Sample Freq Response Post ETF/Symetrix EQ

Discussion in 'Archived Threads 2001-2004' started by Guy Kuo, Oct 30, 2001.

  1. Guy Kuo

    Guy Kuo Supporting Actor

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    Here is a jpeg from ETF5 showing the low freq in room response of my SVS subs before equalization (orange) and after equalization (blue).
    [​IMG]
    You can see it tamed some nasty room mode peaks. I doubt I could have done it as neatly without the rapid graphic feedback of ETF or the precisely aimable bands of a parametric EQ.
    ------------------
    Guy Kuo
    www.ovationsw.com
    Ovation Software, the Home of AVIA DVD
    [Edited last by Guy Kuo on October 30, 2001 at 08:29 PM]
     
  2. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    Guy, this included repositioning of the subs and/or listening positions(mic positions) to some degree..yes?
    Usually, it's impossible to EQ out a severe null like that(if it's modal produced).
    TV
     
  3. Guy Kuo

    Guy Kuo Supporting Actor

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    Amazingly these both were taken today without moving anything. I was surprised at how well the nulls worked out. However, I did cheat a little and put in some broader boost in the valleys. I've also spent some time without any boost. Haven't had time to compare the two yet.
    [Edited last by Guy Kuo on October 30, 2001 at 08:36 PM]
     
  4. Guy Kuo

    Guy Kuo Supporting Actor

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    Here is what RPG's Room Optimizer predicted for the same positions in my room. You can see that it parallels the actual measured response pretty well - not exact but pretty good for just a software model.
    [​IMG]
     
  5. Kevin C Brown

    Kevin C Brown Producer

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    Guy- Nice job!
    I currently have a Behringer DSP-1100p and the AutoSounds test tone CD on the way. Hopefully I can approach the results you've gotten.
    I have to learn more about the RPG software you're using... [​IMG]
    ------------------
     
  6. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    Wow, that is interesting. the only drawback is if you have to boost 15dBs...you're killing the amp headroom [​IMG]
    It would be better to find a spot that has severe peaks than nulls...and then tame them with the EQ.
    TV
     
  7. Guy Kuo

    Guy Kuo Supporting Actor

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    Went back to doing it without any boosting - just cutting of peaks. Yes, it does allow more headroom. Definitely nicer despite the variations being about 5 dB from top to bottom. Still sounds a LOT more solid than without the EQ.
     
  8. StaceyS

    StaceyS Stunt Coordinator

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    Guy, which EQ are you using?
     
  9. Guy Kuo

    Guy Kuo Supporting Actor

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    I'm using the Symetrix 551E. It works quite well, but the pots are very very touchy. A little touch moves the center frequency a fair amount. That's not a problem if you can see the response in near real time, but would drive you nuts if one used a more tedious measurement method than the ETF program.
    ------------------
    Guy Kuo
    www.ovationsw.com
    Ovation Software, the Home of AVIA DVD
     
  10. StaceyS

    StaceyS Stunt Coordinator

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    I suppose if I would have read the title of the thread instead of just following the link, I might have known which eq. [​IMG] I think I have had one too many KK treats in the last 24 hours. Or perhaps it was the 2.5 hour wait in line.
     
  11. StaceyS

    StaceyS Stunt Coordinator

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    Guy, the ETF is 1/3 only, correct? Wouldn't this be less than optimal for sub measuring?
     
  12. Guy Kuo

    Guy Kuo Supporting Actor

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    If you have it in fractional octave mode, yes. In that mode you can actually set even finer resolution than 1/3 octave. The mode I had it in for the EQ work was not fractional octave but fines resolution. It's much more resolution than you'd need. If you put a 1/30 octave null on the EQ, the ETF program in low freq response mode shows it as a nice narrow notch in the measured response.
    ------------------
    Guy Kuo
    www.ovationsw.com
    Ovation Software, the Home of AVIA DVD
     
  13. Larry Newcomb

    Larry Newcomb Auditioning

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    Larry Newcomb
    Guy, even though there's already not enough hours in the day, you're getting me thinking about acquiring the ETF software.
    I looked at their website awhile back but couldn't get much of a feel for the utility of this software.
    A couple of quick questions:
    1) Do you need to use the preamp/calibrated microphone (for useful results)?
    2) Can I do this my "dragging" in my desktop (equipped with a Soundblaster Live Value card)?
    Thanks, Larry
     
  14. Guy Kuo

    Guy Kuo Supporting Actor

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    It doesn't help that there isn't a separate manual for the program. All the documentation is part of the program's on-line help. I'd recommend bringing it down and running it in demo mode. You'll get access to the manual. It's a pretty complex to operate but powerful program. It supplies a multitude of analysis and data gathering options. Go to their "demo room" on the website and it walks you through some examples of using the program to analyze and then correct a room. I'm still learning how to use the program myself.
    Haven't tried it with just a RS SPL meter as the microphone. I didn't want any extra things to worry about so I just went for the calibrated mic and preamp combo. Pricey but it's one less variable to be concerned about.
    I run it by dragging my desktop to the room and putting the desktop on the big screen. The program has an option for looping a channel back into the sound card for compensating and checking for sound card problems.
    All in all, its a nice piece that I'm still happy to have picked up.
    BTW how is the D50 doing?
    ------------------
    Guy Kuo
    www.ovationsw.com
    Ovation Software, the Home of AVIA DVD
     
  15. BruceD

    BruceD Screenwriter

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    I didn't do extensive comparisons between my RS SPL and my calibrated mic/preamp, but I did notice a few differences.
    Yes, the Soundblaster Live is even a recommended card that does full duplex (send and receive simultaneously) for the program.
    If you use an RS correction calibration file with the ETF program and the RS meter, I think your results should still be really good. Especially if you use it to evaluate options -like changing speaker positions, changing crossovers, changing bass volume levels, etc.
    Great thing about a PC with a soundcard and game port (MIDI) is that the BFD 1100P parametric EQ (connected to MIDI) and ETF can both be run on the PC screen at the same time and you can do parametric EQ on frequency graphs from the PC's screen in real time.
    The BFD 1100P also allows you to save different programs (sets of filters) for different purposes (10 different PGMs). For example you could have PGM1 for 2-channel, PGM2 for DD 5.1 and PGM3 for DTS all with different bass filter level settings.
    Bruce
    [Edited last by BruceD on November 01, 2001 at 11:01 AM]
    [Edited last by BruceD on November 01, 2001 at 11:06 AM]
     
  16. StaceyS

    StaceyS Stunt Coordinator

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    Guy,
    Have you used ETF to set phase and xover on the subs?
    Have you played with ETF and high-freq signals in combination with room treatment? It would be interesting to test with and without ceiling treatment.
     
  17. StephenMSmith

    StephenMSmith Stunt Coordinator

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    I use SpectraLabs for the same purpose as ETF, and found it absolutely invaluable for sub integration and then some. I tried the ETF demo but found SpectraLabs much easier to figure out even though it isn't dedicated to measuring room response like ETF, mainly because ETF assumes you understand what it's doing (which I didn't at the time) while SpectraLabs does not.
    I use SpectraLabs + AVIA's full range pink noise tracks to set x-over and level for my sub with much better results than using the sub level matching tones + SPL meter. My sub also has a continuously variable phase control, and I was astonished to see in SpectraLabs just how critical it is in integrating my sub with any of my other 5 speakers. It affects the much more than just the frequency band at the x-over point. As I rotate it through it's -180 to +180 range, I see peaks and valleys appear and disappear throughout the entire bass decade (possibly due mainly to my non-rectangluar room and speaker layout). I never got satisfactory sub integration when I was trying to adjust all this with just my ears and a SPL.
    Another bonus for SpectraLabs (and ETF maybe, I don't know) is being able to measure individual speaker time delays down to 1/10th of a microsecond. Using SpectrabLab's delay finder function in real time transfer mode with a large FFT, I've been able to time align all 5 of my speakers to within 1/10th ms of each other by making slight positioning changes to each speaker using SpectraLabs as my guide. Very cool!
    Steve
     
  18. Gary Thomas

    Gary Thomas Second Unit

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    Steve: Where can I find some info on SpectraLabs? I couldn't locate it w/ a web search.
     
  19. BruceD

    BruceD Screenwriter

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    I might be mistaken, but I think ETF is about half the cost of the Spectralabs software (ETF $150), if you purchase the software.
    ETF's functional capabilities are optimized for room/speaker integration, especially the capability of monitoring changes in the frequency graph in real-time as you "tweak" your system.
    Steve's quote:
    "Another bonus for SpectraLabs (and ETF maybe, I don't know) is being able to measure individual speaker time delays down to 1/10th of a microsecond."
    Answer: Yes, ETF also provides this function with resolution to 0.05 ms for measuring distance from speaker to microphone.
    Bruce
    [Edited last by BruceD on November 03, 2001 at 10:56 AM]
     
  20. StephenMSmith

    StephenMSmith Stunt Coordinator

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    You can download a free 30-day trial of SpectraLabs here: http://www.soundtechnology.com/download-center.htm .
    They also have a cheaper program called SpectraRTA, which has a simpler interface optimized for just that -- RTA.
    I didn't mean to imply that SpectraLabs is a better tool than ETF. I just found SpectraLabs easier to figure out for the purpose of dialing in my sub's phase, x-over, and level, which is all I wanted to do. ETF was clearly a featured-packed program intended for professional room analysis and correction using acoustic paneling, etc., which made it much harder for me (well, too hard for a newbie like me at the time) to figure out how to just use it more as an RTA for simpler tasks like sub integration.
    Steve
     

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