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Why should I disable the crossover on my sub?

Discussion in 'Subwoofers' started by Jules, Sep 1, 2004.

  1. Jules

    Jules
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    With my Denon A1SE amp, and SVS PC Ultra sub, the recommended settings appear to be with the speakers set to 'small' on the amp, and the sub's crossover disabled.

    But it sounds better to me with the sub's crossover set at 80Hz and the speakers set to large.
    There seems to be less of a 'phase' issue with these settings.

    I think the Denon's crossover is mucking around with phase, whereas the sub appears not to affect it.
    So why should I disable the crossover on my sub? After all, isn't additional filtration at the crossover frequencies a good thing?
     
  2. Dfour

    Dfour
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    Its only advice. I say you should play about and see what sounds better to you and then stick with it:D
     
  3. Jeff

    Jeff
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    If you set your speakers to large you will loose the low frequency sound they can't reproduce and will distort more trying to do so. If you set the subwoofer crossover frequency to 80 Hz you will loose some LFE channel sound since it is designed to work up to 120Hz.
     
  4. rob_w

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    If you set your mains to large there will be no 'phasiness' between the sub and the mains as they will not share any signal.

    Thats assuming the sub is connected to the sub out of the amp.

    The xo on the sub shouldn't be needed unless you're crossing it to your mains without using an av amp for x/o duties. (mainly for stereo type setups, or where each channel has it's own sub type thing)

    As Jeff said leave it open at least to 120Hz.

    Cheers,

    Rob
     
  5. tk2001

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    Jules,

    My sub has an internal cross-over and after alternating between the 'enable' switch and 'disable' in the cross-over, I have decided it best to leave the subs internal cross-over on which sound best to my ears. All this will do combine with your A1SE's cross-over is make the sub roll-off more quickly at 80hz.

    I have my speakers set to small and the cross-over set to 80hz and IMO this gives the most cleanest sound between both the speakers and sub.
     
  6. samhain

    samhain
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    That seems unusually high for a low pass crossover point ?
     
  7. Matt Horne

    Matt Horne
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    I use a 120Hz crossover on my av32r.. sounds better than 80Hz imho
     
  8. jdl

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    If you set your mains to large there will be no 'phasiness' between the sub and the mains as they will not share any signal.

    Not true. The crossover is not a brick wall that means even if you set your speakers as small and the crossover at 80Hz that does not mean that your speakers will play all the frequencies down to 80Hz and not the 79Hz.
    How much down they will go and with what volume depents strongly on the amp and the characteristics of its internal crossover. :cool:

    My suggestion as sound engineer is to set all of your speakers as small (exept of course if you have monsters like the B&W 801 :rolleyes:)
    Set the crossover at 80Hz, ideally if your subwoofer has a LFE input use it, because with that connection you disabling the sub's crossover (i crossover better than 2 in the row).
    If you don't have LFE input for your sub then set its crossover at 90Hz sounds odd but do it.
    Remember what you like is not always correct. :)
     
  9. Arcangel

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    Matt

    Depends what speakers you've got. I'll stick with 80hz and not worry about the 80-120hz I'm losing in the LFE channel. ;)
     
  10. tk2001

    tk2001
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    jdl,

    Can please explain why using 1 cross-over is better than 2?
     
  11. jdl

    jdl
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    Well its very complicated and i must use a lot of heavy tech talk so to bring it as simple as possible lets say that you will get better sound quality using 1 crossover for a lot of reasons :
    First your signal is processed only once (and this is very good trust me) second the amps crossover in most situations is a better one built with better materials and third each crossover has different characteristics this is vital.
    So at the end is better to run your signal only through one crossover.
    I know this is more than plain english this good that bad but i want all the people to understand it.
     
  12. eviljohn2

    eviljohn2
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    I'm not convinced, most amplifiers use a software crossover whilst the subwoofers use a hardware crossover.

    Both also have a significant rolloff at either end.

    PS: Tech talk is often welcomed by people on this forum :)
     
  13. rob_w

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    There -is- no crossover to the mains if they're set to large. Therefore the sub is just getting the lfe, which is limited anyway to 120Hz max (usually to about 80Hz in practice), and possibly the surrounds, centre bass which will be redirected at the av amps settings (80Hz for thx) if set to small.

    ie the av amp will do the crossover-ing, and the subs own one should be disabled or set as high as possible so as not to interfere with the av amps xo .



    ""If you set your mains to large there will be no 'phasiness' between the sub and the mains as they will not share any signal.

    Not true. The crossover is not a brick wall that means even if you set your speakers as small and the crossover at 80Hz that does not mean that your speakers will play all the frequencies down to 80Hz and not the 79Hz.
    How much down they will go and with what volume depents strongly on the amp and the characteristics of its internal crossover. ""

    True - If the mains are set to LARGE there is no crossover in use between the sub and the mains :D - the mains get a full range signal with no bass re-directed to sub.

    I know the crossover is not 'brick wall' - 4th order on the low pass, second on the high pass blah blah blah...

    Btw - unless your mains/ surrounds/ centre are designed to roll of at 12dB / octave with a -3dB point at the av amps crossover setting then you'll be getting less than perfect results. Ported speaker users take note :devil:

    Cheers,

    Rob
     

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