MultEQ vs other equalization methods?

How is MultEQ different from other equalization methods?

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    Chris Kyriakakis

    There are two fundamental differences from every other method available in AV receivers today. The first is that MultEQ is not based on parametric equalization. Parametric equalization relies on a few bands that are centered at certain frequencies. These bands do not provide sufficient resolution to address many room acoustical problems. Also, parametric bands tend to interact so that changes at one frequency have undesirable results at nearby frequencies. Moreover, parametric equalization methods use a particular type of digital filter called Infinite Impulse Response (IIR) that only attempts to correct the magnitude response in the frequency domain. These filters can cause unwanted effects, such as ringing or smearing, in the time domain particularly as the bands get narrower. MultEQ uses Finite Impulse Response (FIR) filters for equalization that use several hundred coefficients to achieve much higher resolution in the frequency domain than parametric bands.  Furthermore, by their nature, FIR filters simultaneously provide correction in the frequency and time domains. FIR filters had been considered to require too many computational resources. But Audyssey solved this problem by using a special frequency scale that allocates more power to the lower frequencies where it is needed the most.

    The second major difference is that MultEQ combines multiple measurements to create equalization filters that better represent the acoustical problems in the room. Most other methods only perform a single point measurement and this can result in making other locations in the room sound worse than before equalization. There are some methods that use spatial averaging to combine multiple room measurements. Although this is a step above single-point correction, it does not provide optimum correction when discussing spatial averaging. For example, it is common to find a peak at a certain frequency in one location and a dip at the same frequency at another nearby location. The averaging methods will add the peak and the dip and this will result in an apparent flat response at that frequency, thus causing the equalization filter to take no action. MultEQ uses a clustering method to combine measurements so that acoustical problems are better represented, thus allowing the equalization filter to perform the appropriate correction at each location.

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    Arif Hussain

    Hello Chris: I hear many great things about Audyssey and would like to purchase a receiver with one of your solutions built in. However I have one caveat. I need to be able to Post EQ the sound from all speakers after they have been calibrated by Audyssey. I have this ability in the Pioneer MCACC. But since Audyssey may be a superior solution, I am inclined to jump ship, as long as I can tweak the EQ settings with the Audyssey Filters online.

    Please advise if this is possible and with what product.

    Thanks,

    Arif

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    Chris Kyriakakis

    Hi Arif,

    It is possible to make manual changes to the target curves using the Audyssey Pro software kit.  The Audyssey Pro software can talk to all installer-ready products.  You can find a list of these here.

     

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    Arif Hussain

    Thanks Chris!

    How can I read up on how the Pro software works, what GUI it uses and if I can tweak it like a graphic/ parametric or paragraphic EQ. Is the software part of the package with these products or needs o be downloaded separately? Can an advanced home enthusiats do it or does it need to be done by an installer only?

     

    best,

    Arif

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    Chris Kyriakakis

    Hi Arif,

    The software is part of the Audyssey Pro kit that is sold separately.  However, we also sell it to enthusiasts who want to experiment on their own.  There is no graphic or parametric EQ in MultEQ.  The correction and adjustment is done using multi-thousand tap time-domain FIR filters.  The adjustment is done using a graphic editor that allows you to draw the desired frequency response on your PC screen.

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    michalis

    hi chris,

    is there any chance to see a new audyssey pro eq system in the near future?

    best regards

    Michalis

     

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    Chris Kyriakakis

    Hi Michael,

    No plans at this time...

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    michalis

    hi Chris,

     

    i am hearing very good things about anthem's arc.

    you think that multi eq xt32 is better?

     

    best regards

     

    Michalis

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    Chris Kyriakakis

    I prefer not to comment on technologies from other companies.  Even though many in the audio industry do it freely, I find it unprofessional to do so.  I hope you understand.

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    michalis

    thank you for your answer.

    my main reason that i will prefer multi eq xt32 is that you answer to our problems almost instantly, something that you cannot find it anywhere else.

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    Peter Tischman

    I've seen some people attempt to verify what Audyssey is doing by using more conventional measurement methods like RTAs or FFT swept sine measurements.  Is there correlation between these methods and Audyssey?  Can Audyssey's EQ be verified by any other measurements?

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    Chris Kyriakakis

    Hi Peter,

    It's usually tough to match results with different methods because they don't have the IP used by Audyssey.  However, reasonable results for verification can be achieved if:

    1. You have a calibrated microphone (i.e. a file used by the measurement program)

    2. You take multiple measurements (in the same locations used when calibrating with Audyssey)

    3. You use an FFT method to find the impulse response of each measured position (RTA only looks at magnitude and ignores time so it doesn't match at all)

    4. You average the multiple measurements to come up with a representation of the listening area response.

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