EQ'ing the room -- BFD and "House Curve"

Discussion in 'Speakers & Subwoofers' started by Anthony Curtas, Jul 31, 2003.

  1. Anthony Curtas

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    Just curious as to your all's recommendations of how to tune this room:

    http://www.geocities.com/acurtas/ht/base_layout.html

    It used to have a shoddily built riser (I should beat up the carpenter, but that would make me a masochist [​IMG] ) that was acting as a pretty good panel resonator. Sucked the bass right out of the room at ~ 70Hz. That's been fixed, but there's still a dip due mostly to room modes, weird shape, etc.

    Before, the "resonator riser" wouldn't respond to EQ'ing. No matter what I threw in, it sucked out. I did a test last night, though, that shows the new room (with a much sturdier and better damped riser) is responding to boosting the bass quite well. However I haven't gotten around to fine tuning the filters yet.

    Any thoughts as to how I should go about this? I've read the articles and debates about flat vs. house curve. I'd like to try it both ways, probably by setting up for a flat and then using the remaining filters to pull everything down from a higher frequency.

    Currently I'm thinking of three filters:
    1: smooth the shelf at 26 Hz for a flatter rolloff
    2: pull up the dip at 55 Hz
    3: Boost the big dip at 71 Hz to pull that whole area up. It's down 10dB, so I know that won't be easy, but I'm not worried about true flat. "Flat-ter" would be fine too.

    Sub is a sealed 12", flat near-field from 28Hz through 100 Hz. Sub amp is crossed at 150 Hz (highest setting, can't be bypassed), crossover for the system is 80Hz.

    I'm no stranger to the BFD, this will be the fifth or sixth time I've EQ'd a room with one. However, this has been the most problematic room yet . . .

    Any ideas? Thanks,
    Anthony
     
  2. Rus Bowisc

    Rus Bowisc Stunt Coordinator

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    Have you tried EQ'ing the room for a more purist approach? Bass-traps in my studio have improved my monitoring a thousand fold. That would be my first approach, if it's practical for you.

    Bass-traps may not be as aesthetically appealing in the living room though, unless you are creative.

    Rus
     
  3. Anthony Curtas

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    It's a dedicated HT / bar room, but space is an issue. Sub's in one corner, the other is where the DVD rack is, gear is up front.

    I was considering a ceiling baffle, but the riser to ceiling height is only 81" and I have friends who are 72" who wouldn't like to hit their heads [​IMG]

    Plus, I thought traps were supposed to lower peaks. How could I use one to boost a valley? If it could hang on the back wall, I'd be all for it!

    thanks,
    a
     
  4. Terry Montlick

    Terry Montlick Stunt Coordinator

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    I have some questions:

    Is the SPL from your mains relatively even, and in the 80-85 dB range like the "good" part of your sub response? Does the sub response rise back up to this level above 80 Hz, which is as high as your graph displays?

    Also, where is your measurement microphone? At the lower seating area at the upper on the riser, or are you doing averaging? Just trying to judge if you still have a "panel resonator" problem.


    Regards,
    Terry
     
  5. Greg Bright

    Greg Bright Second Unit

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    Gregory Bright
    You might try turning up the sub volume about 10 dB so that the valley is flat with the rest of the mid- and uppper-frequency response. Then use the BFD to cut everything else about 10 dB. Worked for me. I just hate to boost anything, anytime. Leads to overdriven amps, distortion, etc. Now I never get more than 3 lights on the BFD. Before it peaked out regularly. Two cents.

    Greg
     
  6. Terry Montlick

    Terry Montlick Stunt Coordinator

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    Greg is right. You definitely want to cut rather than boost.

    It looks like you've got about 15 dB over a broad range, though, and this is a little excessive. An acoustical solution (if it exists) is preferable to this degree of EQing.

    Regards,
    Terry
     
  7. Anthony Curtas

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    Thanks for the inputs.

    The actual curve stays down, only coming up to about 71dB at 85Hz and staying relatively flat up to 100 or so and then dropping off rather rapidly (and staying below the noise floor at 120Hz).

    As for the mains, I have not tested them, just set the levels with broadband pink noise. I usually keep the sub 1dB or so higher than the mains, but within the error margin, I set all the levels even.

    If I do still have a panel resonator problem, I should probably look elsewhere b/c the riser is stiffer than most of the floors in the house now. My friend asked me if I poured concrete in it, it was so sturdy.

    Most likely, I'm getting "semi-null" effects from three ways, across the room (50Hz), riser to ceiling (82Hz) and slab floor to ceiling (72Hz).

    None of the listening position dimensions is on a perfect null (although I can find it by moving around), but a null isn't a cliff, so anywhere close to the null will be attenuated.

    At 71Hz, I found I cat get 3 to 5 dB louder by moving the listening position left or right about a foot. I think for the final measurements, I will average all three positions (left, center, right) on the couch so I don't overboost the ends while making the middle flat. Moving front to back doesn't do anything for me, and moving the listening position up only takes me closer to the ceiling nulls.

    Ugh.

    And yes, I would like to only cut frequencies, but I have such a nice flat response in the middle octave that I would hate to try and pull all of that down when I could boost a narrower range.

    In closing, though, let me just say that just fixing the riser has made a huge difference in sound; so eq or no, I'm pretty sure I'll be happy. But I have the BFD anyway, so might as well play around with it! [​IMG]

    Thanks again,
    Anthony
     

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