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Does 12's + 15's = phase cancellation?

Discussion in 'Amps and Cabs [BG]' started by scrotimusprime, Sep 12, 2008.

  1. I know that 15's and 18's have a problem and they are somewhat similarly sized. Would I have a similar issue with 12's and 15's?
  2. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    I have never heard of this problem between 15's and 18's, and I don't see how phase cancellation would be relevant to speaker diameter.
  3. I run a 2X12 on top of a 2X15 with no problems
  4. 76Dub

    76Dub Guest

    Jul 9, 2008
    Sounds good to me together. But then again I am not into the equations and formulas of what should go with what...I just play
  5. I've never heard of this problem either, but I've never knew anyone who would run a rig with that particular setup either.

    From what I understand "Phase cancellation" only happens when two speakers have the polarity reversed on one of the speakers.
  6. Warpeg

    Warpeg Supporting Member

    Jun 20, 2005
    I don't think phase cancellation would be the issue. Inaccurate sound reproduction is the real issue. This is not limited to speaker size. Any two or more differing speakers, receiving the same exact signal, have the probability of having this issue. However, most of these "issues" are inaudible or unnoticeable to most people.

    Imagine that you have a 2x10" cabinet. Each speaker has its own sealed, separate area of equal size. Now, imagine that you put two different types of 10" speakers in this box and give each speaker an identical signal. Each of these speakers will be voiced differently, handle current differently, and achieve different dB's at different frequencies. What this equates to is, with the combined tones of the speakers, an overall sound that has inaccurate loud and quiet volumes based on the frequency reproduced by the speakers. Perhaps there is some phase cancellation going on during this process.

    Many people like this type of a tone...more power to them! Tone is tone and preference is preference. Personally, I always stick with either a 8x10 or 6x10 for this reason. :)

    BTW, speaker phasing problems are normally caused by one of two problems:
    1. Backwards input polarity on at least one, but not all, involved speakers
    2. A crossover network that was calculated incorrectly.
  7. selfblessed


    Dec 29, 2006
    Phoenix, AZ
  8. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    It CAN cause phasing on certain freqs, but the likelihood of it depends on the cabs themselves. A lot of people use mismatched cabs and sound great. I did for a while, too. I thought I sounded great.
  9. It can happen in other ways also, but miswired speakers is the most likely scenario you would run across.

    I have biamped a 12 and a 15 for years with no problems.
  10. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    All speakers have differing phase responses, so mixing them will cause response humps and dips. For the most part they're not all that obvious, and you wouldn't notice them at all unless you had the opportunity to compare it side by side with another speaker system of similar capabilities but with smooth response.
    In other words, you can't appreciate how bad a cheap steak is until you've had a filet mignon.
  11. eastcoasteddie


    Mar 24, 2006
    I only heard of something like this happening if different sized speakers are in the same cabinet. It shouldn't happen in separate cabinets.
  12. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Whether they're in one cab or not makes no difference. That's why PA and hi-fi systems use crossovers, passive or electronic, so that different drivers/cabs don't operate in the same bandwidth.
  13. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Ya, all I can say is that when I do what you say, I am much happier with my tone than when I don't. Except where my old straightback SVT cab is concerned...and then all that stuff goes out the window because I so love its sound. Hate moving it, but that's another thread ;)
  14. Rooster009


    Feb 27, 2008
    one of the all time greats for concert venues,,,,,,,,,,,
    the sunn coliseum 1x18 + 1x12. no doubt used by most of your favorite groups at some of the biggest concerts. about 6 of these on each side of the stage with about 4000 watts is all you need.:)

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