What happens when an 7 channel A/V receiever only drives 5 speakers? (1 Viewer)

[Pablo Abularach]

What happens when a 7 channel reciever/amp (100Wx7), only drives 5 speakers, does the channels stay in 100W or do the extra 200W divide into the five channels ending up with something like 140W per channel?

Thanks,
Pablo

 

[Mark Dickerson]

pablo,

It stays at 100 wpc, although it does mean that the active channels do not "run out of gas" as quickly on demanding material because the power supply is only having to drive five speakers instead of seven.

 

[Jim_P]

And the channels that don't run out of gas as quickly are the ones that share the same transformers.

I don't know if this is standard, but my 5 channel amp has two transformers. Each transformer drives different channels.

 

[HienD]

Can someone please clarify. There's two max watt ratings on a receiver. One for the amplifiers and one for the power supply. If you have 7-100watt amps and only a 400watt power supply, does that mean the max watts/channel would be 400/7 or 57watts for all channels driving?

 

[Mark Dickerson]

HienD:

You have correctly identified the great scandal in HT receivers. In your example, that is pretty much what it means--57 wpc if you are lucky. Most receivers have badly undersized power supplies and that is why most of these receiver makers rate their product only two channels at a time (i.e., 100 wpc for fronts; 100 wpc for the center channel; and, 100 wpc for surrounds--note it never says 100 wpc x 5!) This problem shows up when you try to drive more than two channels, like listening to a DVD or SACD. If you want more info here, check out this link:

http://www.geocities.com/Area51/Holl...1/ratevsac.htm

This is a chart compiling the results of the equipment test reports done by Sound & Vision magazine on HT receivers. You will note how few receivers are able to make their rated power. The worst appears to be the Marantz 7200, which although rated at over 100 wpc, can only make 27 wpc when all channels are driven. Also note the Sony 4ES, which S&V did not even test because, as a footnote explains, Sony told S&V that the receiver was "not meant to have all channels driven at the same time." (Personally, I think Sony should be compelled to print that statement on all of their product literature and the product itself just like the warning labels on the side of cigarette packs!)

 

[HienD]

My Onkyo sr600 has this in the manual:

"80watts per channel min. RMS at 8 ohms, 2
channels driven from 20 Hz to 20
kHz with no more than 0.08% total
harmonic distortion.
105 W min. RMS at 6 ohms, 2 channels
driven from 1 kHz with no more
than 0.1% total harmonic distortion."


It actually states with 2 channels driven. Of course, you'll never see that on the box or unit it self.

I guess all those electrical courses :frowning: in my "computer egineering tech" program came in handy after all