Is there an easy way to correct phase by 90 degrees?

Discussion in 'Home Theater Projects' started by Justin Ward, Feb 29, 2004.

  1. Justin Ward

    Justin Ward Supporting Actor

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    I've got my SBB4 Tempest currently powered by a Technics 220 watt amp. I find that when switching the leads, applying a 180 degree phase change, the sound level is not noticeably different. To confirm this I conducted the following experiment:

    I hooked one VC up to the A set of the amp - with normal polarity.

    I hooked up the other VC to the B set of the amp - with reversed polarity.

    I put on some bass heavy music and raised the sub volume very high so volume differences would be noticeable. I then changed back and forth from the A and B speaker sets and I couldn't detect any difference. My rudimentary knowledge of waveforms tell me that this means that it is 90 degrees out of phase.

    So my question is: Other than buying a plate amp, is there any other way to apple a phase correction of 90 degrees? I wouldn't mind building something simple but I don't want to spend much if possible.

    Thanks in advance,
    Justin
     
  2. AndersP

    AndersP Stunt Coordinator

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    Justin,

    To perform such a test the front speakers should have the same output level as the sub. You want to detect the difference in phase between the fronts and the sub. Ideally you use a sine frequency test signal equal to the xover freq.
    Out of phase - reduced output of test tone
    In phase - max output of test tone.

    With your test you are trying to access the finer nouances of absolute phase which is another matter entirely. That one is better discussed in a HiFi forum.[​IMG][​IMG]

    Keep the Technics if it works and build this:

    http://www.lcaudio.dk/subfilter.htm

    It can correct every practical phase problem and could be built for less than $20US if you shop at the right places.
     
  3. Justin Ward

    Justin Ward Supporting Actor

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    I've got sine waves burned onto a CD-R. I'll test it with a 100hz tone, which is the same as my crossover.
     
  4. Chad B

    Chad B Stunt Coordinator

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    Justin,

    Yes, I agree with AndersP- your levels should be matched (acoustically). If you pump up the sub too high, any phase problems will be less audible because the cancellation will be dramatically reduced.

    Chad
     
  5. Ellen

    Ellen Stunt Coordinator

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    Real Name:
    Ellen

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