Equalization using TrueRTA software

Discussion in 'Speakers & Subwoofers' started by Jud, Apr 14, 2003.

  1. Jud

    Jud Extra

    Joined:
    Feb 1, 2003
    Messages:
    22
    Likes Received:
    0
    Trophy Points:
    0
    I just picked up a BFD the other day, and have been doing experiments to try to equalize my sub (SVS 20-39PC+). I did a search to see if I could find any software that could make this task easier, and found out about TrueRTA (www.trueaudio.com). They've got a free download, but the free version doesn't have the resolution I would need.

    I was wondering if anyone has used one of the full versions of this software, and if it was helpful in equalizing your setup.
     
  2. I have the pro version, and it is rather helpfull [​IMG]

    For the room, you can probably get away with the 1/12th octave version.

    To measure, I use the Wallin Pre-ampII and a panasonic WM-61A mic capsule.
     
  3. VinhT

    VinhT Second Unit

    Joined:
    Feb 14, 2002
    Messages:
    357
    Likes Received:
    0
    Trophy Points:
    0
    I went ahead and purchased the complete version of TrueRTA, and it has proved to be an excellent tool for use with the BFD. It is much faster and more accurate than doing test tones by hand.

    Here's my 25-31PC+ response as an example:
    (warning, very large files, may not display correctly in IE)

    Tuned to 16Hz, with subsonic filter at 16Hz
    http://filebox.vt.edu/users/vitran/s... d%20ss16.jpg

    To remove that hump around 14Hz, I switched the subsonic filter to 25Hz
    http://filebox.vt.edu/users/vitran/s... d%20ss25.jpg

    Ta da! Flat to ~14Hz, +/- 2dB! [​IMG] Here's a 1/24th octave view.
    http://filebox.vt.edu/users/vitran/s... fd%20ss25.jpg

    TrueRTA makes it ridiculously easy to work with the BFD because you can see the effects of changes immediately. I highly recommend it.
     
  4. Jud

    Jud Extra

    Joined:
    Feb 1, 2003
    Messages:
    22
    Likes Received:
    0
    Trophy Points:
    0
    I'm almost ready to go ahead and order, but I have one more question: has anyone used TrueRTA with the Rat Shack SPL meter as a microphone? If so, what settings did you use on the meter?

    I suppose I can go out and buy a different mic, but why not use the one I've alread got?
     
  5. Vinh, is that with the quick sweep, or averaged pinknoise?
     
  6. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Jud,

    You can use the RS SPL meter with the ETF5 acoustic measurement software ETF5.

    They also provide a free demo version and a whole lot of tutorial information with a demo room model.

    Highly recommended.
     
  7. Jud

    Jud Extra

    Joined:
    Feb 1, 2003
    Messages:
    22
    Likes Received:
    0
    Trophy Points:
    0
    Well, I got impatient and bought the full version of TrueRTA. And the verdict is . . .

    . . . whoa, did that make equalization easy! I went from way out of whack to ruler flat to nice house curve in about 30 minutes. No burning test tones, no excel spreadsheets, no mind-numbing lists of numbers. Just the 1/24th octave spectrum analyzer and the averaged pink noise.

    Oh, and the Rat Shack SPL mic worked perfectly fine. I can't get absolute SPL measurements, but that's no big deal. Actually, I probably could get them if I had a voltmeter to do some calibration, but the relative SPL is all I need for now.
     
  8. VinhT

    VinhT Second Unit

    Joined:
    Feb 14, 2002
    Messages:
    357
    Likes Received:
    0
    Trophy Points:
    0
    Anthony, I used the quick sweep. Should I have used the pink noise instead? Thankfully, I can redo everything in about 10 minutes if necessary.

    Jud, I used the Radio Shack analog SPL meter on a tripod with corrections.
     
  9. Jud

    Jud Extra

    Joined:
    Feb 1, 2003
    Messages:
    22
    Likes Received:
    0
    Trophy Points:
    0
    Vinh, either the pink noise or sweep is okay, but I found the averaged pink noise to be the most beneficial. It allowed me, for instance, to play with the phase dial on my SVS and see in real-time how it affected frequency response. The ideal phase setting for me ended up being rather narrow, and it's unlikely I would have found it without TrueRTA. Likewise with the BFD I could adjust a filter and see the change in response as soon as I saved the changes.

    For pink noise, set the speed tradeoff to slow for best low-end accuracy. I used 10 averages, but you might want more or fewer depending on how long you want the graph to "catch up" to your new settings. I just played around a bit until I got it to do what I wanted.
     
  10. VinhT

    VinhT Second Unit

    Joined:
    Feb 14, 2002
    Messages:
    357
    Likes Received:
    0
    Trophy Points:
    0
    Jud, that's cool, I never thought about actually utilizing the real-time analyzer feature of TrueRTA. [​IMG] That makes things even easier!

    (I'm not a total idiot though! I use the RTA function for car audio equalization, but for some reason it never occurred to me to use it for home theater as well.)
     
  11. I remember reading somewhere that the RS SPL meter couldn't be used with spectasoft with the faster sweeps. The meter wouldn't respond fast enough. The quick sweep is VERY fast, and I wonder if (if the above statement is true)your results are "smoothed" artificially.
     

Share This Page