Loudspeaker

Details Loudspeaker Loudspeaker

2001-12-10

2003-02-04

Le, Huyen (Department: 2643)

Electrical audio signal processing systems and devices

Electro-acoustic audio transducer

Having acoustic wave modifying structure

C381S386000, C381S182000, C181S155000

Reexamination Certificate

active

06516072

ABSTRACT:

The present invention relates to the field of electroacoustics and may be used in loud-speaker constructions for high-quality reproduction of music and voice in domestic conditions as well as in public-culture and professional audio reproduction systems, specifically in sound control channels, station announcement systems, transport means cabins and other places where an improved articulation is required, particularly in conditions of noise pollution and interferences.
PRIOR ART
Loudspeakers having a direct radiating electrodynamic driver (EDD) installed at the outer surface of the driver enclosure cabinet are well known and most widely used (see V. K. Iofe and others, HandBook of Acoustics, Moscow, “Svyaz”, 1979).
Disadvantages of said devices, namely insufficient details and articulation of sound re-production, abrupt relationship between sound volume and distance R to EDD (by inverse-square law 1/R
2
), are associated to considerable dominance of a reactive (vector) component of their radiation over a necessary active (scalar) component.
These disadvantages are successfully overcome in a counteraperture loudspeaker comprising a module having a pair of identical, coaxial and inphase-counterradiating electrodynamic drivers transforming an electric signal into acoustic one at least in the middle-frequency part of the acoustic frequency range (see the International Application WO 95/05057, IPC
6
H04R5/02, 1995).
In said counteraperture loudspeaker, the active components of the counterdirected radiation of the identical electrodynamic driver pairs are added together while the vector components are mutually subtracted and thereby compensated.
Disadvantages of such devices are requirement of paired number of the electrodynamic drivers having identical characteristics in the pairs and enlarged loudspeaker dimensions due to the interaperture space volume.
Essence of the Invention
The main object of the present invention is to provide such loudspeaker construction which, on the one hand, would ensure high-quality sound reproduction by reducing the reactive component of the loudspeaker radiation and the parametric distortions (Doppler effect), associated to said component, and on the other hand, would not require use of pairs of identical band electrodynamic drivers, at the expense of that could be more compact and more simple to manufacture and adjust thereby would have relatively low manufacturing cost.
The basis for the present invention is the principle of operation of a counteraperture loudspeaker as well as the physico-mathematical idea of that the symmetry plane of given counteraperture loudspeaker, which is perpendicular to the common axis of the radiating apertures, is a plane of mirror symmetry. Symmetry is herein taken to mean not only a constructive symmetry, but also symmetry of dynamic of physical processes taking place at operation of the loudspeaker. Therefore, if any reflector overlapping the area of interaction of the vector, or velocity streams radiated by the electrodynamic drivers of the counteraperture pairs is placed in said plane, neither physical phenomena nor a degree of their development during the loudspeaker operation will not vary. Thus, a counteraperture loudspeaker having a reflector located in the above-mentioned plane may be formally represented as a pair of coaxial, counter-disposed, independent semicounteraperture loudspeakers, each of which is an independent module, all radiation aspects of which have full complex of unique positive properties of the counteraperture loudspeaker and which is more compact and less materials-intensive by comparison to the counteraperture loudspeaker.
The main object of the present invention is reached by that in a loudspeaker comprising a module having a direct radiating base electrodynamic driver (EDD) to transform an electrical signal into acoustic one at least in the middle-frequency part of the acoustic frequency range and an enclosure cabinet of said base EDD having a cone overlapping the mounting hole in the outside surface of said cabinet, according to the invention, the module is provided with an axial-symmetric acoustic reflector faced the radiating aperture of said base EDD and placed outside said enclosure cabinet and coaxially with said base EDD, wherein the distance &Dgr; from the radiating aperture of the base EDD to the acoustic reflector is no less than half the radius R
E
of the effective area of the radiating surface of the base EDD but no more than a quarter of the maximal acoustic wavelength &lgr;
max
in air, which is reproduced by the base EDD while the area S
R
of the acoustic reflector is no less than one third of and no more than the quadruple effective area S
E
of the radiating surface of the base EDD, that is:
0,5R
E
≦&Dgr;≦0,25&lgr;
max
,  (1)
 
S
R
=(⅓÷4)
S
E
.  (2)
To get the most uniformity of the acoustic field in a comfort insonification zone, specifically in a comfort insonification plane (that is in the plane where presence of listener heads is supposed), the claimed loudspeaker is disposed in a room so that the base EDD axis would be normal to the plane of comfort insonification while this plane would intersect said axis between the base EDD and its acoustic reflector. So, if a room subject to insonification has a horizontal floor (for example, a dancing hall or a fashion demonstration hall), the axis of the base EDD is located vertically while the height of the loudspeaker placing corresponds to the position of listeners heads. When a room floor is slanted, the axis of the base EDD of the loudspeaker module is located perpendicularly to the plane of the floor room envelope. If a room subject to insonification has a ceiling, the base EDD is essentially faced upward while the acoustic reflector is placed above the base EDD. When the insonification is being performed in an unclosed space, the base EDD is faced downwards (to a floor) while the acoustic reflector is placed under the base EDD.
Further, according to the invention, the loudspeaker module may be provided with at least one high-frequency EDD (hereinafter HF EDD) which may be installed coaxially to the base EDD. The coaxial HF EDD and base EDD may be placed both unidirectionally and counterdirectionally. When the HF EDD and base EDD are placed counterdirectionally, the distance &Dgr;
H
between their radiating apertures is no less than radius R
EH
of the effective area of the HF EDD radiating surface but no more than the distance &Dgr; from the radiating aperture of the base EDD to the acoustic reflector, that is:
R
EH
≦&Dgr;
H
≦&Dgr;.  (3)
One of the HF EDD may be installed coaxially and unidirectionally with the base EDD behind the backside of the acoustic reflector.
The above-mentioned placing the HF EDD (coaxially with the base EDD) assists in providing the most uniformity (non-directivity) of the resulting loudspeaker radiation.
If it is necessary to provide radiation directivity, the axis at least one of the HF EDD, according to the invention, is normal to the axis of the base EDD.
Further, the module of the claimed loudspeaker may be provided with a direct radiating low-frequency EDD (hereinafter LF EDD), a cone of which overlaps the mounting hole in the outside surface of an enclosure cabinet of the LF EDD, and also with an axial-symmetric low-frequency radiation acoustic reflector (hereinafter LF acoustic reflector), faced the radiating aperture of the LF EDD and placed outside the enclosure cabinet of the LF EDD and coaxially with the base EDD and LF EDD. Thus the LF EDD is placed co-axially with the base EDD. At that the distance &Dgr;
L
from the radiating aperture of the LF EDD to the LF acoustic reflector is no less than half the radius R
EL
of the effective area of the radiating surface of the LF EDD but no more than a quarter of the maximal acoustic wavelength &lgr;
L max
in air, which is reproduced by the LF EDD while the area S
RL
of the LF acoustic reflector is no less than one third of and no more than the quadruple effective area

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