TREA

Electroacoustical transducing

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Information

  • Patent Application
  • 20080031472
  • Publication Number
    20080031472
  • Date Filed
    August 04, 2006
    18 years ago
  • Date Published
    February 07, 2008
    16 years ago
Information
Abstract
Electroacoustical apparatus includes at least first and second acoustically coupled electroacoustical drivers. An electrical network couples their inputs so that an electrical drive signal applied to one reduces the effect of acoustic coupling from that one to the other.
Description

BRIEF DESCRIPTION OF DRAWING


FIG. 1 is a combined pictorial-block diagram of an exemplary embodiment of the invention;



FIG. 2 is a combined pictorial-block diagram of a modification of the embodiment shown in FIG. 1;



FIG. 3 is a graphical representation of the excursion transfer function X_21 with and without an H_22 filter;



FIG. 4 is a graphical representation of net excursion attenuation;



FIG. 5 is a perspective view of the commercially available Bose Companion 5 satellite speakers; and



FIG. 6 is a block diagram of an embodiment with filters 16 and 16′ and summing circuits 17 and 17′.





DETAILED DESCRIPTION

With reference now to the drawing and more particularly FIG. 1, there is shown a combined pictorial-block diagram of an embodiment of the invention. Electroacoustical transducer 111 and electroacoustical transducer 212 reside in enclosure 13 and have first and second inputs 14 and 15, respectively, for receiving first and second electrical drive signals V1 and V2, respectively. The first filter 16, having a transfer characteristic H22, couples input 14 to the −input of summing circuit 17 whose +input receives a second input signal Vii and provides as an output the electrical drive signal V2.


Having described the physical arrangement of the embodiment, the mode of operation will be described. It is convenient to describe the mechanical excursion of the cone of transducer 2 in response to the electrical drive signal V1 caused by acoustic coupling from the movement of the cone of transducer 1 as X21 per unit of V1 and its mechanical excursion in response to the electrical drive signal V2 as X22 per unit of V2. The resultant excursion X2 of the cone of transducer 2 in response to the input signals Vi and Vii in the absence of circuits 16 and 17 is:













X
2

=



V
1

*

X
21


+


V
2

*

X
22









=



V
i

*

X
21


+


V
ii

*

X
22













(
1
)






(

1

a

)










It is convenient to define a filter based on the first two transfer functions as:






H
22
=X
21
/X
22   (2)


The output signal from filter 16 with transfer characteristic H22 corresponds to the input signal Vi multiplied by transfer characteristic H22. Applying this output signal with phase reversed through summing circuit 17 creates a component of the electrical drive signal V2 applied to transducer 2 that cancels the sympathetic vibration of transducer 2 caused by the acoustic coupling from transducer 1 in enclosure 13.


The modified excursion of transducer 2, X2′, is expressed:






X
2
′=X
2
−V
i
*H
22
*X
22   (3)


Substituting equations (1a) and (2) for terms X2 and H22 respectively gives:






X
2
′=V
i
*X
21
+V
ii
*X
22
−V
i*(X21/X22)*X22   (4)


Note that the first and third terms of equation (4) cancel, leaving:






X
2
′=V
ii
*X
22   (5)


So the mechanical response of the cone of transducer 2 to the input Vi is identically 0.


Referring to FIG. 2, there is shown another embodiment of the invention having a second filter 16′ having a transfer characteristic H′22 providing an output delivered to the −input of summing circuit 17′ that receives the input signal Vi on the +input to provide a signal Vi′ including a component that cancels the sympathetic vibration of transducer 1 in response to the signal V2.


Referring to FIG. 3, there is shown a graphical representation of the excursion transfer function X21 as a function of frequency with and without filter 16, respectively.


Referring to FIG. 4, there is shown a graphical representation of the net excursion attenuation with filter minus excursion without filter.


Referring to FIG. 5, there is shown a perspective view of a commercial embodiment of the invention in the Bose Companion 5 satellite cabinet enclosure showing transducers 1 and 2 in a sealed enclosure. In the specific embodiment of this invention, transducers 1 and 2 are 50 mm drivers in a sealed cabinet enclosure angled at 51 degrees with the enclosure volume 11.1 inch3.


Referring to FIG. 6, there is shown a block diagram of an embodiment showing filter 16 and 16′ and summing circuits 17 and 17′ combined.


In a specific form of the invention a Texas Instruments DA708E001RFP250 DSP chip loaded with the ASCII representation of hex code in the appended text file implements the sympathetic vibration cancellation.


While the invention has been illustrated with two electroacoustical drivers, the principles of the invention may be extended to a larger plurality of drivers.


The invention has a number of advantages. In a system where a plurality of drivers in a common enclosure each receive different signals, the distortion in the acoustic output generated by any one of the drivers due to the acoustic coupling between it and the other drivers is significantly reduced. It helps maintain the excursion of the driver cones within the linear region of the transducers to facilitate reproducing sound at substantial levels without audible distortion. It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments disclosed herein without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited only by the spirit and scope of the appended claims.

Claims
  • 1. Electroacoustical apparatus comprising, a cabinet enclosure,at least first and second electroacoustical drivers acoustically coupled in said cabinet enclosure each having first and second inputs respectively for receiving first and second electrical drive signals respectively,and an electrical network intercoupling said first and second inputs constructed and arranged to provide a first opposition signal on said second input in phase opposition to a first electrical drive signal on said first input to reduce the effect of acoustic coupling from said first electroacoustical driver to said second electroacoustical driver when said first electrical drive signal is applied to said first input.
  • 2. Electroacoustical apparatus in accordance with claim 1 wherein said first and second electroacoustical drivers are of the same design.
  • 3. Electroacoustical apparatus in accordance with claim 1 wherein said first and second electroacoustical drivers are of differing design
  • 4. Electroacoustical apparatus in accordance with claim 1 wherein said electrical network is constructed and arranged to provide a second opposition signal on said first input in phase opposition to a second electrical drive signal on said second input to reduce the effect of acoustic coupling from said second electroacoustical driver to said first electroacoustical driver when said second electrical driver signal is applied to said second input.
  • 5. Electroacoustical apparatus in accordance with claim 4 wherein said first and second electroacoustical drivers are of the same design
  • 6. Electroacoustical apparatus in accordance with claim 4 wherein said first and second electroacoustical drivers are of differing design.
  • 7. Electroacoustical apparatus in accordance with claim 1 wherein said enclosure is sealed.