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US 20010018621A1
(19) United States
(12) Patent Application Publication (10) Pub. No.: US 2001/0018621 A1
Weikel et al.
(54)
(43) Pub. Date:
MULTIMEDIA COMPUTER SPEAKER
(52)
Aug. 30, 2001
US. Cl. .............................................................. .. 700/94
SYSTEM WITH BRIDGE-COUPLED
SUBWOOFER
(75) Inventors: Raymond K. Weikel, Beaverton, OR
(US); Je?'rey S. Anderson, Camas, WA
(US)
(57)
ABSTRACT
A multimedia computer speaker system includes a pair of
ampli?ers that provide ampli?ed right and left audio signals
porrespondence Address?
to a pair of Wide-band speakers. The ampli?ers are con?g
lpsolon up _ _
Mark M‘ Memmger
4370 NE Halsey Street
Portland’ OR 97213 (Us)
ured to provide the ampli?ed right and left audio signals that
are out of phase With each other. The ampli?ed right and left
audio signals are applied to opposite terminals of the tWo
(73) Assigneez Labtec Corporation 1499 SE Tech Cen_
ter Place Suite 350’ Vancouver 98683
WA (Us),
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Wide-band speakers. These reversed terminal couplings to
the Wide-band speakers of the phase-reversed signals pro
vide phase-aligned right and left audio playback at the
speakers. AsubWoofer and a low pass ?lter are connected as
a bridge-tied load to receive the ampli?ed right and left
(21) APPL N0.
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09/440 153
audio signals. The phase of one ampli?ed audio signal is in
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Nov. 15, 1999
subWoofer. As a result, loW fre q uenc Y com P onents of a
effect reversed by applying it to the negative terminal of the
phase reversed ampli?ed audio signal are summed by the
subWoofer With loW frequency components of the other
ampli?ed audio signal to provide a low frequency audio
Publication Classi?cation
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Aug. 30, 2001
US 2001/0018621 A1
MULTIMEDIA COMPUTER SPEAKER SYSTEM
WITH BRIDGE-COUPLED SUBWOOFER
signal is applied to the negative terminal of the other
Wide-band speaker. These reversed terminal couplings to the
Wide-band speakers of the phase-reversed signals provide
Summary of Invention
phase-aligned right and left audio playback at the Wideband
speakers.
[0001]
The present invention relates to multimedia com
puter speaker systems connectable to audio system control
circuits (e.g., ”sound cards”) of multimedia computers and,
[0007]
A subWoofer is connected as a bridge-tied load to
receive the ampli?ed right and left audio signals. The phase
in particular, to such a system that employs a ”bridge
coupled” subWoofer to reduce the number of ampli?ers in
the system.
of one ampli?ed audio signal is in effect reversed by
applying it to the negative terminal of the subWoofer. In one
implementation, the right and left audio signals delivered to
the subWoofer are electrically loW-pass ?ltered. As a result,
[0002] Speaker systems With integral ampli?cation elec
loW frequency components of the phase reversed ampli?ed
tronics provide simple, compact audio reproducers for mul
timedia personal computers. These speaker systems, some
typically include pairs of Wide-band speakers mounted in
audio signal are summed by the subWoofer With loW fre
quency components of the other ampli?ed audio signal to
provide a loW frequency audio playback. In another imple
mentation, the subWoofer is contained Within a ported enclo
separate housings With ampli?cation electronics incorpo
sure that functions as an acoustic loW pass ?lter. As a result,
rated into one or both housings. Because compactness is
desirable, small, Wide-band speakers (e.g., 3-inch diameter
the phase-reversed audio signals are summed by the sub
Woofer to provide audio playback that is acoustically loW
cone speaker drivers) are commonly used.
pass ?ltered.
[0003] Many conventional multimedia computer systems
include tWo-channel (stereo) multimedia computer speaker
[0008] The speaker system of the present invention uti
times referred to as multimedia computer speaker systems,
systems. Typically, a conventional tWo-channel computer
audio system includes a tWo-channel audio system control
circuit, Which is commonly con?gured as a separate com
puter eXpansion board called a ”sound card,” and tWo
Wide-band audio transducers or speakers. A sub-Woofer
audio transducer or speaker is also included in many imple
mentations. Conventional tWo-channel speaker systems are
con?gured to provide at the tWo Wide-band speakers distinct
audio playback according to tWo distinct audio channels
included in a multimedia computer Work such as a game,
music, etc. Playback at the subWoofer is typically a summed
combination of the tWo distinct audio channels.
[0004] Typically, the speaker system includes a pair of
ampli?ers that provide ampli?ed right and left audio signals
liZes only tWo ampli?ers to drive three audio speakers: tWo
Wide-band speakers and a subWoofer. This speaker system
employs feWer ampli?ers than are used in conventional
multimedia computer speaker systems. Such a reduction in
electronic componentry can be signi?cant for generally
loW-cost consumer articles such as multimedia computer
speaker systems. The con?guration of single ended ampli
?ers for the Wideband speakers and the bridge coupled
subWoofer delivers more poWer to the subWoofer than to the
Wideband speakers. The higher poWer demands of bass
frequency audio playback are met With this con?guration.
[0009] Additional objects and advantages of the present
invention Will be apparent from the detailed description of
the preferred embodiment thereof, Which proceeds With
reference to the accompanying draWings.
to corresponding ones of the Wide-band speakers. The
subWoofer receives an audio signal that typically is gener
ated from the right and left audio channels. In particular, the
left and right audio channels are summed, and the sum is
passed through a loW pass ?lter to a sub-Woofer ampli?er.
The subWoofer ampli?er is coupled to the sub-Woofer and
drives it With a sum of the loW-frequency components of the
right and left audio channels.
[0011] Fig. 2 is a simpli?ed block diagram of a three-piece
multimedia computer speaker system according to the
[0005]
present invention coupled to a computer such as a personal
SubWoofers are desirable because of the richer and
deeper sounds that they provide in comparison to most
tWo-piece multimedia computer speaker systems. HoWever,
Brief Description of DraWings
[0010]
Fig. 1 is a simpli?ed block diagram of a prior art
three-piece multimedia computer speaker system coupled to
a computer such as a personal computer.
computer.
[0012]
Fig. 3 is a simpli?ed block diagram of an additional
a conventional subWoofer is a relatively expensive compo
nent of such a system due to the signi?cant cost of the
implementation of a three piece computer speaker system
ampli?er required for the subWoofer. It Would be desired,
therefore, to provide a three-piece multimedia computer
speaker system that avoids the signi?cant expense of con
ventional systems.
such as a personal computer.
[0006] Accordingly, the present invention provides a mul
timedia computer speaker system With a pair of ampli?ers
that provide ampli?ed right and left audio signals to a pair
of Wide-band speakers. The ampli?ers are con?gured to
provide the ampli?ed right and left audio signals that are out
of phase With each other. The ampli?ed right and left audio
signals are applied to opposite terminals of the tWo Wide
band speakers. For eXample, one signal is applied to the
positive terminal of one Wide-band speaker, and the other
according to the present invention coupled to a computer
[0013] Fig. 4 is a schematic block diagram illustrating
housings for the speakers of the speaker system of Fig. 2 and
the circuit components contained Within the housings.
Detailed Description
[0014]
Fig. 1 is a simpli?ed block diagram of a prior art
three-piece multimedia computer speaker system 10, Which
includes a pair of ampli?ed Wide-band speakers 12 and 14
and a sub-Woofer 16. Speakers 12 and 14 and subWoofer 16
are commonly contained Within separate housings With
speakers 12 and 14 sometimes referred to as satellite speak
Aug. 30, 2001
US 2001/0018621 A1
ers. Speaker system 10 receives an audio signal from an
and 96, respectively, that block loW frequency audio signal
audio output circuit (e.g., a ”sound card,”not shown) of a
multimedia computer 20. Typically, the audio signal is a
stereo audio signal that includes separate right and left audio
channels that are applied to speakers 12 and 14, respectively.
Speaker system 10 includes pair of equalizers 21 and 23 and
a pair of ampli?ers 22 and 24 that provide ampli?ed right
and left audio signals through high pass ?lters 25 and 27 to
components. High pass ?lters 94 and 96 are illustrated as
respective speakers 12 and 14.
[0015] Sub-Woofer 16 receives an audio signal that typi
cally is generated from the right and left audio channels. In
series-connected capacitors, but may be implemented in a
variety of other Ways.
[0020]
SubWoofer 56 is connected as a bridge-tied load to
receive ampli?ed right and left audio signals 80 and 82 at
positive terminal 102 and negative terminal 104, respec
tively. In one implementation, a loW pass ?lter 98 is con
nected in series With subWoofer 56 and is illustrated as a
series-connected inductor, but may be implemented in a
variety of other circuit implementations.
particular, the right and left audio channels are passed to an
adder or miXer 26 that sums the audio channels. The sum of
[0021] The phase of ampli?ed left audio signal 82 is in
the audio channels is passed through a loW pass ?lter 28 to
a sub-Woofer ampli?er 30 that is coupled to sub-Woofer 16.
result, loW frequency components of the phase reversed
effect reversed by applying it to negative terminal 104. As a
As a result, subWoofer 16 is driven With a sum of the
ampli?ed left audio signal 82 are summed by subWoofer 56
loW-frequency components of the right and left audio chan
nels. Speaker system 10 also commonly includes a volume
control, such as a ground-connected potentiometer (not
shoWn), that coupled betWeen ampli?ers 22, 24, and 30 and
speakers 12, 14, and 16 to control the volume of audio
With loW frequency components of ampli?ed right audio
signal 80 to provide loW frequency audio playback 110.
Moreover, loW frequency audio playback 110 is phase
playback provided by speaker system 10.
[0016] Fig. 2 is a simpli?ed block diagram of a three-piece
multimedia computer speaker system 50 according to the
present invention. Speaker system 50 includes a pair of
ampli?ed Wide-band speakers 52 and 54, and a sub-Woofer
56. Speaker system 50 receives an audio signal from an
audio output circuit (e.g., a ”sound card,” not shoWn) of a
multimedia computer 60, such as a personal computer. The
audio signal is a multi-channel (e.g., stereo) audio signal that
includes separate right and left audio channels 62 and 64.
[0017] Speaker system 50 includes a pair of volume
control potentiometers 66 and 68, a pair of equalizers 72 and
74, and a pair of ampli?ers 76 and 78 that provide ampli?ed
right and left audio signals 80 and 82 to speakers 52 and 54,
respectively. Potentiometers 66 and 68 are tied together
(indicated schematically by dashed line 70) to provide user
control of the volume of right and left audio channels 62 and
64. Ampli?ers 76 and 78 are con?gured to provide ampli?ed
right and left audio signals 80 and 82 out of phase With each
other. For eXample, one of ampli?ers 76 and 78 is con?gured
to provide non-inverting ampli?cation, and the other of
ampli?ers 76 and 78 is con?gured to provide inverting
ampli?cation. For purposes of illustration, ampli?ers 76 and
78 are shoWn as providing non-inverting and inverting
ampli?cation, respectively.
[0018] The combination of inverting and non-inverting
ampli?cation provided by ampli?ers 76 and 78 results in
ampli?ed right and left audio signals 80 and 82 having
betWeen them a phase difference of 180 degrees. Ampli?ed
right and left audio signals 80 and 82 are applied to the
terminals of speakers 52 and 54 in opposite phase. For
eXample, ampli?ed right audio signal 80 is applied to a
positive terminal 90 of speaker 52, and ampli?ed left audio
signal 82 is applied to a negative terminal 92 of speaker 54.
A positive terminal of a speaker is characteriZed as the
aligned With right- and left-audio outputs 86 and 88 at
speakers 52 and 54The bridge mode coupling of subWoofer
5 6, in combination With the opposed phase of ampli?ed right
and left audio signals 80 and 82, alloWs ampli?ers 76 and 78
to drive speakers 52 and 54, as Well as subWoofer 56. As a
result, speaker system 50 may be implemented With only one
pair of ampli?ers 76 and 78, rather than including one or
more separate ampli?ers that are dedicated to driving sub
Woofer 56. Such a reduction in electronic componentry can
be signi?cant for generally loW-cost consumer articles such
as multimedia computer speaker systems. The con?guration
of single ended ampli?ers for Wideband speakers 52 and 54
and bridge coupled subWoofer 56 delivers more poWer to
subWoofer 56 than to Wideband speakers 52 and 54. The
higher poWer demands of bass frequency audio playback are
met With this con?guration. More speci?cally, bridge
coupled ampli?ers have a 6dB voltage gain, or theoretically
4 times poWer the output of a single ended ampli?er,
assuming a ?Xed supply voltage and ?X impedance load.
[0022] Fig. 3 is a simpli?ed block diagram of another
implementation of a three-piece multimedia computer
speaker system 120 according to the present invention.
Speaker system 120 is substantially the same as speaker
system 50, With common components being identi?ed by
common reference numerals.
[0023] Speaker system 120 differs from speaker system 50
in that subWoofer 56 is acoustically loW pass ?ltered in the
former and electrically loW pass ?ltered in the latter. Speaker
system 120 includes a ported enclosure 122 that contains
subWoofer 56 and functions to provide acoustic loW pass
?ltering, as is knoWn in the art. Accordingly, speaker system
120 does not include an electrical loW pass ?lter 98 (e.g., an
inductor, as shoWn in Fig. 2) that ?lters the electrical signal
provided to subWoofer 56.
[0024] Fig. 4 is a schematic block diagram illustrating
housings 132, 134, and 136 for respective speakers 52, 54,
terminal that provides outWard movement of the diaphragm
When a positive voltage or current is applied. These reversed
terminal couplings to speakers 52 and 54 of the phase
and 56 of speaker system 50 and circuit components con
tained Within the housings. Housings 132, 134, and 136 are
reversed signals 80 and 82 provide phase-aligned right and
housing 136 for speaker system 120 includes one or more
left audio playback 86 and 88 at speakers 52 and 54.
[0019] Ampli?ed right and left audio signals 80 and 82 are
delivered to speakers 52 and 54 through high pass ?lters 94
similarly applicable to speaker system 120, eXcept that
ports to provide acoustic loW pass ?ltering.
[0025] Housing 132 includes inputs 140 and 142 to
receive cables carrying respective right and left audio chan
Aug. 30, 2001
US 2001/0018621 A1
nels 62 and 64. Inputs 140 and 142 may be integrated into
a single multi-channel coupling or plug. Housing 132 also
contains potentiometers 66 and 68 and a user accessible
knob (not shoWn) to control the volume of speaker system
50. An output 144 is connectable to a cable to carry the
volume-controlled audio channels to an input 146 of sub
4. The system of claim 1 further comprising no ampli?er
other than the ?rst and second ampli?ers coupled to the
subWoofer.
5. The system of claim 1 further comprising a loW pass
?lter connected in series With one terminal of the subWoofer
Woofer housing 136.
to pass selectively loW frequency components of the ampli
?ed ?rst and second audio signals.
[0026] Housing 136 contains all the active circuitry of
speaker system 50 (e.g., ampli?ers 76 and 78). As a result,
only housing 136 includes an input (not shoWn) for receiv
ing DC poWer. Housing includes audio outputs 150 and 152
6. The system of claim 5 in Which the loW pass ?lter is a
series-connected inductor.
7. The system of claim 1 further comprising an acoustic
loW pass ?lter that contains the subWoofer such that it
that are connectable to cables to carry ampli?ed right and
left audio signals 80 and 82 to inputs 154 and 156 on
housings 132 and 134, respectively. Housings 132 and 134
are shoWn as including high pass ?lters 94 and 96. It Will be
appreciated, hoWever, that high pass ?lters 94 and 96 could
alternatively be included in housing 136.
[0027] The arrangement of components Within housings
selectively provides loW frequency playback of the ampli
?ed ?rst and second audio signals.
8. The system of claim 7 further comprising no electrical
loW pass ?ltering of the ampli?ed ?rst and second audio
signals coupled to the subWoofer.
9. The system of claim 1 further comprising a high pass
?lter connected in series With one terminal of each of the
left audio channels 62 and 64 alloWs all active circuit
?rst and second Wide-band speakers, each high pass ?lter to
receive one of the ampli?ed ?rst and second audio signals.
10. The system of claim 9 in Which each high pass ?lter
is a series-connected capacitor.
11. The system of claim 1 in Which the ?rst and second
elements to be positioned in subWoofer housing 136, thereby
Wide-band speakers and a subWoofer are each contained in
132, 134, and 136 provides a user-manipulated volume
control at a Wideband or satellite speaker in combination
With a simpli?ed cable arrangement. Controlling the volume
of speaker system 50 With direct manipulation of right and
eliminating a common requirement for poWer to be deliv
ered to a satellite speaker.
a separate housing, and the ?rst and second ampli?ers are
the only active components of the system and are contained
in the housing With the subWoofer.
[0028] Having described and illustrated the principles of
12. The system of claim 11 further comprising a user
our invention With reference to a preferred embodiment
manipulated volume control in the housing for one of the
thereof, it Will be apparent that the invention can be modi?ed
in arrangement and detail Without departing from such
principles. In vieW of the many possible embodiments to
Which the principles may be put, it should be recogniZed that
the detailed embodiment is illustrative only and should not
Wide-band speakers, the volume control controlling the
be taken as limiting the scope of our invention. Accordingly,
We claim as our invention all such modi?cations as may
come Within the scope and spirit of the folloWing claims and
equivalents thereto.
multi-channel audio signal from the audio output circuit of
a multimedia computer.
13. In a multimedia computer speaker system having ?rst
and second Wide-band speakers and a subWoofer for trans
ducing a multi-channel audio signal from an audio output
circuit of a multimedia computer, the improvement com
prising: only one pair of ampli?ers that receive and amplify
?rst and second channels of the audio signal and apply them
to the ?rst and second Wide-band speakers, respectively, and
to the subWoofer.
Claims
14. The system of claim 13 in Which the one pair of
1. In a multimedia computer speaker system having ?rst
ampli?ers provide phase-reversed ampli?cation of the ?rst
and second Wide-band speakers and a subWoofer for trans
ducing a multi-channel audio signal from an audio output
circuit of a multimedia computer, the system including ?rst
and second channels of the audio signal to provide ampli?ed
?rst and second audio signals With reversed phase, the
system further comprising: reversed terminal couplings of
the ?rst and second Wide-band speakers to the ampli?ed ?rst
and second audio signals; and couplings betWeen the sub
Woofer and the ampli?ed ?rst and second audio signals, one
each being coupled to each of opposed terminals of the
and second ampli?ers that receive and amplify ?rst and
second channels of the audio signal and apply them to the
?rst and second Wide-band speakers, respectively, the
improvement comprising: phase-reversed ampli?cation of
the ?rst and second channels of the audio signal to provide
ampli?ed ?rst and second audio signals With reversed phase;
reversed terminal couplings of the ?rst and second Wide
band speakers to the ampli?ed ?rst and second audio sig
nals; and couplings betWeen the subWoofer and the ampli
?ed ?rst and second audio signals, one each being coupled
to each of opposed terminals of the subWoofer.
2. The system of claim 1 in Which the phase reversed
ampli?cation includes inverted ampli?cation of the ?rst
channel and non-inverted ampli?cation of the second chan
subWoofer.
15. The system of claim 13 in Which the phase reversed
ampli?cation includes inverted ampli?cation of the ?rst
channel and non-inverted ampli?cation of the second chan
nel.
16. The system of claim 13 in Which the subWoofer is a
bridge-tied load on the ampli?ed ?rst and second audio
signals.
17. The system of claim 13 in Which the ?rst and second
Wide-band speakers and a subWoofer are each contained in
nel.
3. The system of claim 1 in Which the subWoofer is a
bridge-tied load on the ampli?ed ?rst and second audio
a separate housing, and the ?rst and second ampli?ers are
contained in the housing With the subWoofer.
signals.
manipulated volume control in the housing for one of the
18. The system of claim 17 further comprising a user
Aug. 30, 2001
US 2001/0018621 A1
Wide-band speakers, the volume control controlling the
multi-channel audio signal from the audio output circuit of
a multimedia computer.
19. The system of claim 13 further comprising a loW pass
?lter connected in series With one terminal of the subWoofer
to pass selectively loW frequency components of the ampli
?ed ?rst and second channels of the audio signal.
20. The system of claim 13 further comprising an acoustic
loW pass ?lter that contains the subWoofer such that it
selectively provides loW frequency playback of the ampli
?ed ?rst and second channels of the audio signal.
21. In a multimedia computer speaker system having ?rst
and second Wide-band speakers and a subWoofer for trans
ducing a multi-channel audio signal from an audio output
circuit of a multimedia computer, the system including ?rst
and second ampli?ers that receive and amplify ?rst and
second channels of the audio signal and apply them to the
?rst and second Wide-band speakers, respectively, a method
comprising: providing phase-reversed ampli?cation of the
?rst and second channels of the audio signal to provide
ampli?ed ?rst and second audio signals With reversed phase;
providing reversed terminal couplings of the ?rst and second
Wide-band speakers to the ampli?ed ?rst and second audio
signals; and providing couplings betWeen the subWoofer and
the ampli?ed ?rst and second audio signals, one each being
coupled to each of opposed terminals of the subWoofer.
22. The method of claim 21 in Which the phase reversed
ampli?cation includes inverted ampli?cation of the ?rst
channel and non-inverted ampli?cation of the second chan
nel.
23. The method of claim 21 in Which providing couplings
26. The method of claim 21 further comprising providing
high pass ?lter in series With one terminal of each of the ?rst
and second Wide-band speakers, each high pass ?lter to
receive one of the ampli?ed ?rst and second audio signals.
27. In a multimedia computer speaker system having ?rst
and second Wide-band speakers and a subWoofer for trans
ducing a multi-channel audio signal from an audio output
circuit of a multimedia computer, the subWoofer being
contained Within a subWoofer housing, the improvement
comprising: one pair of ampli?ers that are contained Within
the subWoofer housing and receive and amplify ?rst and
second channels of the audio signal and apply them to the
?rst and second Wide-band speakers, respectively, and to the
subWoofer.
28. The system of claim 27 in Which the pair of ampli?ers
provide phase-reversed ampli?cation of the ?rst and second
channels of the audio signal to provide ampli?ed ?rst and
second audio signals With reversed phase, the system further
comprising: reversed terminal couplings of the ?rst and
second Wide-band speakers to the ampli?ed ?rst and second
audio signals; and couplings betWeen the subWoofer and the
ampli?ed ?rst and second audio signals, one each being
coupled to each of opposed terminals of the subWoofer.
29. The system of claim 27 in Which the phase reversed
ampli?cation includes inverted ampli?cation of the ?rst
channel and non-inverted ampli?cation of the second chan
nel.
30. The system of claim 27 in Which the subWoofer is a
bridge-tied load on the ampli?ed ?rst and second audio
betWeen the subWoofer and the ampli?ed ?rst and second
audio signals includes providing the subWoofer as a bridge
tied load on the ampli?ed ?rst and second audio signals.
24. The method of claim 21 further comprising providing
loW pass ?ltering in series With one terminal of the sub
Woofer to pass selectively loW frequency components of the
Wide-band speakers are contained in one or more housings
ampli?ed ?rst and second audio signals.
25. The method of claim 21 further comprising providing
volume control controlling the multi-channel audio signal
acoustic loW pass ?ltering of the subWoofer so it selectively
from the audio output circuit of a multimedia computer.
provides loW frequency playback of the ampli?ed ?rst and
second audio signals.
signals.
31. The system of claim 27 in Which the ?rst and second
separate from the subWoofer housing, the system further
comprising a user-manipulated volume control in one of the
one or more housings for the Wide-band speakers, the
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