Increase total Speaker Impedance Question

Good comments by Bill, as always.

I'll add that connecting speakers in series will usually result in poor sonics unless the speakers are identical models. The voltage and power put out by the amplifier will divide up between series connected speakers based on the relation between their impedances. If the two speakers are identical the voltage and power put out by the amplifier at any instant of time will divide up equally between them. If they are not identical models, the relation between their impedances will almost always be significantly different at different frequencies, resulting in the voltage and power put out by the amplifier dividing up between them differently at different frequencies, resulting in arbitrary frequency response irregularities in each speaker, as you found.

Regards,
-- Al

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.