[sdiy] Speaker Impedance

[rkmoore at memphis.edu]

Hi Rafael,

If you use a speaker with higher impedance than shown in a schematic, 
everything should still work, but you'll get lower output.  Depending 
on your needs, this may not be a problem.  You also may be able to 
increase the gain and get a decent output before the amp starts 
clipping.  To get maximum output from your speakers you need the 
output impedance of the amplifier to match the impedance of the 
speaker (the real part, I mean).  To decrease the output you can 
decrease the gain of the amplifier driving the speaker or add 
resistance in series with the speaker.  

I guess a suitable solution would really depend on the circuit you 
were trying to modify.  Different types of amplifying circuits would 
require different alterations to decrease output impedance.  To use a 
smaller than rated speaker load I think you could always used a 
resistor of sufficient wattage in series with the speaker to produce a 
lower output.

To check the impedance of a speaker I just use a multimeter to measure 
ohms.

Richard Moore


----- Original Message -----
From: Rafael_Cohen at prusec.com
Date: Monday, May 23, 2005 11:55 am
Subject: [sdiy] Speaker Impedance

> 
> Hey everybody,
> Guess what... it's another newbie question!!
> 
> I have some schematics requiring 8 ohm speakers, and in some of my
> DIY/scavenging I come across speakers of various other impedance, 
> usuallyhigher than 8ohm.  Everything from 16ohms to 45 ohms... 
> sometimes computer
> speakers or speakerphones, etc...
> 
> My question is, what do I need to do in order to adapt the circuit to
> speakers of different imedance?  Also, is there a simple way to 
> test the
> imedance of a speaker?
> 
> Thanks again,
> Rafael
> 
>