Measuring Speaker Impedence

rpr

Ok.. i have an old HH studio 50 combo here. was thinking about buying a small mini valve head and using the speaker as a cab. However, sods law being what it is, one of the screws on the backplate is rusted solid and gnawed to bits.  Is it possible to measure the speakers impedence from the speaker jack socket or is this just a silly stupid idea?

ICBM

Pull out the speaker plug and measure the resistance from tip to sleeve. The resistance you get will be about 2/3 to 7/8 of the nominal impedance, ie for an 8-ohm speaker it will be somewhere between about 5 and 7 ohms (it varies depending on the speaker type).

I'd be surprised if it isn't 8 ohms, if it's the original speaker - I'm pretty sure they were.

If the amp doesn't have a plugged-in speaker but does have a speaker *output* jack on the back of the amp - I can't remember for sure about this amp - then no you cannot either measure the impedance directly or use that jack as a speaker *input*, because it will still be connected to the power amp.