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Wattages at different impedence

post #1 of 5
10/26/06 at 5:06pm
Thread Starter 
Can someone tell me how to figure the wattage with difference impedence speakers? Im looking at the Yamaha RX-V459 or V559 receiver and they said 90 and 95 watts/channel respectively, but does this change if were to set it for six ohm speakers or even four? Im guessing the wattage given in the specs is under an 8 ohm load. Thanks.
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post #2 of 5
10/27/06 at 8:44am

Re: Wattages at different impedence

The impedance of speakers is a nominal one and varies with frequency, hence even an 8 ohm speaker will have impedance dips requiring the amp or receiver to deliver more current. Aside from that, Audioholics had some nice articles written by Gene that had to do with receiver settings and different nominal impedance speakers. If you can't find it, I'll try and dig up the relevent link.
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post #3 of 5
10/27/06 at 10:44am

Re: Wattages at different impedence

For receivers, the wattage rating is basically always at 8 Ohms nominal.
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post #4 of 5
10/27/06 at 3:32pm

Re: Wattages at different impedence

I don't think there is an actual formula for converting wpc from an 8 ohm load to a 4 ohm load but magazines often test avr's with 4 and 8 ohm loads. As an example, the Marantz 4500, tested with two channels driven @ .1 % thd and an 8 ohm load, produced 100.4 wpc. With a 4 ohm load it was 128.2. The Harman Kardon 7300 was 181 @ 8 ohms and 290 @ 4 ohms. It looks like the differences can range from minimal to dramatic. But read the owners manual first. Many avr's aren't designed to handle a 4 ohm load.
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post #5 of 5
10/28/06 at 8:35am

Re: Wattages at different impedence

Theoretically it should double going from 8 to 4 ohms but this never happens in practice. One of the most common weak points is the power supply.
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