How do I measure the Impedance of an unknown speaker

Discussion in 'Amps and Cabs [BG]' started by Gerard Rizzardo, Jul 16, 2003.

  1. Hi Guys, I was wondering if someone could possibly tell me how can I measure the impedance value of an unknown speaker?? I want to build a cab for it, so that I can incorperate it into my present system. However, if it's impedance is incompatiable (unmatched) i.e 4ohm with a 8ohm I can't use it. It's a 12" speaker, which came out of an old blown 250 watt keyboard combo, but there is no info plate on it, stating ohmage. Is it just a matter of putting a 'Multimeter' across the poles, and it will give a reading of 4 or 8 ohms ?? Cheers, Rizz.
  2. bben


    Feb 28, 2002
    Santa Fe, NM
    Yes, just put a multimeter across it. The dc resistance will be a bit less than the nominal 4 or 8 ohms, but you will be able to tell which it is, no problem.
  3. Petebass


    Dec 22, 2002
    QLD Australia
    That's right. My 8 ohm speakers produce a reading of about 6.8 ish. My 4 ohm speakers produce a reading of 3.2 ish.

    The readings are lower because you're actually measuring DC resistance, which is not the same as nominal impedance. They're both measured in Ohms so people sometimes confuse the 2.