Subwoofer calibration questions

Discussion in 'Speakers & Subwoofers' started by MarkJH, Jan 19, 2005.

  1. MarkJH

    MarkJH Extra

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    So I finally purchased a sub-woofer after having had a pretty complete home theater system for almost 3 years.

    I set it up, threw in the Avia disk and started messing around with the Radio Shack SPL meter. I think I mostly have it set right, but had a couple quick questions.

    I set my receiver so the speakers are "Small" and the cut-off filter is set to 100 Hz. Where should I set the crossover frequency on the subwoofer? (variable from 60-160 Hz)

    When I have the Avia test tones playing the needle on my meter moves around about 3-5 db when the subwoofer tone is playing (weighting set to C, response is slow). Is this normal, and how do I decide where to set the volume on the subwoofer? For lack of anything better I set the volume so that the needle's low reading is equal to the other speakers' output.

    Thanks,

    Mark
     
  2. Jeff Gatie

    Jeff Gatie Lead Actor

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    This is normal. I usually try to get the middle of the swing to equal the target output (85dB with Avia).
     
  3. Nathan Stohler

    Nathan Stohler Second Unit

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    Mark,

    If the cut-off filter in your receiver is already set, you don't want your subwoofer's crossover interfering, so this setting on the sub should be as high as possible (160 Hz in your case). Some subs also have an input jack that bypasses the internal crossover of the sub, so that would be your best option if it's available.

    As far as the fluctuation of the subwoofer tone, I've experienced the same thing. I tried to get as close as possible, erring on the high side if anything. I wonder if this fluctuation is because Avia is generating white noise at different frequencies and some frequencies are louder than others (i.e. the sub's frequency response is not flat)?
     
  4. MarkJH

    MarkJH Extra

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    You both say to set the crossover frequency at max (160 Hz), but the manual says to start at the lowest setting and only to advance it until you can get "the best blend between the subwoofer and the main speakers in the midbass crossover region." It also says "Advancing the control too far will cause a "boominess" in the overall sound..."

    As you can see this is the exact opposite of what you recommend. Is there some reason why I should ignore the manual?

    Mark
     
  5. Jeff Gatie

    Jeff Gatie Lead Actor

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    Because the manual does not know there is a crossover in the receiver. You do not want to double up on a crossover, it can cause nulls where they overlap. Setting it to maximum gets it out of the loop entirely, letting the receiver do the crossover instead.
     
  6. MarkJH

    MarkJH Extra

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    Ah, I see. Thanks for clarifying!

    Mark
     

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