GB2045578A

GB2045578A - Speaker device

Info

Publication number: GB2045578A
Application number: GB7909529A
Authority: GB
Original assignee: KERNO R P LASIS D A BALODIS I; Rudzitis A A
Current assignee: KERNO R P LASIS D A BALODIS I; Rudzitis A A
Priority date: 1978-08-11
Filing date: 1979-03-19
Publication date: 1980-10-29
Also published as: DE2911849C3; GB2045578B; FR2433268A1; FR2433268B1; DE2911849A1; DE2911849B2; FI790850A; GR66647B

Abstract

A loud-speaker unit composes a box 1 housing a loud-speaker 2 and an air chamber 3 bounded by walls 4. The walls 4 of the air chamber 3 are made of elastic-porous material, e.g. foamed rubber-like plastics material, to minimise unwanted resonances of the unit. The walls 4 may be surrounded by a rigid housing 5. The loud-speaker unit can be used in household audio systems such as radio-sets and record players, as well as in special purpose acoustic systems, such as cinema and studio apparatus. <IMAGE>

Description

SPECIFICATION Speaker device The present invention relates to the field of electro-acoustics and more particularly to speaker devices of phase inverting type.

It is of the most advantage to use the present invention in the house-hold audio systems such as radio-sets and electric phonographs, as well as in specially purposed acoustic systems, such as cinema and monitoring-studio apparatus.

According to the invention there is proposed a speaker device comprising a box with a speaker and an air chamber mounted therein, wherein, according to the invention, the air chamber walls are made of elasticporous material.

The air chamber walls made from elasticporous material make the effective resistance of the walls to the air stream higher than the acoustic reactance of the air mass in the chamber on the frequencies close to the basic resonance frequency of the speaker device.

Owing to that, the air chamber wall affect little the resonant properties of the speaker device, but significantly absorb standing waves, thus eliminating unwanted by-sounds.

It is expedient the specific volume elasticity of the elastic-porous material be from 4 10-6 to 5010-6 m2/N, and the specific volume resistance to the air stream passing through the chamber wall be from 0.1 10-3 to 5 10-3 mech.ohm.m.

The specific volume elasticity of the elasticporous material being less than 4.106 m2/N and the specific volume resistance to the air stream passing through the chamber walls being higher than 5 10-3 mech.ohm.m., there appear standing waves in the air chamber, this leading to an unwanted amplification of by-sounds.

If the specific volume elasticity of the elastic-porous material is higher than 50 1 0-6 m2/N and the specific volume resistance to the air stream through the chamber wall is less tha 0.1 10-3 mech.ohm.m, then the air stream would pass through the chamber walls and detune the speaker device. Moreover, such an eiastic-porous material cannot be mounted within the box without any additional rigid frame.

It is advisable to fix a rigid housing on the outer sides of the air chamber walls.

The rigid housing being fixed on the outer sides of the air chamber walls enables to use the elastic-porous material with higher specific volume elasticity and less specific volume resistance to the air stream passing through the air chamber walls, which, in turn, ensure more dependable elimination of standing waves in the air chamber with resultant weakening of the unwanted by-sounds.

It is desirable to use the elastic-porous material having the specific volume elasticity ranging from 4.10-6 to 1 50.10-6 m2/N and the specific volume resistance to the air stream passing through the chamber walls, from 0.05 10-3 to 5.10-3 mech.ohm.m.

If the specific volume elasticity of the elas tic-porous material is higher than 1 50'1 0-6 m2/N and the specific volume resistance to the air stream passing through the chamber walls is less than 0.0510-3 mech.ohm.m., then the structural rupture of the elastic-po rous material would occur.

The present invention will become herei nafter more apparent from the following de tailed description of the embodiments taken in conjunction with the accompanying drawings, in which: Figure 1 represents a speaker device, ac cording to the invention; Figure 2 represents an other embodiment of the speaker device, according to the inven tion; Figure 3 represents a graph showing by sound level in the air chamber versus fre quency response, according to the invention; Figure 4 represents a graph showing sound pressure-frequency response, according to the invention.

The speaker device comprises a box 1 (Fig.

1) wherein a speaker 2 and an air chamber 3 formed by walls 4 are mounted. The walls 4 of the air chamber 3 are made of elastic porous material with the specific volume elas ticity ranging from 4.10-6 to 50.10-6 m2/N and the specific volume resistance to the air stream from 0.1 10-3 to 5.10-3 mech.ohm.m.

For instance, the walls 4 may be made of latex or porolone (foamed rubber-like plastic) etc.

Fig. 2 shows a speaker device with a rigid housing 5 fixed to the outer sides of the air chamber walls 4.

In this case the walls 4 can be made of elastic-porous material with the specific vol ume elasticity ranging from 4.10-6 to 150 10-6 m2/N and with the specific resis tance to the air stream from 0.0510-3 to 5 10-3 mech.ohm.m.

For example, to line the walls 4 one may utilize felt, sheet wadding, etc.

The speaker system operates as follows.

When high power signals are radiated by the speaker 2 on frequencies close to the basic resonance frequency of the speaker device, air mass oscillations of large amplitude are gener ated in the air chamber 3 wherein standing waves are excited and are successively ab sorbed by the walls 4 of the chamber 3, thus banishing appearance of unwanted by-sounds.

On the graph shown in Fig. 3 a curve "A" represents the by-sounds level in the chamber 3 versus frequency response in the band of 1/3 octave, in case the walls 4 of the cham ber 3 are made of hard material; a curve "B" represents the by-sound level in the chamber 3 versus frequency response in the band of 1/3 octave, in case the walls 4 of the chamber 3 are made of elastic-porous material /latex, for example/ having the specific volume elasticity from 4.10-6 to 50.10-6 m2/N and the specific volume resistance to the air stream from 0.1 10-3 to 5-10-3 mech.ohm.m; a curve "C" represents the by-sound level in the chamber 3 versus frequency response in the band of 1/3 octave, in case the rigid housing 5 is fixed on the outer sides of the walls 4 of the chamber 3 and the walls 4 are made of elastic-porous material/sheet wadding, for example/ with the specific volume elasticity from 4.10-6 to 150.10-6 m2/N and the specific volume resistance from 0.05 10-3 to 5 10-3 mech.ohm.m; the frequency "f", given in Hz, is plotted on X-axis while the bysound level, given in dB, is plotted on Y-axis.

While examining the curves "B" and "A" /Fig. 3/, it can be seen that the speaker device with the walls 4 made of latex, when reproducing low frequencies approaching the standing waves, in the range from 1000 to 300 Hz provides for by-sounds attenuation approximately by 8-9 dN in comparison with the speaker device whose walls are made of hard material.

While examining the curves "C" and "B", it is seen that the speaker device with the rigid housing 5 fixed on the outer sides of the walls 4 the walls 4 themselves being made of sheet wadding, when reproducing low frequencies approaching the standing waves, in the range from 1000 to 12,0000 Hz provides for by-sounds attenuation, approximately by 2-8 dB as compared with the speaker device having the walls 4 made of latex.

On the graph shown in Fig. 4 a curve "D" represents the pressure-frequency response of the speaker device whose walls 4 of the air chamber 3 are made of hard material; a curve "E" represents the pressure-frequency response of the speaker device whose walls 4 of the air chamber 3 are made of elasticporous material /latex, for example/ having the specific volume elsaticity ranging from 4.10-6 to 50.10-6 m2/N and the specific volume resistance to the air stream from 0.1 10-3 to 510-3 mech.ohm.m.; a curve "F" represents the pressure-frequency response of the speaker device having the rigid housing 5 fixed on the outer sides of the walls 4 of the air chamber 3 the walls 4 themselves being made of elastic-porous material /sheet wadding, for example/ having the specific volume elasticity from 4 10-6 to 150 10-6 m2/N and the specific volume resistance to the air stream from 0.05 10-3 to 5.10-3 mech.ohm.m.; the frequency "f", given in Hz, is plotted on X-axis, while the sound pressure, given in dB, is plotted on Y-axis.

While examining the curves "E" and "D" /Fig. 4/, it can be seen that the speaker device whose walls 4 are made of latex, has a non-uniform pressure-frequency response in the range from 1000 to 3000 Hz, which is approximately by 5 dB less than that of the speaker device whose walls 4 are made of hard material.

While examining the curves "F" and "D", it can be seen that the speaker device with the rigid housing 5 fixed on the outer sides of the walls 4, the walls 4 themselves being made of a sheet wadding, has a non-uniform pressure-frequency response in the range from 1000 to 12,000 Hz, which is approximately by 0.5 to 1 dB less than that of the speaker device having walls 4 made of latex.

Thus, fabrication of the walls 4 of elasticporous material gives a possibility, on great oscillation rates of air in the air chamber 3, to eliminate the by-sounds excited by standing waves without decrease in sound pressure on the frequencies close to the natural resonance frequencies of the speaker device, as well as to level the frequency response in the range of standing waves absorption in the air chamber 3 of the speaker device.

Although, the present invention has been hereinbefore described with respect to the preferred embodiment, it should be also apparent for those skilled in the art that various modifications and substitutions of the proposed speaker device might be made without departing from the spirit and scope of the invention.

Claims

1. A speaker device comprising a box wherein a speaker and an air chamber are mounted, the walls of the air chamber being made of an elastic-porous material.

2. A speaker device as set forth in Claim 1 wherein the elastic-porous material has a specific volume elasticity from 4'1 0-6 to 50.10-6 m2/N and a specific volume resistance to the air stream passing through the walls of the air chamber from 0.1 10-3 to 5 10-3 mech.ohm.m.

3. A speaker device as set forth in claim 1 wherein a rigid housing is fixed on the outer sides of the walls of the air chamber.

4. A speaker device as set forth in claim 3 wherein the elastic-porous material has a specific volume elasticity from 4 10-6 to 150 10-6 m2/N and a specific volume resistance to the air stream passing through the walls of the air, chamber from 0.05 10-3 to 5 10-3 mech.ohm.m.

5. A loudspeaker unit substantially as hereinbefore described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.

5. A speaker device essentially as hereinbefore described and shown in Figs. 1 and 2 of the accompanying drawings.

CLAIMS (11 Feb 1980)

1. A loudspeaker unit of phase inverting type comprising a box wherein a speaker and an air chamber are mounted, the air chamber leading from the interior to the exterior of the box and internal walls of the air chamber being made of an elastic-porous material.

2. A loudspeaker unit as set forth in claim 1 wherein the elastic-porous material has a volume compressability from 4. 10-6 to 50.10-6 Pa-' and a volume permeability to the air stream passing through the walls of the air chamber from 0.12.10-5 to

6.10-5m2/sec Pa.

3. A loudspeaker unit as set forth in claim 1 wherein a rigid housing surrounds the outer surface of the walls of the air chamber.

4. A loudspeaker unit as set forth in claim 3 wherein the elastic-porous material has a volume compressability from 4,10-6 to 1 50.10-6 Pa-l and a volume permeability to the air stream passing through the walls of the air chamber from 0.12.10-3 to 12.10-5 m2/sec Pa.