The ohm's thing

Discussion in 'Amps and Cabs [BG]' started by RJRoper, Feb 15, 2001.

  1. I know this has been a topic before and I've read alot of good info relating to amps and the ohm's requirements that amps have. I was hoping someone could address some question I have.
    The amp I use is a Fender BXR 200 and the spec says 4 ohm min. on the back panel. The cab is a Fender 410 rated at 8 ohm, so far no problem. I just a picked up a used Marshall cab with one 15 in. speaker. This speaker is rated at 8 ohms also, as I understand it I could plug both cabs into the amp with no problems. OK here's my concern when I checked the Marshall Speaker with an ohms meter it read 6.5 ohm. Using that number I would be running less than the 4 ohms min. that the amp is rated for. Is this correct?

  2. MikeyD


    Sep 9, 2000
    It'll work just fine. The cabinets' impedance is nominally 8 ohms. This is what the manufacturer uses as a representative value. Impedance has two components: resistance and reactance. An ohmmeter only measures the resistance component. The reactance varies with frequency, and adds to the resistance. Your ohmmeter is essentially measuring the DC (meaning 0 Hz.) impedance, which is the resistance. A reading of 6.5 ohms resistance is very typical for an 8-ohm nominal impedance speaker.

    - Mike
  3. Thanks Mike, I appreciate the help.