Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Electromagnetic
Reexamination Certificate
1999-12-10
2004-02-17
Le, Huyen (Department: 2743)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Electromagnetic
C381S401000
Reexamination Certificate
active
06694037
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the fields of audio loudspeakers, and more particularly to a speaker suspended without a “spider” or “surround,” wherein the motion of the speaker is controlled by an active restoring apparatus.
BACKGROUND OF THE INVENTION
A representative prior art audio speaker
10
is illustrated in FIG.
1
. Most speakers, like speaker
10
, comprise a diaphragm
12
driven by a voice coil
14
. The voice coil
14
is mounted in a magnetic field created by magnet
22
. The magnet
22
is supported on a back plate
18
and has a top plate
16
and a pole piece
20
forming a magnetic assembly
23
. The diaphragm
12
is supported in such a way that it is free to vibrate in a linear direction, restrained by a spring apparatus. Usually the spring apparatus takes the form of a surround
24
and a spider
26
. When an audio signal is fed to the coil
14
, the diaphragm
12
moves away from a neutral position. The spider
26
and surround
24
act both to constrain speaker to a linear motion and to provide a restoring force, returning the diaphragm
12
to the neutral position in the absence of a displacing force provided by the coil
14
.
The spring action in the spider and surround are potentially distorting to sound reproduction, particularly where wide ranges of frequencies or amplitudes are expected. The spider and surround usually act as linear springs over most of their range of motion, coming to a relatively abrupt stop at maximum extension in either the forward or backward direction. In certain situations, particularly with high audio power and at low bass frequencies, the speaker may be driven beyond its physical constraints, striking a hard constraint or straining against the suspension at its limit, a phenomenon referred to as “bottoming.” Bottoming can introduce serious distortion and risk physical damage or deterioration of the speaker.
It is an object therefore, of our invention, to provide a speaker system without a spring-type suspension.
It is also an object of our invention to provide a speaker with an active restoring apparatus.
Another feature or object of our invention is to provide a speaker with a frictionless bearing, that is, negligible friction, constraint, the constraint limiting direction travel of the diaphragm to a linear direction.
SUMMARY OF THE INVENTION
The objects of our invention have been accomplished by providing a spider-less and suspension-less speaker system, having a diaphragm constrained to move in a linear direction and supported by a frictionless or low friction support. A voice coil coupled to an audio input drives the speaker diaphragm. A position sensor determines the physical position of the diaphragm. A control circuit uses the sensed position information to modify the audio signal in such a way that the interaction of the voice coil and the magnetic field both drives the diaphragm to produce an audible output and restores the diaphragm to a neutral position in the absence of a further audio signal.
REFERENCES:
patent: 1822450 (1931-09-01), Nystrom
patent: 4207430 (1980-06-01), Harada et al.
patent: 4334127 (1982-06-01), Shimada et al.
patent: 4727584 (1988-02-01), Hall
patent: 5408533 (1995-04-01), Reiffin
patent: 5748759 (1998-05-01), Croft et al.
patent: 5786741 (1998-07-01), Leibzon
patent: 5828767 (1998-10-01), Button
patent: 5848173 (1998-12-01), Sato et al.
Robinson Robert Steven
Rottenberg William B.
Routh Andre G.
Ensey Brian
Le Huyen
Merkling John R.
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