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Re: home stereo impedance matching

Question: it has two pair of outputs, one 8 the other 16 * or one rated
for 8=> 16 Ohms?

Have some fun and measure the impedance of your spks. The easiest
method is to insert a rheostat in series and adjust 'till the EMF drop
across the resistor equals that of the speaker.

BTW in some cases reducing the damping from the amplifier improves the
sound. The effect is most noticeable in the bass. If your room is
"dead" in the low frequencies, this will compensate. The amp. damping
helps "cheap" speakers which are not enclosure well damped.

One may find the output impedance of the amp. by varying its load and
calculating from the EMF at the output and the resistance of the load.

NB you must use a 'scope (DC) or a DMM that claims (is) flat over the
range of interest.

* If so, you may be "in luck". The difference between (in my
experience) the 8 and 16 Z terminals is closer to 4 than 8 Ohms.


Matt Harding wrote:

I have a pair of old (relatively) Bose 501 speakers that are marked a=
s 4
Ohms, that I would like to use with a new receiver that only offers 8=
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 associa=
with lower resistance. =20
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 thi=
I'll leave the speakers in storage.
In the past, my father had wired a 4 Ohm resistor (rated at 15 Watts)=
series with the speaker so that the amp would see 8 Ohms. Is it that

"An expert is a man who has made all the mistakes which can be made i=
n a
very narrow field."
- Niels Bohr

-----Original Message-----
=46rom: Forum for Physics Educators [] On
Behalf Of Justin Parke
Sent: Tuesday, February 17, 2004 1:54 PM
Subject: Re: rolling

I just discovered that the latest edition of Halliday, Resnick, and
Walker has the correct answers (i.e. .5 L and L) in the back of the


In a message dated 2/4/2004 8:11:12 AM Eastern Standard Time,
FIZIX29@AOL.COM writes:

I need some help with the following question from Halliday et al


ch. 12 question 5:

"A woman rolls a cylindrical drum, by means of a board on top,


h the
distance L/2, which is half the board's length. The drum rolls


hly, and
the board does not slide over the drum.
a) What length of board has rolled over the top of the drum?
b) How far has the woman walked?"

The answers in the book are L and 1.5 L. I am not sure I underst=


what is
meant by "what length of board has rolled over the top of the dru=


It seems
to me that it should be L/2. If the questions means how

far has the =3D

moved with respect to the ground then I agree it is L.

Answers in algebraic form (plus verbal explanations) are
preferable t=3D
strictly verbal arguments.


Justin Parke
Oakland Mills High School
Columbia, MD