How do find the ohm rating on a speaker cabinent?

January 29, 2004 7:40 PM

Is there a way, without a meter to find out the ohm rating on a speaker cabinet? Is as easy as just putting the leads up to the input if you use a meter?
posted by drezdn to technology (3 comments total)

Here's an article which might help. It's probably more information than you want but it's a good start.

I can't think of a useful means to measure the impedance of a speaker (the ohm rating is really impedance, if it was purely resistive it'd be called a resistance but it's not. As a result the impedance will change with frequency).
posted by substrate at 7:59 PM on January 29, 2004

you could put a small resistance in series with the speaker, connect one channel of an oscilloscope across the resistance, another across the speaker and look at the trace as you play some music. that effectively plots V against I, so you get an idea of both the magnitude of the impedance and the various phase shifts.

if you know the efficiency of the speaker you could, in theory, calculate the resistive impedence from the output for a given input, i think. but that requires even fancier equipment.
posted by andrew cooke at 4:12 AM on January 30, 2004

if you just want a number you could unscrew the driver and have a look at what's printed on it. if you find something then either directly or via a catalogue that might give you the driver's nominal rating. for a simple speaker that's probably (?) a good guide to the speaker's rating.
posted by andrew cooke at 4:14 AM on January 30, 2004