Re: Speaker impedances

[Steve Luzader <sluzader@fre.fsu.umd.edu>]

A good estimate of speaker impedance can be gotten just by measuring
the "DC" resistance with an ohmmeter.  For example, I have a speaker
sitting in my office that is marked "8 ohms", and an ohmmeter connected
to the speaker's leads reads 7.6 ohms.  The impedance does vary with
frequency, of course, and reaches a maximum at the speaker's mechanical
resonant frequency and may be lower than 8 ohms at some frequencies.
However, as has been noted in other comments, the actual impedance isn't
very important in most applications.  Modern solid state amplifiers are
nearly ideal voltage sources with very low output impedance, so they
don't care very much exactly what impedance is connected.

Steve Luzader
Frostburg State University
http://antoine.fsu.umd.edu/phys/luzader

GARY HEMMINGER wrote:
> I have been given a large subwoofer by a student, and it looks like a
> fairly expensive speaker which I coulds make good use of in class with
> either a stereo receiver, or a bass guitar amplifier.  However, I
> have no specs for this speaker.  Can anyone suggest a simple way to
> determine its impedance?  And how necessary is it to know the
> impedance?
>
> *****************************************
>   Gary Hemminger
>   Dwight-Engelwood School
>   315 E. Palisade Ave.
>   Englewood, New Jersey
>              07631
>   e-mail: hemmig@d-e.pvt.k12.nj.us
> ********************************************