Re: home stereo impedance matching

["Shapiro, Mark" <mshapiro@EXCHANGE.FULLERTON.EDU>]

If you are going to drive the speakers at low power levels compared to
the rated power output of the amplifier, they can be connected to the 8
ohm output without too much of a problem.

If you are going to use more of the rated power of the amplifier, then
the load should be matched to the output impedance to prevent
overheating the output transistors.  Adding 4 ohm resistors in series
will work provided that the resistors have an adequate power rating.


Dr. Mark H. Shapiro
Professor of Physics, Emeritus
California State University, Fullerton
Phone: 714 278-3884
FAX: 714 278-5810
email: mshapiro@fullerton.edu
web: http://chaos.fullerton.edu/Shapiro.html
travel and family pictures:
http://community.webshots.com/user/mhshapiro 
 
 

-----Original Message-----
From: Forum for Physics Educators [mailto:PHYS-L@lists.nau.edu] On
Behalf Of Matt Harding
Sent: Tuesday, February 17, 2004 12:44 PM
To: PHYS-L@lists.nau.edu
Subject: home stereo impedance matching

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=
-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 associa=
ted
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=
nk
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



"An expert is a man who has made all the mistakes which can be made i=
n a
very narrow field."
=20
-  Niels Bohr


-----Original Message-----
=46rom: Forum for Physics Educators [mailto:PHYS-L@lists.nau.edu] On
Behalf Of Justin Parke
Sent: Tuesday, February 17, 2004 1:54 PM
To: PHYS-L@lists.nau.edu
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
book!

Justin

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
(6th=3D
> > ed.),
> > ch. 12 question 5:
> >
> > "A woman rolls a cylindrical drum, by means of a board on top,
throug=3D
> > h the
> > distance L/2, which is half the board's length.  The drum rolls
smoot=3D
> > 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=
and
=3D
> > what is
> > meant by "what length of board has rolled over the top of the dru=
m."
=3D
> > It seems
> > to me that it should be L/2.  If the questions means how
> far has the =3D
> > board
> > moved with respect to the ground then I agree it is L.
> >
> > Answers in algebraic form (plus verbal explanations) are
> > preferable t=3D
> > o
> > strictly verbal arguments.
> >
> > Justin

Justin Parke
Oakland Mills High School
Columbia, MD