GB2045028A

GB2045028A - Improvements to loudspeaking devices

Info

Publication number: GB2045028A
Application number: GB7910246A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-03-23
Filing date: 1979-03-23
Publication date: 1980-10-22

Abstract

A loudspeaker arrangement comprises a number of loudspeaker diaphragms stacked coaxially one behind the other and tightly coupled together so that they move coherently. Gas may be used as coupling medium. The distance apart of the diaphragms is small compared with the wavelength of the sound in the coupling medium. In one embodiment (Figure 1c) two planar diaphragms (3, 9) are each located between magnet elements (1, 5, 7, 11) and the coils are connected in series aiding relationship. In a second embodiment (Figures 1a, 1b, not shown) two electrostatic loudspeakers are stacked one behind the other. <IMAGE>

Description

SPECIFICATION Improvements to loudspeaking devices The power radiated as sound from a system consisting of a body vibrating due to an applied force is proportional to the square of the applied force, and the amplitude of vibration is proportional to the quotient of the applied force and moving mass. If the body can be considered to have negligible mass at the frequency of vibration and two such bodies are mounted axially on a common axis of coherent vibration in close proximity such that the acoustic coupling between the bodies can be considered tight; that is, the distance between the bodies is small compared to the wavelength of sound in the medium coupling the two bodies together. The force applied to either body will be doubled and the power radiated as sound, if it were not for the mass of the coupling medium would be quadrupled.Any number of such bodies may be coupled together to increase the radiated power as desired.

Unlike present known art where increased power output is obtained by mounting loudspeaking devices with their radiating surfaces coplaner and such increase in radiated sound power being proportional to the radiating area, the present invention will permit the power output to be increased without increasing the frontal area of the radiating surface, and if the acoustic coupling is made very tight, a power increase near to the ideal mentioned in paragraph one above can be obtained. This principle may be applied to any form of loudspeaking device.

A practical embodiment of the invention where the coupling medium is a gas would be in the case of an electrostatic loudspeaking device. A number of such devices may be stacked axially one behind the other in such a way that electrical breakdown between devices is avoided and mechanical movement is not restricted. One possible arrangement is shown in Figure lcwherethe number of devices has been restricted to two for the sake of clarity. An exploded view of the assembly is shown in Figure ib, and a possible electrical arrangement in Figure la. Items 1,5,7, & 11 are fixed elements, items 3 & 9 are moving elements, and items 2,4,6,8 & 10 are spacers.

A second practical embodiment would be in the case of an orthodynamic loudspeaking device, where the fixed elements of Figure 1 b would be an arrangement of magnetic elements, and the moving electrodes would consist of coils or conductors on a suitable carrier.

In this case the coils or conductors would be connected so that the resulting forces are series aiding.

With either of the above embodiments it would be possible to delete redundant items in Figure 1 b & c by combining the functions of fixed elements 5 & 7, and the functions of all fixed elements and spacers.

CLAIM

If two or more bodies vibrating axially and coherently are tightly coupled together mechanically or electrically the power radiated as sound wi increase without the need to increase the area of the radiating surface and if the moving mass of the coupling medium and the mass of the bodies themselves are made negligible at the frequency of operation the increase of radiated sound power per unit area can be made to exceed the linear law P2 = kP1 of current coplanar art to that of a theoretical maximum of P2 = mmP1 where k is the factor by which the frontal radiating area has been increased and where m is the number of axially stacked devices and that any loudspeaking devices whatsoever with their sound power generators axially arranged and tightly coupled to a single or multiplicity of axially arranged radiating surfaces that are themselves tightly coupled and moving coherently over the same frequency range will benefit from this invention.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

SPECIFICATION Improvements to loudspeaking devices The power radiated as sound from a system consisting of a body vibrating due to an applied force is proportional to the square of the applied force, and the amplitude of vibration is proportional to the quotient of the applied force and moving mass. If the body can be considered to have negligible mass at the frequency of vibration and two such bodies are mounted axially on a common axis of coherent vibration in close proximity such that the acoustic coupling between the bodies can be considered tight; that is, the distance between the bodies is small compared to the wavelength of sound in the medium coupling the two bodies together. The force applied to either body will be doubled and the power radiated as sound, if it were not for the mass of the coupling medium would be quadrupled.Any number of such bodies may be coupled together to increase the radiated power as desired.

Unlike present known art where increased power output is obtained by mounting loudspeaking devices with their radiating surfaces coplaner and such increase in radiated sound power being proportional to the radiating area, the present invention will permit the power output to be increased without increasing the frontal area of the radiating surface, and if the acoustic coupling is made very tight, a power increase near to the ideal mentioned in paragraph one above can be obtained. This principle may be applied to any form of loudspeaking device.

A practical embodiment of the invention where the coupling medium is a gas would be in the case of an electrostatic loudspeaking device. A number of such devices may be stacked axially one behind the other in such a way that electrical breakdown between devices is avoided and mechanical movement is not restricted. One possible arrangement is shown in Figure lcwherethe number of devices has been restricted to two for the sake of clarity. An exploded view of the assembly is shown in Figure ib, and a possible electrical arrangement in Figure la. Items 1,5,7, & 11 are fixed elements, items 3 & 9 are moving elements, and items 2,4,6,8 & 10 are spacers.

A second practical embodiment would be in the case of an orthodynamic loudspeaking device, where the fixed elements of Figure 1 b would be an arrangement of magnetic elements, and the moving electrodes would consist of coils or conductors on a suitable carrier.

In this case the coils or conductors would be connected so that the resulting forces are series aiding.

With either of the above embodiments it would be possible to delete redundant items in Figure 1 b & c by combining the functions of fixed elements 5 & 7, and the functions of all fixed elements and spacers.

CLAIM

If two or more bodies vibrating axially and coherently are tightly coupled together mechanically or electrically the power radiated as sound wi increase without the need to increase the area of the radiating surface and if the moving mass of the coupling medium and the mass of the bodies themselves are made negligible at the frequency of operation the increase of radiated sound power per unit area can be made to exceed the linear law P2 = kP1 of current coplanar art to that of a theoretical maximum of P2 = mmP1 where k is the factor by which the frontal radiating area has been increased and where m is the number of axially stacked devices and that any loudspeaking devices whatsoever with their sound power generators axially arranged and tightly coupled to a single or multiplicity of axially arranged radiating surfaces that are themselves tightly coupled and moving coherently over the same frequency range will benefit from this invention.