Re: Speaker impedances

[Tony Wayne <wayne@pen.k12.va.us>]

At 8:46 AM -0500 6/10/97, 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
> ********************************************

Use an ohm meter to get a dc resistance. Multiply this resistance by
1.333333333333. It will give you the approximate impedance of the driver.

Of course you could always use the voltage-current method and sweep over a
range of frequencies. But then you will find the impedance will peak at the
resonant frequency (when the reactance drops to zero), dip to normal and
then rise again because the voice coil is a massive inductor on a woofer.
But why do all that if you just want to connect it to a stereo. If I can
help with anything let me know. (I teach basic stereo speaker design from
scratch as an elective. :)  )
-tony


_____________________________________________________________________
Tony Wayne
Those that can, do.
wayne@pen.k12.va.us
Those that understand, teach.
Check out the Virginia Instructors of Physics' Physics Pavillion at
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