and 5 Watts. The feed cable is connected to
the common and any one of the other taps. This allows the relative volume of the
speaker to be set during the installation. For example the speaker in a high noise
room might be set on 20 Watts, while the speaker in a small, low noise area might
be set on 5 watts.
All amplifiers designed for use with distributed speakers systems have a step-up
transformer built-in. It is also possible to add an external transformer to an amplifier
without an integrated transformer. Simply use a speaker transformer in reverse that is, connect the common and 8 ohm transformer connection to the common and
8 ohm speaker output of the amplifier. Just make sure the amplifier and transformer
are rated with enough power to drive all the speakers to be connected (see
Connecting Multiple Speakers below).
Speakers
Any speaker can be used in a distributed speaker system, as long as a step-down
transformer is used. Many manufacturers produce speakers with integrated
transformers for use in distributed speaker systems.

<img
class="alignright wp-image-3238" src="http://geofthegreygeek.com/wpcontent/uploads/sm-ceiling-spkr-300x296.png" alt="ceiling spkr for distributed
speaker systems" width="189" height="186" />
Ceiling Speakers
Ceiling speakers are used in many distributed speaker system installations to cover
large areas and/or multiple small rooms or areas. The speaker cable is normally
connected directly to the transformer. To change the power settings you need to
connect the speaker cable to a diferent transformer tap. In the speaker pictured,
this is a simple matter of moving the speaker wire to a diferent terminal connector.
Cabinet Speakers (Speaker Boxes)
<img class="wp-image-3240 alignleft"

src="http://geofthegreygeek.com/wp-content/uploads/100-volt-speaker.png"
alt="100 volt box speaker for distributed speaker systems" width="115"
height="173" />
Speaker boxes come in all sorts of shapes and sizes. Many manufactures make a
version of their cabinets with an integrated transformer. Connections are often by
some form of speaker terminals. To change taps, simply rotate the switch to the
desired power setting. Often these switches also have a position for 8 ohms
(bypassing the transformer) - this makes them very versatile speakers for the
installer. Speaker boxes are used where ceiling speakers aren't practical, or where
higher sound levels are required.
<img class="alignright wp-image-3241"

src="http://geofthegreygeek.com/wp-content/uploads/rear-horn-speakers300x238.png" alt="rear of horn speaker for use with distributed speaker systems"
width="168" height="134" />
Horn Speakers
Horn speakers are very efficient, but not very good quality. They are mostly used
outdoors when coverage of a large, or high noise, area is required. For example in
car parks, sports grounds, school yards and other outdoor areas. In the picture
shown, the rear of the horn has a selector switch which needs a flat bladed screwdriver to operate. This is useful to reduce the likelihood of inadvertent changing of
the settings after the install.
Connecting Multiple Speakers
This is the fun bit, because there is no need to calculate the total impedance. To
connect multiple speakers in distributed speaker systems, just wire them all in
parallel and add up the total watts.
Example 1: A PA amplifier is rated at 120 watts @100 volt line. Therefore you could
connect:
20 x 5 Watt (100 volt) ceiling speakers (total 100 Watts), or
40 x 2.5 Watt (100 volt) ceiling speakers (total 100 Watts), or
10 x 5 Watt (100 volts) ceiling speakers and 20 x 2.5 Watts (100 volt) ceiling
speakers (total 100 Watts), or
any combination of speakers that add up to no more than 120 Watts.
Example 2: A small church has a small 25 Watt (70 Volt) PA amplifier with 4 small
speakers mounted in the church (2 down each side). They now want to add a
speaker in a separate room for an overflow and creche area.
4 existing speakers can be wired at 2.5 Watts (70 Volt), total of 10 Watts
A new box speaker can be wired at 10 Watts (70 Volt), this allows it to be louder
than any of the small church speakers (since the creche area has much more
ambient noise levels).
As shown, it is easy to add the individual speaker watts together. This is much
easier than calculating the total impedance.This makes installation much simpler.
Tips for Using Distributed Speaker Systems
Following are some practical tips for installing distributed speaker systems:
Keep all the speakers in phase. This means the the "O volt" or the "Com" of the
amplifier speaker terminal should be connected to the "O Volt" or "Com" of each
speaker transformer.
It is good practice to design distributed speaker systems to use up to only 80% of
the amplifier's total available power. For example, a 120 Watt PA amplifier should
only connected to a maximum of around 100 Watts of speakers. This helps avoid
the amplifier's transformer distorting from saturation (overload), allows for
inefficiencies in the system, and allows an extra speaker to be added if required in
the future.
When designing distributed speaker systems, calculate the total watts of the
speakers, and select an amplifier larger than required. For example, If an install
requires 10 speakers at 5 Watts each (total load of 50 Watts), a 60 Watt amplifier
could be used, but selecting a 100 Watt or 120 Watt amplifier will allow speaker taps
to be changed or extra speakers added in the future. It is a relative small increase in

price to up-size the amplifier before purchase, rather than have to buy a new one
later.
When selecting speakers, chose a higher power one than required. For example: If a
5 Watt ceiling speaker is required, chose a 10 Watt or 15 Watt speaker and use the 5
Watt tap on the transformer. This again reduces the likelihood of overloading
cheaper transformers, and gives the ability to increase the power level (volume) if
required.
When connecting many speakers, it is good to have multiple feed cables. For
example; if connecting 60 speakers, it is possible to use one speaker cable run and
loop in and out of each speaker. However it is better to have several feed cables to
smaller groups of speakers. This way if a fault occurs, it is easier to isolate which
feed the fault in on.
It is possible to get some speakers with a built-in attenuator to control the volume of
the speaker. This is useful in situations when you want the listener to control the
volume. For example in a creche. It is also possible to get external attenuators to
control the volume in a room or for an individual speaker.
If possible, measure the impedance of each speaker feed cable before connecting
the amplifier. This is best done with an impedance meter. If installing a number of
distributed speaker systems, an impedance meter is very useful. For examples of
impedance meters, view Amazon's range here. <img style="border: none !
important; margin: 0px !important;" src="https://ir-na.amazon-adsystem.com/e/ir?
t=geothegregee-20&l=ur2&o=1" alt="" width="1" height="1" border="0" />
Don't connect a 4 ohm or 8 ohm speaker directly to a 100 volt line or 70 volt line
speaker cable. Apart from severely overloading the speaker (and possibly burning it
out) a 4-8 ohm speaker efectively puts a short circuit on the speaker line and
overloads the amplifier. See the calculations below for the mathematical
explanation of this.
If a 100 Volt line amplifier is overloaded, connecting the load to the 70 Volt line
efectively halves the load on the amplifier and it will not be overloaded. Example 1:
The total watts of all the (100 Volt) speakers totals 200 Watts. If connected to the
100 Volt line speaker terminals of a 120 watt (100 Volt) amplifier, the amplifier will
be overloaded. Connect the same speakers to the 70 Volt line terminals of the same
120 watt amplifier and the amplifier will only see a load of 100 Watts. Example 2:
The total watts of all the (70 Volt) speakers totals 50 Watts. If connected to the 70
Volt line speaker terminals of a 40 watt (70 Volt) amplifier, the amplifier will be
overloaded. Connect the same speakers to the 50 Volt line terminals of the same 40
Watt amplifier and the amplifier will only see a load of 25 Watts. See the
calculations below for the mathematical explanation of this.
Summary
Distributed speaker systems are ideal for multiple speaker installations. They allow
long speaker cables and calculation of the total load is easy. Distributed speaker
systems are normally mono (not stereo). They are mostly used for paging and
background music situations. Although normally used for commercial installations,
they can be used in domestic installations for background music systems
Below are some of the major calculations used with distributed speaker systems
(you can stop reading now if you are not into calculations).
Calculations for Distribution Speaker Systems
The following calculations are for those who like to understand the mathematics
behind the principles outlined above. You don't need to understand these
calculations to use distributed speaker systems, but it will help you understand and
design systems better.
Several principles of distributed speaker systems have been outlined above. A
mathematical explanation of each principle is now given under the following subheadings:
Adding the Power of Each Speaker
As an example, four 5 Watt speakers are connected together (in parallel) to a 100
Volt line amplifier.
The simple way to calculate the total load is to add 5 + 5 + 5 + 5 = 20 Watts.
The harder way (which is why its not normally done) is to calculate the impedance
of one speaker, and then calculate the total impedance of 4 such speakers in
parallel, and then calculate the total power.
So the impedance of a 5 Watt speaker on a 100 volt line:
Impedance=Volts 2 Power =100 2 5 =10,0005 =2,000ohms
That's right, the impedance of a 5 Watt speaker with a 100 volt transformer is 2,000
ohms. Now to calculate the total impedance of four of these connected in parallel:
1R Total =1R 1 +1R 2 +1R 3 +1R 4 so 1R Total =12000 +12000 +12000 +12000
=1500 therefore R (total) = 500 ohms.
Now the total power of 100 Volts with a total impedance of 500 ohms can be
calculated:
Power=Volts 2 Impedance =100 2 500 =10,000500 =20Watts
Low and behold, that is the same as simply adding the speaker watts together which is much simpler!
Changing the Amplifier Connection Halves the Load
Example 1: The total impedance of 200 watts of 100 Volt speakers can be
calculated:
Impedance=Volts 2 Power =100 2 200 =10,000200 =50ohms
Now look what happens when that same 50 ohm speaker load is connected to the
70 Volt terminal of the amplifier:
Power=Volts 2 Impedance =70.71 2 50 =5,00050 =100Watts .
Amazing, the same 50 ohm load draws 200 watts of power on a 100 volt line
system, but only 100 watts on a 70 volt line system.
Example 2: The total impedance of 50 watts of 70 Volt speakers can be calculated
(remember 70 Volt line is actually 70.71 Volts):
Impedance=Volts 2 Power =70.71 2 50 =5,00050 =100ohms
Now look what happens when that same 100 ohm speaker load is connected to the
50 Volt terminal of the amplifier:
Power=Volts 2 Impedance =50 2 100 =2,500100 =25Watts .
This principle is very handy to the installer if the power required by the speaker load
is greater than what the amplifier can deliver. Simply move to the lower line voltage
speaker connection and the power drawn is halved.
A 8 Ohm Speaker will Overload a Distributed Speaker System
In the examples above we saw the speaker impedance of distributed speaker
systems is reasonably high. For example a 5 watt speaker on a 100 Volt line has an
impedance of 2,000 ohms. Even a 125 Watt load of 100 Volt speakers is 80 ohms.
So imagine the load if the total impedance is only 8 ohms. It should be 10 times the
load right? This scenario can be calculated:
Power=Volts 2 Impedance =100 2 8 =10,0008 =1250Watts .
That's right, connecting a low impedance speaker (4 or 8 ohms) to distributed
speaker systems will drastically increase the load on the amplifier.
Understanding Distributed Speaker Systems was last modified: January 11th, 2015
by Geof
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All About 70-volt Speaker Systems

Posted by: Steve Lampen on August 09, 2012
Almost everyone has hooked up a speaker to an amplifier. Two wires from each speaker to two terminals on your
amplifier or receiver. If this was in your home, you probably didn't think about how far this cable would go. Likewise,
you probably didn't think about how much power you were losing on the cable. The table below is from the Belden
website and shows how far you can go before you get to a specific loss.
In this case, we show three values of loss: 11% (-0.5 dB), 21% (-1 dB) and 50% (-3 dB) for 4 and 8 ohm speaker
impedance. But you'll notice a third section there, titled 70V (volt) speaker. You will also notice the astounding
distances that 70-volt distributed systems can go.
So how do you use this kind of system? First, you need to buy an amplifier that has a 70-volt output. These are
commercial-grade products so you won't find one at a hi-fi or home theater store. The second thing is that you will
need to buy a special transformer for every speaker running off this system. The picture below was provided by Parts
Express.
Photo used by permission from Parts Express

The real problem is that all your audio is going to run through these transformers, so the quality of the audio is directly
related to the quality of these transformers. If you try and buy a high-quality, high-power 70-volt transformer, so if you
can find one you are going to spend a bunch of cash.
So the 70-volt distributed speaker systems are mostly confined to low audio-quality applications such as background
music or paging. Supermarkets, hotels, hospitals, airports are where you will find 70-volt distributed loudspeaker
systems; anywhere you have more than a dozen speakers. While the power amp might be a few hundred watts, most
speakers have a transformer that is designed for maybe 5 or 10 watts.
Even with all these drawbacks, there are things that 70-volt systems can do that regular systems cannot. One, as you
can see from the chart above, is distance. You need a speaker out in the parking lot a mile away? No problem! In
fact, within a building, the gauge of the wire almost doesn't matter at all.
Note that 24 AWG wire, like some bell wire or spare Category 5, is only 1 dB down at 900 feet!! The cost of the wire in
such an installation becomes incidental. Another unique feature is that the transformer on each speaker has a
number of taps on the output. It might be a 10-watt transformer but it will allow you to hook up that particular speaker
at a number of lower power levels. This means you can decide as you're installing, or even afterwards, if a particular
speaker is too loud or not loud enough.
I put a 70-volt system in a radio station. The level in the reception lobby was a gentle low volume. In the bathroom, I
put that transformer/speaker at full throttle, so the DJ could hear his cut running out! And once you have set up the
entire system, with soft and loud speakers, the master volume control on the power amp takes the entire system up
or down with the softest speakers still being the softest, and the loudest still the loudest.
There are a number of other tricks you can do with 70-volt systems. Do you know some of them? Send them to me at
steve.lampen@belden.com and I will print them in a following blog.
Tags: Speaker Cable, Speaker, Distributed Speakers, 70 Volts, Speaker Transformers
Comments
Steve Lampen on October 22, 2014 at 12:08
Since amplifiers are not balanced line devices, and therefore the pairs attached are not balanced lines, it
doesn't matter if the pairs are twisted or not. (In fact, our speaker cables are very casually twisted, making
them easier to assemble. Remember having an argument with a customer if this twisting is the same as real
twisted pairs, such as 9451 etc. There is NO specified lay length for speaker cable. So you can use pretty
much anything for 70v systems (which is the whole idea behind 70-volts) and I have in the past, including
NON-TWISTED multiconductor cable.
Alex on October 22, 2014 at 12:08
Do you happen to know of any data on the effect of using twisted vs. non-twisted speaker cable for 70V
systems?
Eddie-The very nature of 70v systems is that all speakers are wired in parallel and the transformers raise the
output impedance to a much higher value where the gage of the wires is no longer critical. This also means
you could turn the all on, or just one, and the amp won't care. If you lift one side of each pair going to a
speaker, that speaker will turn off. Is that what your box does? Lift (open) one side of each pair? Then the
only thing I would suggest is that you make sure this box can handle 70 volts since that is higher than most
speaker outputs (until you get to really high-power amplifiers and speakers). Of course, this means the
switches would only be in one place in the house. Wouldn't it make more sense to put them in the room
where each speaker is? A very simple SPST switch would allow you to turn off that local speaker.
Edward on October 01, 2014 at 10:29
I have a whole bunch of speakers throughout my house hooked up to a 70V system. Works great, except I
would love to have the option of turning of some speakers in certain rooms when they are not needed. I
bought a simple speaker selector switch box at Radioshack, but now, looking at the manual I am confused
since there are different impedance (ohms) values when certain channels are selected. Will this work for a
70V system? In your opinion, what would be the best way to incorporate a selector switch system? Right
now, all the individual speaker cables run down the inside walls where I have connected them together in
parallel.
Steve Lampen on September 19, 2014 at 08:33
Ed- I find it hard to believe that your AM-FM receiver has 3000 watts of audio available. 300 I could believe,
and I would bet it might be 30 watts, which is still enough to drive a bunch of speakers. If your speakers
really are 100-watts, then you would need 100-watt 70-volt transformers on each one. If these are wooden
boxes with speakers, you could mount the transformers on the outside of the speaker or even inside the box
(would look better). Be sure to label the screw terminals as "70-volts" so you don't create a problem for
someone in the future.
Ed on August 04, 2014 at 10:55
I have 8ohms speaker system ceiling installed; I just bought an AM/FM tuner 3000 watts amp; it has the 70V
out put for the speakers system; I am afraid that it could blow up my speaker if I connect them; my question,
can they be connected? if so, what is the differences? my speakers are 8 ohms / 100 watts.
Steve Lampen on July 28, 2014 at 10:00
Jay- 70-volt systems are limited in power by the size of the amplifier and the power rating of the
transformers on each speaker. This is why you rarely see 70v used in giant stadium systems. Instead they
run the power amps as close to the speakers as they can get to minimize cable loss. How far is it from the
amplifier to where the speaker would be mounted? We now make giant speaker cables (up to 6 AWG) but I
would bet this is overkill for what you want and something like 5T00UP, 10 AWG speaker cable, would
probably do the job.
jay on July 22, 2014 at 09:04
My father wants a very loud out door sound system to play rock music and annoy his neighbors. (Water
fued) we are considering a 70v system but distance isn't so much an issue as loudness, (distance the sound
will travel) should we bother with 70v or just look into larger speakers /amps?
Jeff- Not sure if I ever replied to you. Apologies! I don't think the 4 ohms or 8 ohms has a lot to do with what
you are hearing. Certainly some speaker are more efficient (louder) than others. This is something that 70volt distributed systems are designed to fix. The transformer on every speaker usually has multiple outputs.
These directly affect the amount if power (watts) driving the speaker. You can either move the quiet
speakers to a louder setting (higher wattage) or move the louder speakers to a lower setting (less watts)
until their level is the same in every speaker. If you want the whole system to be louder, turn up the volume
at the power amplifier . If you hear distortion, it probably means that the amplifier cannot deliver the
appropriate amount of watts to drive everything to the level you need. You need a more powerful amp. Does
this make sense? Do some experiments and get back to me with what happened.
Brian- It is extremely unlikely that the speaker, volume control or cable could be introducing the hum. Since it
gets worse with time, this sounds exactly like the capacitors in the power supply section of the amplifier. (As
it warms up, the capacitors get worse - very common.) Put in a new amp or have the old one fixed. That
should solve your problem.

Ash - If you are running 70-volt distributed speakers, you should have no problem running 20 ft. or 150 ft.
You can find a chart of distances at 70v here http://www.belden.com/docs/upload/Speaker-Cable-SelectionGuide.pdf and this lets you choose what wire gage you can use.
Brian W on September 08, 2013 at 01:25
Hello, have a 70 volt system in our church foyer and have a hum that only becomes apparent after the
system has been on for about 45- 1 hr. There are about 10 ceiling grills on the amp that is being used. I am
not sure if the amp is causing the hum or if maybe there is a bad 70 volt speaker transformer or volumn
control. Any thoughts?
ash on August 26, 2013 at 09:05
I need comments re an outdoor speaker system for background music and Public Address system in a
church/temple. The system will have 12 outdoor (soffitt mounted) speakers.. The shortest run is 30 feet and
the longest is 120 feet from the amplifier. Any suggestions will be greatly appreciated. Ash
Steve Lampen on April 30, 2013 at 05:13
Antonio- Can we reprint your comment in a future blog? 8 AWG and 6 AWG were originally suggest by
Crown, to wire up their 5-kilowatt and 10-kilowatt power amps in large venues (stadiums etc.). Of course you
can use 4x14 AWG to get to the same 8 AWG. (Every time you add two identical conductors, the resultant
gage is 3 below what you started. So 2 x 14 AWG = 11 AWG and 2 x 11 AWG = 8 AWG.) The one thing that
is missing however is a safety rating. Power amplifiers over 1 kW can be lethal if you touch the speaker
terminals with audio present. Most of those amps should have a notice over the speaker terminals that says
"Class 1 Wiring" or something similar. This is a UL safety rating. We have an entire line of Class 1 speaker
cables: 14 AWG, 12 AWG, 10 AWG, 8 AWG and 6 AWG. The part numbers are "88" followed by the gage
size (i.e. 8814 to 8806). I'll bet that your 4x14 AWG cable is not Class 1. Most traditional Class 1 cables are
like house wiring, solid conductors, and very stiff. They don;t lend themselves very easily to speaker wiring.
Hope that answers your question.
Antonio on April 29, 2013 at 02:31
Hi Steve What would be the case that according to the distance and power requirements in a 70Volt system
I need to run a 8 AWG, but since comercially is not very available I use 4x14 insted. Since is the same
copper area apparently it should work, but is there any inconvenience regarding other factors, change of
impedance, distortion, etc?
Steve Lampen on April 15, 2013 at 03:21
Dave- What a great question! I sent an inquiry to one of my "guru's", Bill Ruck: Bill- I remember reading
somewhere that you can directly drive a 70v speaker system by using a high-power amplifier. I assume the
voltage output is somewhere around 70 volts. If P=E sqd/R then the amp needs to be above 600 watts.
Correct? Do you know anything about this? I had an inquiry from a customer. Here is his response: Yes,
your math is correct. At lower power a step-up transformer is commonly used on the output of the amplifier.
Those are generally rated in "Watts" rather than impedance. But if you took the nominal 8 Ohms up to 100
Ohms then 70 Volt line would be only 50 Watts. Speaker systems are not constant impedance. They're
designed in Watts for convenience. Say you want 12 speakers at 5 Watts each. You select a "70 volt"
transformer that matches the rated speaker impedance and use the "5W tap". That is a load of 60 Watts so
you find an amplifier that has at least that rated power with an output transformer for 70 volt line or find an
amplifier that has at least that rated power and use a 70 volt step-up transformer with the "60 Watt" tap. If I
remember correctly "70 volts" is an arbitrary number that just falls under the NEC high voltage
requirements.\ The higher the voltage and the higher the system impedance the lower loss in copper. Same
thing for the power company.-Bill So, Dave, the answer is YES. Your 900-watt amp would be more than
adequate, assuming the total wattage of the speakers you're driving is no more than around 900 watts.Steve
Dave on April 11, 2013 at 02:10
Is there a way to temporarily use a 900 watt amp to drive a 70 volt speaker system?
Jeff on February 18, 2013 at 04:09
We ran into an installation where a 70 v system was installed at 4ohms conversion along with some earlier
installed 8 ohm cabinets (non-70 v system). Result is the older 8 ohm/45W cabs are a lot softer than the
new 70 v ceiling system but the clinet wants these older cabinets to be as loud or louder to fill the area they
were designed for where no other cabinets exist. the cabinets TOA - F-10W -no transformers added but they
are tied into the whole 70 volt system and not easy to access. What it s the best way to remedy this? change
out the cabinets and/or add transformers if possible?
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The right Wireless Solutions for your communication needs.
What is a LoudMouth Wireless PA? The system consists of a 1 channel
radio receiver, flex antenna, a rechargeable emergency back-up battery,
a 110VAC power supply, and a separate PA horn/ speaker that attaches
to the receiver. The receiver and PA are activated by the 2-way radio.
The radio serves as a microphone and allows live voice messages to
be delivered to the PA speaker from long-range i.e. across the factory
floor or from across a parking lot.
Features/Benefits
Field Programmable Frequencies
VHF: select 1 of 26 frequencies, UHF: select 1 of 77 frequencies.
Field Programmable Privacy Codes (digital and analog)
Choose from 153 possible codes for added PA security access
Field Programmable Paging Codes
Select 1 of 9 diferent paging codes for added PA security access
Each model can also be PC programmed to a custom frequency, a
privacy code and paging code using dealer only programming software.
Field Programmable to 5 diferent Volume Settings
Allows best-fit for a variety of applications
9 Auto Speaker Reset Timer Selections (5 seconds up to 4 minutes).
After receiver is successfully paged a pre-set timer will begin to count
down, a valid radio signal must be received before the receiver re-sets.
VHF/UHF industrial grade receiver is small, lightweight and housed in
a rugged, sealed weather-resistant housing. Includes a wall mounting
bracket. Receiver should be mounted in a protected area away from
the elements (7h x 5w x 3d, 2lbs).
Rechargeable Back-up Battery automatically provides power to the
receiver in case of power failure. Enables an additional 8 hours of
communication over the PA speaker, at a reduced audio output level.
One LoudMouth receiver can support up to 2 separate Ritron PA horn
speakers in parallel for additional PA coverage
System allows for multiple paging zones so portable radio can
access more than one PA speaker/zone.
The indoor or outdoor PA horn speaker delivers 95dB of audio output
@50 feet, so even in noisy environments, you can get your message
out loud and clear.
Operating Temperature is 22 F to +140 F
Receiver sensitivity .20uV @12dB SINAD
Frequency Response 300 to 3000 Hz de-emphasied
Signaling CTCSS and DCS decode, 2-Tone Decode and
Optional DTMF (Touch-Tone) Decode.
Accessories
RAM-1545 -Mag Mount Antenna. If additional receiver range is needed,
an optional external antenna with 25 feet of cable can be connected to
the receiver and installed outdoors.
BP-LM6 -Replacement Rechargeable Back-up Battery. 800mAh capacity,
will power the LoudMouth radio receiver/PA at reduced audio level for
approximately 10 hours if 110VAC power source fails. (10 hour operation
@ a duty cycle of 10 pages/hr @ 5 second duration per page.
PN# 05500040 -Optional LoudMouth PA Horn Speaker
LMH-100 -Weather proof, tamper resistant fiberglass housing for
LoudMouth receiver.
RSS-100 Solar Power Package -Solar Power Package. 10Watt solar panel,
charge controller, lead-acid battery and NEMA-3 enclosure.

LM-DTMF -Optional DTMF (touch-tone) decoder (factory installed).
Allows keypad equipped radios to selectively page LoudMouth receiver/PA.
Optional DTMD decoder allows use of the Ritron Quick Talk 24/7 Voice Alarm
Reporter. If Sensor or switch connected to the Quick Talk changes state,
unit will automatically deliver a stored voice message directly to the
LoudMouth receiver and PA speaker.
Note: For proper operation the LoudMouth radio receiver and 2-way radio
must operate on the same frequency and tone. For selective paging
capability 2-way radio must be capable of 2-tone encoding.
The following Ritron radio models offer two-tone encode capability:
VHF models: SLX-100, JMX-144D, J-V110 portables and
JBS-146D base station, RPM-160 mobile
UHF models: SLX-400, JMX-446D, JMX-444D, J-U410 portables and
JBS-446D base station, RPM-460 mobile
Models with firmware revision 6.0
Audio feedback is a function of the activating radio. To minimize feedback, a distance of
at least 50 feet should be maintained between the radio sending the page and the horn
speaker. If radio sending the page is equipped with a headset or other noise-canceling
audio accessory the likelihood of audio feedback is greatly reduced. All applications are
diferent and the distance required may vary.
Your Ritron Dealer:
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Public Address / 'Tannoy'
Commercial IP Audio
IP 'Tannoy', IP Public Address
IP Music / IP Radio
IP Intercom
IP Broadcast / Talkback
Fore / Background Audio
Factory PA / Tannoy
Voice Alarm (VA & EVAC)

Assistive Hearing
Help & Information

PA / 'Tannoy' Guide
DIY PA / 'Tannoy'
Telephone Interface
Our Customers
Work with Abletek
Terms and Conditions

Useful Links
Customers
Food Production / Factory
Commercial / Offices
Lister Hospital A&E

Click HERE for more......
'Tannoy'
There are very few products and inventions impact to our lives so strongly that their name becomes synonymous with
the function they perform. 'Tannoy' is one such product that immediately identifies against the speaker and audio
function it performs. In fact, the term 'Tannoy', is widely recognised colloquially and generically to mean any Public
Address
(PA)
system.
As one of the oldest (and most recognisable) audio brands in the world, Tannoy, is a UK company (based in
Scotland), manufacturing speakers and Public Address (PA) systems. The company was founded as Tulsemere
Manufacturing
Company
in
London
in
1926.
Tannoy made its name during and shortly after World War II, supplying PA systems to the armed forces and then to
holiday
camps
such
as
Butlins
and
Pontins.
Public Address (PA)

Public Address or 'PA' is generic term, essentially describing an audio / sound based electronic amplification system,
that
is
typically
used
to
communicate
audio
messages,
tones
and
music.
However, whilst understanding this generic basis, it is because of the different PA market applications, that there is
often confusion and sometimes disagreement in describing PA systems. For example, we often observe the term 'PA'
being used interchangeably to describe an audio solution providing function against different foreground and
background audio applications. Both function similarly, but it is important to distinguish the two by system design,
capabilities
and
product
technologies
(Foreground
and
Background
Audio).
Abletek installation services and product sales are focused towards 'installed' background commercial audio
solutions. We use the terms PA and 'Tannoy' interchangeably to describe announcement, radio and music based
solutions.
How does a Public Address (PA) System work?

The simplest Public Address (PA) systems (eg. a small school or library) employ three basic components: a
microphone, amplifier and speaker/s. The microphone is the audio source; in use, it simply 'keys' or controls the
amplifier as well as providing the audio input. The amplifier provides basis of power output levels and power delivery
to the speakers, which obviously then create the noise or sound output to the local area/s.
Most PA systems follow the same basic working pattern as described above. However, many employ additional
components that allow for larger, flexible and more integrated solutions. The following are some examples of PA
components
that
are
regularly
used
within
such
systems:
Multi Output / Zone Amplifiers: Selectively allow the larger PA systems to output to single/multi or all local areas
(eg. you may want office pages/calls to reach the offices only, and not in the factory / site wide.
Audio 'Mixer': An electronic device for combining two or more audio signals. Mixers can be analogue or digital, but
perform the same function of producing a summed audio output signal. Mixers and Mixing Desks (also known as
audio
boards)
form
one
of
the
main
components
within
many
PA
systems.
Audio Sources / Inputs: Announcements through demand based microphone use is clearly one type of audio
source. Many PA systems connect other audio sources such as music (cd player) or perhaps the radio (tuner).
Integrated Inputs: Found commonly in commercial and industrial environments, we can integrate the PA system to a
telephone system (PABX). Many commercial telephone systems perform a function known as 'paging' this allows us
to connect the PABX to the PA system (normally the amplifier), and use telephone handsets to 'key' the amplifier.
Many organisations elect not to use dedicated microphones, but use telephone handsets to make their 'Tannoy' calls
and
announcements
in
this
way.
Alarm, Fire and EVAC: Generated under 'alarm' conditions, pre-recorded announcements can be made through the
PA system - providing details and evacuation procedure information. It is important to follow recognised policy and
standards with these types of systems (eg. BS5839, BS5588 & BE EN 60849). Click for more details about Voice
Alarm
(VA)
/
EVAC.
Public Address over IP (IP PA): It is now possible to manage and configure PA systems via a data(IP) network. It is
also possible to transport audio streams to output devices (speakers) via the same network. To achieve this, IP PA
employs two additional components. 1 - audio codecs to transition from audio to IP and 2 - network interface/s to
connect
to
the
network.
Click
for
more
details
about
IP
PA
and
IP
Tannoy.
Questions
or
queries
regarding
Abletek
Public
Address
Telephone: 0345 387 0123 | Fax: 01733 60 0123 | Contact | Site Map | Privacy Policy
(PA),
please
Contact
Us.
2012 | Abletek Commercial Audio Solutions
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About Abletek
Services
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Customers
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Commercial Audio Markets

Markets Overview
Public Address / 'Tannoy'
Commercial IP Audio
IP 'Tannoy', IP Public Address
IP Music / IP Radio
IP Intercom
IP Broadcast / Talkback
Fore / Background Audio
Factory PA / Tannoy
Voice Alarm (VA & EVAC)

Assistive Hearing
Help & Information

PA / 'Tannoy' Guide
DIY PA / 'Tannoy'
Telephone Interface
Our Customers
Work with Abletek

Terms and Conditions
Useful Links
Customers
Food Production / Factory
Commercial / Offices
Lister Hospital A&E

Click HERE for more......
Traditional Public Address (PA) & 'Tannoy' Systems

Industrial, Commercial, Retail, Factories, Local Authorities, Education, public buildings & public spaces.... the list
goes
on.....
......many employ voice announcement services through Public Address (PA), 'Tannoy' and Background Music (BGM)
systems.
Traditional Public Address (PA) or 'Tannoy' systems, leverage the concept and design of providing announcement
systems that have stood the test of time. Whilst many of these systems have grown in capability, the basic design has
changed little over the years - the three main components: input devices (typically microphones), amplifier & output
devices
(speakers)
remain
at
the
heart
of
all
traditional
PA
and
'Tannoy'
systems.
Many of our customers want the dependency of 'solid' purposeful and dedicated products and solutions that provide a
quality solution for their voice announcements and other sound based public address (eg. background music, time
clock tones & voice alarm / evacuation). Today's demand is changing however. Traditional PA and Tannoy systems
are
becoming
much
more
complex
and
integrated.
For many customers, a traditional PA, 'Tannoy' or BGM application design meets their demand - for some, newer IP
based technologies provide meaningful benefit and application capabilities (IP 'Tannoy' and IP PA).
Abletek are industry leading suppliers, designers, installers and maintainers of traditional PA, 'Tannoy' and BGM
systems. We are experienced contractors, providing service and support to customers across all business sectors.
PA, 'Tannoy' and BGM is what we know, and what we do - select Abletek for your commercial audio project!
Traditional 'Tannoy' Public Address (PA) - Example Abletek Customers:
Murata PS - Milton Keynes
View
Have
some
a
of
question
our
or
Tesco - Daventry
other
query
about
recent
Traditional
traditional
PA
&
Sweet 'n' Low - Cambridge
PA
Tannoy
&
'Tannoy'
services?
customer
Please
Telephone: 0345 387 0123 | Fax: 01733 60 0123 | Contact | Site Map | Privacy Policy
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Feedback
It is a centralized amplifier based system thats been designed to provide voice

paging and to broadcast alarm tone during emergencies.
External Ringer
Integrated PA & Intercom System
Industrial
Communication
System
The system can transmit alarm tone and routine voice messages, from a central
location, to all or selected areas of the facility, in a reliable and safe manner, by the
use of loudspeakers.
The entire operational area / facility can be divided into one or more zones, which
can be accessed independently either for announcements or for alarm broadcasting.
The loudspeakers are installed in these zones.
There are no limitations to number of zones in the system or number of

loudspeakers in each zone. Each loudspeaker is connected to the central equipment
for amplification and other control functions.
Depending on the surrounding environment, either flameproof loudspeakers (for
hazardous atmospheres) or weatherproof loudspeakers (for safe & non-hazardous
atmospheres) or indoor loudspeakers (for indoor areas) are installed in each zone.
The loudspeakers are available in different wattage, sizes, types and constructions.
The system is designed to offer clear reproduction of sound and intelligibility of
speech even in high noisy areas.
Multiple control desks can be installed in the same system, for paging access (with
priority) from more locations.
The system uses high reliability amplifiers with built in over load protection
circuitry, short circuit protection, open circuit protection and thermal protection.
Key Advantages :
Simple, reduced and economical field cabling
Trouble free system
Flexibility to connect the loudspeakers at longer distance.
Modular architecture
Flexibility to build the system for the present need with

enough provision for future expansion.
Connectivity of p. a. system with the EPABX System
Monitoring the healthiness of all associated equipment in the

PA System
Call attention chime tome prior to all announcements

channel
No use of AC Power source in the field

Highest priority for control desk paging
Bass and Treble control to custom-tailor the frequency

response, for poor acoustic or highly noisy environments
LED Bar graph in dB scale to read the relative power

Distribution of audio signal through buffered O/P
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PLANT COMMUNICATION SYSTEM (PCS) is a

microprocessor controlled, software
programmable, central exchange based paging
Feedback
External Ringer
Integrated PA & Intercom
System
Industrial Communication
System
Party Channel is used for carrying prolonged

conversations in private mode, which is not heard over
the loudspeakers. The system possess multiple party
channels i.e. one dedicated channel for each field
handset station. Thus each field operator can carry his
separate, independent and simultaneous conversation.
The field call stations and loudspeakers are

installed at various locations throughout the
facility. The person can communicate from any
field call station of the system.
The loudspeakers and field call stations are indoor type

for indoor areas, weatherproof type for outdoor safe (i.e.
non-hazardous) areas and explosion proof type for
hazardous areas. The loudspeakers are available in
different wattages & sound pressure levels and in
different sizes & constructions to meet all types of the
requirements.
The system provides excellent reproduction of sound,
clear audible announcements and high intelligibility of
speech, even in high noisy areas.
Key Features:
Paging + Alarm broadcasting facility
Master-Slave Configuration with facility to connect multiple
master control desks
Direct Communication between the field operators and the
control room operator
Direct communication between the two field operators (i.e.
without routing any calls through central control room)
Communication between the two field operators with the help
of Master Control Station (MCS)
Individual zone, Multiple zone and All zone selection for
announcements
channel
Digital display at MCS for identification of field call station
number / area name
Call holding, call waiting, page priority, override and central
monitoring facility at MCS
No requirement of AC mains for operating any field equipment
Access to features can be restricted (by software programming) for few call stations
No correlation between the field handset stations and the loudspeakers. Their quantity,
location and their functioning are 100% independent
Open system to facilitate its integration with EPABX, Fire alarm etc.
Easy and quickly expandable by adding the relevant card in central equipment
Host of various unique and useful features
Key Advantages:
State of the art technology
Software programmable for communication options, features and system access
Simple and economical field cabling
Cost effective design and hardware
Trouble free system
Modular architecture, offering the flexibility to build the system block by block
Centralized monitoring for system operation, performance and equipment healthiness
High flexibility and adaptability
100% non-blocking communication facility to all users
Minimum downtime, easy system operation and maximum safety
Easy and Quick to expand
For more information and product catalogue please write to us.
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Skills & Techniques Equipment & Software Beginners Guide To PA Systems, Part
1: Basics
Beginners Guide To PA Systems, Part 1: Basics
April 25, 2013 by Terry 42 40 Comments
The Mackie Thump is a popular PA for DJs, with the speakers containing the
amplifiers meaning there's no need to carry separate amps. Here the speakers are
pictured with a small PA mixer.
Stuck understanding PA systems? Need to rent or buy one for your shows? Scared
about plugging into or playing on a PA? Want to know why you need one at all, when
you could take your home stereo speakers to the party and use those instead? If so,
trust me - youre not alone. This guide is here to help. Ive helped lots of DJs like
you, as well as many live acts, with getting the best from PA systems, and Ive been
doing it for a long time - even longer than the 15 years Ive been DJing. In that time
I have used lots of diferent PA systems, in places from small wedding venues right
up to festivals with tens of thousands of people.
Furthermore, in my role as moderator of the Digital DJ Tips forum, I know full well
how many DJs know very little about this important subject, judging by the number
of questions asked about PAs. Which is why we decided it's high time to start
unravelling some of the mysteries of PA systems from the point of view of DJs.
Just a word: What Im ofering here are views based on my own experience over that
time. While I have not studied theoretical physics to prove what I believe, I have
seen and heard enough to be pretty sure these guidelines are right. So experts
might think diferently about some of the minutae of whats here, and who knows,
on some points they might be right - but on the other hand I cant remember a time
that things havent work out well for me with PA systems, and I get a lot of
compliments for my great sound. So having made that clear let's go!
What this series does and doesnt cover
Looking for the low-down on this type of PA ( a 'line array' system)? Sorry, we're not
going there...
This is a big subject, so let's narrow down what we're going to look at. This guide
discusses low to mid-range PA systems, because these are the types of system that
reader of this website are going to want to buy and are most likely to find
themselves using. So I will not touch line array systems, for instance, as that is a
whole diferent world and frankly if youre DJing on that scale there will be audio
engineers about to help anyway. (And if you do not know what a line array is, do not
worry about it.) Also I am not touching big club gear in this guide. Big clubs present
a very diferent environment to simple venues. The basics still apply, but you
have to consider more things. Possibly well cover these in a later guide or course.
Finally, I also get a lot of questions regarding new stuf like PA mixers that you can
configure with iPads, active speakers that look like trumpets and so on. While we
cant cover all of this in a basic guide, the basics do apply in my experience. Whats
more, if you familiarise yourself with these basics, you can more easy decide what
is real innovation and what might in your case turn out to be only "for show"...
What is a PA? Why is it diferent from hi-fi system?
PA means public address and basically a PA is a system that is meant to provide a
public (audience) with a constant quality of sound for a long period of time. Hence a
PA system has some qualities that are diferent from common hi-fi-type equipment.
We will cover the diferences as we work through the guide.
Usually a PA system consists of three parts: A sound source (for DJs this is your
sound card or controller line output), an amplification system, and a speaker
system. But before we look more closely at each component of a PA system, lets
think first what we actually need from a PA system, as the needs of most DJs are
diferent from a band or vocal presenter, and these needs will determine how our DJ
PA is put together. It's time to look at some basic set-ups.
The most common DJ PA set-ups
1. The basic DJ set-up
So heres a simple, basic set-up. (Note that in all these block diagrams, the sound
travels from source [left] to output [right]. Also you can substitute DJ controller for
DJ mixer, DJ audio interface etc - basically, its the master output from your DJ
system.)
Basic DJ set-up.
This is the most basic set-up. Indeed, if you decide on active speakers (speakers
with the amplifiers already built in) it can get even down to DJ controller and
speakers! However the blocks are still there, it is just the routing with cables from
the amplifier to your speakers has already been done for you by the manufacturer
in the one cabinet.
2. The "enhanced" DJ set-up
Enhanced DJ set-up.
The PA mixer is really no diferent to a DJ mixer in what it does (mix sound sources).
Indeed, one might think that a PA mixer is not actually needed if you only use your
controller. However, there is one big advantage to using a very small PA mixer, even
in such a case: You can set up your DJ controller totally flat (ie all EQs are to middle
and the master output is to 50%) and then do the sound check (see later in the
series) from the PA mixer.
This way, you can still perform easily on your DJ controller and if you do not touch
the PA mixer after the soundcheck everything should stay OK and sound will be
good. That is why I recommend this set-up as enhanced over the above one.
3. The mobile DJ set-up
Mobile DJ set-up.
Again, in this set-up you can substitute the sound sources for other things; the
microphone could be wireless, the iPod could be an iPad and of course it could also
be a spare CD player or whatever... but the idea is the same. The point is that the
PA mixer is the hub to joins all the connections from sound sources.
Now some DJ controllers do have microphone inputs, but most DJs prefer this kind of
set-up as the talkover function on DJ controllers (the thing that ducks the music
volume when the mic is in use) is in most cases not as good (if it exists at all) in a DJ
controller, and a PA mixer will usually give you a greater level of control.
(Note that in established venues with DJ booths, often a pro DJ mixer either takes
the place of the PA mixer here, feeding straight to the PA amps, or comes before the
PA mixer, feeding into it, in which case the PA mixer is where you'll typically find the
dedicated venue sound engineer lurking...)
However, there are times when you may be forced to use the microphone input on
your DJ controller, which is when you might encounter...
4. The "mini mobile set-up"
Mini mobile set-up.

I know some mobile DJs who use this set-up instead. These DJs tend to be new and
dont yet have the money to buy a PA mixer (even though such mixers relatively
cheap, as well find out). Indeed, some DJ controllers even have another Aux in,
where you can connect an iPod or CD player. The better your DJ controller, the more
likely such a set-up is to deliver good results for you.
Next time...
So these are the very basic set-ups. I hope you can see that it is very simple if you
think in these building blocks, there is no magic or voodoo about it. Nothing to be
afraid of.
Where it all gets a bit more technical is in choosing a PA system, as there are lots of
factors involved in choosing correctly. So in the next part we answer some common
PA questions to help get you set..
Check out the other parts in this series:
Beginners Guide To PA Systems, Part 2: Common Questions
Beginners Guide To PA Systems, Part 3: Amps & Speakers
Beginners Guide To PA Systems, Part 4: Cables & Soundchecking
Do you struggle understanding how all the parts fit together in PA system? Are you
considering buying one for yourself? Or are you scared about plugging into someone
else's, or one at a venue? Let us know your thoughts in the comments.
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So here's our best of 2013: From DJs wages to laptops in the booth, music "all
sounding the same" to PA systems, heartfelt career advice to picking a great DJ
name, this is the very best of Digital DJ Tips the past 12 months.
December 31, 2013
In "Latest News"
Small PA System Vs Monitor Speakers For DJing

Is it a good idea to buy a PA system as a DJ, even over and above buying monitor
speakers for home practice? A look at the pros and cons.
November 8, 2012
In "Equipment & Software"
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Filed Under: Equipment & Software, Skills & Techniques Tagged With: Dj Pa Systems,
dj speakers, pa systems, Speakers For Parties
Comments
Chuck "DJ Vintage" van Eekelen says:

April 25, 2013 at 7:49 am
Hey Terry,
Good write-up, thanks.
I wonder though about the PA Mixer in between the DJ setup and the Amp/Speaker
combo. I have worked that way quite a few times in the past, but I always find a lot
to be desired. Here are my concerns.
1) More sh*t to carry :-). It is getting noticeably less fun to haul equipment around
these day, I know: I am getting too old.
2) Another mixer, even a small one, takes up more of the -in many cases- limited
space. If I have my DJ coffin up on the stand, there isnt any room left for a mixer
that I can easily reach.
3) Its another cost factor. As you well know even a small, but decent PA mixer runs
a couple of hundred bucks, which is money that cant go to other things
4) I find it rather unpractical having to use two boards to do my gig. If you use a mic
often or two as in my case, or you need a lot of aux possibilities, I think it is better
to take that into account when buying your controller/mixer.
5) I doubt that many DJs can or want to sound out a room before they start playing.
And sounding out a room decently, youd need a (preferably 31-band) graphic EQ,
or at the very least, a full parametric EQ. Both are hardly ever found on smaller
and/or cheaper PA mixers. Besides the process takes quite some time and
experienced ears if you are not using measuring equipment to do it right. Time you
dont get paid for usually.
I am mainly a mobile jock too. And I do own my own (Mackie HD) PA which sounds
relatively flat (tested with RTA in a neutral room). 99 out of a 100 times it will sound
good in the wedding/party venues I go too. The 1 time it doesnt, the problems are
usually too big to overcome, like big reverb issues and frequency-holes due to
shape or construction of a venue. Problems that cant be fixed by having just a
simple PA mixer in between.
It is a very handy option, as you said on forum before, if you have a multiple DJ
setup. Cause all DJs can plug in on their own two channels on the PA mixer without
the need to switch the amp/speaker over between the DJs sets.
Again, as you said, we all have our own experience and workflow we used over the
years. I noticed I am going leaner and leaner. Not so much the size of the gear, but
the actual amount of boxes (flightcases) and cables I have to connect/disconnect
every time. Less setup and breakdown time and less walks to and from the car have
become a focal point in setting up my gear.
Thanks again for the write-up, I see all the relevant questions on the forum too and
there are many of them.
Greetinx,
C.
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Irvin Cee says:

April 25, 2013 at 9:35 am
agree on the multiple band EQ.
Better of with an EQ than a PA mixer. Easyer to carry and more powerfull to tune the
sound.
BUT, if you are not used to configure a multiple band EQ, you probably gonna make
things worse than without an eq.
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Bart says:
April 25, 2013 at 9:27 pm
Is a 200 euro PA mixer behind an allen&heath xone mixer and before more than
decent powered mobile sound system (qsc, rcf, turbosound, whateve) really going
to sound better.
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April 25, 2013 at 10:49 pm
Well, the point Terry was making is that with a dedicated PA mixer, you can set EQ
for the room/PA combination. That way on your DJ mixer/controller you can use your
EQ freely without having to worry about messing up the room EQ. I get that,
although as stated, a multiband EQ would be a more preferable piece of outboard
kit.
And no, Id dread to think someone had a 5-year old PA mixer from a less desirable
brand, like say Behringer, and then hook up a 1200 dollar controller with top of line
sound card built in. Yikes!
Greetinx,
C.
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Janne Huotari says:

April 25, 2013 at 8:03 am
I have a really nice 5.1 with yamaha rx-v371 amp, and jamo speakers, which cost
me a pretty penny. However i am having a bit of a latency (that i did not notice
earlier, as my ear was not as developed as it is now), which is just annoying enough
for me to not to be able to beatmatch by covering one ear with headphones.
I found a lot of people with similar problems from the interwebs on various gear set
ups, and some digital processing seemed to be the main reason for this in HI-FI
amps, so, almost without exception, everyone was told to rethink their PA solution.
Which is the situation i am now facing as well.
I am considering of changing/upgrading, but i am not too sure of what direction id
like to take. I absolutely love my 5.1, and it is so crisp when used with my full hd
projector, so i would not really want to let it go.
Any advice of what i should do? The amp+speakers cost me ~800 euros 2years
back, and i am too fond of them to let them go.
Would setting the DJ PA next to my current PA be a solution if i run them through PA
mixer?
I am with:
S2 (currently all audio comes through S2 soundcard for me)
Desktop
Yamaha rx-v371 amp
Jamo 5.1
Thanks in advance,
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April 25, 2013 at 10:31 am

Point in case being made by Terry in his articel. Dont use Hifi amps to do PA stuf.
The Jamos borderline. You can use them on the road (depending on the type),
but they are made for home use too really. Surround (5.x, 7.x) is something I
wouldnt want in a PA anyway.
Your best bet is to either rent a PA when you are playing out (you getter way better
gear than you would usually purchase yourself, unless you play out two nights a
week with your own gear) or to get a decent set of active speakers with or without
subwoofer(s). I love active speakers, because you can never lose your amplifier
through a defect and be left without sound, if push comes to shove you can finish
the night on 1 speaker and perhaps your sub if you have one.
Beware though! As has been stated here and on the forum time and time again
when it comes to PA: You get what you pay for. There is no cheap shortcut to
excellent sound at decent volumes.
Greetinx and good luck with your decision,
C.
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Foldable disco says:

April 25, 2013 at 12:38 pm
True, no surround. Because surround systems use all sorts of enhancers and spatial
algorithms to let your music sounds like a movie. That could be a reason of the
latency you are experiencing. For example, just a clean 2.1 set up with 2 tops and a
(mono)sub would do it. If you want more bass? Just add another sub.
I use the Mackie Thump 15 tops with a 18 Mackie subwoofer, gives me all the
power I need for now. The sound is maybe a little bit to clean, but we like it and it
was in my budget.
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Shenoizy says:
April 25, 2013 at 1:32 pm
I use/used a surround sound amp for my home DJ-set up without any problems. The
key is to not use it in any kind of surround mode as that will introduce delay and
unwanted processing into the sound. Most modern amps have a direct, pure or
multi-channel input mode that will not add any further processing to the signal
coming in. I personally use the multi-channel mode and feed my DJ mixer output to
the surround rear channel speakers which are set up directly next to my mixing
area. No audio delay, excellent sound quality and no extra cost.
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Foldable disco says:

April 25, 2013 at 2:44 pm
If you use your surround as a multi output amp, it shouldnt be a problem. So at
home it can fit perfect, but as a pa system I would say no.
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Janne Huotari says:

April 30, 2013 at 9:13 am
Thanks guys, appreciated
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Dirty Disco Soundsystem says:

April 25, 2013 at 8:51 am
At last! Thanks. Looking forward to next parts. If only this had appeared in Aug 2012
when I was about my first rig. Ah well
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King of Snake says:

April 25, 2013 at 1:57 pm
Godsend Terry!
just about to buy a new PA myself
cant wait for the next articles

(was looking at peavy triflex II, any remarks on that?)
regards
KoS
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Michael Hertzog says:

April 25, 2013 at 2:47 pm
Thanks for this post. It really applies to people who want to get into the DJ world
who dont know a thing (like me). Thanks again.
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Daryl Northrop says:

April 25, 2013 at 4:40 pm
Thank you SO much for posting this!
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atom12 says:
April 26, 2013 at 12:20 am
No PA Mixer but a DriveRack PX, always sound check with measurement mic.
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DJ Forced Hand says:

April 26, 2013 at 3:21 am
This is a very good article on the basics of P.A.s. Certainly, if youre bringing your
own sound someplace SOMEONE has to run it. Many people are tempted to EQ onthe-fly or default to scared and set their levels to Noon (just to play safe) and
leave the settings there all night. You *can* get away with this about 85% of the
time as long as the speakers are set up properly, theyre angled to cross over in the
middle of the target (dance) area, and theyre a matched pair. Remember that the
room sound changes when people start filling up the dance area and the
temperature/humidity changes (due to people sweating) so make changes
accordingly.
Most (good) P.A. speakers will be self-powered or have the amplifier built into the
case of the speaker. Dont forget that when you set your speakers to have them
around 6 of the ground (whether you hang them or have them on speaker stands)
but never have them on the same surface as the DJ gear, especially turntables, this
is a good general rule. For added Oomph! get the sub-woofer not a larger speaker
set to Deep mode. sub-woofers are a diferent creature and need to be set up a
little diferently.
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djdubc says:
April 26, 2013 at 3:44 am
man i would just get a mixer with xlr outputs..im using american audio dv2
mixer with the xlr outputs.then just chain ur subs to the speakers through the
outputs into the inputs of the subwoofers problem solved lol. no pa mixer etc. just
have long enough xlr wires
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April 26, 2013 at 8:07 pm
You dont even need the XLR outputs. There are D.I. converters that will take (2)
RCA in and (2)XLR out. I have one called a Whirlwind PCDI, but there are other
manufacturers.
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April 26, 2013 at 8:13 pm
Silly me, I didnt leave the price You can find a Whirlwind PCDI for about $120$140.
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Pascal Dorion says:

April 26, 2013 at 4:43 am
Great article! I was going to ask you a piece on just that!
I started playing clubs here in Montreal and found that the sound quality was
abysmal! On my last venue I was able to fiddle around with the setup to get the
sound to 70% optimum but need a crash course of club PA systems.
Here is the setup for my last club and the one I am most likely to play at again in
the near future:
6 monitors on the ceiling, one is the booth monitor for us DJs.

a PA speaker set (221 subs and 215 tops) for concerts
an Allen & Heath console, 16 tracks
A Numark iCDMIX 3 for CDJ/iPod/Mixer functions
a speaker management thingy from DBX, does crossover and limiter stuf
an EQ for the monitors that will go on the stage during shows.
All speakers are active.

Anyways, I put all the EQ in the middle, killed some mids from the A&E and things
got acceptable but not optimum. My question is how to deal with the levels from the
diferent components (controler, mixer, console, speakers, DBX thingy) ?
Also is there a device or app to help me with improving the audio? Something that
can hint at causes for bad sound?
I got some names of soundmen from the local PA rental powerhouse so I might hire
a guy to help me out one night.
Anyways, cant wait for more of this, videos and a course would be great too.
Carry on!
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Pascal Dorion says:

April 26, 2013 at 5:18 am
Here is the gear:
DBX DriveRack 260
DBX 231 EQ
A&E MixWizard3 16:2
ART HQ231 EQ
What is this about using a MIC for soundcheck with my DriveRack?
I just wanna play my CDs but bands play there hence the advanced gear. Id just
wanna pass the whole sound in my DJ Controller or at least have the gear in passthru mode as much as possible.
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April 26, 2013 at 7:49 am
I would think it is the responsibility of the venue to provide a sound system that is
optimised for their space. Doing that correctly is a rather complex matter. Changing
one parameter usually introduces one or two other results.
The best way to do it, these days, is to use pink/white noise and a RTA (Real Time
Analyzer). Tweaking a PA like that can take a fair bit of time.
One of the major issues with tweaking a PA is that the only time you can do it is in
an empty house. The impact of the amount of people present is tremendous. I have
heard rooms that sounded perfect dry, i.e. no people in it and went to horrible as
soon as it filled up about to half its capacity.
The other way around too. I have played in a venue once where I played a tune in
the afternoon (getting acquainted with the setup for the night) and just went This
suck, I am out of here. The resident DJ who was there showing me around just said
chill, wait for tonight. And indeed, as soon as the place filled up you could actually
hear the sharp edges disappear and the sound settling in just right.
As a mobile jock I dont usually bother with sounding out a room anymore. If your
performance, entertainment value and musical selection are spot on and the gear
you have is intrinsically good (meaning your PA doesnt do the harm itself by being
of low sound quality), than I am sure nobody in the room is gonna remember if the
lows or mids sat just right.
We have a lot of cellars in the city where I live and playing in those it is impossible
to get a really good sound (trust me, we have tried). Yet all visitors just chalk that
up to venue appeal.
My advice: get really good gear if you need to own your own or rent very good gear
and dont worry too much about it. We are talking 100dB sound level venues, not
whispered stageplay in a theater.
And 5 minutes into that kind of sound attack, your ears just go screw it Ill just
give you the highlights anyway.
Greetinx,
C.
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Pascal Dorion says:

April 26, 2013 at 2:29 pm
LOL no. The venue I am at now had 60 people on opening night and maybe 6 of
them danced and these people usually ALWAYS dance in other venues. The sound
sucked so bad, like a bad mono sound from a toy of the 80s. No highs or lows, just
distorted mids. I will try soon with my own source gear (A&E Xone:DX or Musiland
Dragon soundcard) and see the impact the source has since I suspect crappy MP3
sound and bad DACs from the Numark CDJ.
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April 26, 2013 at 8:40 pm
I am sympathetic to your situation. It sucks if you cant ignite the fire because the
house PA sucks, but if they turn a deaf ear to your recommendations, I think Id go
hunt down another venue :-).
Greetinx,
C.
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April 27, 2013 at 4:32 am
One more piece of advice for mixers: If youre going to run sound through a mixer,
make sure you have enough channels to support the gear thats playing, and the
gear that will be playing. You really dont want to be troubleshooting problems on a
change-over. Any problems you have will kill a groove. Also, switching active
channels while live adds stress to an already stressful moment. There are mixers
available with 4 (or more) mono channels (one channel left, one channel right) or
two stereo channels (one for each DJ rig), do yourself a favor and get one of these if
youre not going to have one mixer/controller for the whole night.
Also, do a sound check with 2 (or more controllers) before the set just to make sure
one controller/mixer isnt louder/quieter than the other(s) ahead of time.
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April 27, 2013 at 8:32 am
We used to have a Sony pre-amp in the old days. It had like one mic and 4 stereo
line inputs. It sat in our 19 rack at 1U height. I believe it had 1/4 jacks for inputs
(balanced). And you could just switch each channel on/of and control the volume
with a rotary knob and it had a rotary master volume knob. So with the amps set to
full you could control it all from that one unit.
It was great for running multiple systems to the PA. We would have a DJ, a VJ and
occasionally a karoake guy playing or sometimes a beamer sound and this way they
could all plug in and of we went.
PA mixer ARE predominantly made for microphone use, stereo line inputs are a bit
of an add-on. If you run two XLR balanced lines into your PA mixer from your
controller, you are actually running your controller output through the mixers MIC
Pre-amps! This may have sound consequences as every mic pre-amp has its own
coloring and it means you have to keep your controller main out really low not to
run the mixer input into the red. The PA circuit now has to amplify that signal back
to a level that your controller could provide too.
I know that many DJs will go hey, I have XLR output, the mixer has XLR input, Ill go
and use XLR-XLR cables, easy!. Unfortunately, not the best solution. Every mic
channel on a PA also has 1/4 balanced jack LINE inputs. Use those and youll
bypass the mic preamp and can just send your full signal from the controller without
redlining the PA mixer input.
If I were to do a gig where more than one DJ was playing and/or where I felt the
need to have a bit of 3-band EQ to slightly adjust to the room acoustics, I would get
a simple analogue DJ mixer to handle that. The only drawback being that the DJ
mixer will lack balanced inputs.
Now if you run line level signals and you keep that extra mixer within 2-3 meter
cable run you should be absolutely fine using regular (GOOD QUALITY!) RCA cables.
And if you need to go further there are ways to make unbalanced RCA into balanced
XLR and back the other way at the other end.
To sum up the things I have said on the topic so far:
* If the reason for the extra mixer is EQ-ing the room, better stick in a good graphic
EQ before the PA.
* If the extra mixer is needed to allow multiple DJs access to the PA, get a simple 4-6
channel analogue DJ mixer (depending on your needs of course).
* If you have a PA mixer to go through (because it is already there for example) be
sure you use one of its stereo inputs or use the line input on the mono channels.
* If I were to have a setup like this, Id get a 19 DJ mixer (maybe onle a few U high,
not a full size) in a rack, mount a stereo graphic 31-band equalizer (19) below it
and have a row of stereo RCA connections in a 19 patchpanel on the front. Id make
sure the door was lockable so once everything was connected and set up, NO ONE
could touch the stuf and fiddle with it anymore :-).
Greetinx,
C.
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MarQwann Brown says:

April 30, 2013 at 3:59 am
Thank you so much! This is a guide Ive been needing for a while now, Ive got my
controller and my software (Mixtrack and Traktor) but PA systems have got me
completely stumped. The guys down at my local GuitarCenter were trying to help
me out but i honestly didnt know what I really needed
Thanks!
Kwann
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scott cairo says:

April 30, 2013 at 7:03 pm
Good article.
One thing I can add from my experience. Is that you cant beat an analogue fader
between your sound card controller etc and the PA amps. It makes for a great way
to kill the output if the digital kit throws a wobbler or indeed another dj throws one
and outputs full line level. An anlogue fader is most unlikely to fail if you need to
turn that of NOW.
I use a wharfedale pro, its tiny has a mic input a headphone output, and is very
handy to check your digital kit is actually outputting something useable before
sending it out live.
If anyones interested I always pack a little analogue mixer, ever since I was playing
my Numark Mixtrack away the Lappy crashed and decided it wanted to send a Full
level HORRIBLE noise to the rather expensive PA set up. And the only way to stop it
was pull the plug at my end-which is not ideal. With a mixer in the chain I can just
close the main fader. And have a emergency CD player hooked up to take over. Its
these panicky moments when you see the advantage.
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Frankqp says:
April 30, 2013 at 7:40 pm
This is a great beginner read. I am a part time new mobile DJ working since summer
of 2011. I started that summer with a laptop a high powered computer speakers.
After several gigs I started looking into the PA world. It did take some time reading
to understand. My personal take was that the source is important. So I went with a
Trakor S4. From there I have added powered speakers as audience has dictated.
Now I have 4 behringer active 12s. Next I will be looking into a sub. The main thing
for me was value. The price point on those were great. So the value is there. So I
would say I have done okay with startup funds and knowledge.
The next step for me is going to be finding the best power/sound weight balance.
Im okay with the weight now of my current setup, but I would project as I increase
work it would be best to not have to manage unnecessary weight.
Anyone have suggestions on the best lightweight active PA?

Thanks for info!
Frank
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DJ Vyshak Bhasi says:

May 1, 2013 at 11:48 am
Hey , i have a doubt in this , In american audio vm4.1 traktors user guide its written
as we shouldnt connect the controllers output with any mixer , and they r telling to
connect the balanced xlr outputs straight to the amps xlr inputs ,If i connect it
straight to the mixer will it get any prob?, or should i follow their user guide?
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DJ Chuck Anthanio says:

May 30, 2013 at 6:16 pm
Good Article. I found out that my DJ Controller was more powerful and flexible than
my small PA Mixer. Here is my setup:
Microphone (Shure Wireless XLR) -> DJ Controller (Hercules RMX2 XLR) -> DBX
Driverack (instead of PA Mixer XLR) > Active (Powered) Speakers (JBL 615M and
Sub)
If I dont need my Subs (JBL 618), I dont use the DBX. It is overkill. Simple setups
sometimes give you the best sound.
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Sylvia says:
July 2, 2013 at 1:26 am
Hi there,
I have had a look at this and it is a huge volume of info and all really good and well
presented/describedit still leaves my head swimming a bit with the technicality
but hey, Im a blonde!
What I am doing is not quite so advanced/professionalas yet..but I want to be able

to have music and voice (like karaoke, for example)without having a dedicated PA
system. I have been told that I will damage or destroy ordinary speakers by putting
live vocal through them, but since my audience is only five, and in a very small
space I wonder if there is a way to prevent speaker damage..
I clearly dont have a good working knowledge of audio systems in general, but I am
pretty sure that technology is out there to do what I needsurely!?
Its going to be me singing along to a backing track, driving a taxi, and the
passengers(behind the standard perspex screen) being able to hear me clearly
enoughAs I said, I am not a professional, this is a one of and also I dont have
bags of money to spend on this
Anything that you are able to suggest would be amazing at this point as all the
experts that I have asked have left me thinking that what I am doing is impossible!
Thanks for taking the time if you have read this far!!!
Sylvia
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Phil Morse says:

July 2, 2013 at 8:18 am
Small karaoke speaker system?
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Jamie says:
January 4, 2014 at 9:43 am
Is it necessary or better to have a PA Amplifier if the Speakers are self Ampd like
my JBLs are? Does it make it sound better or worse?
Love these articles, I have been DJing for better part of 15 years now and its
amazing to me that I am Always learning from every article. I am excited to utilize
things I have learned to better my style, brand and company in 2014 and beyond!!
Thank You!!
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Phil Morse says:
January 4, 2014 at 1:08 pm

No, its totally unnecessary.
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KelComman2 says:
Great ArticleThank you for taking the time to put this sort of info out there for
people like myselfnewbie and excited to start DJing.
Anyone out thereI am looking into PA systems to go with a DJ Controller/Mixer
specifically, I like the DDJ-SX from Pioneer with the BEHRINGER EUROLIVE B815NEO
or the B615D (which one would you or anyone recommend better of the two PAs
B815NEO or the B615D?). I have been reading a bit about both, still undecided.
The BEHRINGER EUROLIVEs mentioned above seem to come with mixers and amps
already built-in (Active), would I need additional Mixers and/or Amplifiers to run
them with the DJ controller?
Thank you for your time and assistance.
Best Regards,
KelComman2
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Phil Morse says:

Best place to ask your question is on the Digital DJ Tips Forum
(http://www.digitaldjtips.com/forum), where the whole community can see your
issue and someone can hopefully help you.
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KelComman2 says:
Thank you Mr. MorseI will re-post.

Best Regards,
KelComman2
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Ed Ferrer says:
December 18, 2014 at 9:48 pm
Hi,
Id like please to know which one better sound performance, to set it up in mono or
stereo mode. As a beginner in this business I need know to more on how to enhance
the performance of my mobile sound system. Right now my set up is, PA speakers in
stereo and I have 4 15 and 4 18 sub-woofers 1000W each which is bridge and
powered by one 2,500w crown amp and 6,000W beiranger amp. All of my power
amps are switch mode power supply, I am asking advise if do I need to replace it
with a linear power supply or just use it for a while. Your advise it will be
appreciated, thanks!
Best regards,
Ed
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Ed Ferrer says:
December 19, 2014 at 10:22 am
Hi,
Id like please to know which one better sound performance, to set it up the amps in
mono or stereo mode? As a beginner in this business I need to know more on how to
enhance the performance of my mobile sound system. Right now my unit composed
of 10-15 1,000w PA speakers in stereo, 4 -15 sub-woofer and 4-18 sub-woofers
rated 1000W each with bridge configuration sub-woofers are driven by one 2,500w
crown amp and one 6,000W beiranger amp and for PA I had a 3,000W beirenger and
for tweeters it driven by 1,600W Geam Sound amp. All amps power supply are
switch mode, I am asking your helpful advise if do I need to replace it with a linear
power supply or Ill just continue using it for a while. Your advise regarding this
matter will be highly appreciated, thanks!
Best regards,
Ed
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Portable PA
systems
All
portable PAs
Up to 30 The diagram below shows the parts of a PA
system and how it all connects together.
people
Up to 75
people
Up to
150 people
Over
150 people
Megaph
ones
All PA Packages
PA Systems for
Halls
Up to
100 people
Up to
View 17 Reviews
Visit What
PA Sound
Equipmen
t Provider
on
FreeIndex
300 people
Over
300 people
PA Packages for
Bands
Up to
100 people
Up to
200 people
Up to
400 people
Up to
600 people
Over
600 people
PA Packages for
Schools
Classroo
m use
Up to
100 people
Up to
300 people
Up to
500 people
Over
500 people
PA Packages for
Meetings
Under
75 people
Source
These are the main sound sources
(instruments and vocals) that you want to
amplify through the PA. Typically, these
would be microphones and keyboards but
could also include electric/acoustic
guitars, bass guitars, drums or CD
players.
Mixer
Depending upon your choice, the mixer
(mixing desk) can be
Passive
Un-powered,
requiring active
speakers or a
separate power
amplifier.
Active
Powered, requiring
passive speakers.
Inputs
The mixer is the device for balancing the
volume between the vocals and the
various instruments. Each input goes into
one channel of the mixing desk. Some
mixers have FX (special effects processor)
built into the mixer, so you can apply
special effects (such as reverb) to any of
the channels.
Outputs
If the mixer does not come with FX they
will have an effect (FX) send/return
facility so that you can process individual
instruments with FX such as reverb or
delay via a DSP - Digital Sound
Processors. An additional facility on a
mixer is a monitor/foldback send button.
Up to
100 people
Up to
200 people
Over
200 people
Speaker
Packages
Passive
speaker
packages
Active
speaker
packages
This allows you to send and control the

signals to the monitor speakers.
Monitors
If you are playing at anything other than
the lowest volume, then it will be difficult
to hear what is coming out of the PA
speakers when you are on stage. Monitors
(also known as foldback) help you to hear
better and also help you to sing in tune!
Monitors can be powered or non-powered.
We would always suggest powered
monitors as you can control the level of
the monitors from the stage. If you have
un-powered monitors then you will need a
separate monitor amplifier. An alternative
to stage monitors are in-ear monitors less gear to carry around!
Conference
Systems Lecterns Amp
Announcement
Systems
If you are not using powered (active)
Soundfield
speakers or a powered mixer you will
Systems Mixers
Powered
mixers
need a Power Amplifier, matched to the

output of the two speakers. See the
Matching Ohms page for more information
about this.
Unpowered
mixers
Power Amps
Speakers
Speakers
The are the main front of house (FOH)
speakers. These can either be
Active
speakers
Passive
speakers
Sub
woofers
100 volt
line speakers
Passive
Active
About
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12.PUBLIC ADDRESS SYSTEM October 16, 2008
Filed under: Uncategorized shivajichoudhury @ 7:21 am
Tags: PUBLIC ADDRESS SYSTEM
12.00.00 PUBLIC ADDRESS SYSTEM
12.01.00 General Requirements
12.01.01 A Public Address System(PAS)common for station shall
be supplied by the Bidder to cover all operational areas
of the complete plant.
12.01.02 Public Address System shall consist of zones, sub-zones
and exchanges to interface all four zones among
themselves and also with employers existing telephone
exchange. The major zones and sub-zones shall be as
under.
(i) Zone 1 for unit area(35 per unit/70 for both unit)
(ii) Zone 2 for common plant area (20 point)
12.01.03(a)Each point shall be provided with a handset station and
its associated loudspeaker. The actual locations of
the handset stations/loudspeakers shall be as finalized
during detailed engineering.
(b) The Bidder shall provide all required cables, junction
boxes, earth wire and accessories like standard
brackets, nut-bolts, glands, lugs, conduit sleeves etc.
as required to complete the installation of all
equipments supplied in the PAS.
12.02.00 System Description
12.02.01 PAS shall have two modes, i.e. Paging mode and Party
mode. Each of the two modes shall be open line, common
talking type. Paging mode shall be used for locating a
person and for general instructions. Party mode shall be
used for conversation between individuals without
broadcasting the same over the loudspeaker.
12.02.02 Whenever the `Press to Page push button is pressed on
any of the handset stations, a pleasant chime shall be
broadcast over all the loudspeaker except the one
associated with that handset station to attract
attention. Conversation, in paging mode shall be heard
over all loudspeakers except the loudspeaker associated
with the handset station whose `Press to Page push
button is being held in pressed condition. When `Press
to Page push button is released the associated handset
shall return to party mode. When a handset station is

being used for party mode its associated loudspeaker
shall be free top receive all paging calls. However, the
operator shall have the option of silencing the
associated loudspeaker by pressing `Loudspeaker
mute push button, should be find it disturbing his
conversation on party mode. The loudspeaker shall
return to normal operation automatically when the
`loudspeaker mute push button is released.
Simultaneous operation on both modes, i.e. some handsets
on party channel and some handsets on paging channel,
shall be possible without any cross talk between the two
channels. Further, suitable indication of `Power supply
On and `party channel busy shall be provided on hand
set stations.
12.02.03 Portable type handsets with multipin plugs shall be
used at certain locations where operational personnel are
not present normally. Necessary sockets, wiring, etc.,
shall be provided at these locations. Quantity of
handsets shall be 5 Nos. for unit area & 5 Nos. for common
area. No.of sockets shall be 10 Nos. for unit area, 10
Nos.for CHP , 5 Nos. for common area and 5 for AHP area.
The location, details shall be finalised during
detailed engineering stage & shall be subject to
MPPGCLs approval.
12.02.04 Inter Zone Communication
Each of the zones, i.e.unit common plant and coal
handling plant are shall be connected to a central
exchange. It shall be possible from a station in one
zone to be connected to another station of a different
zone through a master control units, to be located in
unit control desk. Another master control unit, in
parallel with the earlier one shall be located in shift
in change room. Further, suitable interface with
telephone exchange (existing)shall be provided so that
it shall be possible to communicate with any station in
any zone through master control unit from a telephone.
The central exchange shall have the capacity of future
expansion in No.of stations, zones, master control unit
and exchange.
12.02.05 Self Diagnostic Facility shall be provided.
12.03.00 Handset Stations
Each handset station shall be capable of continuous
satisfactory operation at ambient temperature of 55 Deg.C
Handset transmitter/receiver shall be noise canceling
type and shall have filters to protect from dust. All
switches and push buttons on the handset stations shall
be excapsulated contact type. Desk mounting type
(indoor) and wall mounting column type(outdoor) handset
stations shall have a degree of protection as per the
requirements specified in GTR of this specification.
12.04.00 Amplifiers
The PAS shall be of distributed amplifier type, i.e.
each loudspeaker shall have a separate power amplifier
of its own which may be located in the associated
handset station enclosure or in a separate enclosure.
Amplifiers shall be solid state, Class B push-pull type,
fully conforming to IS:1301 and IS:10426 or equivalent

international standard, with modular construction (card
type with edge connectors). Each amplifier shall have 0100% volume control setting, with bass cut filter and
external short circuit protection. Electronically
operated idle power cutoff feature shall be provided
for both pre-amplifiers and power amplifiers.
12.05.00 Loudspeakers
Indoor loudspeakers shall be cone type housed in sturdy
metal cabinet treated with acoustic undercoats to
prevent resonance and shall be suitable for wall/column
mounting. Outdoor loudspeakers shall be horn type. The
mounting brackets shall be with adjustable base suitable
for vertical and horizontal orientation. Acoustic hoods
shall be provided for handset stations located in noisy
areas like BFP, turbine firing floors, mills fans etc.
The design noise level within the hood shall be
limited to a maximum of 60 dB S.I.L.
12.06.00 Power Supply & Grounding
The Bidder shall provide stable, reliable and regulated
power supply and grounding system as required by the
system. Grounding shall be as per Indian Standard.
12.07.00 Technical Parameters
PAS shall conform to the following.
12.07.01 For overall installation Bandwidth (+/-3 dB shall be
400-6000 Hz.
12.07.02 For Amplifiers Bandwidth (+/- 3 dB) shall be 200-10000
Hz; Total Harmonic distribution shall be less than 1% at
rated output at 1 KHz; Signal/Noise ratio shall be 60
dB.
12.07.03 For Microphone Bandwidth (+/- 3 dB) shall be 200-7000
Hz; Type shall be noise canceling type.
12.07.04 For outdoor wall/column mounted horn type loudspeakers
capacity and bandwidth (+/- 3 dB)shall be 15 W (RMS)
and 200-7000 Hz respectively.
12.07.05 For indoor wall/column mounted cone type loudspeakers
capacity and bandwidth (+/- 3 dB)shall be 4 W (RMS)
and 200-7000 Hz respectively.
12.08.00 Signal Loop Length
Signal Loop Length (Cable) shall be as per requirement.
12.09.00 Cables, Junction Boxes & Other Accessories
The bidder shall supply all cables, junction boxes and
other accessories required for PAS. All cables shall be
standard copper conductors, PVC insulated, extruded PVC
inner sheathed, overall PVC sheathed & shielded. All
junction boxes and accessories shall meet all the
specification requirements as specified at relevant
clause of this specification.
12.10.00 Testing, Calibration & Maintenance Equipment
(a) Digital Multimeters - 4
(b) Megger - 1
(c) Stand Tool Box (with - 2
Multipurpose tool box,
Screw drivers, spanners,
Allen key, nose plier,
Files etc.
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1.SPECIFICATION OF INSTRUMENTATION
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ANALYSERSbopcontrol philosophyddcDESIGN CRITERIAElectrical actuatorinstrumentationinstrumentation cableInstrumentation

TestingINSTRUMENTATION VENDERSplcProcess connectionPUBLIC ADDRESS SYSTEMSG/TG INSTRUMENTATIONSpecification of
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PLANT COMMUNICATION SYSTEM (PCS) is a

microprocessor controlled, software programmable, central

The field call stations and loudspeakers are installed at various

high noisy areas.

No requirement of AC mains for operating any field equipment

Public Address System

Plant Communication System

It is a centralized amplifier based system thats been designed to provide voice

There are no limitations to number of zones in the system or number of

Reduced and easy maintenance

Flexibility to build the system for the present need with

Connectivity of p. a. system with the EPABX System

Monitoring the healthiness of all associated equipment in the

Call attention chime tome prior to all announcements

No use of AC Power source in the field

Bass and Treble control to custom-tailor the frequency

LED Bar graph in dB scale to read the relative power

| Plant Communication System | Explosion Proof Telephone

| Profile | Applications | Products | Contact Us | Enquiry | Involvement

P.A. System (Public Address System)

PA/Emergency Voice Alarm Communications System (EVACS)

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4.8.5.4 Services Noise

account in the design of the ventilation system design. Air velocities

c) Mounting locations to provide optimal sound coverage to passenger

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