Signal Processing Scaling System

Signal Processing Scaling System
US 20060233378Al
(19) United States
(12) Patent Application Publication (10) Pub. No.: US 2006/0233378 A1
(43) Pub. Date:
Kim et al.
(54)
MULTI-CHANNEL BASS MANAGEMENT
Oct. 19, 2006
Publication Classi?cation
(51)
(76) Inventors: Wontak Kim, Cambridge, MA (U S);
Int. Cl.
H04R 5/00
George Nichols’ Dover’ MA (Us); Guy
(52)
A. Tor1o,Ashland, MA (US)
(57)
(200601)
US. Cl. ................................................................ .. 381/1
ABSTRACT
A multi-channel audio system including ?rst combining
Correspondence Address:
FISH & RICHARDSON PC
circuitry, for combining a ?rst spectral band of a ?rst
plurality channels to provide a ?rst bass audio signal stream;
PO. BOX 1022
second combining circuitry, for combining the ?rst spectral
MINNEAPOLIS, MN 55440-1022 (US)
band of a second plurality channels to provide a second bass
(21) Appl, No.1
11/104,746
audio signal stream; and third combining circuitry, for
combining a second spectral band, the second spectral band
including loWer frequencies than the ?rst spectral band, of
(22)
Apr. 13, 2005
the ?rst plurality of channels and the second plurality of
channels to provide a third bass audio signal stream.
Filed:
n
Channel
Audio
Source
Signal
Routing,
Mixing, and
Playback
Signal
Processing
Scaling
System
Source
Circuitry
Circuitry
6
2
4
10
8
14
12
Patent Application Publication Oct. 19, 2006 Sheet 1 of 11
US 2006/0233378 A1
n
Channel
Audio
Source
Signal
Routing,
Mixing, and
Playback
Signal
Processing
Scaling
System
Source
Circuitry
Circuitry
6
2
4
10
8
28
m
co
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B
14
302
B
i
i
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(B
E
E
[If
Hr1
If
frequency Hz
Hf2
frequency Hz
FIG.
12
32-2
Patent Application Publication Oct. 19, 2006 Sheet 2 0f 11
US 2006/0233378 A1
TwN ®|oN
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Patent Application Publication Oct. 19, 2006 Sheet 4 0f 11
US 2006/0233378 A1
(ABass)
(ABass)
(ABass)
FBass
Lout
FBass
Cout
FBass
Rout
34L
34C
34LS
Lsout
RBass
(ABass)
was
?\ .
ABass
(RBass)
(FBass)
FIG. 4A
34R
34RS
RSOUt
RBass
(ABass)
Patent Application Publication Oct. 19, 2006 Sheet 5 0f 11
US 2006/0233378 A1
FBass
(A ass)
Lout
Cout
40L
4o|_s
Rout
40C
40R
V
40RS
42R
LSout
;
RSout
RBass
ABass
FIG. 4B
Patent Application Publication Oct. 19, 2006 Sheet 6 0f 11
(ABass)
FBass
Lout
US 2006/0233378 A1
(ABass)
Gout
34L
40C
34LS
FBass
Rout
34R
34RS
\d/ 38
Lsout
RBass
ABass
FIG. 4c '
RSOUt
RBass
Patent Application Publication Oct. 19, 2006 Sheet 7 0f 11
LOT
Cout
34L
<
US 2006/0233378 A1
Rout
34R
40C
38R
'
36
ABass
ABass
LtBass
~
RtBass
34RS
38L
34LS
RSout
LSout
FIG. 4D
Patent Application Publication Oct. 19, 2006 Sheet 8 0f 11
US 2006/0233378 A1
FBass
Lout
Gout
Rout
37F
40L
40C
40R
37L
37R
LtBass
RtBass
36
40RS
40LS
37R
RSout
LSout
38
RBass
ABass
FIG. 4E
Patent Application Publication Oct. 19, 2006 Sheet 9 0f 11
US 2006/0233378 A1
46FL
46|L
46FR
46BR
46BL
FIG. 5
Patent Application Publication Oct. 19, 2006 Sheet 11 0f 11
Loudspeaker
Audio Signal Streams
46FL
0.7 Lout + 0.3 Cout + 1.0 ABass + 1.0 FBass
46FR
0.7 Rout + 0.3 Cout + 1.0 ABass + 1.0 FBass
44FC
0.2 Lout + 0.2 Rout + 0.6 Cout
46E
0.5 Lout + 0.5 LSout + 1.0 RBass + 1.0 ABass
46IR
0.5 Rout + 0.5 RSout + 1.0 RBass + 1.0 ABass
46BL
1.0 LSout + 1.0 RBass
46BR
1.0 RSout +1.0 RBass
48
1.0 Rbass + 1.0 ABass
FIG. 7
US 2006/0233378 A1
Oct. 19, 2006
US 2006/0233378 A1
MULTI-CHANNEL BASS MANAGEMENT
[0001] This speci?cation describes the management of the
bass portion of a multi-channel audio system.
second bass audio signal stream to a second loudspeaker;
and a third transmitting, of the third bass audio signal stream
to a third loudspeaker.
[0012] The method for processing audio signals may fur
having a plurality of input channels, a method for processing
ther include combining the ?rst bass audio stream, the
second bass audio signal stream, and the third bass audio
signal stream to provide a combined bass audio signal
stream; and transmitting the combined bass audio signal
audio signals includes a ?rst combinatorial processing of a
?rst group of the plurality channels to provide a ?rst bass
energy corresponding to the combined bass audio signal
SUMMARY OF THE INVENTION
[0002]
In one aspect of the invention, an audio system
audio signal stream including frequencies in a ?rst spectral
stream to the third loudspeaker for transduction to acoustic
stream.
band; a second combinatorial processing of a second group
of the plurality of channels to provide a second bass audio
[0013] The combining may include scaling the ?rst audio
signal stream including frequencies in the ?rst spectral band;
signal stream and the third bass signal stream.
and a third combinatorial processing of the plurality of
channels to provide a third bass audio signal stream includ
ing frequencies in a second spectral band, the second spec
[0014] The ?rst combinatorial processing may include
combining the ?rst group of the plurality of channels to
tral band including loWer frequencies than the ?rst spectral
band.
[0003] The ?rst combinatorial processing may include
combining front channels and the second combinatorial
processing may include combining rear channels.
[0004] The ?rst combinatorial processing may include
combining left hemisphere channels and the second combi
natorial processing may include combining right hemisphere
channels.
create a ?rst combined signal and ?ltering the combined
signal With a band pass ?lter.
[0015]
The ?ltering may include ?ltering the ?rst com
bined audio signal With a band pass ?lter that has an upper
break frequency of less than 300 HZ.
[0016] The third combinatorial processing may include
combining the plurality of channels to create a combined
signal and ?ltering the combined signal With a ?lter that
attenuates frequencies above about 80 HZ.
[0005] The ?rst combinatorial processing may include
combining ?rst adjacent directional channels of a multichan
nel audio system and the second combinatorial processing
[0017]
?lter.
The ?ltering may include ?ltering With a loW pass
[0018]
The ?ltering may include ?ltering With a band pass
may include combining second adjacent channels of a
multichannel audio system.
?lter.
[0006] The method for processing audio signals may also
ther include a ?rst ?ltering, of one of the ?rst group of the
include transmitting the ?rst bass audio signal stream to a
?rst full range loudspeaker for transduction to acoustic
energy corresponding to the ?rst bass audio signal stream;
and transmitting the second bass audio signal stream to a
second full range loudspeaker for transduction to acoustic
energy corresponding to the second bass audio signal
plurality of channels to provide a ?rst high frequency audio
signal stream;. a second ?ltering, of another of the ?rst group
of the plurality of channels to provide a second high fre
[0019] The method for processing audio signals may fur
stream.
[0007] The method for processing audio signals may fur
ther include transmitting the third bass audio signal stream
to a Woofer or subWoofer loudspeaker for transduction to
acoustic energy corresponding to the third bass audio signal
stream.
[0008] The method for processing audio signals may fur
ther comprising combining the second bass audio signal
stream and the third bass audio signal stream to provide a
combined bass audio signal stream.
[0009] The method for processing audio signals may fur
ther include transmitting the combined audio signal stream
to a ?rst full range loudspeaker for transduction to acoustic
energy
[0010] The method for processing audio signals may fur
quency audio signal stream; a third ?ltering, of one of the
second group of the plurality of channels to provide a third
high frequency audio signal stream; and a fourth ?ltering, of
another of the second group of the plurality of channels to
provide a fourth high frequency audio signal stream.
[0020] The method may further include transmitting the
?rst high frequency audio signal stream to a ?rst loud
speaker for transduction to acoustic energy; transmitting the
second high frequency audio signal stream to a second
loudspeaker for transduction to acoustic energy; transmit
ting the third high frequency audio signal stream to a third
loudspeaker for transduction to acoustic energy; transmit
ting the fourth high frequency audio signal stream to a fourth
loudspeaker for transduction to acoustic energy; transmit
ting the ?rst bass audio signal stream to the ?rst loudspeaker
and the second loudspeaker for transduction to acoustic
energy; and transmitting the second bass audio signal stream
to the third loudspeaker and the fourth loudspeaker for
transduction to acoustic energy.
ther include transmitting the combined audio signal to a
[0021]
Woofer or subWoofer loudspeaker for transduction to acous
third bass audio signal stream to a Woofer or subWoofer
tic energy.
audio loudspeaker for transduction to acoustic energy.
[0011] The method for processing audio signals may fur
[0022] The ?ltering of at least one of the plurality of input
channels may include ?ltering the input channel signal With
ther include a ?rst transmitting, of the ?rst bass audio signal
stream to a ?rst loudspeaker; and second transmitting, of the
The method may further include transmitting the
a high pass ?lter.
Oct. 19, 2006
US 2006/0233378 A1
[0023] The combinatorial processing may include ?ltering
the plurality of input channels to provide a high frequency
spectral portion, a loW frequency spectral portion, and a very
loW frequency spectral portion for each of the plurality of
channels; combining the loW frequency portion of a ?rst
subset of the plurality of spectral portions to provide a ?rst
combined loW frequency audio signal stream; combining the
loW frequency portion of a second subset of the plurality of
spectral portions to provide a second combined loW fre
quency audio signal stream, Wherein the ?rst subset and the
second subset are not identical; and combining the very loW
frequency portion of the plurality of input channels to
provide a very loW frequency signal stream.
[0024] In another aspect of the invention, a multi-channel
audio system may include ?rst combining circuitry, for
combining a ?rst spectral band of a ?rst plurality channels
to provide a ?rst bass audio signal stream; second combining
circuitry, for combining the ?rst spectral band of a second
plurality channels to provide a second bass audio signal
stream; and third combining circuitry, for combining a
second spectral band, the second spectral band including
loWer frequencies than the ?rst spectral band, of the ?rst
plurality of channels and the second plurality of channels to
provide a third bass audio signal stream.
[0025] The ?rst combining circuitry may include elements
for combining front channels and the second combining
for transmitting the second bass audio signal stream to a
second loudspeaker; and third transmitting circuitry, for
transmitting the third bass audio signal stream to a third
loudspeaker.
[0033] The multi-channel audio may include transmitting
circuitry for transmitting the second audio signal stream to
the third loudspeaker; combining circuitry, for combining
the ?rst audio signal stream With the bass audio signal
streams to provide a combined audio signal stream; and
transmitting the combined audio signal stream to the third
loudspeaker.
[0034] The multi-channel audio system may include cir
cuitry comprises a scaler for scaling the ?rst audio signal
stream and the third bass signal stream.
[0035] The ?rst combining circuitry may include circuitry
for combining the ?rst plurality of channels to create a ?rst
combined signal and ?ltering the combined signal With a
band pass ?lter.
[0036]
The ?ltering circuitry may include a band pass
?lter that has an upper break frequency of less than 300 HZ.
[0037] The third combining circuitry may include cir
cuitry for combining the plurality of channels to create a
combined signal and ?ltering the second combined signal
With a loW pass ?lter.
[0038]
The multi-channel audio system may further
circuitry may include elements for combining rear channels.
include a ?rst high pass ?lter, for ?ltering one of the ?rst
[0026] The ?rst combining circuitry may include elements
plurality of channels to provide a ?rst high frequency audio
signal stream;. a second high pass ?lter, for ?ltering another
for combining left hemisphere channels and the second
combining circuitry may include elements for combining
right hemisphere channels.
[0027] The multi-channel audio system may further
include ?rst transmitting circuitry, for transmitting the ?rst
bass audio signal stream to a ?rst full range loudspeaker for
transduction to acoustic energy corresponding to the ?rst
bass audio signal stream; and second transmitting circuitry,
of the ?rst plurality of channels to provide a second high
frequency audio signal stream; a third high pass ?lter, for
?ltering one of the second plurality of channels to provide a
third high frequency audio signal stream; and a fourth high
pass ?lter, for ?ltering another of the second plurality of
channels to provide a fourth high frequency audio signal
stream.
for transmitting the second bass audio signal stream to a
second full range loudspeaker for transduction to acoustic
[0039] The multi-channel audio system may further
include ?rst transmitting circuitry, for transmitting the ?rst
energy corresponding to the second bass audio signal
high frequency audio signal stream to a ?rst loudspeaker for
transduction to acoustic energy; second transmitting cir
stream.
[0028]
The multi-channel audio system may include third
transmitting circuitry, for transmitting the third bass audio
signal stream to a Woofer or subWoofer loudspeaker for
transduction to acoustic energy corresponding to the third
bass audio signal stream.
cuitry, for transmitting the second high frequency audio
signal stream to a second loudspeaker for transduction to
acoustic energy; third transmitting circuitry, for transmitting
the third high frequency audio signal stream to a third
loudspeaker for transduction to acoustic energy;. fourth
transmitting circuitry, for transmitting the fourth high fre
The multi-channel audio may include fourth com
quency audio signal stream to a fourth loudspeaker for
bining circuitry for combining the second bass audio signal
transduction to acoustic energy; ?fth transmitting circuitry,
for transmitting the ?rst bass audio signal stream to the ?rst
loudspeaker and the second loudspeaker for transduction to
acoustic energy; and sixth transmitting circuitry, for trans
mitting the second bass audio signal stream to the third
loudspeaker and the fourth loudspeaker for transduction to
[0029]
stream and the third bass audio signal stream to provide a
combined bass audio signal stream.
[0030]
The multi-channel audio may include fourth trans
mitting circuitry for transmitting the combined audio signal
stream to a ?rst full range loudspeaker for transduction to
acoustic energy.
acoustic energy.
[0031]
include seventh transmitting circuitry, for transmitting the
The multi-channel audio may include ?fth trans
[0040]
The multi-channel audio system may further
mitting circuitry for transmitting the combined audio signal
third bass audio signal stream to a Woofer or subWoofer
to a Woofer or subWoofer loudspeaker for transduction to
audio loudspeaker for transduction to acoustic energy.
acoustic energy.
[0032]
The multi-channel audio may include ?rst trans
mitting circuitry, for transmitting the ?rst bass audio signal
stream to a ?rst loudspeaker; second transmitting circuitry,
[0041] Other features Will become apparent from the fol
loWing description and claims. The audio system described
in this speci?cation is best understood by reference to the
draWing, in Which:
Oct. 19, 2006
US 2006/0233378 A1
BRIEF DESCRIPTION OF THE SEVERAL
VIEWS OF THE DRAWING
[0042]
FIG. 1 is a block diagram of a multi-channel audio
high frequency acoustic energy and to originate in an area
more speci?c than the very loW frequency bass acoustic
energy.
system;
[0053] Conventional audio systems are typically con?g
[0043]
ured to combine the bass spectral portion of the directional
channels to provide a single monaural bass signal (Which
may be combined With a loW frequency effects channels, if
FIGS. 2A and 2B are block diagrams of a portion
of the multi-channel audio system of FIG. 1, With showing
one of the elements in greater detail;
present) and to provide discrete high frequency directional
[0044]
output channels corresponding to the input channels; or to
provide full range output channels corresponding to the
directional input channels.
FIG. 3 shoW curves shoWing frequency responses
of some of the elements of FIGS. 1, 2A and 2B;
[0045]
FIGS. 4A-4E are diagrammatic vieWs of alternate
implementations of the audio system;
[0046] FIG. 5 is a diagrammatic vieW of the audio system
implemented in a vehicle cabin;
[0054] An audio system according to the speci?cation has
advantages over conventional audio systems. The very loW
frequency audio signal stream is not routed to any loud
[0047] FIG. 6 is a block diagram of the audio system of
FIG. 1, shoWing one of the elements in greater detail; and
speaker that Would be overloaded by the signal, but may be
routed to any loudspeaker in the system capable of repro
ducing the very loW frequency audio signal stream. The very
loW frequency spectral portion, for Which there is little
[0048] FIG. 7 is a chart shoWing the contents of the audio
signal streams transmitted to the various loudspeakers in one
advantage in maintaining directionality, can be radiated by
a single loudspeaker that is especially suited to radiating
implementation of the audio system.
very loW frequencies. This maximizes the headroom of the
complete system and alloWs great ?exibility in selection of
DETAILED DESCRIPTION
[0049]
Though the elements of the several vieWs of the
draWing are shoWn as discrete elements in a block diagram
and are referred to as “circuitry”, unless otherWise indicated,
the elements may be implemented as a microprocessor
executing software instructions, Which may include digital
signal processing (DSP) instructions. Unless otherWise indi
cated, signal lines may be implemented as discrete analog
signal lines, as a single discrete digital signal line With
appropriate signal processing to process separate streams of
audio signals, or as elements of a Wireless communication
system. If the signal lines are implemented as a single
discrete signal line, the number and nature of the input and
output terminals of the elements may be implemented as
loudspeaker capabilities. The high frequency spectral por
tion of the directional channels can be radiated by small,
conveniently placed loudspeakers, While the loW frequency
spectral portions can be radiated by loudspeakers that main
tain some directionality.
[0055] With reference noW to the draWing and more
particularly to FIG. 1, there is shoWn a block diagram of an
audio system. An n-channel audio signal source 2 is com
municatingly coupled to source signal processing circuitry 4
by signal lines 6. Source signal processing circuitry 4 is
communicatingly coupled to routing, mixing, and scaling
circuitry 8 by signal lines 10. Routing, mixing, and scaling
circuitry 8 is coupled to elements of playback system 12 by
signal lines 14.
single input and output terminals. Unless otherWise noted,
audio signals may be either encoded in either digital or
analog form.
[0050] For simplicity of Wording “channel x” may be used
instead of “audio signals corresponding to channel x.”. For
example “Channel Lin is high pass ?ltered” means that that
the audio signals corresponding to channel Lin are high pass
?ltered.
[0051] In general, this speci?cation describes an audio
system that is con?gured to combine spectral bands of
directional channels to form multiple bass streams. Each of
the multiple bass streams may be a linear combination of a
spectral band of tWo or more input channels.
[0056] N-channel audio signal source 2 may be a conven
tional source of audio signals, such as a CD or DVD player
or a radio tuner. The examples folloWing Will use a 5.1 (i.e.
n=5.1, Where “.1” refers to a limited bandWidth loW fre
quency effects channel) channel source. The audio signal
source could have more than ?ve directional channels (i.e.
n=6.1, 7.1, . . . ) and may not have the loW frequency effects
channel (i.e. n=5, 6, 7, . . . ). The ?ve directional channels
in a 5 or 5.1 channel system typically include a left, right,
center, left surround, and right surround channels. Herein
after, the left, right, and center channels may be referred to
as “front” channels, While the right surround and left sur
round channels may be referred to as “rear” channels. In
bands. The bass frequency band is divided into tWo fre
quency bands, a loW frequency band and a very loW fre
quency band. The very loW frequency bands from all the
systems having more than ?ve channels, channels that are
intended to represent a source in the front hemisphere
relative to a normal listening location may be considered
“front” channels and channels that are intended to represent
a source in the rear hemisphere relative to a normal listening
directional channels and the loW frequency effects channel,
position may be considered “rear” positions. Channels that
[0052] The audio spectrum is divided into frequency
if present, are combined to provide a single monaural very
are intended to represent channels directly to the left or
loW frequency audio signal stream. The loW frequency bands
directly to the right of a normal listening position may be
considered either front channels, rear channels, both front
from combinations of subsets of the directional channels are
combined to provide bass Zone audio signal streams. The
bass Zone audio signal streams are combinations of a subset
of the directional input channels that represent bass acoustic
energy intended to originate in an area less speci?c than the
and rear channels, or neither front not rear channels. Chan
nels that are intended to represent a source in the left
hemisphere relative to a normal listening location may be
considered “left hemisphere” channels and channels that are
Oct. 19, 2006
US 2006/0233378 A1
intended to represent a source in the right hemisphere
relative to a normal listening position may be considered
“right hemisphere” channels. Center or center surround
channels may be considered left hemisphere or right hemi
sphere channels, or both hemispheres, or neither hemi
sphere.
[0057] Source signal processing circuitry 4 receives as
input signals the n channels from the audio signal source,
processes the signals, and provides as output streams of
audio signals that have a directionality and spectral content
appropriate for the playback system 12. Included in the
streams of audio signals are multiple streams of audio
signals in the bass frequency range. The number and nature
of the bass audio signal streams depends on the number,
capabilities, and location of speakers that radiate bass acous
Audio Signal Combining”. Many other combinations of
summers and loW pass, high pass, and band pass ?lters may
be used to produce audio signal streams containing different
combinations of signals. For example, the RBass signal may
include LSin and RSin (but not LFEin) band passed. The
speci?c combinations of input signals and the ?lters that are
applied depend on the number, location, frequency range
capability of the elements of the playback system 12, and
Will be discussed beloW.
[0060]
FIG. 2B shoWs another implementation of source
signal processing circuitry 4. In the implementation of FIG.
2B, the directional input channels Lin, Rin, Cin, LSin, and
RSin are ?ltered by high pass ?lters 18HP-1-18HP-5,
respectively, to provide output audio streams Lout, Rout,
Cout, LSout, and RSout, respectively at output terminals
tic energy. The source signal processing circuitry 4 Will be
20-1-20-5, respectively. The directional channels are also
discussed in more detail in the discussion of FIGS. 2A and
?ltered by band pass ?lters 18BP-1-18BP-5, respectively,
and by loW pass ?lters 18LP-1-18LP-5, respectively. The
2B. Routing, mixing, and scaling circuitry 8 receives as
input the multiple streams of audio signals from source
signal processing circuitry 4 and outputs streams of audio
band passed L, LS, and C signals are combined at summer
22-9 to provide left bass output audio stream LtBass at
signals that are appropriate for each of the elements of the
output terminal 20-9. The band passed R, RS, and C signals
playback system 12. The routing, mixing, and scaling cir
are combined at summer 22-7 to provide output audio
cuitry 8 Will be discussed in more detail beloW. Playback
stream RtBass at output terminal 20-10. The loW passed L,
R, C, LS, RS, and the LFE signals are combined at summers
22-8 to provide the ABass audio signal stream at output
system 12 includes electroacoustical transducers, ampli?ers,
equalizers, compressors, clippers, and like elements typi
cally associated With transduction of audio signals to acous
tic energy. Examples of combinations of electroacoustical
transducers Will be described beloW in the discussion of
FIGS. 4A-4E and 5.
[0058] FIG. 2A shoWs an implementation of source signal
processing circuitry 4 in more detail. Source signal process
ing circuitry has six input terminals 16L, 16R, 16C, 16LS,
16RS, and 16LFE corresponding to the n channels (labeled,
respectively, Lin, Rin, Cin, LSin, RSin, and LFEin), of audio
signal source 2.
[0059] Channel Lin is high pass ?ltered by high pass ?lter
18-1 to provide output audio stream Lout at output terminal
20-1. Channel Rin is high pass ?ltered by high pass ?lter
18-2 to provide output audio stream Rout at output terminal
20-2. Channel Cin is high pass ?ltered by high pass ?lter
18-3 to provide output audio stream Cout at output terminal
20-3. Channel LSin is high pass ?ltered by high pass ?lter
terminal 20-7. Summers 22-8 can be multiple summers as
shoWn or may include one or more summers With multiple
input terminals. The implementation of FIG. 2B shoWs that
the multiple bass streams do not need to be combinations of
the front and rear channels, but may also be combinations of
left and right channels. The implementations of FIGS. 2A
and 2B also shoW that the ?ltering can be done either prior
to or after the combining.
[0061] The implementations of FIGS. 2A and 2B may be
combined in more complex arrangements. For example,
input channels in a 7.1 or 8.1 channel system could be
?ltered and combined to provide left front bass, right front
bass, left rear bass, and right rear bass audio signal streams.
Similar to FIG. 2A, any plurality of the summers can be
implemented by a single summer With multiple input ter
minals.
20-4. Channel RSin is high pass ?ltered by high pass ?lter
[0062] FIG. 3 shoWs the crossover characteristics of the
?lters of FIGS. 2A and 2B. Curve 28 may represent the
frequency response of loW pass ?lter 26 of FIG. 2A or one
18-5 to provide output audio stream RSout at output termi
nal 20-5. Channel LFEin is combined With channel RSin at
represent the frequency response of band pass ?lter 24-2 of
18-4 to provide output audio stream LSout at output terminal
of more of 18LP-1 - 18LP-5 of FIG. 2B, curve 30-1 may
summer 22-1 and With channel LSin at summer 22-2 and
FIG. 2A or one or more of 18BP-1-18BP-5 of FIG. 2B;
band pass ?ltered at band pass ?lter 24-1 to provide output
curve 30-2 may represent the frequency response of band
rear bass audio audio stream RBass at output terminal 20-6.
Channel Cin is combined With channel Rin at summer 22-3
and With channel Lin at summer 22-4 and band pass ?ltered
pass ?lter 24-1 of FIG. 2 or one or more of band pass ?lters
at band pass ?lter 24-2 to provide output front bass audio
stream FBass at output terminal 20-8. For clarity, summers
of FIG. 2A or some or all of high pass ?lters 18HP-1
22-1 and 22-2 are shoWn as a pair of summers, and summers
22-3 and 22-4 are shoWn as a pair of summers. Each of the
frequency response of high pass ?lters 18-4 and 18-5 of
FIG. 2A or some or all of high pass ?lters 18HP-1-18HP-5
pairs of summers can also be implemented as a single
of FIG. 2B. Typically crossover frequency lf betWeen loW
summer With multiple input terminals. The output signals
pass ?lter 26 and band pass ?lter 24-1 is the same as
from summers 22-2 and 22-4 are combined at summer 22-5
crossover frequency lf betWeen loW pass ?lter 26 and band
pass ?lter 24-2. Crossover frequency hf1 betWeen band pass
?lter 24-1 and high pass ?lters 18-1, 18-2, and 18-3 may be
and loW pass ?ltered at loW pass ?lter 26 to provide all bass
audio stream ABass at output terminal 20-7. Summers
22-1-22-5 may incorporate the bass signal combining tech
niques described in US. patent application Ser. No.
09/735123, ?led Dec. 12, 2000, entitled “Phase Shifting
18L-1-18LP-5 of FIG. 2B ; curve 32-1 may represent the
frequency response of high pass ?lters 18-1, 18-2, and 18-3
18HP-5 of FIG. 2B; and curve 32-2 may represent the
the same or may be different than crossover frequency hf2
betWeen band pass ?lter 24-2 and high pass ?lters 18-4 and
18-5. In some implementations, the frequency response of
Oct. 19, 2006
US 2006/0233378 A1
high pass ?lter 18-4 may be different from the frequency
response of high pass ?lter 18-5, so the crossover frequency
betWeen high pass ?lters 18-4 and 18-5 and band pass ?lter
24-1 are different. Similarly, the frequency response of high
pass ?lter 18-1, the frequency response of high pass ?lter
18-2, and the frequency response of high pass ?lter 18-3
may be different so that the crossover frequency betWeen
band pass ?lter 24-2 and high pass ?lters 18-1, 18-2, and
18-3 are different. In one implementation, crossover fre
quency If is 80 HZ and crossover frequencies hf1 and hf2 are
less than 300 HZ, for example 200 HZ. In this speci?cation,
frequencies below If may be referred to as “very loW
frequencies” and frequencies above If but beloW hfl and hf2
may be referred to as “loW frequencies.”
[0063]
In other implementations, loW pass ?lter 26 may be
a band pass ?lter, With a loW frequency break point set to
?lter out loW frequency noise signals and similarly one or
more of high pass ?lters 18-1-18-5 may be band pass ?lters
to ?lter out high frequency noise. Any of the ?lters can be
implemented as an acoustic ?lter, for example by radiating
the output signal streams to loudspeakers With acoustic
a factor <1) the amplitude of the ABass audio stream
transmitted to the loudspeakers to obtain the proper balance
of acoustic energy corresponding to the ABass audio signal
stream With acoustic energy corresponding to the other
audio signal streams.
[0066] Referring to FIG. 4B, there is shoWn another
exemplary playback system 12 of FIG. 1. This playback
system includes limited range loudspeakers (such as tWeet
ers, tWiddlers, or mid-range loudspeakers or combinations
thereof) 40L, 40C, and 40R, positioned in front of and to the
left, center, and right, respectively of listener 36 in an
intended listening position and limited range loudspeakers
40LS, 40RS positioned behind and to the left and right,
respectively, of listener 36. The loudspeakers may have tWo
or more acoustic drivers operating in different frequency
ranges (for example a mid-range acoustic driver and an
tWeeter), With appropriate crossover circuitry (not shoWn).
Additionally, front subWoofer 42F is positioned at a conve
nient location in front of listener 36 and rear subWoofer 42R
is positioned at a convenient location behind listener 36.
SubWoofers also may have tWo or more acoustic drivers.
drivers and loudspeaker enclosures designed to cause acous
Routing, mixing, and scaling circuitry 8 of FIG. 1 is
tic roll off at appropriate frequencies. Filtering can also be
done electrically, With either active or passive elements.
con?gured to transmit to loudspeaker 40L audio stream
Lout; to loudspeaker 40C audio stream Cout; to loudspeaker
40R Rout; to loudspeaker 40LS audio stream LSout; and to
[0064]
The output terminals 20-1-20-7 of FIG. 2A and
output terminals 20-1-20-10 of FIG. 2B are mixed and
routed by routing, mixing, and scaling circuitry 8 and output
as streams of audio signals to playback system 12.
[0065] Referring to FIG. 4A, there is shoWn an exemplary
playback system 12 of FIG. 1. Elements other than loud
speakers, such as ampli?ers, equaliZers, compressors, clip
loudspeaker 40RS audio stream RSout. In addition, routing,
mixing, and scaling circuitry 8 of FIG. 1 is con?gured to
transmit to rear subWoofer 42R audio signal stream RBass,
and to front subWoofer 42F audio signal stream FBass.
Routing, mixing, and scaling circuitry 8 of FIG. 1 is also
con?gured to transmit signal stream ABass to one or both of
front subWoofer 42F and rear subWoofer 42R. As With the
pers, and the like are not shoWn in this vieW. The playback
example of FIG. 4A, the routing, mixing, and scaling
system includes full range loudspeakers 34L, 34R, 34C,
positioned in front of and to the left, right, and center,
circuitry 8 of FIG. 1 may be con?gured to scale the audio
signal streams to obtain the proper balance of acoustic
energy corresponding to the several audio streams.
respectively, of listener 36 in an intended listening position.
The playback system also includes full range loudspeakers
34LS and 34RS, positioned behind and to the left and right,
respectively, of listener 36. The playback system also
includes subWoofer 38 positioned, at a convenient location,
in this example behind listener 36; the location of subWoofer
38 is not as important as the location of the other loudspeak
ers. Routing, mixing, and scaling circuitry 8 of FIG. 1 is
con?gured to transmit to loudspeaker 34L audio signal
streams FBass and Lout and optionally audio signal stream
ABass; to transmit to loudspeaker 34C audio signal streams
FBass and Cout and optionally audio signal stream ABass;
to transmit to loudspeaker 34R audio signal streams FBass
and Rout and optionally audio stream ABass; to loudspeaker
34LS audio signal streams RBass and LSout and optionally
audio stream ABass; to transmit to loudspeaker 34RS audio
signal streams RBass and RSout and optionally audio stream
ABass; and to transmit to subWoofer 38 audio stream ABass
and optionally audio stream RBass or audio stream FBass ,
or both, depending on the location of the subWoofer and
other criteria. Loudspeakers 34L-34RS and subWoofer 38
transduce the audio signal streams to acoustic energy cor
responding to the audio signal streams. If audio stream
ABass is radiated by all six loudspeakers, then the frequency
response at the location of listener 36 may contain more
acoustic energy corresponding to the ABass audio signal
stream than acoustic energy corresponding to other audio
signal streams. It may be desirable for routing, mixing, and
scaling circuitry 8 of FIG. 1 to attenuate (that is to scale, by
[0067] Other playback systems may be constructed by
combining aspects of the implementations of the systems of
4A and 4B. For example, the playback system of FIG. 4C
is similar to the playback system of FIG. 4A, except full
range loudspeaker 34C of FIG. 4A has been replaced by a
limited range loudspeaker 40C. Routing, mixing, and scal
ing circuitry 8 of FIG. 1 is con?gured to transmit to limited
range loudspeaker 40C audio signal stream Cout. As With
the systems of the previous ?gures, the routing, mixing, and
scaling circuitry 8 of FIG. 1 may be con?gured to scale the
audio signal streams to obtain the proper balance of acoustic
energy corresponding to the several audio streams.
[0068] FIG. 4D shoWs another exemplary playback sys
tem 12, designed to be used With the circuitry of FIG. 2B.
Routing, mixing, and scaling circuitry 8 of FIG. 1 is
con?gured to transmit to limited range loudspeaker 34L
audio signal stream Lout; to transmit to limited range
loudspeaker 40C audio signal steam Cout; to transmit to
limited range loudspeaker 34R audio signal stream Rout; to
transmit to limited range loudspeaker 34LS audio signal
stream LSout; to limited range loudspeaker 34RS audio
signal stream RSout; to left subWoofer 38L audio signal
stream ABass and LtBass; and to right subWoofer 38R audio
signal streams ABass and RtBass.
[0069] FIG. 4E shoWs yet another exemplary playback
system 12. In FIG. 4E, channels Lout, Rout, Cout, LSout,
Oct. 19, 2006
US 2006/0233378 A1
and RSout are transmitted to limited range loudspeakers
audio signal streams to the loudspeakers of the playback
34L, 34R, 40C, 34LS and 34RS, respectively. The loW
frequencies of the L, C, and R input channels have been
system of FIG. 5 as shoWn in FIG. 7.
combined to provide front bass audio signal stream FBass,
Which is transmitted to front bass loudspeaker 37F. The loW
frequencies of the C, L and LS input channels have been
combined to provide left bass audio signal stream LtBass,
Which is transmitted to left bass loudspeaker 37L. The loW
frequencies of the LS and RS input channels have been
combined to provide rear bass audio signal stream RBass,
Which is transmitted to rear bass loudspeaker 37R. The loW
frequencies of the C, R and RS channels have been com
bined to provide right bass audio signal stream RtBass,
Which is transmitted to right bass loudspeaker 37Rt. The
very loW frequencies of the input channels have been
combined to provide audio signal stream ABass, Which is
[0073] A loudspeaker system according to the invention is
advantageous over conventional loudspeaker systems,
because it provides better front/back separation and provides
improved balance of bass energy, and alloWs for a Wide
range of loudspeaker frequency ranges and placement, espe
cially in vehicle audio systems.
[0074] It is evident that those skilled in the art may noW
make numerous uses of and departures from the speci?c
apparatus and techniques disclosed herein Without departing
from the inventive concepts. Consequently, the invention is
to be construed as embracing each and every novel feature
and novel combination of features disclosed herein and
limited only by the spirit and scope of the appended claims.
transmitted to subWoofer 38. The implementation of FIG.
4E shoWs that any tWo or more adjacent channels can be
combined to form a bass “Zone”; that a channels may be
included in more than one Zone, or in other Words that the
Zones may overlap; that the bass audio signal streams may
be radiated by dedicated loudspeakers.
[0070] Aspects of the implementations of FIGS. 4A-4E
can be combined to form many other con?gurations. If there
is a subWoofer, the signal ABass transmitted to the sub
Woofer. In any of the implementations or variations of
FIGS. 4A-4E in Which only the ABass audio stream is
transmitted to a subWoofer 38, the placement of a subWoofer
such as subWoofer 38 is arbitrary. Depending on the place
ment of the subWoofer(s), and additional appropriate bass
signal can be transmitted to the subWoofer. For example, in
FIG. 4D, With subWoofers 38L and 38R placed to the left
and right, respetively, of the listener, the left loW frequency
signal LtBass is transmitted to the left subWoofer 38L and
the right loW frequency signal RtBass is transmitted to the
right subWoofer 38R.
[0071] Referring noW to FIG. 5, there is shoWn a playback
system 12 of FIG. 1, designed for a vehicle passenger cabin.
An audio system according to the invention is especially
advantageous in vehicle passenger cabins because of the
limitations on the type of loudspeakers that can be installed
and on the limitations of Where the loudspeakers can be
What is claimed is:
1. In an audio system having a plurality of input channels,
a method for processing audio signals comprising:
a ?rst combinatorial processing of a ?rst group of said
plurality channels to provide a ?rst bass audio signal
stream including frequencies in a ?rst spectral band;
a second combinatorial processing of a second group of
said plurality of channels to provide a second bass
audio signal stream including frequencies in said ?rst
spectral band; and
a third combinatorial processing of said plurality of
channels to provide a third bass audio signal stream
including frequencies in a second spectral band, said
second spectral band including loWer frequencies than
said ?rst spectral band.
2. A method for processing audio signals in accordance
With claim 1, Wherein said ?rst combinatorial processing
comprises combining front channels and Wherein said sec
ond combinatorial processing comprises combining rear
channels.
3. A method for processing audio signals in accordance
With claim 1, Wherein said ?rst combinatorial processing
comprises combining left hemisphere channels and Wherein
said second combinatorial processing comprises combining
right hemisphere channels.
installed. In the playback system of FIG. 5, front center
loudspeaker 44FC is a limited range speaker positioned near
the lateral center of the instrument panel; front left loud
speaker 46FL and front right loudspeaker 46FR are full
range loudspeakers installed in the front left and front right
multichannel audio system and Wherein said second com
doors respectively; intermediate left loudspeaker 46IL and
binatorial processing comprises combining second adjacent
intermediate right loudspeaker 46IR are full range loud
speakers installed at intermediate locations, behind the front
channels of a multichannel audio system.
seat passenger locations and in front of the rear seat pas
4. A method for processing audio signals in accordance
With claim 1, Wherein said ?rst combinatorial processing
comprises combining ?rst adjacent directional channels of a
5. A method for processing audio signals in accordance
With claim 1, further comprising
senger locations, in the left rear door and right rear door,
respectively; back left loudspeaker 46BL and back right
loudspeaker 46BR are full range loudspeakers installed in
the back of the vehicle in the parcel shelf on the left and
right, respectively; and Woofer 48 is installed in a convenient
location, such as in the parcel shelf or under one of the seats.
In other vehicle con?gurations, there may also be loud
speakers at other locations, and there may also be additional
roWs of seats.
transmitting said ?rst bass audio signal stream to a ?rst
full range loudspeaker for transduction to acoustic
energy corresponding to said ?rst bass audio signal
stream; and
transmitting said second bass audio signal stream to a
second full range loudspeaker for transduction to
acoustic energy corresponding to said second bass
designed to be used With the playback system of FIG. 5. The
audio signal stream.
6. A method for processing audio signals in accordance
With claim 1, further comprising transmitting said third bass
routing mixing and scaling circuitry is con?gured to transmit
audio signal stream to a Woofer or subWoofer loudspeaker
[0072] FIG. 6 shoWs routing, mixing, and scaling circuitry
Oct. 19, 2006
US 2006/0233378 A1
for transduction to acoustic energy corresponding to said
third bass audio signal stream.
7. A method for processing audio signals in accordance
With claim 1, further comprising combining said second bass
audio signal stream and said third bass audio signal stream
to provide a combined bass audio signal stream.
8. A method for processing audio signals in accordance
With claim 7, further comprising transmitting said combined
a fourth ?ltering, of another of said second group of said
plurality of channels to provide a fourth high frequency
audio signal stream.
19. A method for processing audio signals in accordance
With claim 18, further comprising
transmitting said ?rst high frequency audio signal stream
to a ?rst loudspeaker for transduction to acoustic
energy;
audio signal stream to a ?rst full range loudspeaker for
transduction to acoustic energy
transmitting said second high frequency audio signal
9. A method for processing audio signals in accordance
With claim 7, further comprising transmitting said combined
stream to a second loudspeaker for transduction to
acoustic energy;
audio signal to a Woofer or subWoofer loudspeaker for
transduction to acoustic energy.
transmitting said third high frequency audio signal stream
10. A method for processing audio signals in accordance
With claim 1, further comprising a ?rst transmitting, of said
to a third loudspeaker for transduction to acoustic
energy;
?rst bass audio signal stream to a ?rst loudspeaker; and
transmitting said fourth high frequency audio signal
second transmitting, of said second bass audio signal stream
to a second loudspeaker; and a third transmitting, of said
third bass audio signal stream to a third loudspeaker.
stream to a fourth loudspeaker for transduction to
acoustic energy;
11. A method for processing audio signals in accordance
With claim 10, further comprising combining said ?rst bass
audio stream, said second bass audio signal stream, and said
transmitting said ?rst bass audio signal stream to said ?rst
third bass audio signal stream to provide a combined bass
transmitting said second bass audio signal stream to said
third loudspeaker and said fourth loudspeaker for trans
audio signal stream; and transmitting said combined bass
audio signal stream to said third loudspeaker for transduc
tion to acoustic energy corresponding to said combined bass
audio signal stream.
12. A method for processing audio signals in accordance
With claim 11, Wherein said combining comprises scaling
said ?rst audio signal stream and said third bass signal
stream.
13. A method for processing audio signal in accordance
With claim 1, Wherein said ?rst combinatorial processing
comprises combining said ?rst group of said plurality of
channels to create a ?rst combined signal and ?ltering said
combined signal With a band pass ?lter.
14. A method for processing audio signals in accordance
With claim 13, Wherein said ?ltering comprises ?ltering said
?rst combined audio signal With a band pass ?lter that has
an upper break frequency of less than 300 HZ.
15. A method for processing audio signals in accordance
With claim 1, Wherein said third combinatorial processing
comprises combining said plurality of channels to create a
combined signal and ?ltering said combined signal With a
?lter that attenuates frequencies above about 80 HZ.
16. A method for processing audio signals in accordance
With claim 15, Wherein said ?ltering comprises ?ltering With
a loW pass ?lter.
17. A method for processing audio signals in accordance
With claim 15, Wherein said ?ltering comprises ?ltering With
a band pass ?lter.
18. A method for processing audio signals in accordance
With claim 1, further comprising
a ?rst ?ltering, of one of said ?rst group of said plurality
of channels to provide a ?rst high frequency audio
signal stream;
a second ?ltering, of another of said ?rst group of said
plurality of channels to provide a second high fre
quency audio signal stream;
a third ?ltering, of one of said second group of said
plurality of channels to provide a third high frequency
audio signal stream; and
loudspeaker and said second loudspeaker for transduc
tion to acoustic energy; and
duction to acoustic energy.
20. A method for processing audio signals in accordance
With claim 19, further comprising
transmitting said third bass audio signal stream to a
Woofer or subWoofer audio loudspeaker for transduc
tion to acoustic energy.
21. A method for processing audio signals in accordance
With claim 18, Wherein said ?ltering of at least one of said
plurality of input channels comprises ?ltering the input
channel signal With a high pass ?lter.
22. A method for processing audio signals in accordance
With claim 1, Wherein said combinatorial processing com
pnses:
?ltering said plurality of input channels to provide a high
frequency spectral portion, a loW frequency spectral
portion, and a very loW frequency spectral portion for
each of said plurality of channels.;
combining said loW frequency portion of a ?rst subset of
said plurality of spectral portions to provide a ?rst
combined loW frequency audio signal stream;
combining said loW frequency portion of a second subset
of said plurality of spectral portions to provide a second
combined loW frequency audio signal stream, Wherein
said ?rst subset and said second subset are not identi
cal; and
combining said very loW frequency portion of said plu
rality of input channels to provide a very loW frequency
signal stream.
23. A multi-channel audio system comprising:
?rst combining circuitry, for combining a ?rst spectral
band of a ?rst plurality channels to provide a ?rst bass
audio signal stream;
second combining circuitry, for combining said ?rst spec
tral band of a second plurality channels to provide a
second bass audio signal stream; and
Oct. 19, 2006
US 2006/0233378 A1
third combining circuitry, for combining a second spectral
band, said second spectral band including loWer fre
quencies than said ?rst spectral band, of said ?rst
plurality of channels and said second plurality of chan
nels to provide a third bass audio signal stream.
24. A multi-channel audio system in accordance With
34. A multi-channel audio system in accordance With
claim 23, Wherein said ?rst combining circuitry comprises
circuitry for combining said ?rst plurality of channels to
create a ?rst combined signal and ?ltering said combined
signal With a band pass ?lter.
35. A method for processing audio signals in accordance
claim 23, Wherein said ?rst combining circuitry comprises
With claim 34, Wherein said ?ltering circuitry comprises a
elements for combining front channels and Wherein said
band pass ?lter that has an upper break frequency of less
than 300 HZ.
36. A multi-channel audio system in accordance With
second combining circuitry comprises elements for combin
ing rear channels.
25. A multi-channel audio system in accordance With
claim 23, Wherein said ?rst combining circuitry comprises
claim 23, Wherein said third combining circuitry comprises
circuitry for combining said plurality of channels to create a
elements for combining left hemisphere channels and the
combined signal and ?ltering said second combined signal
second combining circuitry comprises elements for combin
With a loW pass ?lter.
ing right hemisphere channels.
26. A multi-channel audio system in accordance With
claim 23, further comprising
?rst transmitting circuitry, for transmitting said ?rst bass
audio signal stream to a ?rst full range loudspeaker for
transduction to acoustic energy corresponding to said
?rst bass audio signal stream; and
second transmitting circuitry, for transmitting said second
bass audio signal stream to a second full range loud
speaker for transduction to acoustic energy correspond
ing to said second bass audio signal stream.
27. A multi-channel audio system in accordance With
claim 23, further comprising third transmitting circuitry, for
transmitting said third bass audio signal stream to a Woofer
or subWoofer loudspeaker for transduction to acoustic
energy corresponding to said third bass audio signal stream.
28. A multi-channel audio system in accordance With
claim 23, further comprising fourth combining circuitry for
combining said second bass audio signal stream and said
third bass audio signal stream to provide a combined bass
audio signal stream.
29. A multi-channel audio system in accordance With
claim 28, further comprising fourth transmitting circuitry for
transmitting said combined audio signal stream to a ?rst full
range loudspeaker for transduction to acoustic energy
30. A multi-channel audio system in accordance With
claim 28, further comprising ?fth transmitting circuitry for
transmitting said combined audio signal to a Woofer or
subWoofer loudspeaker for transduction to acoustic energy.
31. A multi-channel audio system in accordance With
37. A multi-channel audio system in accordance With
claim 23, further comprising
a ?rst high pass ?lter, for ?ltering one of said ?rst plurality
of channels to provide a ?rst high frequency audio
signal stream;
a second high pass ?lter, for ?ltering another of said ?rst
plurality of channels to provide a second high fre
quency audio signal stream;
a third high pass ?lter, for ?ltering one of said second
plurality of channels to provide a third high frequency
audio signal stream; and
a fourth high pass ?lter, for ?ltering another of said
second plurality of channels to provide a fourth high
frequency audio signal stream.
38. A multi-channel audio system in accordance With
claim 37, further comprising
?rst transmitting circuitry, for transmitting said ?rst high
frequency audio signal stream to a ?rst loudspeaker for
transduction to acoustic energy;
second transmitting circuitry, for transmitting said second
high frequency audio signal stream to a second loud
speaker for transduction to acoustic energy;
third transmitting circuitry, for transmitting said third high
frequency audio signal stream to a third loudspeaker for
transduction to acoustic energy;
fourth transmitting circuitry, for transmitting said fourth
claim 23, further comprising ?rst transmitting circuitry, for
high frequency audio signal stream to a fourth loud
speaker for transduction to acoustic energy;
transmitting said ?rst bass audio signal stream to a ?rst
?fth transmitting circuitry, for transmitting said ?rst bass
loudspeaker; second transmitting circuitry, for transmitting
speaker; and third transmitting circuitry, for transmitting
audio signal stream to said ?rst loudspeaker and said
second loudspeaker for transduction to acoustic energy;
and
said third bass audio signal stream to a third loudspeaker.
32. A multi-channel audio system in accordance With
sixth transmitting circuitry, for transmitting said second
said second bass audio signal stream to a second loud
claim 31, further comprising transmitting circuitry for trans
mitting said second audio signal stream to said third loud
speaker; combining circuitry, for combining said ?rst audio
signal stream With said bass audio signal streams to provide
a combined audio signal stream; and transmitting said
combined audio signal stream to said third loudspeaker.
33. A multi-channel audio system in accordance With
claim 32, Wherein said combining circuitry comprises a
scaler for scaling said ?rst audio signal stream and said third
bass signal stream.
bass audio signal stream to said third loudspeaker and
said fourth loudspeaker for transduction to acoustic
energy.
39. A multi-channel audio system in accordance With
claim 38, further comprising
seventh transmitting circuitry, for transmitting said third
bass audio signal stream to a Woofer or subWoofer
audio loudspeaker for transduction to acoustic energy.
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