Subwoofer EQ questions

Discussion in 'Speakers & Subwoofers' started by Rick Cohen, Apr 25, 2004.

  1. Rick Cohen

    Rick Cohen Agent

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    Should the sub be flat or near flat with the mains in or out? How should the phase be setup when the phase can really impact the overall output combination? THIS IS GETTING COMPLICATED! [​IMG]

    I recently worked through the EQ on my sub. When I did the EQ it was done with stereo test tones. My mains were on with the sub. I achieved a pretty flat curve. On a lark I turned the mains off and rechecked. I get significantly different results with mains in or out. I had the mains crossed at 90Hz and set to small.

    The mains are JBL L-100s with 12 inch woofers and usable output down to 25Hz. The sub is an SVS PB2+ tuned at 20HZ. I checked the mains alone with the sub off but still set to small. With the crossover set to 90Hz there is apparently still output down to 40 - 50Hz since the crossover is a slope. I also set the mains to large and found I liked the less localized sound with bass all around rather than tied to the sub.

    Not all DVDs operate all speakers at once so should the EQ be optimized with all speakers in or to handle the output of the sub alone?

    THANKS FOR YOUR THOUGHTS RICK [​IMG]
     
  2. GrahamT

    GrahamT Supporting Actor

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    I have been at the same point you are now. My solution was to plot with the sub and mains together, the sub at different phase positions and compare the plots. I tried to pick the phase position with the flattest response. This was the same process with mains set to small or large.

    Next I identified where I wanted to add EQ filters. I started at the bottom, and replotted after ever filter. It takes a long time, I have spent over 20 hours with phase, positioning and eqing. The results are worth it. You definitely want to plot the mains and sub together.
     
  3. Rick Cohen

    Rick Cohen Agent

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    Graham,

    Thanks for the reply. I have done the plot with the two together and with the sub alone. I did get a fairly flat response following EQ with them together. At times on a DVD they will not play together like with LFE on a DTS DVD. At that point it seems like the curve will be screwed up and no longer flat since the deep base will not go to the sub??

    Do you have your mains crossed out high or low or set to full?

    RICK
     
  4. GrahamT

    GrahamT Supporting Actor

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    I have a Behringer Feedback destroyer($120 US)so I made two programs. I use two sets of test tones and try and take the averages. I made one program for music, 2CH large with sub. Then a HT program all speakers small(100hz). So I just change the program and the sub stays pretty flat.

    I dont go crazy with the filters, I just take out the big humps and try to fill in the small nulls a little. I also put in a small house curve. It is about 9 dB higher at 25 Hz than at 100 Hz
     
  5. Rick Cohen

    Rick Cohen Agent

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    Graham,

    I am using an ART 351 and have the option of either a dB setting or 6dB setting. I am using it in a similar fashion with the 12dB set up being used to create a really flat curve with the mains in. I have the 6dB setting with more of a hump.

    I am surprised there has not been more discussion on the impact of speaker interaction. When LFE is on the sub hitting low notes alone there is no interaction with the mains and so it seems to me the EQ would no longer be flat?

    Any others have thoughts on this??
     
  6. Kevin C Brown

    Kevin C Brown Producer

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    There have been many thoughts on this, in the past. [​IMG]

    Here's the way that I did it:

    (I started using a discrete test tone CD too, then migrated to my PC with www.etfacoustic.com software. Much faster. [​IMG]) Crossover engaged the whole time.

    1) Plot my sub by itself.
    2) Plot the mains by themselves.
    3) Do all the equalizing with only my sub.
    4) With both sub and mains, I plot through the crossover freq and set the phase for the maximum SPL with the eq. (That phase relationship can and will change with an eq in the loop.)
    5) Then I look for that total sub+mains response with and without the EQ and compare to what the sub looked like alone with and without the eq.
    6) Make adjustments from there.

    I always did the sub by itself first, because it's a lot easier to see the effects of the changes. But. Bottom line is the total freq response of the subs and mains.

    It is fun, isn't it? [​IMG]

    Same here: BFD.
     
  7. Rick Cohen

    Rick Cohen Agent

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    I checked my Sony DB 840 reciever and found some very interesting things with the variable cross overs. Setting speakers to small and running mains alone I checked the output at the various crossover setting available. I can set crossover to 60hz, 90, 120, 150 or 180 hz. The differences between them were not nearly as severe as I expected.
     

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