Quote Originally Posted by astravitz
I'm a bit confused by all of the specifications presented by vendors sometimes. For example, Arcam provides the following specifications:

8 Ohms, five channels 70W
8 Ohms, two channels 90W
8 Ohms, single channel 100W

However, they allow you to set the amplifier to either 4 ohms or 8 ohms depending on the speakers. When you set it to less ohms do you get more or less wattage? What are you supposed to set it to if your speakers say Nominal 6 Ohms, Minimum 4 Ohms. What is the difference between Nominal and minimum? If a speaker is rated from 10-150 Watts (Program 100 / Dynamic Peak 200), what size receiver do you need each channel to put out for a good match? Is 70 Watts enough, or is 100 Watts Better?
RE: the Arcam, when all the channels are being driven simultaneously, the amps is capable of putting out 70 watts per channel. When two channels are driven 90 watts per channel. One channel driven 100 watts per channel. In this case, either the power supply is sagging, running out of steam, or the unit is designed to limit the output as the # of channels driven increases.

The lower the impedance (ohms), the greater the current draw on the output devices and the greater the power in watts.

For nominal 6 ohm speakers either the 4 or 8 ohm position should suffice. Nominal is the average impedance whereas minimum is just that, the lowest impedance the speaker reaches.

You can't IMO, have too much power. The difference between 70 and 100 watts is on the order of 1db, an insignificant difference at best.