HELP SAVE HOME AUDIO - This application from Creative Labs seeks to patent the general idea of a self-calibrating audio systems! Help narrow US patent applications before they become patents.... HERE!

QUESTION - Have you seen anything that was published before Dec, 2010 that discusses:

  1. Determining physical features around speakers and calibrating at least one of the speakers; where
  2. Physical features are determined by sending a test signal from the speaker and calibrating the speakers based on the test signal

If so, please submit evidence of prior art as an answer to this question. Only one piece of prior art per answer below. We welcome multiple answers from the same individual

HINT - Haven’t self-calibrating speaker systems or networks been around for a while? Did Dynaudio AIR do this? Can you help find evidence that Dynaudio AIR or any other system did this prior to Dec 2010?


Summary: [Translated from Legalish into English] A method for calibrating multi-speaker audio system wherein an audio test signal is sent from a speaker and the test signal is used to measure a physical features of the speaker. This physical feature (for example, volume) is used to calibrate the speaker.

  • Publication Number: US 20130051572 A1
  • Assignee: Creative Labs, Inc.
  • Prior Art Date: Seeking prior Art predating December, 2010

Claim 1 requires each and every step below:

A calibration method for calibrating a variable number of speakers, the method comprising: 1. Determining physical features around a location of each of the variable number of speakers and calibrating at least one of the variable number of speakers;

  1. Wherein the physical features around a location of each of the variable number of speakers are determinable by:

  2. Transmitting an instruction signal, the instruction signal being transmittable from a device which is indicative of listener location;

  3. Communicating a test signal based on the instruction signal, the test signal being communicable from at least one of the variable number of speakers to the device; and

  4. Receiving and processing the test signal by the device in a manner so as to produce calibration signals, and
  5. Wherein the calibration signals are communicable from the device to at least one of the variable number of speakers so as to calibrate at least one of the variable number of speakers.

In English this means:

A method for calibrating audio speakers; 1. Determining physical features of the audio speakers using an audio test signal from at least one of the speakers; 2. Using the physical features which have been determined to calibrate at least one of the speakers.

Good prior art would be evidence of a system that did each and every one of these steps prior to the Dec, 2010.

You're probably aware of ten pieces of art that meet this criteria already - haven’t self-calibrating speaker systems or networks been around for a while? Did Dynaudio AIR do this? Can you help find evidence that Dynaudio AIR or any other system did this prior to Dec 2010?

The method of self-calibrating speaker systems from the Applicant

What is good prior art? Please see our FAQ.

Want to help? Please vote or comment on submissions below. We welcome you to post your own request for prior art on other questionable US Patent Applications.

  • This question appeared to be a discussion about a specific invention and was closed. However, I believe the question is actually a prior-art-request for US20130051572, which is a docketed application waiting for review by USPTO. Re-opened the question and reformatted it as a prior-art-request. This process involved substantial revision to the original text. I don't believe I changed the meaning but FEEL FREE to edit this if the question no longer reflects the the intent of the questioner. Thanks for participating in Ask Patents! Jun 20, 2013 at 1:04

24 Answers 24


Audyssey Laboratories has a technology called MultEQ that they've been integrating into home and professional theaters for several years. Not sure if that's exactly what you're looking for.

  • 2
    My 3-year-old Dennon receiver uses this. You plug in your speakers and a microphone, hit "calibrate" and it blasts test signals out, listening for room acoustics. Jul 22, 2013 at 15:56
  • Audyssey timeline shows that they started partnering with major receiver producers in 2004 and 2005. So speaker calibration became mainstream then. Research into this area was started in 1996 by Audyssey. Jul 23, 2013 at 11:13

Published in 2001:

"A multi-channel surround sound system and method is described that allows automatic and independent calibration and adjustment of the frequency, amplitude and time response of each channel of the surround sound system."



My Onkyo TX-SR506 which I purchased in 2007 has this feature:


See "First Time Setup" on page 36:

"With the supplied calibrated microphone, Audyssey 2EQ automatically determines the number of speakers connected, their size for purposes of bass management, optimum crossover frequencies to the subwoofer (if present), and distances from the primary listening position. Audyssey 2EQ then removes the distortion caused by room acoustics by capturing room acoustical problems over the listening area in both the frequency and time domain. The result is clear, well-balanced sound for everyone. Enabling Audyssey 2EQ allows you to also use Audyssey Dynamic EQ, which maintains the proper octave-to-octave balance at any volume level."

  • 1
    The TX-SR506 manual is copyright 2008 which should be good enough but, The TX-SR604 manual (see below) has a copyright of 2006. It is the same technology overall though.
    – James
    Jul 22, 2013 at 18:00

Genelec are offering this technology under the name of "AutoCal"; There's a human-readable explanation on a subpage on the Genelec website [1]. The product is mentioned in at least two press releases before December 2010 [2][3]. Also, on Youtube there is a video explaining the usage of their AutoCal System, which also clearly predates December 2010 [4]


I purchased an Onkyo TX-SR604 in 2007 with an Auto Calibration feature called "Audyssey 2EQ".

It did require an external microphone be attached, and the calibration to be initiated.


Official Users Manual with original Copyright Year of 2006 http://filedepot.onkyousa.com/Files/own_manuals/TX-SR604_674_En.pdf?CFID=2679429 Page 38 Starts the description of Auto Calibration.


To me this sounds like Digital Room Correction (DRC), which is commonly used to calibrate for speakers and/or the room. My reading of the claim is that "determining physical features" refers to determining acoustic properties (i.e. the impulse response) of the room around the speakers.

Digital Room Correction is a vast field. But to name one product that fits the bill, how about Juice Audiolens. There is an introduction here that steps through the whole process of capturing and calibrating a speaker system: (see navagation links on the left)


Juice Audiolens has been around since before 2010. For example here is an editorial mentioning a review for version 3.0 in 2008: http://www.anandtech.com/show/2677


John Eargle at JBL published a white paper about Room Mode Correction in 2003 http://www.jblpro.com/BackOffice/ProductAttachments/White%20Papers.pdf


B&O Beolab 5 did this in 2005:

Product page: http://www.bang-olufsen.com/da/sound/loudspeakers/beolab-5

Audio Critic review which explains how the Beolab 5 works in detail: http://theaudiocritic.com/plog/index.php?op=ViewArticle&articleId=34&blogId=1


DEQX is another example of this technology. They have been around since at least 2004 and they are different from some of the above as they process the signal between the preamp and amp. The claim gets a little confusing when and where the correction is done.



The Pioneer VSX-AX5Ai-S receiver released 2003 had auto surround sound setup via microphone. Page 13 of the manual issued 01/07/2003:

If setting up your surround sound speakers seems like it's going to be an involved task you only need to use this quick, automatic method, known as the MCACC system, to achieve good surround sound. You'll need to hook up the microphone so that the receiver can hear and judge the distance, size, sound character and sound pressure level of the speakers and thus know what settings to make.

In 2004 the updated VSX-AX5Ai-S could also display the audio calibration data with the Advanced MCACC PC Display Software.


I recall seeing a Pioneer in-car head unit offer automated calibration the late 1990s, however I can't find the original item.

However, there's a similar one from Blaupunkt mentioned in 2001. http://forums.anandtech.com/showpost.php?p=2015498&postcount=13

They use a microphone attached to the receiver in order to handle the automatic calibration.


My Sony DVD player w/ surround sound also does this. I've had it for more than 3 years, and the prior year's model also did this.


Several Bose home theater systems use "ADAPTiQ". A person wears a special headset with a microphone and sits in one of various room locations, then the system generates a series of tones from each speaker that is received by the user's microphone and adjustments are made to the speaker response. This has been around for a decade or so. It was in the Lifestyle 28 system, available since 2002 or so.

http://www.bose.com/popup/tech_details/pop_adaptiq_page2.jsp http://en.wikipedia.org/wiki/Bose_5.1_home_entertainment_systems#AdaptIQ


Project Athena of the Canadian Audio Research Consortium, did research and prototyping of dynamic room correction for loudspeakers back around 1992. Floyd Toole, Peter Schuck, Marc Bonneville, Sean Olive, Eric Verrault et al. Consortium members included PSB, Bryston, Paradigm and others.


Behringer has similar features in their ultra-drive pro, which has been out for at least 5, if not 10 years.

Essentially connect a microphone and it automatically corrects for phasing, equalization, and delay to the microphone using test signals.

DAK Industries was selling an equalizer - the BSR EQ-3000 back in the mid 80's with a condenser mike. The Equalizer would provide a pink noise source and then automatically adjust the equalization to match based on what was heard by the condenser microphone.


the att merlin pbx phone system did this in the 80's. You pushed a button, and the merlin phone on your desk made an escalating set of beeps in ever higher pitch, to calibrate the speakerphone. I'd bet that att has a patent on this, as merlin was designed in the shadows, if not during, divestiture.

Look for a manual for the att merlin bis in 88 or therebouts.

  • I believe that was to calibrate the room, not the speakers. Some echo canceling systems did that rather than adapt from the voice's output.
    – George White
    Jul 25, 2013 at 21:45


How does the ADAPTiQ audio calibration system work?

  1. Measures The system evaluates your room's acoustics.

  2. Adjusts Then it automatically customizes the sound to fit your room.

  3. Optimizes You enjoy performance customized to your room.


Not sure when this was first used, but here's some folks discussing it back in 2004



The IEEE Transactions on Speech and Audio Processing paper "Position Calibration of Microphones and Loudspeakers in Distributed" Computing Platforms by Raykar, Kozintsev and Lienhart describes the same technique in a very slightly different, more general context of a group of laptops in a room.



The JBL MSC1 Monitor System Controller with Room Mode Correction has done this prior to 2011. http://www.jblpro.com/MSC1/MSC1_Overview.html

The JBL LSR4300 has the Room Mode Correction feature and has been shipping prior to 2008. The following spec sheet is dated 2008. http://www.jblpro.com/BackOffice/ProductAttachments/LSR4300brochurelow.pdf

This spec sheet is Copyright 2006 with the Room Mode Correction. http://www.jblpro.com/BackOffice/ProductAttachments/LSR4312SP[1].pdf


As User4816 points our above for AT&T phones, Avaya analog phones do this too. The 8410, for example, manual says "When you reset the speakerphone on your voice terminal, you hear a set of tones as the speakerphone performs an acoustic test of the environment. When the tones stop, your speakerphone has finished adjusting itself for optimal performance and is ready for use."


The manual is dated June 1997.


Automatic corrective loudspeaker equalization has been available in the professional audio industry since at least 1989 from Peavey Electronics Corporation. Here is a manual for a product called the CEQ 28.


The CEQ 28 is a stand alone single channel equalizer that is microprocessor controlled. You can connect a microphone to this device and have it automatically equalize the loudspeaker's response in the room according to the room's environment. The method to do this is described on page 19 of the above PDF.

Also, the original dbx DriveRack PA provided a similar feature in the early 2000's, but I have been unable to find a date when it was introduced.


The EQ1 (or if the spelling is "EQ One", who know after all these years) AFAIK did this back in 1985/86. Maybe less automatic, but still the same.

It's not like this claimed "invention" allows both gain response curves and sub-microsecond delays on every frequency from 20 to 40kHz - that would potentially be an invention, but as I have now listed it here, it's forever prior art.

This "patent" seems to be more like a crappy auto-EQ any moron with a mic, sampler, DSP (or even just an A/D) and a 2 day course in BASIC could do. Maybe 2 days experience with BASIC is too much.


Meyer Sound has been doing self-calibrating speakers since introducing SpeakerSense in the 70s. http://www.meyersound.com/products/technology/

e.g. Loudspeaker System with Feedback Control for Improved Bandwidth and Distortion Reduction US Patent: 6,584,204


This technology has been on the market since at least 2007 from multiple vendors. Yamaha calls it YPAO.

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