measuring speaker ohms?

Dave Van Allen · Post by **Dave Van Allen** » 20 Feb 2002 11:08 am

stupid question of the day... If a speaker's impedance is not labeled (4,8.16 ohms etc) can one measure it with a multimeter?

Jim Smith · Post by **Jim Smith** » 20 Feb 2002 1:36 pm

Yes, just unplug the speaker from the amp first. The voltage from the meter will probably make a popping noise through the speaker, but it won't hurt it, and 8 ohms equals 8 ohms, etc.

Donny Hinson · Post by **Donny Hinson** » 20 Feb 2002 2:12 pm

Well, what you're measuring is resistance, and speakers are rated in impedance. Of course, depending on the speaker's voice coil design, they're usually close. But sometimes, they can fool you. If a speaker measures out at 6.2 ohms resistance, it is probably an 8-ohm speaker. But it could also be a 4-ohm, especially if it's a "cheapie". Usually, the resistances and impedances are in the ball park, and it doesn't matter much with tube amps, anyway. Solid-state amps are more finnicky, but as long as you don't hook speakers together in parallel (which lowers the impedance) you should be OK.

Jim Phelps · Post by **Jim Phelps** » 21 Feb 2002 2:21 pm

The "right way" to do it requires a frequency generator....You can get close by using your multimeter to measure the DC resistance of across the speaker terminals (with nothing else connected) and multiply the answer by 1.3. So if the DC resistance is 6 ohms then the speaker is nominally 8 ohm impedance.