1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

BFD And Two Subs, Coupled or Seperate?

Discussion in 'Subwoofers' started by whmacs, Jul 5, 2005.

  1. whmacs

    whmacs
    Active Member

    Joined:
    Oct 9, 2003
    Messages:
    77
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    11
    Location:
    Australia
    Ratings:
    +5
    Hi,
    I've just ordered a BFD to help equalise my room which contains two subs (15" and 10"). I'm currently wading through the BFD 101 guide on snapbug, but its not clear whether with two subs do you couple the two channels together and EQ with both subs operating, or do you keep each sub separate and EQ them individually using the BFD left channel for one sub (and having the other sub turned off at the time), then repeat the process for the other sub on the right channel and have the left channel sub turned off? Any thoughts would be greatly appreciated.

    Regards,
    Stephen
     
  2. eviljohn2

    eviljohn2
    Well-known Member

    Joined:
    Jul 8, 2002
    Messages:
    7,529
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    86
    Location:
    Near London.
    Ratings:
    +208
    If the 2 subs are colocated (ie. next to each other) then you can couple them to the same BFD channel. If they're in seperate locations then you really need to EQ them seperately.

    Having said that, I used both channels despite having the subs stacked as it's very easy to adjust both channels at the same time. :)
     
  3. bigmacx

    bigmacx
    Active Member

    Joined:
    May 15, 2001
    Messages:
    232
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +11
    Bit tricky this one. I use a Behringer DEQ2496 on my main speakers to flatten the freq response between 20hz to 120hz. If I EQ each speaker separately, so individually they measure flat, then the measured response of them both together is not flat (although it's much better than no EQ at all). Presumably this is caused by the interaction of the speakers with each other. If I provide an EQ that takes the total response into consideration then I do get a flat measurement. HOWEVER common sense tells me this EQ will only provide a flat reponse when both speakers are playing the same note at the same volume at the same time - something you're not guaranteed with a stereo signal.
    For this reason I've stuck with using separate EQs, if you've got a mono signal, like a sub feed, then a linked EQ might be the way to go.
    Another thing to consider is where the audience will be sitting, an EQ that gives a flat response at one spot might not be ideal at another spot. I think separate EQ's might be more resistant to this behaviour than a linked EQ (although I have no proof of this).
    The only way to be sure will be to try both methods, measure and see what gives the best response (and remember to measure at a few different seating places).

    Hope this helps,

    Mac.
     
  4. whmacs

    whmacs
    Active Member

    Joined:
    Oct 9, 2003
    Messages:
    77
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    11
    Location:
    Australia
    Ratings:
    +5
    Hi Guys,
    Thanks for taking the time to reply, I really appreciate it. Before I do anything with the BFD (which should arrive on Friday) I take some measurements using test tones with both subs going, then with each individual sub and see how the graphs pan out. Being a mono signal I'm hoping that I will be able to EQ both subs together.

    cheers,
    Stephen
     
  5. eviljohn2

    eviljohn2
    Well-known Member

    Joined:
    Jul 8, 2002
    Messages:
    7,529
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    86
    Location:
    Near London.
    Ratings:
    +208
    That will only be possible (or at least sensible) if you have the 2 subs colocated as I mentioned earlier. :)
     
  6. bigmacx

    bigmacx
    Active Member

    Joined:
    May 15, 2001
    Messages:
    232
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +11
    Not really, because if you measure both together (regardless of where they are) and calculate an EQ for that response, then not only are you correcting for room nodes but also the subs interaction with each other.
    I'm not saying that this is the best method (for reasons I outlined earlier) but it's not an inherently bad method either.

    As always, experimenting and seeing which one you think sounds best is the way to go.

    Mac.
     
  7. Nimby

    Nimby
    Member

    Joined:
    Jan 27, 2004
    Messages:
    9,198
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    The Danish Bacon Factory
    Ratings:
    +669
    I would think that trying to match a 10" and a 15" sub will be very difficult.
    Co-location might or might not be the answer. I would guess that the 10" will be struggling to keep up with the 15". While the 15" will just be ticking over if level matched to the 10". This is likely to defeat the object of the exercise unless you actually enjoy playing with your toys.

    I suppose you could try using the small guy to fill in any holes in the large sub's in-room response.

    Sometimes less is more. :lesson:

    Nimby
     
  8. whmacs

    whmacs
    Active Member

    Joined:
    Oct 9, 2003
    Messages:
    77
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    11
    Location:
    Australia
    Ratings:
    +5
    Hi All,
    My BFD has been delayed a couple of days, so in the mean time I've graphed the response with both subs operating using an RS meter. I had the volume of my processor (RSP-1098)set at normal listen level and cross over is set at 80Hz. Currently the processor is giving the subs a +7db boost (speaker levels)

    I was wondering is someone could advise how to get started with the BFD calibration, should I try and get a 'house curve' by cutting the peaks between 45-20 Hz and 63-45Hz, decreasing the processor boast of +7db a bit and remeasuring? Any suggestions would be greatly appreciated as I'm a bit uncertain how to begin.

    Regards,
    Stephen
     
  9. eviljohn2

    eviljohn2
    Well-known Member

    Joined:
    Jul 8, 2002
    Messages:
    7,529
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    86
    Location:
    Near London.
    Ratings:
    +208
    Have a read of Nimby's SPL Meter sticky at the top of this forum which should get you on the right track. :)
     

Share This Page

Loading...