Impedance question:

[shawn474]

I have a Yamaha RX-V995 receiver with the Polk RM6005 staellite system. My question is that during hook-up I had the impedance switch in the top position and noticed that it sounded better than the bottom switch. The sepcifications are below:

Switch in Upper Position-
Center - impedabce must be 4 ohms or higher
Rear - impedance of each speaker must be 6 ohms or higher
Main - If using one pair of main speakers, impedance of each speaker must be 4 ohms or higher. If using two pair of main speakers, impedance of each speaker must be 8 ohms or higher.

Switch in Lower Position-
Center - impedance of the speaker must be 8 ohms or higher
Rear - impedance of each speaker must be 8 ohms or higher
Main - If using on epair of main speakers, impedance of each speaker must be 8 ohms or higher. If using two pair of main speakers, impedance of each speaker must be 16 ohms or higher.

Seeing as the Polk RM6005 is advertised as "Impedance : Compatible with 8 ohm amplifiers", would I be doing any damage to keeping the switch in the upper position? Also, what are the benefits / drawbacks to each position?

Thanks you tyo everyone who takes the time to read this post and especially those who can give me some input.

Take care and Happy Holidays to all.

[Tour2ma]

No... upper position is fine. As your manual states "x-ohm or higher", and 8-ohm is higher...

My guess is that the upper position engages some sort of protection circuitry to guard against overdriving the AVR into low impedance loads...

[jcaut]

I agree with Tour2ma. I'd be a little surprised that the "low impedance" position on the switch sounds better, but that's your call. You won't hurt anything running it that way.

Jason

[John K.]

Shawn, why Jason was probably surprised that you preferred the upper position is that in that position the maximum voltage that the power supply section of the receiver can output is reduced. The reason for this is that when the voltage is reduced the maximum current and power is also reduced(Ohm's Law)and this might prevent overheating and shut-off when 4 ohm speakers were being used. But if this isn't necessary(and it shouldn't be with your speakers), the lower position should generally be used so that the maximum voltage, current and power that the receiver is capable of are available. Now you might not ever need the maximum power, and if so, no harm's done; but try again and unless you're really sure that it sounds better in the upper position, use the bottom setting.