CA1229309A - Filter system - Google Patents
Filter systemInfo
- Publication number
- CA1229309A CA1229309A CA000470002A CA470002A CA1229309A CA 1229309 A CA1229309 A CA 1229309A CA 000470002 A CA000470002 A CA 000470002A CA 470002 A CA470002 A CA 470002A CA 1229309 A CA1229309 A CA 1229309A
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- CA
- Canada
- Prior art keywords
- channel
- unit
- output
- delay
- channels
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G5/00—Tone control or bandwidth control in amplifiers
- H03G5/02—Manually-operated control
- H03G5/025—Equalizers; Volume or gain control in limited frequency bands
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
- H04R3/12—Circuits for transducers, loudspeakers or microphones for distributing signals to two or more loudspeakers
- H04R3/14—Cross-over networks
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- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Otolaryngology (AREA)
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Filters That Use Time-Delay Elements (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A filter system for a plurality of channels, each pass-in a range of frequencies. A first delay is introduced into one of the channels and a second delay into another of the channels with the delay characteristics being selected so that the output of each channel is in phase with the output of each other channels and the sum of all the outputs being sub-stantially unitary in magnitude. The system is particularly applicable to loudspeaker systems.
A filter system for a plurality of channels, each pass-in a range of frequencies. A first delay is introduced into one of the channels and a second delay into another of the channels with the delay characteristics being selected so that the output of each channel is in phase with the output of each other channels and the sum of all the outputs being sub-stantially unitary in magnitude. The system is particularly applicable to loudspeaker systems.
Description
Sue FILTER SIESTA
This invention relates to filter networks for signal pro-cussing systems.
One application is in a loudspeaker soys em using two loud-speakers wherein there is often a difference in the time taken for sound from each loudspeaker to arrive at the ears of a listener. The special separation between the drivers in a loudspeaker system affect the radiation pattern over the ire-quench range where more than one driver contributes to the 10 total acoustic output.
BACKGROUND OF THE INVENTION
A proposal has been made to provide additional active delay networks to compensate for offsets in the acoustical planes from which the individual drivers radiate. A proposal 15 has also been made to provide cross-over networks and equalizers incorporating delay compensation for the distance traveled by sound from each loudspeaker. These proposals are particular-lye concerned with the acoustic section of the system and go in after the position of the loudspeakers has been determined.
The present invention is not concerned with the delays introduced due to the positioning of the loudspeakers in the system but is concerned with the delays which are introduced by the circuit components when a plurality of outputs are pro-voided in view of the number of loudspeakers used. It has been 25 discovered that inequalities may be introduced in the phase as well as variations in the amplitude output whereby the rest posse of the filter system did not yield a perfectly flat am-plotted response (within + or - 0.1 dub).
The above-mentioned inequalities are particularly pronounced 30 when more than a 2 way cross-over network is utilized.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved filter system in which the above-mentioned inequalities are obviated or substantially reduced, According to the present invention there is provided a filter system comprising at least three channels, each channel being adapted to pass a selected range of frequencies, a first I
delay means connected in one of said channels and a second delay means connected in another of said channels, the delay characteristics of said first and second delay means being selected whereby the output of each channel is in phase with the output of each other channel, the sum of all said outputs being substantially unitary in magnitude.
DESCRIPTION OF TEE DRAWINGS
One embodiment of the invention will now be described by way of example, with reference to the accompanying drawings in which:
Figure 1 is a block schematic representation of an embodiment of the invention which provides four outputs, and Figure 2 is a more detailed diagrammatic representation of the embodiment of Figure 1.
DESCRIPTION OF ONE EMBODIMENT
.. .. . ... _ Referring to Figure 1, two input lines 2 and 4 are connected through Radio Frequency Interference (R.F.I.) filter unit 6 to the input lines of an input signal conditioner unit 8.
pa The output of the signal conditioner unit 8 is fed to a delay equalizer unit 10 as well as to a delay equalizer unit 12. A further delay equalizer unit 16 has its input connected to the output of unit 12 whilst the output of unit 10 is connected to one terminal 38 of a three-terminal jumper unit 62. The second terminal 40 provides a non-delayed line from the output of the unit 8 whilst the third terminal 42 is shown as being "jumped" to terminal 38. Terminal 42 is connect ted to the input of the delay equalizer unit 14 in a first channel and is also connected to a high pass filter unit 20 in a second channel. The function of the jumpers is to pro-vise two, three or four frequency channels (bands). In Figure 1, the jumper units are shown connected for four-way operation with all the delay units utilized.
The first channel also includes a delay equalizer unit 14, a jumper unit I and a low pass filter unit 18 having an output connected to the first output channel terminal 30.
~2;~3~
The second channel includes the further high pass filter unit 20, and a low pass filter unit I The output of filter 22 is connected to a first terminal of a jumper unit 66, a second terminal facilitating a direct connection to the output of high pass filter unit 20 and a third terminal 54 providing an output connection to the second channel's output terminal 32.
The output of delay equalizer unit 12 is connected to the input of a high pass filter unit 24 in a third channel and the delay equalizer unit 16 in a fourth channel.
Ire output of high pass filter unit 24 passes through a low pass filter unit 26, to a first terminal 56 of a jumper unit 68 having a second terminal 58 facilitating a direct connection to the output of high pass filter 24. A third lo terminal 60 of jumper unit 61 is connected to the third channel output terminal 34.
The output of delay equalizer unit 16 in the fourth channel is connected through high pass filter unit 28 to the fourth channel's output terminal 36.
A summing amplifier unit 70 is connected to the output of each of the four channels, as shown in Figure 1 to verify the flatness of the summed response at test point 72.
In Figure 1, the delay equalizer units are identified by the word DELAY whilst the low pass and high pass filter US are identified by the word LOW or HIGH respectively.
Letters A, B, and C have been applied to the units of Figure 1. By a suitable combination of the units, one can achieve equality of the phase response of all channels, for example:
For four-way r there should always be a unit A, a unit B, and a unit C in each channel;
For three-way, there should be a unit A and a unit B;
For five-way, A B + C + a further unit.
The different delay v. frequency characteristics of units A, B, and C are identical, whether they arise from a delay unit low pass filter or a high pass filter. The total delay of any one channel is the sum of A B + C, all channels being identical.
~Z293~3 In Figure 2, the units of Figure l are shown in greater detail.
The same reference numerals are used in Figure l as have been applied to the corresponding units in Figure 2.
Referring to Figures 1 and 2, in use, an input signal is applied across lines 2 and 4 and after passing through the R.F.I. filter 6, it is applied to the input signal conditioner unit 8. The signal is then applied to a delay equalizer unit 10 in the first channel as well as to a delay equalizer unit 12 for the third and fourth channels. These delay equalizer units are of flat magnitude response and constitute a phase filter which is an all-pass network. The unit lo in the first channel is followed by another unit 14 constituting a delay equalizer of flat magnitude response and forming a second phase filter in the first channel These are followed in the first channel by the low-pass filter unit 18.
The low-pass filter unit 18 constitutes an amplitude filter which is an all-pass type, as a result of the cascading of two end order Butter worth filters to yield a 24db per okay ; low-pass filter.
In combination with a second order all-pass delay equalizer having identical phase response to that of the cascaded second order Butter worth filters one achieves the advantages of the described embodiment of the invention.
s will be seen, delay equalizer unit lo is common to the second channel, as well as the first channel, whilst the second channel also includes high-pass filter unit 20 followed by low-pass filter unit 22, which latter is similar to the low-pass filter unit 18. The high-pass filter unit 20 also constitutes an amplitude (magnitude) filter of an all-pass type which is achieved by the cascading of two end order Butter worth filters to yield a 24db per octave high-pass filter.
This is followed by the low-pass filter unit 22.
The phase filter comprising the delay equalizer unit 12 is common to the third and fourth channels and, in the third ~22~3~,~i9 channel is followed by a high-pass filter unit and a low-pass filter unit, as shown in the Figures.
In the fourth channel a phase filter, constituting delay equalizer unit 16 follows the delay equalizer unit 12 5 and is succeeded by an amplitude (magnitude) filter comprising high-pass filter unit 28.
It will be seen that the illustrated circuit is a multi-way crossover filter network and it does have a unique property in that all outputs, at terminals 30, 32, 34 and 36 are sub-10 staunchly in phase at all frequencies, whether the circuit misarranged as a 2-way, 3-way or 4-way crossover network, or even if more terminal outputs are provided by circuit extension to 5-way or more, whilst at the same time maintaining a high degree of out of band attenuation of 24db per octave. This 15 "equality" of phase is accomplished concurrently with a well defined amplitude response whereby a direct sum of all the out-puts of the multi-way filter system yields a perfectly flat amplitude response (within + or - 0.ldb).
As shown, the circuit consists of two basic elements which are the amplitude (or magnitude) filter and the phase filter. The linking of these two filters in a complimentary fashion appears to give rise to the uniqueness of the illustrated circuit and the advantages thereof.
In previous circuits the cascading of low-pass and high-25 pass sections to form band pass sections required for more thin crossovers gives a band pass output which is no longer in phase with the low-pass or high-pass outputs, since these are only made up of single section (i.e. frequency filters.
The described embodiment in Figures 1 and 2, overcomes this 30 limitation by ensuring that all filter bands in a multi-way crossover system have the same total delay (and thus phase) as a function of frequency, whether a single band uses one, two or more filter sections in cascade, by adding delay equalizers which have identical delay vs. frequency kirk-35 teristics to those of filter sections of a given frequency not included in any one band. As an illustration, a 3-way crossover system would use a single low-pass section of ~.2~3~
frequency Fly for the first band, and then a cascade of high-pass section of frequency Fly and a low-pass section of frequency F2 for the end band, and finally a high-pass section of frequency F2 for the last band. The illustrated circuit 5 adds a delay equalizer to the first band so as to compensate for the inherent added delay of the low-pass filter section of frequency F2 of the end band, and thus brings the outputs of both the sty and end bands (channels in phase at all frequent ales. The expansion to the next band (channel 3) and to larger lo systems is then apparent.
A mathematical proof of the phase "equality" and flat summed magnitude response of the illustrated circuit is as follows for a 3-way crossover system. The proofs are of a similar form for other multi-way systems or for other filter 15 response types.
~2~3~
_ Best c Cowan on .
Band 1: dot a (F2) *l opus (Fly ) Eland 2: h i gh--pass t F 1 ) *1 opus ( F2 ) Eland 3: dot a (Fly ) phi gh--pass (F2) Where F1 F2 art thief crossover frequencies.
Residency unctions ox the bus c blocks.
s= j w wow Dælay(F1) S - I S
H ( s ) Delphi) Ho -- So I
Lopez tFl ) S r So S J
Low-pass OF ) I, Ho r _ AL .
us L Sly Hi gh--pass ( F 1 H I) = I 5 S + Lo High-pass(F2) 2 - Jo 30H~s) -- r 1 s L 7LS We I
Phase responses Del a OF 1 ) Lopez F 1 ) r L
- Hi gh--pass t F 1 ) lo L I. -Delphi) , L 3 Lopez ~F2) Hi gh--p~ss (F2) pa It may be observed that the delay sections have the aye phase responses as thy f i 1 ton sect Ought of the sap frequency tF1 or F7), whether the filters be high or Lopez.
This i 5 fundamental to the circuit Boeing described.
Lowry tune response 5 Delay fly ) Del a ~F2) G AYE ) _ I
Low-pass (Fly ) I, f Pi I Z
Lopez ~F2) 5 t I) =
This invention relates to filter networks for signal pro-cussing systems.
One application is in a loudspeaker soys em using two loud-speakers wherein there is often a difference in the time taken for sound from each loudspeaker to arrive at the ears of a listener. The special separation between the drivers in a loudspeaker system affect the radiation pattern over the ire-quench range where more than one driver contributes to the 10 total acoustic output.
BACKGROUND OF THE INVENTION
A proposal has been made to provide additional active delay networks to compensate for offsets in the acoustical planes from which the individual drivers radiate. A proposal 15 has also been made to provide cross-over networks and equalizers incorporating delay compensation for the distance traveled by sound from each loudspeaker. These proposals are particular-lye concerned with the acoustic section of the system and go in after the position of the loudspeakers has been determined.
The present invention is not concerned with the delays introduced due to the positioning of the loudspeakers in the system but is concerned with the delays which are introduced by the circuit components when a plurality of outputs are pro-voided in view of the number of loudspeakers used. It has been 25 discovered that inequalities may be introduced in the phase as well as variations in the amplitude output whereby the rest posse of the filter system did not yield a perfectly flat am-plotted response (within + or - 0.1 dub).
The above-mentioned inequalities are particularly pronounced 30 when more than a 2 way cross-over network is utilized.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved filter system in which the above-mentioned inequalities are obviated or substantially reduced, According to the present invention there is provided a filter system comprising at least three channels, each channel being adapted to pass a selected range of frequencies, a first I
delay means connected in one of said channels and a second delay means connected in another of said channels, the delay characteristics of said first and second delay means being selected whereby the output of each channel is in phase with the output of each other channel, the sum of all said outputs being substantially unitary in magnitude.
DESCRIPTION OF TEE DRAWINGS
One embodiment of the invention will now be described by way of example, with reference to the accompanying drawings in which:
Figure 1 is a block schematic representation of an embodiment of the invention which provides four outputs, and Figure 2 is a more detailed diagrammatic representation of the embodiment of Figure 1.
DESCRIPTION OF ONE EMBODIMENT
.. .. . ... _ Referring to Figure 1, two input lines 2 and 4 are connected through Radio Frequency Interference (R.F.I.) filter unit 6 to the input lines of an input signal conditioner unit 8.
pa The output of the signal conditioner unit 8 is fed to a delay equalizer unit 10 as well as to a delay equalizer unit 12. A further delay equalizer unit 16 has its input connected to the output of unit 12 whilst the output of unit 10 is connected to one terminal 38 of a three-terminal jumper unit 62. The second terminal 40 provides a non-delayed line from the output of the unit 8 whilst the third terminal 42 is shown as being "jumped" to terminal 38. Terminal 42 is connect ted to the input of the delay equalizer unit 14 in a first channel and is also connected to a high pass filter unit 20 in a second channel. The function of the jumpers is to pro-vise two, three or four frequency channels (bands). In Figure 1, the jumper units are shown connected for four-way operation with all the delay units utilized.
The first channel also includes a delay equalizer unit 14, a jumper unit I and a low pass filter unit 18 having an output connected to the first output channel terminal 30.
~2;~3~
The second channel includes the further high pass filter unit 20, and a low pass filter unit I The output of filter 22 is connected to a first terminal of a jumper unit 66, a second terminal facilitating a direct connection to the output of high pass filter unit 20 and a third terminal 54 providing an output connection to the second channel's output terminal 32.
The output of delay equalizer unit 12 is connected to the input of a high pass filter unit 24 in a third channel and the delay equalizer unit 16 in a fourth channel.
Ire output of high pass filter unit 24 passes through a low pass filter unit 26, to a first terminal 56 of a jumper unit 68 having a second terminal 58 facilitating a direct connection to the output of high pass filter 24. A third lo terminal 60 of jumper unit 61 is connected to the third channel output terminal 34.
The output of delay equalizer unit 16 in the fourth channel is connected through high pass filter unit 28 to the fourth channel's output terminal 36.
A summing amplifier unit 70 is connected to the output of each of the four channels, as shown in Figure 1 to verify the flatness of the summed response at test point 72.
In Figure 1, the delay equalizer units are identified by the word DELAY whilst the low pass and high pass filter US are identified by the word LOW or HIGH respectively.
Letters A, B, and C have been applied to the units of Figure 1. By a suitable combination of the units, one can achieve equality of the phase response of all channels, for example:
For four-way r there should always be a unit A, a unit B, and a unit C in each channel;
For three-way, there should be a unit A and a unit B;
For five-way, A B + C + a further unit.
The different delay v. frequency characteristics of units A, B, and C are identical, whether they arise from a delay unit low pass filter or a high pass filter. The total delay of any one channel is the sum of A B + C, all channels being identical.
~Z293~3 In Figure 2, the units of Figure l are shown in greater detail.
The same reference numerals are used in Figure l as have been applied to the corresponding units in Figure 2.
Referring to Figures 1 and 2, in use, an input signal is applied across lines 2 and 4 and after passing through the R.F.I. filter 6, it is applied to the input signal conditioner unit 8. The signal is then applied to a delay equalizer unit 10 in the first channel as well as to a delay equalizer unit 12 for the third and fourth channels. These delay equalizer units are of flat magnitude response and constitute a phase filter which is an all-pass network. The unit lo in the first channel is followed by another unit 14 constituting a delay equalizer of flat magnitude response and forming a second phase filter in the first channel These are followed in the first channel by the low-pass filter unit 18.
The low-pass filter unit 18 constitutes an amplitude filter which is an all-pass type, as a result of the cascading of two end order Butter worth filters to yield a 24db per okay ; low-pass filter.
In combination with a second order all-pass delay equalizer having identical phase response to that of the cascaded second order Butter worth filters one achieves the advantages of the described embodiment of the invention.
s will be seen, delay equalizer unit lo is common to the second channel, as well as the first channel, whilst the second channel also includes high-pass filter unit 20 followed by low-pass filter unit 22, which latter is similar to the low-pass filter unit 18. The high-pass filter unit 20 also constitutes an amplitude (magnitude) filter of an all-pass type which is achieved by the cascading of two end order Butter worth filters to yield a 24db per octave high-pass filter.
This is followed by the low-pass filter unit 22.
The phase filter comprising the delay equalizer unit 12 is common to the third and fourth channels and, in the third ~22~3~,~i9 channel is followed by a high-pass filter unit and a low-pass filter unit, as shown in the Figures.
In the fourth channel a phase filter, constituting delay equalizer unit 16 follows the delay equalizer unit 12 5 and is succeeded by an amplitude (magnitude) filter comprising high-pass filter unit 28.
It will be seen that the illustrated circuit is a multi-way crossover filter network and it does have a unique property in that all outputs, at terminals 30, 32, 34 and 36 are sub-10 staunchly in phase at all frequencies, whether the circuit misarranged as a 2-way, 3-way or 4-way crossover network, or even if more terminal outputs are provided by circuit extension to 5-way or more, whilst at the same time maintaining a high degree of out of band attenuation of 24db per octave. This 15 "equality" of phase is accomplished concurrently with a well defined amplitude response whereby a direct sum of all the out-puts of the multi-way filter system yields a perfectly flat amplitude response (within + or - 0.ldb).
As shown, the circuit consists of two basic elements which are the amplitude (or magnitude) filter and the phase filter. The linking of these two filters in a complimentary fashion appears to give rise to the uniqueness of the illustrated circuit and the advantages thereof.
In previous circuits the cascading of low-pass and high-25 pass sections to form band pass sections required for more thin crossovers gives a band pass output which is no longer in phase with the low-pass or high-pass outputs, since these are only made up of single section (i.e. frequency filters.
The described embodiment in Figures 1 and 2, overcomes this 30 limitation by ensuring that all filter bands in a multi-way crossover system have the same total delay (and thus phase) as a function of frequency, whether a single band uses one, two or more filter sections in cascade, by adding delay equalizers which have identical delay vs. frequency kirk-35 teristics to those of filter sections of a given frequency not included in any one band. As an illustration, a 3-way crossover system would use a single low-pass section of ~.2~3~
frequency Fly for the first band, and then a cascade of high-pass section of frequency Fly and a low-pass section of frequency F2 for the end band, and finally a high-pass section of frequency F2 for the last band. The illustrated circuit 5 adds a delay equalizer to the first band so as to compensate for the inherent added delay of the low-pass filter section of frequency F2 of the end band, and thus brings the outputs of both the sty and end bands (channels in phase at all frequent ales. The expansion to the next band (channel 3) and to larger lo systems is then apparent.
A mathematical proof of the phase "equality" and flat summed magnitude response of the illustrated circuit is as follows for a 3-way crossover system. The proofs are of a similar form for other multi-way systems or for other filter 15 response types.
~2~3~
_ Best c Cowan on .
Band 1: dot a (F2) *l opus (Fly ) Eland 2: h i gh--pass t F 1 ) *1 opus ( F2 ) Eland 3: dot a (Fly ) phi gh--pass (F2) Where F1 F2 art thief crossover frequencies.
Residency unctions ox the bus c blocks.
s= j w wow Dælay(F1) S - I S
H ( s ) Delphi) Ho -- So I
Lopez tFl ) S r So S J
Low-pass OF ) I, Ho r _ AL .
us L Sly Hi gh--pass ( F 1 H I) = I 5 S + Lo High-pass(F2) 2 - Jo 30H~s) -- r 1 s L 7LS We I
Phase responses Del a OF 1 ) Lopez F 1 ) r L
- Hi gh--pass t F 1 ) lo L I. -Delphi) , L 3 Lopez ~F2) Hi gh--p~ss (F2) pa It may be observed that the delay sections have the aye phase responses as thy f i 1 ton sect Ought of the sap frequency tF1 or F7), whether the filters be high or Lopez.
This i 5 fundamental to the circuit Boeing described.
Lowry tune response 5 Delay fly ) Del a ~F2) G AYE ) _ I
Low-pass (Fly ) I, f Pi I Z
Lopez ~F2) 5 t I) =
2 ",~ to So ., I
g Hi gh--pas~; fly ) of , 3 Hi gyps tF2) Y
6 (pa) = , Comb nod resDclnses ED
Band 1 H < S ) =
I AL S + I LO 2~LS t' ) Eland 2 S So sty fly )LS~L~2~J
Band I y Jo H US) = S ( S
(S ~rL~S~ 4~,L)(S~ )z.S~z) I Cobb noted phase rosins End 1 ] lo}
land 2 AL AL
Andy 3 Lo AL aye e v L
The combined phase responses art found to be identical for all bands and thus the cruiser filter stem Avis toe stated characteristic of phase 'ec~ualit~, of all outputs (bands ) .
Summed r en con so ( s ) _ ( 5 w, S Lo 2 So f ~"~ r y Y
) f Jo Y AL
A summed magnitude response, GO is obtained which for any realistic set of frequencies has an amplitude flatness of + or - 0.ldb.
In the illustrated embodiment each channel may include a four pole filter and each delay means may be a two pole delay means.
It Jill also be understood that the invention is equally applicable to higher numbers of channels (bands), for example five, six, or ten channels, by appropriate extension of the basic configuration.
It will be seen from the above discussion that a specific set of properties, i.e. phase and magnitude response, may be obtained using the descried circuit. One obvious use for the circuit is as a loudspeaker active cross-over network, but it will be understood that the invention is not restricted thereto and the circuit could readily find use in other signal processing applications.
It will be readily apparent to a person swilled in the art that a number of variations and modifications can be made without departing from the true spirit of the invention which will now be pointed out in the appended claims.
US
g Hi gh--pas~; fly ) of , 3 Hi gyps tF2) Y
6 (pa) = , Comb nod resDclnses ED
Band 1 H < S ) =
I AL S + I LO 2~LS t' ) Eland 2 S So sty fly )LS~L~2~J
Band I y Jo H US) = S ( S
(S ~rL~S~ 4~,L)(S~ )z.S~z) I Cobb noted phase rosins End 1 ] lo}
land 2 AL AL
Andy 3 Lo AL aye e v L
The combined phase responses art found to be identical for all bands and thus the cruiser filter stem Avis toe stated characteristic of phase 'ec~ualit~, of all outputs (bands ) .
Summed r en con so ( s ) _ ( 5 w, S Lo 2 So f ~"~ r y Y
) f Jo Y AL
A summed magnitude response, GO is obtained which for any realistic set of frequencies has an amplitude flatness of + or - 0.ldb.
In the illustrated embodiment each channel may include a four pole filter and each delay means may be a two pole delay means.
It Jill also be understood that the invention is equally applicable to higher numbers of channels (bands), for example five, six, or ten channels, by appropriate extension of the basic configuration.
It will be seen from the above discussion that a specific set of properties, i.e. phase and magnitude response, may be obtained using the descried circuit. One obvious use for the circuit is as a loudspeaker active cross-over network, but it will be understood that the invention is not restricted thereto and the circuit could readily find use in other signal processing applications.
It will be readily apparent to a person swilled in the art that a number of variations and modifications can be made without departing from the true spirit of the invention which will now be pointed out in the appended claims.
US
Claims (6)
1. A filter system comprising at least three channels, each channel being adapted to pass a selected range of fxequencies, a first delay means connected in one of said channels and a second delay means connected in another of said channels, the delay characteristics of said first and second delay means being selected whereby the output of each channel is in phase with the output of each other channel, the sum of all said outputs being substantially unitary in magnitude.
2. A loudspeaker filter system comprising at least three channels, each channel being adapted to pass a selected range of frequencies, a first delay means connected in one of said channels and a second delay means connected in another of said channels, the delay characteristics of said first and second delay means being selected whereby the output of each channel is in phase with the output of each other channel, the sum of all said outputs being substantially unitary in magnitude.
3. A loudspeaker filter system according to Claim 2 comprising three channels, two of said channels having delay means therein and the third channel having no delay means therein.
4. A loudspeaker filter system according to Claim 2 wherein each channel has a delay means therein.
5. A loudspeaker filter system according to Claim 2 wherein each channel includes a four pole filter and each delay means is a two pole delay means.
6. A loudspeaker filter system comprising:
(a) a first input line connected through a first cross over filter unit to one input of an input signal conditioner unit, (b) a second input line connected through a second cross-over filter unit to another input of an input signal conditioner unit, (c) the output of an input signal conditioner unit being connected to the input of a first deIay equalizer unit and the input of a second delay equalizer unit, (d) the output of said first delay equalizer unit being connectable to the input of a first output channel and a second output channel, (e) said first output channel including a third equalizer unit and a first low-pass filter unit connected in series, f) said second output channel including a first high-pass filter unit and a second low-pass filter unit connectable in series, (g) the output of said second delay equalizer unit being connected to the input of a third output channel and the input of a fourth output channel, (h) said third output channel including a second high-pass filter unit and a third low-pass filter unit connectable in series, (i) the fourth output channel including a fourth delay equalizer unit and a third high-pass filter unit connected in series, (j) the output of each output channel being con-nected to a summation amplifier to facilitate verification of the flatness of the summed response of said four channels, (k) each delay equalizer unit comprising an all-pass network of flat magnitude response, and (l) said low and high-pass filter units each comprising a pair of cascaded second order Butterworth filters.
(a) a first input line connected through a first cross over filter unit to one input of an input signal conditioner unit, (b) a second input line connected through a second cross-over filter unit to another input of an input signal conditioner unit, (c) the output of an input signal conditioner unit being connected to the input of a first deIay equalizer unit and the input of a second delay equalizer unit, (d) the output of said first delay equalizer unit being connectable to the input of a first output channel and a second output channel, (e) said first output channel including a third equalizer unit and a first low-pass filter unit connected in series, f) said second output channel including a first high-pass filter unit and a second low-pass filter unit connectable in series, (g) the output of said second delay equalizer unit being connected to the input of a third output channel and the input of a fourth output channel, (h) said third output channel including a second high-pass filter unit and a third low-pass filter unit connectable in series, (i) the fourth output channel including a fourth delay equalizer unit and a third high-pass filter unit connected in series, (j) the output of each output channel being con-nected to a summation amplifier to facilitate verification of the flatness of the summed response of said four channels, (k) each delay equalizer unit comprising an all-pass network of flat magnitude response, and (l) said low and high-pass filter units each comprising a pair of cascaded second order Butterworth filters.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000470002A CA1229309A (en) | 1984-12-13 | 1984-12-13 | Filter system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000470002A CA1229309A (en) | 1984-12-13 | 1984-12-13 | Filter system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1229309A true CA1229309A (en) | 1987-11-17 |
Family
ID=4129373
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000470002A Expired CA1229309A (en) | 1984-12-13 | 1984-12-13 | Filter system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1229309A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1494504A2 (en) * | 2003-07-04 | 2005-01-05 | Pioneer Corporation | Audio data processing device, audio data processing method, program for the same, and recording medium for the program recorded therein |
-
1984
- 1984-12-13 CA CA000470002A patent/CA1229309A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1494504A2 (en) * | 2003-07-04 | 2005-01-05 | Pioneer Corporation | Audio data processing device, audio data processing method, program for the same, and recording medium for the program recorded therein |
| EP1494504A3 (en) * | 2003-07-04 | 2006-02-08 | Pioneer Corporation | Audio data processing device, audio data processing method, program for the same, and recording medium for the program recorded therein |
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