Expert: Cleggsan - 12/31/2010

Question
Hi Cleggsan, my apologies if this is a stupid question as I am not very knowledgeable in this area.  I have a Technics receiver model SA-202 which is rated as 30 RMS watts per channel, 8 ohms but I have no speakers.  My father has an old pair of Telefunken RB-50 speakers which is rated as 50 RMS watts per channel, 4 ohms.

Do you see any issue in using these components together as I don't want to risk damaging either?

Thanks very much.

Answer
Power ratings on loudspeakers are not important because they are mostly fictional numbers for the advertising departments.

In matching loudspeakers and power amplifiers the most important matter is impedance.  Here is the rule:  The impedance of the speaker should be equal or greater than the rated load impedance of the amplifier.

So, in your case the Telefunken speakers are rated at 4 ohms.  The Technics amplifier is rated for 8 ohms (at 30w).  (BTW, there is no such thing as RMS watts).

So, the question is whether the lower impedance of the speakers will damage the amp or will it just derate the power output of its amplification?  

And, the answer is:  This model was a robust design with a strong power supply and well voltage protected output amplification stage.  It will drive a 4 ohm load ok and produce about the same amount of power as it would into an 8 ohm load.  However, my recommendation is to be very careful not to overdrive the amp (In other words, don't drive it too hard.)

All the best.