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Thread: Testing room/speaker acoustics

  1. #21
    oferab Guest

    Default Re: Testing room/speaker acoustics

    I use Audio Precision MLS measurement to measure the frequency response of the speaker, you can eliminate the reflection problem using this system, and if you have a anechoic room, you can also measure low frequencies

  2. #22
    Join Date
    Jan 2006
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    4,265

    Default Re: Testing room/speaker acoustics

    That's an extremely expensive system! I think you'll find that LOG CHIRP (a sort of swept sine) is more useful in reflective environments than windowed MLS. You do not need an anechoic room to measure the low frequencies: you can use a stitched near-field measurement if you are very careful.

    MLS doesn't really put enough energy into the low frequencies to get a truly reliable/believable result in my experience but the AP kit is very fine indeed for amplifier measurement.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  3. #23
    Join Date
    Sep 2007
    Location
    United Kingdom
    Posts
    34

    Default Re: Brass instruments - very difficult to reproduce ....

    Quote Originally Posted by Alan Shaw
    You can not chemically remove the taste of peat from whisky; it is bound up into the fabric of the final experience.
    Very true but sadly they are still finding ways to add the peaty taste that so many of us love with additives.
    If they can find a way to ruin perfection for sound commercial reasons they will.

    Just as an aside what is your favoured malt ? Mine is Aardbeg the original 10 year old but I know it is a little too idiosyncratic for some.

  4. #24
    Join Date
    Sep 2009
    Location
    Malaysia
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    508

    Default REW Room Analyzer - help needed

    Hi everyone and especially to Alan,

    This is my first attempt using REW and not sure if I have done it correctly. I used a SPL meter and also a small condenser mic used to setup my Onyko AV but found the waterfall plot didn't reflect what I hear in the room. The bass in my listening room is sufficient but the waterfall plot shows it is lacking. I suspect I didn't calibrate the sound card correctly or there could be software error in not compensating for the C or A weighting. There is slight error in the reading around 50Hz which is due to the air cond hum like noise.

    Any help is greatly appreciated. I tried at REW forum but so far no response.

    Thanks in advance.
    ST





  5. #25
    Join Date
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    Default

    OK I'm just passing by.

    First, and I'm not criticising you please understand, what do you think those pretty charts are actually saying to you, the reader? Before we can even begin to interpret them as science we have to understand why they are not just attractive pictures.

    What are they attempting to convey? Or specifically, why have you been persuaded to invest your valuable time and money in this measurement system as opposed to any other? What convinced you of its merits? Why not just trust your ears as you have before? I really like the colours of the top chart - would make a great wall-picture!

    P.S. Don't forget what we said here about reporting and influencing!
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  6. #26
    Join Date
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    Default Retitled: REW Analyzer - Criticism and Sarcasm needed

    Quote Originally Posted by A.S. View Post
    ....First, and I'm not criticising you please understand...
    ...... I really like the colours of the top chart - would make a great wall-picture!
    There goes whatever hope of getting any help about those pretty pictures.

    ST

  7. #27
    Join Date
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    Default

    Would you mind giving me a decent answer to my entirely reasonable question if you don't mind? I really don't have the time to waste on sarcasm.

    I am not here to sell or advise on third party room correction systems and whatever input I care to make deserves a proper answer. If you are unable to advise us here on how you interpret those graphs, as you have experienced from the manufacturers themselves, you can't expect me to do all the thinking.

    But I do like those colours very much. They remind me of a pull-up poster we designed and still sometimes use at exhibitions.
    Attached Images Attached Images
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  8. #28
    Join Date
    Jan 2010
    Location
    Canada
    Posts
    30

    Default Interpretation of plots

    Hi ST,

    Probably better suited you ask in the REW forum (google it). Two things I can think of off the top of my head:is your mic calibrated to account for bias it may be introducing? Same applies to the sound card. Next you should minimize ambient noise such as you a/c unit as it introduces further bias.

    To Alan's question what this plot will identify (in theory) are room modes whereby certain frequencies will appear as peaks and nulls depending on how your speaker interacts with the room. In my case I have a 80hz peak in my room (resonant freq.) and I could probably benefit by adding some additional absorption or by repositioning my speakers. Either way you don't need to rely on a plot to tell you if something doesn't sound right, try experimenting with the above suggestions and see if that helps.

  9. #29
    Join Date
    Jan 2014
    Location
    England
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    15

    Default Room measurement - essential for adjusting for the best sound

    This is my process for testing room and speaker acoustics.

    First I measure with software and microphone to get a reasonably accurate picture. Then I use test tones and my ears to finish. Then I check with music.

    I use REW (Room EQ Wizard), a free software, and a microphone (Behringer ECM8000), along with suitable associated gear. REW does take some setting up and learning.

    I place the microphone (m/f) exactly where each of my ears will be when listening. For measuring the left speaker, the m/f is placed where the left ear will be. REW plays what's called a 'logarithmically swept sine signal' through the chosen speaker (it sounds like a sliding whistle). As a result it can generate various charts of controllable detail (smoothness), including a full frequency response and waterfall plot.

    For finding the best speaker and ear positions, I only use 30-500Hz plots and am looking for the smoothest response; that is fewest peaks and dips. However even the best location will leave some problems. The object is to minimise them (I tame the worst peaks later with an equaliser). The dips I have, which look awful on the charts, do not seem to have an impact on the sound. This illustrates a key point; these charts are only a guide to getting good sound. For getting the best sound for you, you must use your ears.

    Microphones don't hear like your ears. For one thing your ears hear differently as you age, or suffer hearing damage. For another our ears (or rather our brain) can differentiate sounds. Microphones pick up everything. Indeed in my room I couldn't rely on measurements of 50Hz and below because of background noise (from traffic and other things I presume which I hardly notice. REW can measure background noise).

    To finish off the measurements then, I use test tones and my ears. I play a full run of 1/3 octave test tones and write down how they compare with each other. I did this for both speakers at the same time. I then adjust my equaliser and repeat. In this way if you have a weakness in hearing this should cover it. I can't hear much above 10kHz, and 6.3 and 8kHz require a 4dB boost to be level with other frequencies.

    Then I play music. I found that a very few tracks were boomy with some bass and, using test tones which go from 10-300Hz in steps of 1Hz, which I got from here:

    http://realtraps.com/test-cd.htm

    I found that 42 and 43Hz had peaks. I was able to knock these down with my equaliser. Incidentally with these test tones I found the large dips had no effect on the sound. Perhaps they are so narrow as to have little effect.

    I'm not saying that all this has resulted in the world's best listening experience, but what it has done is improve what I hear from my system. It took me some eight months to get to what I have now. I found there were two speaker and ear locations in my room that gave the best measurements. These corresponded to roughly 'the thirds' and 'the fifths' - speakers and ears one third or one fifth in from each wall and ears the same from the back wall. After a four month trial I found 'the thirds', whilst interesting for three dimensional sound, never seemed quite right. Either this was because I hadn't done it right, or because the Red Book CDs I play - mostly studio recordings - just didn't offer the right information. So now I use 'the fifths' for a wider but shallower soundstage, and that's what I prefer.

    Room measurement is complicated but I consider it essential for adjusting speaker and listening positions. Ultimately it must be based on what you hear and how the music sounds to you.

  10. #30
    Join Date
    Apr 2011
    Location
    Germany
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    82

    Default Where?

    Quote Originally Posted by A.S. View Post
    You may be interested in our User Group thread on room acoustics: http://www.harbeth.co.uk/usergroup/showthread.php?t=257
    >>>If you want to see the process in action, become a tester for the streamed a/v from my very own listening room - see the thread in Misc. - you'll see how I do it, live<<<

    Sorry, I can't find the two threads. Could anybody give me a working link?

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