Impedance measuring jig

[catalin gramada]

Hallo. How can I measure the impedance peaks of a speaker at resonant frequency, please ?
I have an 600ohm output audio generator. A hefty 100w 2k output transformer and a multimeter. Thanks

[xtian]

I don't know! But I'm curious! Why do you need to know?

[catalin gramada]

Trying to dampen impedance peaks at resonant frequency using different methods. I wonder how effective are? I have a good signal generator and the 2k OT will help to drive the speaker. But have no ideea how to make a resistive jig and how to translate the voltage values readings into some useful stuff. A measuring precision of 10% should be enough for my purpose. Thanks

[Helmholtz]

Hallo. How can I measure the impedance peaks of a speaker at resonant frequency, please ?
I have an 600ohm output audio generator. A hefty 100w 2k output transformer and a multimeter. Thanks

To measure speaker you connect the speaker in series with a 1k resistor directly to your generator (no transformer) and sweep frequency while measuring the voltage across the speaker with a mV meter of sufficient bandwidth or a scope. Speaker voltage will be approximately proportional to impedance.

[catalin gramada]

To measure speaker you connect the speaker in series with a 1k resistor directly to your generator (no transformer) and sweep frequency while measuring the voltage across the speaker with a mV meter of sufficient bandwidth or a scope. Speaker voltage will be approximately proportional to impedance. For calculating exact impedance from the voltage use the voltage divider formula and add your generator impedance to 1k.

Thank You. How accurate this method is, please ?

[Helmholtz]

Thank You. How accurate this method is, please ?

Best you use the speaker voltage at 400Hz as reference because that's were guitar speakers show nominal impedance. So if you measure twice this voltage at some other frequency impedance will be about doubled.
I would estimate the accuracy to about 10%. For better accuracy I use a good SS power amp and a higher value series resistor. Lower series resistance tends to squeeze the peaks.
But mind that a tube guitar/bass amp squeezes the peaks even more as its output impedance (between 2R and 100R) damps the resonances.

[catalin gramada]

Thank You