BFD sub EQ... Mains/all speakers on with sub?

Discussion in 'Speakers' started by Glenn Baumann, Jul 28, 2003.

  1. Glenn Baumann

    Glenn Baumann Stunt Coordinator

    Mar 31, 1999
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    I would like to use a Behringer Feedback Destroyer to EQ my subwoofers in room response and I have a question. From some of the threads I have searched I have come to the general conclusion... that ultimately, I should probably be EQ'ing the sub along with the main speakers on as the mains also contribute to the overall SPL output that I am taming, is this correct?
    Secondly, I was wondering if maybe I should run my sine wave test tones while I am running not only the left/right front speakers in my receivers stereo mode but maybe I should be running ALL the speakers via Pro Logic mode so as the center, surrounds and mains ALL contibute to the overall SPL output I am charting! Is this logic correct?

  2. Kevin C Brown

    Kevin C Brown Producer

    Aug 3, 2000
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    Here's how I did it:

    Sub by itself 1st. Makes sure that I'm getting any improvement at all.

    Then I test with the sub and mains on. Make sure that the sub and mains are in phase. Compare with the eq on and off. The difference will be less because you have the mains running *with* the sub.

    Personally, I never did it with all the speakers, because I consider the mains most important (80% music, 20% HT). But it wouldn't be a bad idea to test it with DPL or maybe a 5 (6, or 7) channel stereo mode.

    I actually tried a high quality analog eq on my mains (Symetrix 552E). (Vs the BFD which is a cheap digital eq. [​IMG] ) I could never get eq'ed sub + eq'ed main to be as flat as eq'ed sub plus normal mains. I tried for a couple of days, and I was even using my PC with which makes the process very fast. Something to think about, but maybe you'd have more luck...
  3. MingL

    MingL Stunt Coordinator

    Mar 26, 2003
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    This is how my EQ-ing is done.

    I tend to EQ with solely the sub alone first. I usually concentrate on freq less than 60hz during this initial try. I'd do a slow sine sweep to chart the response to the sub alone. I'd then use white noise to verify the response. This step is so as to have an idea as to what kind of frequency response the sub has on its own.

    I would then proceed with sub and mains on in stereo mode. With mains set to small and all bass to sub, I'd run the same sine sweep from 10hz to 200hz (or more) to plot the response. Focus is on getting the phasing and sub level right this time round. I'd like to compare the freq response of sub alone, the fronts alone and both sub and mains to see whats happening. Usually, a smooth transition from mains to sub with little change in apparent loudness (both on charting and hearing) works for me. Remember to add in a house curve to get things to sound right.

    The final step is to pop in Avia and to get all the speaker channels to be calibrated towards the front L/R.

    For some reason, I don't like to calibrate in PL mode. I believe the steering logic may screw up the calibration process, thou I've not gotten round to identifying what can go wrong if calibrating in PL mode.

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