Checked the FR of my room. Yeesh!!! Now what?

Discussion in 'Archived Threads 2001-2004' started by Steve Stogel, Feb 13, 2002.

  1. Steve Stogel

    Steve Stogel Supporting Actor

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    Here are the ugly corrected numbers.
    10Hz - 75dB
    12.5 - 77.5
    15 - 88.5
    17.5 - 87.5
    20 - 84.5
    22 - 87
    25 - 85.5
    28 - 83
    32 - 83.5 (yeah, so far so good, but watch this)
    36 - 92.5
    40 - 99.5
    45 - 97
    50 - 95.5
    56 - 90.5
    63 - 91.5 (95.5)
    71 - 85.5 (85.5)
    80 - 87 (86)
    89 - 85.5 (81.5)
    100 - 78 (69)
    112 - 78 (75.5)
    126 - 73 (73)
    The parenthetical numbers are the readings I got when turning the front speakers on. Notice at 100Hz that with just the sub, I'm getting 78dB and with the sub and speakers I'm getting 69dB [​IMG]. Whatup with that? The speakers shouldn't even be getting a signal until 80Hz, I thought, as I have my Technics SH-AC300 set to sub - yes and speakers - small. Obviously either the Technics decoder or the Technics receiver is not doing its job (correct?).
    Anyway, those are my numbers. My brother-in-law has a Behringer DSP 8000 (looks old) that he's not using. It says it's a 31-band stereo graphic EQ/realtime analyzer/auto room EQ/parametric EQ/feedback destroyer/delay/gate/limiter/level meter (whew). Is anyone familiar with this unit, and could I use it to help tame my nasty peaks at 40,45,50,56, and 63? It has mic inputs on the back and what appear to be 1/4 inch analog inputs and outputs (?). So, if I can use it, how do you do it?
    I used Stryke's test CD with the 1KHz test tone registering 77dB at my seat (was going to go up to 80, but it was rather loud). All readings are at my primary listening position about six feet from the sub. Any opinions would be appreciated. Thanks.
    Steve
    P.S. I'm starting to think I was better off not knowing, as I was already very impressed with the sub [​IMG]. Oh, well, nothing I can do about it now. I was just hoping to have one of those magical rooms that was relatively kind to the FR. Doh!
     
  2. BruceD

    BruceD Screenwriter

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    If your Technics SH300 is anything like my SH500 the crossover frequency between mains and sub-out is somewhere between 100Hz and 120Hz. Since xover slopes are just that "slopes" they don't just cut-off. So frequencies slightly above 100Hz will still be output by your sub.

    Which is why I went to a separate electronic crossover and sub on my mains (Large) and left sub-out empty and sub=NO in the Technics setup menu.

    Can you adjust the phase switch on you sub? That may help reduce the frequency cancellation occurring between your sub and mains at 80Hz, 89Hz, 100Hz, and 112Hz.

    You are on the right track, a parametric EQ will help cut those room mode peaks.
     
  3. Steve Stogel

    Steve Stogel Supporting Actor

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    Thanks, Bruce.

    That makes a lot of sense. I never even thought about the rolling off. I just thought "Sub gets up to 80Hz and speaks get 81Hz on up." I knew there'd be a little overlap, but I didn't think about the rolloff stuff. Thanks for suggesting reversing the phase (you can do that simply by switching the pos and neg wires to the sub, right?). I'll try it and take some more measurements.

    What electronic crossover are you using, BTW, and how much do they run, if you don't mind me asking? Thanks again.

    Steve
     
  4. Jeffrey Noel

    Jeffrey Noel Screenwriter

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    Steve, I would highly recommend a Behringer Feedback Destroyer. It has worked wonders for my subs frequency response. You can get one from www.lentines.com for ~$135 including shipping! Great buy!
     
  5. BruceD

    BruceD Screenwriter

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    Steve,
    I use a Marchand XM9-L electronic xover, kinda expensive $399, but it is on my mains so I didn't want to skimp.
    They are at Marchand
    I also use a BFD 1100P (now the 1124P) parametric EQ on my sub. (click on my equipment list below).
    Your sub may have a phase switch on it (0, 180 degrees), or as you say you can switch the + and - cables.
     

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