Re: home stereo impedance matching

[Brian Whatcott <betwys1@SBCGLOBAL.NET>]

At 02:44 PM 2/17/2004, you wrote:
> I have a pair of old (relatively) Bose 501 speakers that are
> marked as 4 Ohms, that I would like to use with a new
> receiver that only offers 8-16 ohm connections.
> From what I've been able to establish, higher end
> speakers tend to be of the 4 Ohm variety due to greater
> power associated with lower resistance.
> What types of problems can I expect if I use 4 Ohm
> speakers with my 8 Ohm system?
> If my only problem will be reduced performance, then
> I'm not terribly concerned.  If I will cause permanent
> damage to my new receiver I think I'll leave the
> speakers in storage.
> In the past, my father had wired a 4 Ohm resistor
> (rated at 15 Watts) in
> series with the speaker so that the amp would see
> 8 Ohms.  Is it that easy?
> Cheers,
> Matt


The usual kind of consumer audio output amplifier
has two protection methods: an over current protection
and a thermal shutdown.   There is a third layer of
protection sometimes seen,  excess power shutdown
which I believe works rather like a CD that has lost its
track momentarily and blanks.

Assuming the first two protections are available,
then an output channel loaded with 4 ohms would
see more transient over current events than an 8 ohm
 load would provoke.
   I am not confident that these are always good for
a large number of cycles, so you might do better going
with your Dad's method. It seems to me that you would not
lose any desired output this way



Brian Whatcott    Altus OK    Eureka!