All phased out! Help needed please

Discussion in 'Subwoofers' started by The Spaniard, Sep 2, 2007.

  1. The Spaniard

    The Spaniard
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    Hi Guys,

    Just trying to set up my new SVS SB12 to work together with my existing Yamaha 320 and have a question on phase settings.

    I was advised by my usually well informed dealer who does a lot of installs to have one sub set at 0 ( in phase with main speakers) and the other sub set at 180 (out of phase).

    Is this correct and if so why?:lease:
     
  2. chrisgeary

    chrisgeary
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    that seems bizarre to me. where are they in your room?
     
  3. Member 96948

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    Doesn't matter where they are in the room Chris, that's just rubbish advice. The correct phase is the one that provides the smoothest transition between the subs/speakers at the listening position.

    In my experience, you can't say 0deg is a definite even if the sub is between the front speakers, but either way it's not related to position per se. It's an adjustment that is more closely related to distance, with the direction being irrelavent. The problem is, is that the distance in question is 'effective' not 'actual' and can vary with frequency due to phase shifts in the the speakers and subs crossovers.

    In other words, if you moved nothing, but changed the speakers, you could end up with completely different phase settings as the 'effective' distance alters regardless of the physical location.

    FWIW, unless you have someway of observing the interaction between two subs and the speakers (REW, SMS-1, etc) you may as well disharge waste liquid against the prevailling air current. There are too many potential interactions to sort out by ear alone. I mean you might manage it eventually, but my money would be on peace in the Middle East breaking out by by Christmas.

    Finally, why would you want to run the Yamaha when you have an SB-12?

    You are diluting the performance of a superior sub with a less capable one. You won't gain any depth of frequency response and unless you're standing one on top of the other, you're gaining virtually nothing in terms of output/headroom. Throw in the fact that you're complicating the matter by trying to integrate two non-identical subs and I believe you are asking for more trouble than it is worth.

    Russell
     
  4. Fjorko

    Fjorko
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    OT ( and appologies to OP for butting in like this ) but Russel, I always wondered what your avatar actually is ?

    Is it :

    1. A monkey sitting on a pole ?
    2. An old record player ( you know the old ones from the 1800's )?
    3. A man smoking a pipe ?
    4. Something completely different than 1,2 and 3

    :D:D:D
     
  5. The Spaniard

    The Spaniard
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    Thanks for the responses.

    Russ, the reasons for trying this were two fold:

    Firstly I thought I could get a better 'spread' of low frequency around the room. The Yammy is located to the side of my sitting position (quite close) but I have done some more drilling, etc, etc and can position the SVS just to the left of the left main speaker. When I tried it on its own (with the yammy turned off) the bass was definitely to the left of me and so I thought I would get a better 'spread' if I had them both on.

    Secondly, I didnt think I would get much for the Yamaha if I sold it and I thought I may as well carry on using it if I could. I have been happy with it for 10 years or so and it does give out a fair amount of oomph.

    I have attached a picture trying to show the various speaker and sub positions relative to where I sit on the settee!

    My room is 4.8m long, 4m deep and 2.3m high.

    Any more thoughts?:lease:
     

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  6. Member 96948

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    Chimpanze on a branch Taronga Zoo, Sydney 2001. One of the most depressing sights I've ever seen. The Zoo that is. Sydney's fine apart from all of the smug Aussies.

    Russell
     
  7. Member 96948

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    Bass is a bit odd in so far as it doesn't image in quite the same way that higher frequencies do. Your ears use the delay between two sources of sound and their relative loudness, to 'place' the audio image in space. The thing is that in an enclosed space, bass does not drop off in the same way and it even increases as you move toward a wall, even if that wall is in a direction away from the subwoofer.

    It is unlikely, unless the basic sub setup is poor (you wouldn't do that, would you? ;) ), or unless you are using very high crossovers, that the sub it's self is actually aurally locatable. It's more likely that rooms booms and nulls (reinforcements and cancellations) are giving the impression (tricking the brain into thinking) that bass is comming from a certain direction.

    I had a weird effect in my room, where a number of modes combined nearer my right ear than the left giving the impression that the bass was emanating from the right. The sub was very definitely against the LEFT wall.:confused:

    Moving my chair so as to place my left ear where the right had been made the sound appear to come from the left. In practice, moving the sub 9" or so up and 2" out from the wall, moved the offending modes away from either ear and the sub was no longer locatable.

    Now adding another sub may have, or may not have improved this problem, but refining the positioning of the one sub will sort the problem and avoid all the pitfalls of integrating two unequal subs and the consequences that will have on bass quality.

    Russell
     

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