Originally Posted by msg464
400+ responses to this great FAQ - my apologies for not reading every one if this has been covered, but how does one properly evaluate an AVR for relative power output to determine whether it's enough to push a set of speakers?
I see everything listed with varying output in watts/channel at various impedance + channels driven, eg, 125w/ch at 8ohms, 1ch driven, etc.
what does this actually mean for a set of speakers rated at say 50w-500w? we all know how much of a letdown it is when speakers are underpowered and sound tinny and empty.
I see old, beautiful and warm sounding stereo receivers with specifications of 25w/channel, and they blow away some of the new stuff with supposedly higher ratings.
I've seen a few units and manufacturers speccing out equipment in w/channel with all channels driven, etc, but this rare.
others state too look for a high current receiver. how is this spec determined?
I see that some of the better revered stuff is heavy, but then others stay that weight is just for tire kickers.
so my question is, how do I properly determine what's what, and what's appropriate for my speakers?
sorry if these are all newbie questions. I'm open to following up on any other resources provided to learn how to pick a good receiver or AVR.
All valid questions. I will do my best to address them.
First off, speaker ratings seem to be of little importance. As you can probably have double the amp power vs the max power you should put into a speaker. Ideally you don't want to overdrive your amp. It's hard to damage speakers when your amp is putting out a clean signal, and your speakers aren't totally wrong for the job ( a one watt speaker driven with 100 watt amp is a bad idea, for example.)
Ratings are not cut in stone. The old FTC rule required quite a bit from a receiver, and therefore the ratings back then compared to modern ratings might be misleading. That's one theory. You can also speculate that some people might ask too much. A modern $500 receiver is chock full of complex functions and often has to amplify seven speakers. It gets a break in many cases, as low freq duties are handled by a powered sub. But maybe it's just not as amazing of a two channel amp compared to some 50 pound Pioneer from the old days. I prefer Yamaha's higher end stuff, which is $1000+. It sounds like a lot of money, but does seem to have more power. I also think people get a little crazy. -10 dB on the volume scale seems plenty loud to me. I have no interest in reference level ( 105+ dB) levels. If you really need such a thing, be prepared to spend some money.
Your point on weight is fair when talking about class AB amplifiers. There's no way around large transformers and capacitors needed for powerful class AB amps. A 20 pound receiver is going to have real limits. With Class D you can expect more power per weight though. Class D still doesn't seem to be the norm for AVRs though.
High current is to some extent marketing. I am no amp designer, but my understand is that you go about things a few ways. You could make an amp that did not put out a ton of power into 8 ohms due to a relatively low voltage power supply. The trade off should be more available current. So you can come close to doubling power into 4 ohm speakers. This used to be the Harmon Kardon approach. If you look at Yamaha schematics, you can see they use a high voltage supply, like 70V in their better models (or used to.) This should allow for some voltage drop and look better into a 8 ohm load. There might be some advantages to either approach, but I can't explain the details without reading my amp books again for clues. I will leave such decisions to the amplifier/receiver designers. That all being said, there were some rabbid Harmon Kardon fans years ago who swore HK sounded better than say Yamaha. I couldn't say from personal experience