EP0546619A2 - Low frequency audio doubling and mixing circuit - Google Patents
Low frequency audio doubling and mixing circuit Download PDFInfo
- Publication number
- EP0546619A2 EP0546619A2 EP92203748A EP92203748A EP0546619A2 EP 0546619 A2 EP0546619 A2 EP 0546619A2 EP 92203748 A EP92203748 A EP 92203748A EP 92203748 A EP92203748 A EP 92203748A EP 0546619 A2 EP0546619 A2 EP 0546619A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- circuit
- low
- frequency
- low frequency
- signal
- 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.)
- Granted
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R5/00—Stereophonic arrangements
- H04R5/04—Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments
-
- 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
- H04R3/04—Circuits for transducers, loudspeakers or microphones for correcting frequency response
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04S—STEREOPHONIC SYSTEMS
- H04S1/00—Two-channel systems
Definitions
- the subject invention relates to the reproduction of audio signals through small-sized speakers.
- High fidelity reproduction of audio signals ideally requires sound transducers capable of reliably reproducing sounds throughout the listening range of human beings. This has been determined to be 20-20,000 Hz. However, realistically, most high fidelity speaker systems are capable of reproducing sounds in the frequency range of 40-20,000 Hz. These high fidelity speaker systems include small transducers (tweeters) for reproducing the high end of the frequency range, and relatively large transducers (woofers) for reproducing the low end of the frequency range. Naturally, these speaker systems are large in size and take up a substantial amount of space in the listening area.
- An object of the present invention is to augment the apparent bass reproduction of small-sized speaker systems without introducing distortion in the sound emanating therefrom.
- a circuit for doubling and mixing low frequency audio signals comprising input means for receiving an audio signal having a substantially wide frequency range, means coupled to said input means for separating signal components in a low frequency band of the audio signal from the wide frequency range thereof, means coupled to said separating means for doubling the frequencies of the signal components in said low frequency band, and means for mixing said frequency doubled signal components with said input audio signal, whereby said signal components in said low frequency band now also appear one octave higher.
- an electronically augmented stethoscope which includes a circuit for raising the audibility of inaudible sound by multiplying or doubling their frequencies.
- the Philips et al. circuit processes signals below 20 Hz., i.e. below the threshold of human hearing, and raise them to an audible level.
- the Philips et al. patent does not address the problem of inadequate speakers which are incapable of reproducing low frequency audio signals, albeit that these signals are already audible to human beings.
- a left channel of a stereo signal applied to input 10 passes through a low-pass filter 12 to one input of a full-wave rectifier 14.
- a right channel of the stereo signal applied to input 16 passes through a phase inverting low-pass filter 18 and is applied to another input of full-wave rectifier 14.
- the low-pass filters 12 and 18 are arranged to pass signals below the frequency of 100 Hz. while attenuating signals above this frequency at 6 dB/octave.
- the full-wave rectifier 14 combines the signals from the low-pass filters 12 and 18 and effectively doubles the frequency of the combined signals.
- the output from the full-wave rectifier 14 is applied to a narrow-band filter 22 having a pass-band of, for example, 100-200 Hz.
- the output from the narrow band filter 22 is applied through a resistor 24 to a left channel output 26, to which the left channel input 10 is connected by a resistor 28.
- the output from the narrow-band filter 22 is also applied through a resistor 30 to a right channel output 32, to which the right channel input 16 is connected by a resistor 34.
- the low frequency signal components in the left and right channels are separated from the main signals, combined and frequency doubled.
- the resultant signal is then frequency limited to a pass-band of, for example, 100-200 Hz. and is then recombined with the original left and right channel signals.
- FIG. 2 A practical embodiment of the circuit of the subject invention is shown in Fig. 2.
- the left input 10 is shown connected to ground via a resistor RI and, through the series arrangement of a capacitor CI and a resistor R2, to the left output 26, which is connected to ground by a resistor R3.
- the right input 16 is shown connected to ground via a resistor R4 and, via the series arrangement of a capacitor C2 and a resistor R5, to the right output 32, which is also connected to ground by a resistor R6.
- the left input is further connected, via the series arrangement of a capacitor C3 and a resistor R7, to the inverting input of amplifier Al, to which the right input 16 is also connected via the series arrangement of a capacitor C4 and a resistor R8.
- the inverting input of amplifier AI is connected to the output thereof by the parallel arrangement of a resistor R9 and a capacitor CS, which is, in turn, connected to the inverting input of amplifier A2 by a resistor R10, this inverting input of amplifier A2 being connected to the output thereof by a resistor RII.
- An 18 vdc supply is connected to ground via the series arrangement of a resistor R12 and the parallel arrangement of a capacitor C6 and a resistor R13, the junction JI between the resistor R13 and the parallel arrangement being coupled to the non-inverting inputs of amplifiers AI and A2.
- the output of amplifier AI is connected to the series arrangement of a capacitor C7 and a diode DI, the junction therebetween being connected to ground via a resistor R14 and to a B + voltage source (which may be the 18 vdc supply noted above) via a resistor R15.
- the output of amplifier A2 is connected to the series arrangement of a capacitor C8 and a diode D2, the junction therebetween being connected to ground via a resistor R16, and to the B + voltage source via a resistor R17.
- the purpose of resistors R15 and R17 is to bias the diodes DI and D2, respectively, into conduction so that a wider range of signal levels will be doubled by the full-wave rectifier, thus making the circuit more effective.
- the diodes DI and D2 are then interconnected and connected via the fixed resistance of a potentiometer PI and resistor R18 to ground.
- the slider of potentiometer PI is connected to a resistor R19 and then, on the one hand, through a resistor R20 to the non-inverting input of amplifier A3, and, on the other hand, through a capacitor C9, to the output of amplifier A3.
- the potentiometer PI is used to allow adjustment of the amount of doubled frequency signal level that one desires to be mixed in with the straight through signals depending on the size of the speakers used in a given application, since larger speakers, in general, require a lesser amount of doubled signal. It should be noted that these doubled signals may become obtrusive if present in too great an amount.
- the non-inverting input of amplifier A3 is also connected to ground via a capacitor C10 and via a resistor R21 to the junction JI.
- the inverting input of amplifier A3 is connected to the junction JI via a resistor R22 and to the output of amplifier A3 via a resistor R23.
- the output of amplifier A3 is connected to ground via the series arrangement of a capacitor CII, a resistor R24 and a further capacitor C12, the junction between the resistor R24 and the capacitor C12 being connected to the left and right outputs 26 and 32 via respective resistors R25 and R26.
- the components R7, R8, R9, C5 and AI form the low-pass filters 12 and 18, the components R14, R15, R16, R17, R18, DI, D2 and PI form the full-wave rectifier 14, and the components R19, R20, R22, R23, C9, C10 and A3 form the narrow-band filter 22.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Stereophonic System (AREA)
- Tone Control, Compression And Expansion, Limiting Amplitude (AREA)
- Circuit For Audible Band Transducer (AREA)
Abstract
Description
- The subject invention relates to the reproduction of audio signals through small-sized speakers.
- High fidelity reproduction of audio signals ideally requires sound transducers capable of reliably reproducing sounds throughout the listening range of human beings. This has been determined to be 20-20,000 Hz. However, realistically, most high fidelity speaker systems are capable of reproducing sounds in the frequency range of 40-20,000 Hz. These high fidelity speaker systems include small transducers (tweeters) for reproducing the high end of the frequency range, and relatively large transducers (woofers) for reproducing the low end of the frequency range. Naturally, these speaker systems are large in size and take up a substantial amount of space in the listening area.
- However, there are many consumers who enjoy high fidelity sound but do not have the space for a high fidelity system with large high fidelity speaker systems. Manufacturers recognizing this problem, have been marketing compact audio systems with small speaker systems for these consumers. However, in view of the relatively small size of the speaker systems, these small speaker systems are not capable of reproducing audio frequencies in the range of 40-100 Hz. The consumer using these compact audio systems are then able to notice this deficiency and are then disappointed with the system.
- This problem in small-sized speakers is not new and has been addressed in the past. In particular, in Radiotron Designer's Handbook, Sections 14.3, page 616 and 15.12, page 676 (1954), a circuit is proposed which applies two or more frequencies to a non-linear amplifier in which the output therefrom includes the sum and difference frequencies located about each of the higher input frequencies. If the lowest output frequencies are attenuated, it states that the sum and difference frequencies tend to create the acoustical impression of bass. Furthermore, it states "With more than two input frequencies the effect is even greater, so that fairly high distortion has the effect of apparently accentuating the bass." An alternate solution appearing in the above reference is to amplify a single tone with harmonics and then suppressing the fundamental frequency.
- An object of the present invention is to augment the apparent bass reproduction of small-sized speaker systems without introducing distortion in the sound emanating therefrom.
- The above object is achieved in a circuit for doubling and mixing low frequency audio signals comprising input means for receiving an audio signal having a substantially wide frequency range, means coupled to said input means for separating signal components in a low frequency band of the audio signal from the wide frequency range thereof, means coupled to said separating means for doubling the frequencies of the signal components in said low frequency band, and means for mixing said frequency doubled signal components with said input audio signal, whereby said signal components in said low frequency band now also appear one octave higher.
- In U.S. Patent 5,003,605 to Philips et al., an electronically augmented stethoscope is disclosed which includes a circuit for raising the audibility of inaudible sound by multiplying or doubling their frequencies. The Philips et al. circuit processes signals below 20 Hz., i.e. below the threshold of human hearing, and raise them to an audible level. However, with regard to the environment of the subject invention, the Philips et al. patent does not address the problem of inadequate speakers which are incapable of reproducing low frequency audio signals, albeit that these signals are already audible to human beings.
- With the above objects and advantages in mind as will hereinafter appear, the invention will be described with reference to the accompanying drawing, in which:
- Fig. 1 is a basic block diagram of the circuit of the subject invention; and
- Fig. 2 is a practical embodiment of the circuit of the subject invention.
- As shown in Fig. 1, a left channel of a stereo signal applied to
input 10, passes through a low-pass filter 12 to one input of a full-wave rectifier 14. A right channel of the stereo signal applied toinput 16, passes through a phase inverting low-pass filter 18 and is applied to another input of full-wave rectifier 14. The low-pass filters wave rectifier 14 combines the signals from the low-pass filters wave rectifier 14 is applied to a narrow-band filter 22 having a pass-band of, for example, 100-200 Hz. for eliminating any residual low and high frequency components. The output from thenarrow band filter 22 is applied through aresistor 24 to aleft channel output 26, to which theleft channel input 10 is connected by aresistor 28. Similarly, the output from the narrow-band filter 22 is also applied through aresistor 30 to aright channel output 32, to which theright channel input 16 is connected by a resistor 34. In operation, the low frequency signal components in the left and right channels are separated from the main signals, combined and frequency doubled. The resultant signal is then frequency limited to a pass-band of, for example, 100-200 Hz. and is then recombined with the original left and right channel signals. - A practical embodiment of the circuit of the subject invention is shown in Fig. 2. The
left input 10 is shown connected to ground via a resistor RI and, through the series arrangement of a capacitor CI and a resistor R2, to theleft output 26, which is connected to ground by a resistor R3. Similarly, theright input 16 is shown connected to ground via a resistor R4 and, via the series arrangement of a capacitor C2 and a resistor R5, to theright output 32, which is also connected to ground by a resistor R6. The left input is further connected, via the series arrangement of a capacitor C3 and a resistor R7, to the inverting input of amplifier Al, to which theright input 16 is also connected via the series arrangement of a capacitor C4 and a resistor R8. The inverting input of amplifier AI is connected to the output thereof by the parallel arrangement of a resistor R9 and a capacitor CS, which is, in turn, connected to the inverting input of amplifier A2 by a resistor R10, this inverting input of amplifier A2 being connected to the output thereof by a resistor RII. An 18 vdc supply is connected to ground via the series arrangement of a resistor R12 and the parallel arrangement of a capacitor C6 and a resistor R13, the junction JI between the resistor R13 and the parallel arrangement being coupled to the non-inverting inputs of amplifiers AI and A2. - The output of amplifier AI is connected to the series arrangement of a capacitor C7 and a diode DI, the junction therebetween being connected to ground via a resistor R14 and to a B + voltage source (which may be the 18 vdc supply noted above) via a resistor R15. Similarly, the output of amplifier A2 is connected to the series arrangement of a capacitor C8 and a diode D2, the junction therebetween being connected to ground via a resistor R16, and to the B + voltage source via a resistor R17. The purpose of resistors R15 and R17 is to bias the diodes DI and D2, respectively, into conduction so that a wider range of signal levels will be doubled by the full-wave rectifier, thus making the circuit more effective. The diodes DI and D2 are then interconnected and connected via the fixed resistance of a potentiometer PI and resistor R18 to ground. The slider of potentiometer PI is connected to a resistor R19 and then, on the one hand, through a resistor R20 to the non-inverting input of amplifier A3, and, on the other hand, through a capacitor C9, to the output of amplifier A3. The potentiometer PI is used to allow adjustment of the amount of doubled frequency signal level that one desires to be mixed in with the straight through signals depending on the size of the speakers used in a given application, since larger speakers, in general, require a lesser amount of doubled signal. It should be noted that these doubled signals may become obtrusive if present in too great an amount. The non-inverting input of amplifier A3 is also connected to ground via a capacitor C10 and via a resistor R21 to the junction JI. The inverting input of amplifier A3 is connected to the junction JI via a resistor R22 and to the output of amplifier A3 via a resistor R23. The output of amplifier A3 is connected to ground via the series arrangement of a capacitor CII, a resistor R24 and a further capacitor C12, the junction between the resistor R24 and the capacitor C12 being connected to the left and
right outputs - In the above embodiment, the components R7, R8, R9, C5 and AI form the low-
pass filters wave rectifier 14, and the components R19, R20, R22, R23, C9, C10 and A3 form the narrow-band filter 22. -
- Numerous alterations and modifications of the structure herein disclosed will present themselves to those skilled in the art. However, it is to be understood that the above described embodiment is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.
Claims (11)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US80535691A | 1991-12-09 | 1991-12-09 | |
US805356 | 1991-12-09 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0546619A2 true EP0546619A2 (en) | 1993-06-16 |
EP0546619A3 EP0546619A3 (en) | 1994-04-20 |
EP0546619B1 EP0546619B1 (en) | 1998-09-23 |
Family
ID=25191353
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19920203748 Expired - Lifetime EP0546619B1 (en) | 1991-12-09 | 1992-12-03 | Low frequency audio doubling and mixing circuit |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0546619B1 (en) |
JP (1) | JPH05328481A (en) |
DE (1) | DE69227091T2 (en) |
Cited By (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0637189A2 (en) * | 1993-07-27 | 1995-02-01 | Kabushiki Kaisha Toshiba | Audio signal processing circuit |
EP0729287A2 (en) * | 1995-02-27 | 1996-08-28 | Matsushita Electric Industrial Co., Ltd. | Low frequency audio conversion circuit |
WO1997042789A1 (en) * | 1996-05-08 | 1997-11-13 | Philips Electronics N.V. | Circuit, audio system and method for processing signals, and a harmonics generator |
WO1998006239A1 (en) * | 1996-08-06 | 1998-02-12 | Sample Rate Systems Oy | Setup in home theatre or other sound reproduction equipment |
WO1998046044A1 (en) * | 1997-04-04 | 1998-10-15 | K.S. Waves Ltd. | Apparatus and method for bass enhancement |
WO1999025151A1 (en) * | 1997-11-07 | 1999-05-20 | Koninklijke Philips Electronics N.V. | Audio system comprising audio signal processing circuit |
WO1999026454A1 (en) * | 1997-11-17 | 1999-05-27 | Srs Labs, Inc. | Low-frequency audio simulation system |
WO2000014998A1 (en) * | 1998-09-08 | 2000-03-16 | Koninklijke Philips Electronics N.V. | Means for bass enhancement in an audio system |
WO2000057673A1 (en) * | 1999-03-24 | 2000-09-28 | Koninklijke Philips Electronics N.V. | Band stop filter |
US6285767B1 (en) | 1998-09-04 | 2001-09-04 | Srs Labs, Inc. | Low-frequency audio enhancement system |
EP1168296A2 (en) * | 2000-05-30 | 2002-01-02 | Yamaha Corporation | Waveform signal generation method with pseudo low tone synthesis |
WO2003028405A1 (en) * | 2001-09-21 | 2003-04-03 | Siemens Aktiengesellschaft | Method and device for controlling the bass reproduction of audio signals in electroacoustic transducers |
US6678380B2 (en) | 1997-11-07 | 2004-01-13 | Koninklijke Philips Electronics N.V. | Audio system |
US6792119B1 (en) | 1997-05-05 | 2004-09-14 | Koninklijke Philips Electronics N.V. | Audio system |
WO2005027568A1 (en) * | 2003-09-16 | 2005-03-24 | Koninklijke Philips Electronics N.V. | Audio frequency range adaptation |
US7907736B2 (en) | 1999-10-04 | 2011-03-15 | Srs Labs, Inc. | Acoustic correction apparatus |
US7987281B2 (en) | 1999-12-10 | 2011-07-26 | Srs Labs, Inc. | System and method for enhanced streaming audio |
US8050434B1 (en) | 2006-12-21 | 2011-11-01 | Srs Labs, Inc. | Multi-channel audio enhancement system |
US9236842B2 (en) | 2011-12-27 | 2016-01-12 | Dts Llc | Bass enhancement system |
US9258664B2 (en) | 2013-05-23 | 2016-02-09 | Comhear, Inc. | Headphone audio enhancement system |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3710146A (en) * | 1970-07-09 | 1973-01-09 | Sony Corp | Frequency doubler circuit |
GB2153187A (en) * | 1984-01-20 | 1985-08-14 | Linn Prod Ltd | A method of processing audio information |
US4607381A (en) * | 1984-10-05 | 1986-08-19 | Sony Corporation | Signal mixing circuit |
US4734591A (en) * | 1985-04-26 | 1988-03-29 | Kabushiki Kaisha Toshiba | Frequency doubler |
-
1992
- 1992-12-03 EP EP19920203748 patent/EP0546619B1/en not_active Expired - Lifetime
- 1992-12-03 DE DE1992627091 patent/DE69227091T2/en not_active Expired - Fee Related
- 1992-12-07 JP JP4326729A patent/JPH05328481A/en active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3710146A (en) * | 1970-07-09 | 1973-01-09 | Sony Corp | Frequency doubler circuit |
GB2153187A (en) * | 1984-01-20 | 1985-08-14 | Linn Prod Ltd | A method of processing audio information |
US4607381A (en) * | 1984-10-05 | 1986-08-19 | Sony Corporation | Signal mixing circuit |
US4734591A (en) * | 1985-04-26 | 1988-03-29 | Kabushiki Kaisha Toshiba | Frequency doubler |
Cited By (37)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0637189A2 (en) * | 1993-07-27 | 1995-02-01 | Kabushiki Kaisha Toshiba | Audio signal processing circuit |
EP0637189A3 (en) * | 1993-07-27 | 1995-04-05 | Tokyo Shibaura Electric Co | Audio signal processing circuit. |
US5500622A (en) * | 1993-07-27 | 1996-03-19 | Kabushiki Kaisha Toshiba | Audio signal processing circuit |
EP0729287A2 (en) * | 1995-02-27 | 1996-08-28 | Matsushita Electric Industrial Co., Ltd. | Low frequency audio conversion circuit |
EP0729287A3 (en) * | 1995-02-27 | 2002-04-24 | Matsushita Electric Industrial Co., Ltd. | Low frequency audio conversion circuit |
US6111960A (en) * | 1996-05-08 | 2000-08-29 | U.S. Philips Corporation | Circuit, audio system and method for processing signals, and a harmonics generator |
USRE38822E1 (en) | 1996-05-08 | 2005-10-11 | Koninklijke Philips Electronics N.V. | Circuit, audio system and method for processing signals, and a harmonics generator |
WO1997042789A1 (en) * | 1996-05-08 | 1997-11-13 | Philips Electronics N.V. | Circuit, audio system and method for processing signals, and a harmonics generator |
US6332026B1 (en) | 1996-08-06 | 2001-12-18 | Flextronics Design Finland Oy | Bass management system for home theater equipment |
WO1998006239A1 (en) * | 1996-08-06 | 1998-02-12 | Sample Rate Systems Oy | Setup in home theatre or other sound reproduction equipment |
WO1998046044A1 (en) * | 1997-04-04 | 1998-10-15 | K.S. Waves Ltd. | Apparatus and method for bass enhancement |
US7054455B2 (en) | 1997-05-05 | 2006-05-30 | Koninklijke Philips Electronics N.V. | Audio system |
US6792119B1 (en) | 1997-05-05 | 2004-09-14 | Koninklijke Philips Electronics N.V. | Audio system |
WO1999025151A1 (en) * | 1997-11-07 | 1999-05-20 | Koninklijke Philips Electronics N.V. | Audio system comprising audio signal processing circuit |
US6678380B2 (en) | 1997-11-07 | 2004-01-13 | Koninklijke Philips Electronics N.V. | Audio system |
WO1999026454A1 (en) * | 1997-11-17 | 1999-05-27 | Srs Labs, Inc. | Low-frequency audio simulation system |
US6285767B1 (en) | 1998-09-04 | 2001-09-04 | Srs Labs, Inc. | Low-frequency audio enhancement system |
WO2000014998A1 (en) * | 1998-09-08 | 2000-03-16 | Koninklijke Philips Electronics N.V. | Means for bass enhancement in an audio system |
US6134330A (en) * | 1998-09-08 | 2000-10-17 | U.S. Philips Corporation | Ultra bass |
WO2000057673A1 (en) * | 1999-03-24 | 2000-09-28 | Koninklijke Philips Electronics N.V. | Band stop filter |
US7907736B2 (en) | 1999-10-04 | 2011-03-15 | Srs Labs, Inc. | Acoustic correction apparatus |
US7987281B2 (en) | 1999-12-10 | 2011-07-26 | Srs Labs, Inc. | System and method for enhanced streaming audio |
US8751028B2 (en) | 1999-12-10 | 2014-06-10 | Dts Llc | System and method for enhanced streaming audio |
US6756532B2 (en) | 2000-05-30 | 2004-06-29 | Yamaha Corporation | Waveform signal generation method with pseudo low tone synthesis |
EP1168296A3 (en) * | 2000-05-30 | 2003-08-20 | Yamaha Corporation | Waveform signal generation method with pseudo low tone synthesis |
EP1168296A2 (en) * | 2000-05-30 | 2002-01-02 | Yamaha Corporation | Waveform signal generation method with pseudo low tone synthesis |
US7574009B2 (en) | 2001-09-21 | 2009-08-11 | Roland Aubauer | Method and apparatus for controlling the reproduction in audio signals in electroacoustic converters |
WO2003028405A1 (en) * | 2001-09-21 | 2003-04-03 | Siemens Aktiengesellschaft | Method and device for controlling the bass reproduction of audio signals in electroacoustic transducers |
WO2005027568A1 (en) * | 2003-09-16 | 2005-03-24 | Koninklijke Philips Electronics N.V. | Audio frequency range adaptation |
US8050434B1 (en) | 2006-12-21 | 2011-11-01 | Srs Labs, Inc. | Multi-channel audio enhancement system |
US8509464B1 (en) | 2006-12-21 | 2013-08-13 | Dts Llc | Multi-channel audio enhancement system |
US9232312B2 (en) | 2006-12-21 | 2016-01-05 | Dts Llc | Multi-channel audio enhancement system |
US9236842B2 (en) | 2011-12-27 | 2016-01-12 | Dts Llc | Bass enhancement system |
US9712916B2 (en) | 2011-12-27 | 2017-07-18 | Dts Llc | Bass enhancement system |
US9258664B2 (en) | 2013-05-23 | 2016-02-09 | Comhear, Inc. | Headphone audio enhancement system |
US9866963B2 (en) | 2013-05-23 | 2018-01-09 | Comhear, Inc. | Headphone audio enhancement system |
US10284955B2 (en) | 2013-05-23 | 2019-05-07 | Comhear, Inc. | Headphone audio enhancement system |
Also Published As
Publication number | Publication date |
---|---|
DE69227091D1 (en) | 1998-10-29 |
DE69227091T2 (en) | 1999-05-20 |
JPH05328481A (en) | 1993-12-10 |
EP0546619B1 (en) | 1998-09-23 |
EP0546619A3 (en) | 1994-04-20 |
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