Date: Wed Mar 11 14:15:48 2009 Back to Contents ------------------------------------------------------------------------

Author: Physics Demo Room UofO

Subject: Re: stereo speakers


My understanding. 8 Ohms is the average a.c. impedance... Matching
impedance is also important, so lowering the impedance may or may not
increase the power delivered to the speaker depending on how the
impedance is matched. Remember that the maximum power is delivered
to a load when the internal resistance of the supply is equal to the
resistance of the load.


On Mar 9, 2009, at 5:17 PM, Anthony Lapinski wrote:

> I was discussing Ohm's law today, and a few students were asking about
> stereo speakers and their resistance. Textbooks do few problems
> involving
> speakers. From my understanding, a typical speaker is 8 ohms. This
> will
> get a certain amount of current and voltage, providing a power (P =
> IV) to
> the speakers. If one replaces the speaker with one that has a lower
> resistance, does this mean that the current (and power) will
> increase for
> a given voltage? Or is it that for a given power (volume), the current
> will increase while the voltage will decrease (since R is now
> less)? And
> the implication is that when the volume is turned up (P increases), an
> amplifier must have a better power rating to supply the sound if the
> speaker resistance is lower.
> Is this correct? Can anyone provide some "basic" physics
> information about
> speakers, amplifiers, and Ohm's law?

From Wed Mar 11 14:15:48 2009