Increase total Speaker Impedance Question

In my response above I was assuming that the four speakers each have identical impedance values. Thanks to Al for kindly confirming my input, as I consider him to be the true authority on any technical issues.

Thank you all for your response and help. Yes, all of the speakers are different models and hence each have its own unique crossover that I ordered from Parts Express. As a results the only way to make it sonically plausible is to wire them in a parallel. However, the current parallel wiring has reduced the total Ohm to 1.6, too dangerous for the amplifier to handle. I have ordered two 3 ohm wirewound resistor rated at 200 watt. It will be placed between the receiver and the speakers. Would that seriously damage sound quality? I'll try it either way and let you know how it turns out. Thanks!!

By the way the receiver is rated at 125 watt each channel, so 200 watt resistor should be sufficient?

The 200 watt power rating of those resistors should be sufficient, but you will then have 3/4.16 or ~72% of your available power being dissipated by the resistors. Only the balance, ~28% of the total power will be available to drive the speakers.

Bill, thanks very much for the nice words. I always find your posts to be particularly knowledgeable, informative, and constructive.

Angelgz2, yes the resistors will certainly affect the sound quality, and most likely for the worse, but the magnitude and character of the effects will depend on the impedance characteristics, damping requirements, and other characteristics of the speakers. If the design of the speakers is such that their impedance and other characteristics are relatively "tube friendly" (for example, if their impedance magnitude doesn't vary greatly as a function of frequency, and if their impedance phase angles are not highly capacitive), their sonics will probably suffer less than they would otherwise.

Also, Bill is right that only a fraction of the amplifier's power capability will be available to the speakers, with the rest being dissipated in the resistors. And his calculation resulted in roughly the right answer, although I think the methodology of the calculation was not quite right.

You didn't say whether the 125 watt rating is for 4 ohms or 8 ohms, but let's assume it is for 4 ohms. And I assume that the receiver is solid state rather than tube-based, at least in its output stage, so that its output impedance can be assumed to be negligible. The receiver would probably be capable of delivering slightly less power than the 125 watts into (3 + 1.6) = 4.6 ohms, but let's ignore that slight difference. 125 watts into 4 ohms corresponds to an output voltage from the amplifier of (square root (125 x 4)) = 22.36 volts. The voltage that would appear across the paralleled speakers under that max power condition would be ((1.6/4.6) x 22.36) = 7.78 volts. That voltage across 1.6 ohms corresponds to (7.78 squared)/1.6 = 37.8 watts. 37.8/125 = 30.2%, close to the bottom line Bill stated.

Good luck. Regards,
-- Al