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Rewiring 8ohm to 4ohm

Discussion in 'Amps and Cabs [BG]' started by Toasted, May 24, 2004.

  1. Toasted


    May 26, 2003
    Leeds, UK
    I did a little search before posting, couldnt find what i want.

    I'm considering a Mesa walkabout + Ashdown 4x8mini rig.

    Currently the 4x8 is 8ohm, is there a way it can be rewired to be 4ohm, and draw the full 300 watts from the walkabout.

    Whilst im at it, sounds like a great rig... dont it :D :hyper:
  2. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
  3. You can't rewire your cab. You would have to purchase 4 new speakers with 16 ohms each, that'd be the easiest but costly way.
  4. Toasted


    May 26, 2003
    Leeds, UK
    thanks. not i feel stupid. not the first time, wont be the last time :)
  5. Suburban


    Jan 15, 2001
    lower mid Sweden
    Makes no sence, fellas!
    If you put in a gadget with an impedance parallel to another gadget with an impedance, you have a new total impedance. Basic electrotheory.

    So, if I have an 8ohm woofer, and put in an 8ohm impedance in parallel, I have a total impedance of 4ohms.

    The possible problem I may face is, that the two impedances have different frequency dependencies. Like if you put in two woofers of different specifications...
  6. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    True, but...

    A woofer's "rated" impedance is the nominal impedance. There are probably only one or two freqencies where the voice coil is truly 8 ohms (or whatever). However, we use the nominal impedance as a worst case value.

    I suspect that some woofers can exhibit an impedance below their rated nominal impedance...hence the Acme-Carvin shutdown problem that we read about occassionally.

    The point of this thread is that you can't take four 8 ohm woofers and interconnect them (in a normal, equal power distribution configuration) to create a 4 ohm nominal impedance...you either get 2 ohms (parallel), 8 ohms (series/parallel) or 32 ohms (series).
  7. So if you start with 16 ohm woofers then you can wire 4 of them to obtain your 4 ohm cab...did I understand this correctly?
  8. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Yep, it you wire them all parallel