GB2388488A

GB2388488A - Loudspeaker with elliptical annular diaphragm

Info

Publication number: GB2388488A
Application number: GB0210314A
Authority: GB
Inventors: Trevor William Stride
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-07
Filing date: 2002-05-07
Publication date: 2003-11-12
Anticipated expiration: 2022-05-07
Also published as: GB0210314D0; GB2388488B

Abstract

A loudspeaker has an elliptical annular diaphragm 1 having elastic suspensions 4 on the inside and outside of the diaphragm. The contour of the diaphragm 1 is formed by two straight lines, or curves (eg hyperbolic) which meet at a point on an ellipse which is substantially the centre of mass of the diaphragm. The diaphragm 1 is driven along this line by an elliptical coil 2 which is suspended in a magnetic field gap between pole pieces 3. The loudspeaker may have a phase plug (6) may be mounted at the throat of a horn section (5).

Description

A Loudspeaker with an elliptical diaphragm.

This invention relates to a loudspeaker with an elliptico-annular diaphragm. For the reproduction of high audio frequencies, moving coil transducers with an annular or circular ring diaphragm are sometimes used. They have the advantage that for a given diaphragm area the distance from the furthest part of the diaphragm from the driving coil is much smaller compared to a conventional cone diaphragm which is driven essentially at the centre or a dome shaped diaphragm which is driven essentially only at the edge. This makes the diaphragm move as a rigid piston up to a much higher frequency, especially if it is driven at it's centre of mass. However the disadvantage of this arrangement is that the ovcral1 diameter of the diaphragm is larger than a cone or dome of similar area and hence the transducer is more directional at high frequencies where the diaphragm dimensions become comparable with the wavelength of the sound being radiated. This prevents sound of good quality from being delivered over a wide horizontal area, as if often required when there are a number of listeners.

According to the present invention there is provided a loudspeaker comprising a rigid elliptico-annular diaphragm with the minor axis being substantially smaller than the major axis, creased along the elliptical line that is substantially its cent re of mass to form two substantially elliptico-conical surfaces to increase the rigidity of the said diaphragm to axial forces, the said diaphragm being driven at substantially its centre of mass by an elliptical coil suspended in a magnetic field gap by means of two elliptical elastic suspensions, one on

the inside of the diaphragm and one on the outside, the driving electrical signal being applied to the conductors in the coil, the diaphragm being mounted so as to facilitate the radiation of sound from it.

An example of an embodjmcnt of the invention is shown in Figure I which shows a perspective section of the assembly through the minor axis of the diaphragm, wherein the diaphragm I is driven by the coil 2 suspended in the magnetic gap between pole pieces 3 by inner and outer elastic suspensions 4. Figure shows a cross section through the minor axis of an embodiment wherein the diaphragm radiates into the throat of a horn 5, with a phase plug 6 occupying the centrc of the diaphragm to improve the acoustic loading and avoid destructive interference at high frequencies. Figure 3 shows the section through the mayor axis of the same assembly. Figure 4 shows a detail of the diaphragm cross section, figure 5 shows the same detail in an embodiment of the design which has a diaphragm with hyperbolic contour and 6 shows an embodiment which has a diaphragm with integral suspensions 7, formed from a flexible material.

Claims

1) A loudspeaker comprising an elliptico-annular diaphragm with the minor axis being substantially smaller than the major axis, creased along the circular dine that is substantially its centre of mass to form two truncated substantially elliptico-conical or elliptico-spherical surfaces to increase the rigidity of the said diaphragm to axial forces, the said diaphragm being driven at substantially its centre of mass by an elliptical coil and suspended in a magnetic field gap by means of two elliptical

elastic suspensions, one on the inside of the diaphragm and one on the outside, the driving electrical signal being applied to the conductors in the coil, and the diaphragm being mounted to facilitate radiation of sound from the diaphragm.

2) A loudspeaker as claimed in claim I that has a central phase plug, elliptical in section, to prevent the destructive interference of high frequency sound radiated from the diaphragm.

3) A loudspeaker as claimed in claims I and 2 that is mounted at the throat of a horn to increase the radiation efficiency.

4) A loudspeaker as claimed in claims 1, 2 and 3 wherein the diaphragm and the supporting former of the coil are made from a material that is substantially thermally conductive and bonded together by thermally conductive means so that heat may be transferred from the coil to the diaphragm to facilitate cooling of the coil.

5) A loudspeaker as claimed in claim l, 2 or 3 wherein the diaphragm is formed from a semi-rigid material that possesses high internal losses in order to damp spurious resonances of the diaphragm. 6) A loudspeaker as claimed in claims l, 2, 3 or 5 wherein the diaphragm is formed of a material flexible enough to allow the forming of integral inner and outer suspensions.

7) A loudspeaker as claimed in claims 1, 2, 3, 4, 5, 6 or 7 in which the profile of the section of the inner and outer portions of the diaphragm follow a substantially hyperbolic contour.