Re: How to test speaker resistance

Arvo W0VRA

On Thu, Mar 22, 2018 at 10:11 am, Jerry Gaffke wrote:
Conclusion:  A 4 ohm speaker can have drastic variations in impedance 
over the audio frequency range.
This is absolutely correct, and one of the biggest challenges high end audio amplifier designers have to deal with.  And making things more complicated (as the article points out), you have the mechanical resonances of the system, which is why bass reflex systems have two peaks, and the electrical resonance of the amplifier-coil system.  And we haven't gotten into multiple driver systems with crossovers, each having their own resonances and poles!  Bob Carver back in the day made a lot of hay out of the interplay between speaker impedance and amplifiers.

Anyway, for a useful approximation of a loose speaker sitting on the workbench, the resistance of the coil is close enough for most purposes.  This is because how an audio amp responds to 4, 8, or 16 ohm loads is typically the same in practicality when listening to SSB or CW.

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