Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Electromagnetic
Reexamination Certificate
1999-08-18
2001-03-27
Le, Huyen (Department: 2743)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Electromagnetic
C381S400000, C381S406000, C381S117000
Reexamination Certificate
active
06208742
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to audio speakers and more particularly to a speaker transducer system which is light-weight and able to produce high quality sound.
High-quality prior art speakers have generally employed transducer systems comprising a permanent magnet and an electrical coil. An audio signal, corresponding to sounds to be generated, would be directed to the coil. The coil then would create a time-varying magnetic field which would interact with the field of the permanent magnet to drive the speaker. This has limited such speakers to relatively fixed installations due to the weight of the magnet.
Somewhat recently the magnet weight problem has been addressed by replacing the magnet with a second electrical coil, as disclosed in Dinh U.S. Pat. No. 5,487,114. The Dinh prior art is illustrated in
FIG. 1
hereof, as indicated by the reference numeral
30
.
Referring now to
FIG. 1
, a speaker
42
is oscillated in correspondence with an audio signal
36
through forces of attraction and repulsion acting on a movable coil
34
. Signal
36
is applied across input lines
38
,
40
. A stationary coil
32
is connected to lines
38
,
40
by lead lines
46
,
44
. Coil
32
generates magnetic flux having a field strength which generally follows the amplitude of signal
36
. When signal
36
changes sign the flux generated by stationary coil
32
reverses direction.
Moveable coil
34
is connected to input line
38
by a bridge arrangement
48
, comprising
4
diodes
48
a
-
48
d.
Bridge
48
connects moveable coil
34
in parallel with stationary coil
32
but rectifies the current flowing through the moveable coil. This rectified current causes moveable coil
34
to generate magnetic flux which follows the amplitude of signal
36
, but without reversal. Thus moveable coil
34
is alternately attracted to and repelled by stationary coil
32
.
The magnetic field at coil
34
due to coil
32
is proportional to sin(&ohgr;t), where &ohgr; is the frequency of the audio signal
36
, and the acceleration force acting on coil
34
is proportional to sin(&ohgr;t)ABS(sin(&ohgr;t)). Ideally the acceleration force should be proportional simply to sin(&ohgr;t), so the factor ABS(sin(&ohgr;t)) introduces a small distortion error. The bridge diodes cannot switch at zero volts. A practical threshold is in a region of about 0.5 to 0.7 volts. Since bridge
48
places two diodes in series, the moveable coil cannot respond to signal reversals below about 1 volt. This is fairly substantial in a typical 5 volt system.
SUMMARY OF THE INVENTION
The present invention reduces distortion in a light weight, coil-driven speaker by minimizing threshold losses in diode switches.
In accordance with the practice of this invention the transducer system comprises three coils, two diodes and a speaker cone. Two of the coils are paired and operate alternately, each operating under switching control of a single diode. The third coil operates continuously and may be either stationary or moveable. The paired coils are fixed relative to each other. Relative motion occurs between the third coil and the paired coils. In a first embodiment of the invention the paired coils are stationary, while the third coil is moveable. In a second embodiment of the invention the third coil is stationary, and the paired coils are moveable.
Further in accordance with the practice of this invention all three coils are connected in parallel for reception of an audio signal. The moveable coil(s) is(are) mounted for driving a speaker cone. Preferably, the paired coils are wound in a bifilar arrangement on a common cylinder. The three coils may be incorporated into a magnetic circuit, if desired.
REFERENCES:
patent: 1733232 (1929-10-01), Miessner
patent: 1743749 (1930-01-01), Arkell
patent: 1763846 (1930-06-01), Fay
patent: 1834820 (1931-12-01), Bobb
patent: 1849495 (1932-03-01), Lyle
patent: 2004735 (1935-06-01), Thomas
patent: 2030574 (1936-02-01), Dull
patent: 2042966 (1936-06-01), Van B. Roberts
patent: 2084944 (1937-06-01), Cornwell
patent: 2217177 (1940-10-01), Massa
patent: 2261111 (1941-11-01), Engholm
patent: 2727949 (1955-12-01), Lokkesmoe
patent: 2770681 (1956-11-01), Perry
patent: 5487114 (1996-01-01), Dinh
patent: WO 94/18806 (1994-08-01), None
Garcia Arturo H.
Garcia Arturo J.
King & Schickli PLLC
Le Huyen
True Dimensional Sound, Inc.
LandOfFree
Electro-acoustic dynamic transducer system for use in a loud... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electro-acoustic dynamic transducer system for use in a loud..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electro-acoustic dynamic transducer system for use in a loud... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2464805