Acoustics – Diaphragm and enclosure – Reflector baffle
Patent
1993-04-28
1995-05-23
Rutledge, D.
Acoustics
Diaphragm and enclosure
Reflector baffle
181156, H04R 132
Patent
active
054183367
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a sound output device or speaker unit which may be incorporated into a stereo audio output system, and more particularly into such a system intended to reproduce sound with high fidelity or near high fidelity and to give rise to a relatively wide field of stereophonic sound.
2. Description of the Prior Art
Our Patent GB-B-2188811 describes a stereo speaker system having a pair of first and second speaker assemblies. Each speaker assembly comprises a speaker having a diaphragm which emits a sound wave in a vertical direction and an acoustic reflector which is disposed above the diaphragm and reflects the sound wave from the diaphragm into a horizontal plane. The surface of the acoustic reflector facing the diaphragm of each speaker assembly is conical with the apex of the cone nearest to the diaphragm. The centre axis of the conical surface of the acoustic reflector is offset from the centre axis of the diaphragm so as to provide a preferential distribution of sound intensity in an intended listening direction and so as to enhance or increase the area over which the stereo image is obtained.
Further aspects of sound output systems using generally conical sound mirrors are disclosed in EP-A-0320270 and EP-A-0409360.
SUMMARY OF THE INVENTION
In one aspect this invention provides a loudspeaker unit comprising an audio mirror and a single drive unit disposed so as to direct sound towards a reflective surface of the audio mirror so that sound is redirected into a predetermined direction, and wherein the drive unit has concentric first and second diaphragms for lower and higher frequencies. It has been found that such a single drive unit which has concentric first and second diaphragms for lower and higher frequencies can be arranged at intermediate and high audible frequencies (e.g frequencies above 5 KHz) to direct a relatively concentrated or narrow beam of sound towards the audio mirror. It has been found that such a relatively concentrated beam of intermediate and high frequency sound when directed onto an audio mirror can be used to produce a distribution of sound which is more reproducible, the sound distribution being controlled by the shape of the diffracting or reflective surface of the audio mirror. Preferably the drive unit is arranged to direct sound downwardly onto the audio mirror or acoustic reflector, referring to the normal attitude in which the loudspeaker unit stands when in use.
The audio mirror or acoustic reflector is arranged to disperse or produce a widened distribution of sound, by reflection or diffraction depending upon frequency, in a first direction and optionally also in a second orthogonal direction, and preferably it has a generally conical surface facing the drive unit with the apex of the cone nearest to the drive unit. The centre of the drive unit may be offset from the axis of the conical surface so as to define a direction for sound leaving the drive unit. The above mentioned requirement for a single drive unit with concentric diaphragms facing the reflective surface of the audio mirror does not exclude the possibility that there may be another speaker, e.g., a bass speaker, which does not direct sound onto the audio mirror.
In one form of the drive unit, the second diaphragm may fit within but be unattached to the first diaphragm, the first and second diaphragms being independently driven by individual voice coils. More preferably, however, the second diaphragm fits within and is attached to the first diaphragm with a single drive vibrating both diaphragms, so that the second diaphragm acts as a so-called "parasitic tweeter", the second diaphragm conveniently being arranged to come into operation at frequencies above 5 KHz. The second diaphragm is preferably relatively narrow and horn-like and assists in the direction of a relatively concentrated beam of high frequency sound towards the audio mirror.
In one form the second diaphragm is circular in outline at its inner and outer ends. The first di
REFERENCES:
patent: 2956636 (1960-10-01), Boersma
patent: 4134471 (1979-01-01), Queen
patent: 4144416 (1979-03-01), Babb
patent: 4620317 (1986-10-01), Anderson
patent: 4836329 (1989-06-01), Klayman
patent: 4907671 (1990-03-01), Wiley
Jewitt Michael D. G.
Negishi Hiro
Canon Research Centre Europe Ltd.
Rutledge D.
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