GB2606586A

GB2606586A - A speaker unit

Info

Publication number: GB2606586A
Application number: GB2108869.5A
Authority: GB
Inventors: Fowler David
Original assignee: Stratton Acoustics Ltd
Current assignee: Stratton Acoustics Ltd
Priority date: 2021-06-21
Filing date: 2021-06-21
Publication date: 2022-11-16
Anticipated expiration: 2041-06-21
Also published as: GB2606586B; GB202108869D0

Abstract

The loudspeaker drive unit 100 is mounted to its housing (700, 800, fig 1) via a vibration isolation assembly 105. The isolation assembly 105 comprises an isolation plate 130 comprising a plurality of radial portions 136 protruding from an annular seat 132 for engaging the diaphragm 120, an elastomeric member 140 defining first and second flanges (142, 144, fig 4b) and a web (146, fig 4b) extending therebetween forming an open box-section in cross-section, and at least one mounting plate 150, 160 rigidly mounted to the housing. The first flange (142) of the elastomeric member 140 is attached to the mounting plate (150, 160). The second flange (144) of the elastomeric member 140 is attached to the isolation plate 130. The diaphragm 120 is located in the annular seat 132.

Description

A Speaker Unit According to the invention there is provided a speaker unit. Preferably, but not exclusively, the speaker unit comprises multiple speakers for transducing audio signals at various frequencies.

Speaker units with multiple speakers are known. Such speaker units may contain a woofer, a mid-range speaker, and a tweeter. However, when such a range of speakers are contained in the same housing, there can be the problem of interference because of vibration through the housing.

This problem is exacerbated in high-power speaker units, such as those in which an amplifier is contained. High-power speaker units can require additional support for woofer speakers, which have larger diameter for producing lower frequencies. Those larger-diameter speakers can oscillate with high amplitudes and lead to unwanted vibrations within the housing that can disrupt the operation of the smaller speakers, such as tweeters. Typically, therefore, for high-power applications, the larger-diameter woofer speakers are separately housed from the tweeter.

The invention deals with this problem by providing an assembly for supporting a tweeter in a manner that is mechanically-isolated from the housing.

A speaker unit is defined in the appended claims.

A preferred speaker unit comprises: a support comprising a housing and a support framework; an optional audio amplifier (the audio amplifier could be provided as a separate component); and at least four speakers (at least four speakers are present in a larger embodiment, but smaller embodiments may have fewer speakers i.e., two or more speakers), wherein the at least four speakers include: a first speaker comprising a transducer and a waveguide having a diameter of less than 50mm; and second, third and fourth speakers, each comprising a frame, a transducer, and a diaphragm supported in the frame having a diameter of more than 60mm and preferably at least 100mm, wherein: the frame of each of the second, third and fourth speakers is rigidly mounted to the housing: the waveguide of the first speaker is mounted to the housing via an isolation assembly; the isolation assembly comprises: an isolation plate comprising a plurality of radial portions protruding from an annular seat for engaging the waveguide; an elastomeric member defining first and second flanges and a web extending therebetween forming an open box-section in cross-section; and at least one mounting plate rigidly mounted to the housing; the first flange of the elastomeric member is attached to the mounting plate; the second flange of the elastomeric member is attached to the isolation plate; the waveguide is located in the annular seat; the isolation device extends to form a loop around isolation plate; and the loop includes a plurality of arc-shaped portions separated by a plurality of radial portions.

The invention is preferably employed in an embodiment that is designed to produce high-power, high-quality audio.

In such an embodiment, the audio amplifier is configured to produce at least 50W, and more preferably at least lkW. A tweeter is provided specifically for high-frequency audio (the first speaker), a speaker is provided for mid-range audio (the second speaker), and two speakers are provided to provide low-frequency audio (the third and fourth speakers).

The power supplied to the low-frequency speakers is such that they benefit from being supported by a sturdy support framework. Moreover, the provision of such supports couples the low-frequency speakers to the housing, such that vibrational interference can distort the sound produced by the other speakers. In embodiments having fewer speakers, similar problems can occur. Even in an embodiment having a tweeter for higher frequencies and a single lower-frequency speaker, the lower frequency speaker can create vibrational interference, benefitting from the vibrational isolation of the tweeter.

The support framework itself can be arranged to comprise an isolation box defining an enclosure in which the second speaker is located for some isolation. However, the tweeter requires more effective isolation, and so a particular isolation assembly is provided.

The isolation assembly comprises an elastomeric loop to prevent a rigid attachment of the tweeter to the housing, thereby isolating it from vibrations passing through the housing. The inventors have realised that a circular loop is limited by its length, and so a more complicated shape of loop is provided. However, a generally circular shape around a waveguide of the tweeter is preferable, and so advantageously, the length can be increased by a plurality of narrow radial extensions. The length and distribution of the extensions can be symmetrical to avoid certain modes of vibration. When four extensions are provided, a sufficient length of extension can ensure that they resist modes of vibration about any diametrical line.

For a better understanding of the invention, and to show how the same may be put into effect, reference will now be made, by way of example only, to the accompanying drawings in which: Figure 1 shows an embodiment of a speaker unit in accordance with the invention; Figures 2a and 2b show a housing for the speaker unit of Figure 1; Figure 3 shows an exploded view of a speaker and isolation assembly for the speaker unit of Figure 1; Figures 4a and 4b shows an elastomeric component of the isolation assembly; Figure 5 shows a further embodiment of a speaker unit in accordance with the invention, having three speakers: Figure 6 shows another alternative embodiment of a speaker unit in accordance with the invention, having two speakers; and Figure 7 shows the isolation plate of Figure 3.

As can be seen in Figure 1, an embodiment of a speaker unit 1 in accordance with the invention comprises: a support 700, 800, an audio amplifier 500, and at least four speakers 100, 200, 300, 400, including a first speaker 100, a second speaker 200, a third speaker 300 and a fourth speaker 400.

The support comprises a housing 700, 800 and a support framework 810, 820, 840 shown in Figures 2a and 2b.

The housing 700, 800 defines a unit in which the audio amplifier 500 and the speakers 100, 200, 300, 400 are mounted. The speakers 100, 200, 300, 400 are mounted in respective speaker openings in the housing 700, 800 for allowing the production of generated sound externally of the speaker unit 1.

The housing 700, 800, comprises a rectangular cover 700 and open box unit 800. The box unit 800 has a top side 802, two opposing left and right sides 804, a bottom side 806, and a back plate 808 and defines a rectangular opening. The top and bottom sides 802, 806 are longer than the left and right sides 804. The box unit 800 is preferably made of plywood. Alternative materials include laminated composites, cast materials (Metals, polymers, composites etc.), glass, and/or moulded polymers. Preferably, when plywood is used, the plywood has a thickness in excess of 6mm.

The box preferably has a width of at least 900mm, a height of at least 800mm, and a depth of at least 500mm.

The cover 700 is sized and shaped to match the opening in the box unit 800.

In addition to the speaker openings, air holes 600 are provided, to allow the free ingress and egress of air into and out of the housing 700, 800. Air holes 600 are particularly needed for the third and fourth speakers 300, 400, and so are located adjacent these speakers. Preferably, at least two air holes 600 are provided adjacent each of the third and fourth speakers 300, 400. More preferably, the air holes 600 have a diameter of at least 35mm. Most preferably, the air holes 600 are within 100mm from the perimeters of the adjacent speaker.

As shown in Figures 2a and 2b, the support framework 810, 820, 840 is comprises: speaker support ribs 840; an isolation box 820; and cover supports 810.

The speaker support ribs 840 are arranged in pairs of perpendicular ribs. A first pair supports the third speaker 300 and a second pair supports the fourth speaker 400.

Preferably, each pair of ribs 840 includes a first rib 840 extending from the top side 802 to the bottom side 806 and a second rib extending from one of the left and right sides 804 to a central support 825.

The central support 825 supports the isolation box 820 such that it abuts the top surface 802. The central support 825 comprises at least one aperture to ensure that the regions behind the third and fourth speakers 300, 400 are in communication.

The isolation box 820 defines an enclosure in which the second speaker 200 is housed. The enclosure can isolate the second speaker from the air pressure fluctuations caused by the third and fourth speakers 300, 400.

Accordingly, the support 700, 800, defines a first enclosure for the first, third and fourth speakers 100, 300, 400, and a second enclosure for the second speaker 200.

No support ribs are provided to support the first speaker 100, which is solely carried by the cover 700.

Each of the second, third and fourth speakers 200, 300, 400 comprises a frame, a transducer, and a diaphragm supported in the frame. Each of the second, third and fourth speakers 200, 300, 400 defines a circular outer perimeter.

The third and fourth speakers 300, 400 have the same size and construction. The second speaker 200 is smaller than the third and fourth speakers 300, 400. Specifically, the second speaker 200 has a smaller diameter than the third and fourth speakers 300, 400.

The diameter of the outer perimeter of the third speaker 300 is the same as the diameter of the outer perimeter of the fourth speaker 400 and this diameter is in the range 200mm to 460mm. The diameter of the outer perimeter of the second speaker 200 is in the range 60mm to 300mm.

The first speaker 100 comprises a waveguide 120 surrounding a transducer 110. The first speaker 100 is preferably a tweeter.

Figure 3 shows an exploded view of a first speaker 100 and isolation assembly 105 for the speaker unit 1.

The isolation assembly 105 comprises an isolation plate 130, an elastomeric member 140, a pair of mounting plates 150, 160, and a set of fixings 170.

The fixings 170 are used to directly engage the pair of mounting plates 150, 160 to the cover 700 to define the only means of mechanical support for the first speaker 100 within the housing 700, 800.

The isolation plate 130 comprises an annular seat 132 for receiving and directly engaging the circular outer rim 122 of the waveguide 120. A plurality of radial portions 136 protrude from the annular seat 132.

The outer perimeter of the isolation plate 130 comprises a plurality of arc-shaped portions 134 separated by a plurality of radial portions 136.

The elastomeric member 140 is in the form of a loop, shaped to have a generally constant cross-section that follows the path of the outer perimeter of the isolation plate 130.

The elastomeric member 140 is shown in more detail in Figures 4a and 4b. As can be seen in Figure 4a, the elastomeric member 140 comprises a plurality of arc-shaped portions 140A separated by a plurality of radial portions 140R. The arc-shaped portions 140A are shaped to match the arc-shaped portions 134 of the isolation plate 130. The radial portions 140A are shaped to match the radial portions 136 of the isolation plate 130.

As shown in Figure 4b, in cross-section, the elastomeric member 140 has a square openbox-section comprising first and second parallel flanges 142, 144 and a web 146 extending therebetween. The first flange 142 is mounted to the mounting plates 150, 160. The second flange 144 is mounted to the isolation plate 130. In this way, the waveguide 120 of the first speaker 100 is mounted to the housing 700, 800 only via the elastomeric member 140.

The circular outer rim 122 of the waveguide 120 has a diameter of from 150mm to 250mm.

The web 146 has a width (perpendicular to the circumferential direction) of from 8mm to 15mm.

The flanges 142 and 144 have a width (perpendicular to the circumferential direction) of from 8mm to 15mm.

The web 146 and flanges 142, 144 have thickness (perpendicular to the circumferential direction and perpendicular to their width) of from 2mm to 4mm.

The elastomeric member 140 preferably comprises one or more of silicone or WE.

The elastomeric member 140 preferably has a Shore A hardness of 50 to 90.

The isolation plate 130 preferably comprises polymethylmethacrylate (PMMA).

The mounting plates 150, 160 are planar, optionally with a generally square outer edge, and comprise an aperture 162 shaped to correspond with the elastomeric member 140. That is, the aperture 162 comprises a plurality of arc-shaped portions 164 separated by a plurality of radial portions 166. The mounting plates 150, 160 are engaged by the fixings 170, such that a pair of fixings extends through the mounting plates 150, 160 either side of each of the radial portions 166 of the aperture 162.

As will be appreciated, the isolation plate 130, the elastomeric member 140 and the mounting plates 15, 160, have corresponding arc-shaped and radial portions. Preferably, there are four radial portions, equally spaced apart by four arc-shaped portions of identical extent.

The radial portions 136 of the isolation plate 130 extend from the radially-outermost edge 132E of the annular seat 132 to the tip 1361 of the radial portion 136.

Preferably, the length 136L of the radial portions 136 of the isolation plate (from the outer edge of the annular seat 132E to the tip 1361 of the radial portion 136) is in the range 17mm to 75mm.

The radial portions 136 of the isolation plate may have curved edges (a curved tip and root portions that gently curved to join the arc-shaped portions tangentially), but for at least 50% of their length have a width that is in the range 8mm to 15mm.

The audio amplifier 500 may form part of the speaker unit 1, but may also be provided separately such that the speaker unit does not comprise an amplifier 500.

The audio amplifier 500 is configured and arranged to receive an input signal and produce an output signal for each speaker 100, 200, 300, 400. The audio amplifier 500 is configured to produce at least 50W, preferably at least 1kW.

The audio amplifier 500 is configured to drive each of the first, second, third, and fourth speakers 100, 200, 300, 400.

The audio amplifier 500 may be arranged to drive the third and fourth speakers 300, 400 with the same signal.

The audio amplifier 500 is configured such that the cross-over point between the third or fourth speakers 300, 400 and the second speaker 200 is from 150Hz to 250Hz, preferably 200Hz.

The audio amplifier 500 is configured such that the cross-over point between the second speaker 200 and the first speaker 100 is at 1.5kHz to 2.5kHz, preferably 2kHz.

Whereas the embodiment described above comprises four speakers, the isolation assembly may be used in smaller speaker units. Figure 5 shows a further embodiment of a speaker unit in accordance with the invention, having three speakers, and Figure 6 shows another alternative embodiment of a speaker unit in accordance with the invention, having two speakers.

Claims

Claims: 1. A speaker unit comprising: a support comprising a housing and a support framework; and at least two speakers, wherein the at least two speakers include: a first speaker comprising a transducer and a waveguide having a diameter of less than 50mm; and a second speaker comprising a frame, a transducer, and a diaphragm supported in the frame having a diameter of more than 60mm, wherein: the frame of the second speaker is rigidly mounted to the housing; the waveguide of the first speaker is mounted to the housing via an isolation assembly; the isolation assembly comprises: an isolation plate comprising a plurality of radial portions protruding from an annular seat for engaging the waveguide; an elastomeric member defining first and second flanges and a web extending therebetween forming an open box-section in cross-section; and at least one mounting plate rigidly mounted to the housing; the first flange of the elastomeric member is attached to the mounting plate; the second flange of the elastomeric member is attached to the isolation plate; the waveguide is located in the annular seat; the isolation device extends to form a loop around isolation plate; and the loop includes a plurality of arc-shaped portions separated by a plurality of radial portions.
2. The speaker unit of claim 1, wherein the length of the radial portions of the isolation plate is in the range 17mm to 75mm.
3. The speaker unit of claim 1 or claim 2, wherein the radial portions of the isolation plate each have a curved tip and root portions that gently curved to join the annular seat.
4. The speaker unit of any preceding claim, wherein at least 50% of the length of each the radial portion of the isolation plate has a width that is in the range 8mm to 50mm.
5. The speaker unit of any preceding claim, wherein the web of the elastomeric member has a width of from 8mm to 15mm.
6. The speaker unit of any preceding claim, wherein the flanges of the elastomeric member have a width of from 8mm to 15mm.
7. The speaker unit of any preceding claim, wherein the web and flanges of the elastomeric member have a thickness of from 2mm to 4mm.
8.. The speaker unit of any preceding claim, wherein the waveguide is mounted to the housing only via the elastomeric member.
9. The speaker unit of any preceding claim, wherein the at least one mounting plate is fixed to the cover and define the only means of mechanical support for the first speaker.
10. The speaker unit of any preceding claim, wherein the at least one mounting plate is engaged by fixings, such that a pair of fixings extends through the at least one mounting plate either side of each of the radial portions of the isolation plate.
11. The speaker unit of any preceding claim, further comprising third and fourth speakers comprising a frame, a transducer, and a diaphragm supported in the frame having a diameter of more than 200mm,
12. The speaker unit of claim 11, wherein the support framework comprises an isolation box defining an enclosure in which the second speaker is located.
13. The speaker unit of any preceding claim, further comprising air holes to allow the free ingress and egress of air into and out of the housing, wherein the air holes are located adjacent the third and fourth speakers.
14. The speaker unit of claim 13, wherein the air holes have a diameter of at least 35mm.
15. The speaker unit of any one of claims 11 to 14, wherein the support framework comprises speaker support ribs are arranged in pairs of perpendicular ribs, wherein a first of the pairs supports the third speaker and a second of the pairs supports the fourth speaker.
16. The speaker unit of claim 15, wherein each pair of ribs includes a first rib extending from a top side of the housing to a bottom side of the housing and a second rib extending perpendicular to the first rib.
17. The speaker unit of any one of claims 11 to 16, wherein: the third and fourth speakers have the same diameter, which is greater than the diameter of the second speaker; and the diameter of the second speaker is greater than the diameter of the waveguide.
18. The speaker unit of any preceding claim, further comprising an audio amplifier is configured to produce at least 1kW.