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Calibrating a PB2+

Discussion in 'Subwoofers' started by MickB, May 20, 2004.

  1. MickB

    MickB
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    Just received this as a replacement for Rel Q200E, and its a monster :clap:

    However, I'm not sure how to map the room response. I've got a copy of DVE, but this only seems to have sweeps, surely I need a disk with fixed freq tones (and my DVD won't play CD-R so I can't download these from the net)?

    I've also got a BFD on the way, but can't progress re-eq until I resolve the above.

    Am I missing something? :lease:
     
  2. Ettepet

    Ettepet
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    Nice sub, got one myself yesterday! :)

    What you need is either a slow subwoofer range sweep (from some surround setup test-disk), seperate sine tones (link mentioned here), or a (calibration) microphone setup and SpectraPlus/SpectraRTA (trial version).

    If you don't want to spend 100 bucks on calibration stuff (Behringer mike + pre-amp), you could opt for an SPL-meter (from Radio Shack or other). You will definetely need a compensation table, because a cheaper model SPL-meter isn't really meant to measure below 100Hz.

    You could do the sweep by ear, and get a pretty decent result on your BFD, but you'd need to know the current frequency. On my test-disk a person tells you what the frequency is, while the sweep is going on.
     
  3. chrisgeary

    chrisgeary
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    further to Ettepet's by ear suggestion, you can probably make a rough guess as to the frequency, but to dial in on it, why not set up a temporary filter on the BFD, set the frequency to be as close to it as you think it is, set the bandwidth to about 20, and the gain to -48. then alter the frequency and the fine settings until you find that you get the most audible cut possible. then that is your frequency - you can check the BFD table to find out what it is.

    when you have done that, you can set the bandwidth down to whatever value works best to tame it without affecting adjacent frequencies - and you have created your filter! :smashin:
     
  4. drum63

    drum63
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    Mick,

    This is probably stating the obvious, but do you have any other device that you could connect to your amp temporarily to play the snapbug sinewaves.

    Maybe portable CD player, MP3 player, or directly from your PC soundcard.

    If not maybe you could beg, borrow or steal something.

    I found the sinewaves to be the easiest way to get an accurate plot compared with sweeps, but that also depends if you really want to know where your peaks and troughs are. :)

    Could be a the start of a long road on the quest for room perfection as can be seen by the many other posts on the subject on these forums.

    Good Luck

    Gary
     
  5. Ettepet

    Ettepet
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    One thing to keep in mind is that few and simple adjustments are what you should be after. I see people going for a +/- 1dB frequency response, which I have found to be a less desirable goal, especially when you need many BFD-adjustments. The BFD isn't some "wonder toy", and among things will add extra (frequency dependent) phase shifts for each PEQ.

    If possible, put the subwoofer on a spot where it sounds good without adjustments, and go from there, then apply 5 or 6 PEQs, max. (meaning you go for the most audible peaks and dips)

    One of the benefits for doing "equalisation by ear" is that (with some luck ;)) you naturaly go for a room-curve, not a flat response. A flat-response, to many people, sounds rather dull. (see other topics for more depth on this)
     
  6. Nimby

    Nimby
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    If you download short sinewave tones onto your computer. You can access them one at a time and feed them to your amp or direct to your subwoofer from your computer "speaker out" socket. (Using as long a phono cable as you need to reach between them. 5 or 10 metre lengths are easy to obtain)

    The files tell you their frequency thanks to the file name given automatically at download. They will apear in "My Music" and can be played at will by opening the file. If you have anything fancy in the way of music file handling software you can arrange a running sequence of test tones rising or falling (to taste)

    I prefer falling tones because you can set the volume at a safe level where the tones are clearly audible. Rather than destroying your subwoofer with 5Hz @ 150dB without knowing anything about it. :devil:

    In theory you should probably use filtered pink noise rather than individual sine waves. But who's listening?

    Final note. :rolleyes: Don't leave your sub running continuously at high level on a low frequency or you could overheat the voice coil. Most test tones are of short enough duration not to worry as long as you don't turn up the volume because everything's suddenly become inaudible at around 20-30Hz. :oops:

    Despite it being possible to set a subwoofer roughly by ear I would urge you to get a RadioShack SPL meter. You'll be amazed what you can't hear at all but the meter can show easily.

    Nimby
     
  7. MickB

    MickB
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    Folks,
    Thanks for all the helpful comments. I do actually have an SPL meter, the prob is getting fixed freq tones as my PC is in a different room, and the DVE only has sweeps.
    Does anyone know if the Avia dvd contains test-tones of fixed freq?

    Cheers
     
  8. Ettepet

    Ettepet
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    The Avia has several different options, even including mixed Front + Sub sweeps, but not all that many test-tones. The quickest and most effective sollution is creating a CD yourself, which you could do this evening.
     
  9. simonthepieman

    simonthepieman
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    mickb

    You can use avia it does a have a 100hz to 20hz sweep but you have to be fairly
    quick to see where your room issues are.
    I did use avia with my bfd and the snapbug graphs and got good results
    with my pb2 (which is awesom as you know).
    You do need to enter the values into the table to get corrected vaules and i have
    ended up with a fairly flat response which does curve towards the very low regions.
    I watched pay check recently amazing bass tight and controlled not ott check the
    truck crash.
    But the ultimate has to be Darla from nemo at -18db (so not too loud) it is bloody
    unbeliveable the whole house seems to shake .
    To get a more accurate calibration I did end up burning the snapbug test tones,
    but I was not far off using avia
    Search for the bfd threads on this forum for more info.
    Enjoy the mother!!
     

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