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Phasing

Discussion in 'Recording' started by djmac, Jan 12, 2004.

  1. djmac

    djmac Guest

    Stupid Question? How do you get speakers out of phase? I it pos>neg and neg>pos? i have never really understood this concept? Please explain
     
  2. bgavin

    bgavin Guest

    In a word, Yes.

    It isn't really a phase issue, but one of polarity.

    Some manufacturers, notably JBL, used Minus (Black) forward cone motion, where most of the industry used Plus (Red) forward. This means if you took a small battery and connected the Black to plus, and the Red to minus, the cone moves forward (away) from the magnetic motor.

    JBL has stopped doing this with their newer drivers, but most of their previous drivers were like this. One has to verify for sure.

    If you get a pair of drivers out of polarity with each other, it kills the bass. One moves forward, the other moves rearward and they cancel each other. This can also occur between two different cabinets. Everything must be checked. Once you've heard it, the sound is obvious.
     
  3. Barkingdogstudios

    Barkingdogstudios Active Member

    Judson,

    The only time I can think that you might want to purposely put speakers out of phase is in a live sound situation. Sometimes, reversing the phase on your monitors can help reduce feedback.

    Bgavin, yes, I have experienced the entertainment aspect of JBL's polarity reversals when trying to wire cabinets with crossovers etc.
     
  4. bgavin

    bgavin Guest

    Gotta love those JBLs.... I've used 'em since the early 1960s. As you point out, the problem is worse with crossovers and compression drives. Harder to tell the movement direction with a HF horn, without a test box.

    JBL publishes a spec of which drivers move which direction.

    [ digging ]

    Link to JBL Polarity Conventions PDF
     

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