STEREO SUB Calibration (BFD)

Discussion in 'Archived Threads 2001-2004' started by Pieter_L, Jul 4, 2001.

  1. Pieter_L

    Pieter_L Guest

    to those courageous HTF'ers about to read all of the following excruciating detail (and provide detailed & helpful suggestions), i salute you! [​IMG]
    STEREO SUB Calibration.
    - i have 2 identical powered subs (they're built into my DefTech 2000tl L & R Tower Speakers - 2x500watt 15", if it makes a difference)
    - i have a nasty room spike around 30Hz
    - i can not change sub locations (obviously)
    - i will be getting a Behringer DSP1100P (BFD) to take care of the spike
    - i'm currently using a Denon5700 a/v receiver
    a few questions:
    ================
    1. i want to impact my actual sound quality as little as possible, by putting a little as possible between the signal origin and the speaker. that means equalizing the low frequencies only. Below what frequency should i stay with BFD adjustments?
    2. at what frequency does "stereo" or "directionality" start?
    3. i find when i calibrate each sub individually to a specific reference dB, i gain +10dB when i play them both together. is this normal? should i stick to the individual reference calibration, OR make sure the combined output plays at the reference dB (turn down the individual output levels)?
    4. between my Denon's bass handling and my DefTech, i have a bewildering number of choices to do may bass hookup. some of the main ones are:
    (i) tell Denon i have or not have a sub (Denon also add THX bass option on top of this)
    (ii) use 1 speaker only wire connect to speaker
    (iii) use bi or tri wire to speaker
    (iv) use speaker wire for mid & hi and a pre-out full range low level RCA into the DefTech sub area (the speaker will then use internal cross over to get low frequencies from this full range low level signal)
    (v) there is also a speaker input for LFE input as well than can be used in addition to any of the above
    my current hookup is: (iv) - not sure if (v) will buy me anything in addition.
    4. when i get the BFD, i will run the full range pre-out (L & R) into BFD, equalize the bass spike, then output low level full range signal into bass input (low level full range) of DefTech. can anyone see a problem w/ this? a better suggestion?
    5. i lied. [​IMG] i actually have 3 powered subs! my center is a DefTech C/L/R 3000 with built-in amp. i guess i will just turn down the bass gain of this speaker if it contributes to the spike (or, reluctantly, define it as "small" and have me pre send its bass to the equalized L & R instead.)
     
  2. Wayne A. Pflughaupt

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    Wayne
    quote: I want to impact my actual sound quality as little as possible, by putting a little as possible between the signal origin and the speaker. that means equalizing the low frequencies only. Below what frequency should i stay with BFD adjustments?[/quote]
    Connect in in-line between the receiver’s LFE output and the sub.
    quote: At what frequency does "stereo" or "directionality" start?[/quote]
    I can localize my subs with 90Hz crossover frequency with 24dB/octave slopes.
    quote: I find when i calibrate each sub individually to a specific reference dB, i gain +10dB when i play them both together. is this normal? should i stick to the individual reference calibration, OR make sure the combined output plays at the reference dB (turn down the individual output levels)?[/quote]
    Their combined output should be set to where it blends well with the mains.
    quote: Between my Denon's bass handling and my DefTech, i have a bewildering number of choices to do may bass hookup. some of the main ones are:
    (i) tell Denon i have or not have a sub (Denon also add THX bass option on top of this)
    (ii) use 1 speaker only wire connect to speaker
    (iii) use bi or tri wire to speaker
    (iv) use speaker wire for mid & hi and a pre-out full range low level RCA into the DefTech sub area (the speaker will then use internal cross over to get low frequencies from this full range low level signal)
    (v) there is also a speaker input for LFE input as well than can be used in addition to any of the above
    my current hookup is: (iv) - not sure if (v) will buy me anything in addition[/QUOTE/
    Adding the BFD will limit your options to line-level only.
    Elsewhere in these articles Ferstler notes that multiple full-range speakers function the same as multiple subs, as far as the acoustical havoc they cause to a room.
    Tom Nousaine tested and measured the response of multiple subs in a room in an Audio magazine article a few years ago (Placing the Bass: 2 subs in the corner beats 5 in the round,” June 1996). He positioned five subs at the main right, main left, center and two rear locations and took measurements of the following configurations: Two subs at left and right positions; three subs at left, center and right positions; three subs at center and rear positions; four subs at left, right, and two rear positions; five subs, one each at all five positions.
    Nousaine’s conclusion was that the smoothest response and best extension were achieved with one or two subs in a corner. With this configuration the room nulls were effectively eliminated. According to Nousaine’s commentary, this was the result of exciting multiple room modes at the same time, a phenomena that can only be achieved with corner placement.
    Good Luck,
    Wayne A. Pflughaupt
     

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