Phase Shift?

Discussion in 'OT Technology' started by Peter O'Hanraha-hanrahan, Oct 9, 2002.

  1. Peter O'Hanraha-hanrahan

    Peter O'Hanraha-hanrahan OT Supporter

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    On my amp, there is a phase shift switch to shift the phase ofthe subwoofer 180 degrees. I took physics, so I know visually what it does, but does it make any audible difference?
     
  2. edrox

    edrox A good man, and thorough

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    phase shifting

    As with most things audio-related, the answer is a firm "that depends"

    A lot of the difference will depend on the type of subwoofers you are using, and their enclosure. If you are using a simple sealed box, or second order enclosure, phase shifting can make a difference. If you are using a third-order or higher enclosure, the difference is more pronounes, and generally bad.

    If you think about the dynamics of sound, you have to ask why you would want your speakers to behave exactly opposite of the way they were intended, or the way the music would dictate.

    Phas shifting will mean a typically looser, muddier bass. In my opinion, not something I want in my stereo system

    Ed
     
  3. 04

    04 Guest

    Re: phase shifting

    :ugh: :ugh: :ugh:

    Ed:

    I know you mean well, but that is incorrect. The phase shift will do NOTHING but invert the signal 180 degrees. That is it. It is the same thing that would happen if you hooked the speaker wire up with opposing polarity. The signal being fed to a speaker is NOT DC, therefore the speakers are not behaving the opposite of the way they were designed.

    The type of enclosure will have NOTHING to do with the fact that you change the polarity by 180 degrees.

    I am curious, why do you think the bass sounds muddier with the phase shifted 180 degrees? All it should do is provide either cancellation or gain with your main speakers at certain frequencies, perhaps this is what you are experiencing.

    I would flip the phase shift to the point where you get the most output, therefore the speakers are the closest to being in phase. You can NEVER have a perfect phase relationship in the real world.

    Think about it this way, when you plug a device such as an ac adaptor in the wall, does it matter which way (phase) you plug it in?
     
  4. 04

    04 Guest

    Yes, in a perfect world if you had two of the same amplifiers with two of the same subwoofers, and fliped the phase switch on one but not the other, you would theoretically have ZERO output, because the drivers would be working completely against each other. In reality, this does not happen though.

    The switch is there so that you can match the polarity with the front speakers correctly, without having to unplug your speaker wires to do so.
     
  5. LOUDSYSTEM

    LOUDSYSTEM Guest

    agree with 04 on this one
     
  6. BobG

    BobG Fuchs.

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    Re: Re: phase shifting

    Ya beat me to it, sir. :fawk: :)
     
  7. edrox

    edrox A good man, and thorough

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    Then let me correct my language. When I said that it would operate the opposite way it was designed, what I am saying is: When signal hits the speaker, instead of the woofer mooving "out" it would move "in", and vice versa. Hence your clarification of phase. Maybe I could have stated it better.

    In my experience, the action of shifting phase has resulted in a sound that was looser, muddier bass, especially in ported enclosures.

    If you have used phase shifting and found it beneficial, you have done it better than I have, or differently. But, as with all things audio, we all have different hearing and different tastes.
     
  8. 04

    04 Guest

    edrox: Do this test, disconnect your main speakers and have a friend be in the back of a car next to the amplifier's phase switch. Have him flip it back and forth repeatedly and see if you can hear a difference then. If only the subwoofer is playing, there should be NO difference, the signal is only inverted 180 degrees, and if you still hear a difference, you are either mr data off of star trek, or the phase shift is not a phase shift.

    The phase shift is benificial so that you can match the phase of the subwoofer to your main speakers. The muddiness you heard was probably associated with phase cancellations between the subwoofer and your main speakers.

    Not saying you didnt hear a difference, but the phase shift will not depend on the persons personal preferences, it will depend on the install.
     
  9. edrox

    edrox A good man, and thorough

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    048..

    Well I have to tell you, its been a good while since I was involved in car audio, so maybe you are more knowledgable than I am. Something I would gladly concede.

    I know what phase shift is, and what it does. That has never changes. And perhaps you are correct in what I heard as a reult of the phase change.

    Shifting phase a full 180 degrees, it seems to me, would not necessarily align phase, unless you are a full 180 out. Perhaps it would bring it closer in some circumstances.

    Maybe I am wrong; something I can accept.
     
  10. flynfrog

    flynfrog Cool isnt Cheap

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    dosent earth quake have a timer of sorts to cahnge the phase of individual speakers

    i think its more for spl
     
  11. 04

    04 Guest

    Precisely that is what it is for. It will bring it closer in some situations, and in others do no good.
     

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