THE ALL CHANNELS DRIVEN FALLACY

[MrMezz]

Hello:
I'm in the process of setting up my dedicated home theater/music room. The room is 18' X 12', so of mid size. I've read with great interest the entries on this forum for several months and have a feel for which components I'd like to purchase.

My question concerns Amp Wattage.... If I buy a 130 watt per channel A/V reciever, is this enough to produce quality sound for a room of this size. Or should I buy a 200 Watt per channel Amp and use my reciever as a pre/pro. How much audible difference is there between 130W and 200W?

My speakers are Anthony Gallo Ref3s, plus Anthony Gallo Dues used for surround. I listen 50/50 to music/movies. My budget for receiver is about $3500.


Any help appreciated!!

[DaveOCP]

130W for a room that size should be plenty. When you are researching, check reviews to see how much power you will have with all channels driven . Wattage per channel does not mean all that much, any product except for the absolute cheapest receivers shouldnt have any trouble reaching their rated power without clipping when driving one channel. Drive 5 or 7 channels at once though, and receivers up to $1K+ may lose half or more of their power per channel, where as megabuck receivers and power amps shouldnt have trouble with rated power when driving all channels at once, though there are a few (the Aragon 2005 and 2007 come to mind) which cant.

Edit: The ref3s are powered towers, right? If the bass section is passive, you're definitely going to want to go power amp.

What products are you thinking about specifically? 130W sounds like maybe an Elite 59TXi?

[Buckeyefan 1]

Nice budget. If you don't go the power amp route, this may suffice.

http://www.audioweb.com/Ad/AdInfo.asp?adid=157782

[MrMezz]

If I go receiver only I was thinking Denon AVR-4806. If I go with receiver used as a pre/pro, I was thinking of using Gene's recommendation of Yamaha RX-V2600 or Denon AVR-3806.

[jcPanny]

Those are great receiver choices. Either one should have ample power for your setup. If you want more power down the road, you could always add a 2 or 3 channel amp to drive the fronts.

[gene]

When you are researching, check reviews to see how much power you will have with all channels driven . Wattage per channel does not mean all that much, any product except for the absolute cheapest receivers shouldnt have any trouble reaching their rated power without clipping when driving one channel. Drive 5 or 7 channels at once though, and receivers up to $1K+ may lose half or more of their power per channel, where as megabuck receivers and power amps shouldnt have trouble with rated power when driving all channels at once, though there are a few (the Aragon 2005 and 2007 come to mind) which cant.

Dave you may wish to read this post to learn more about this topic:
Does your RX-V4600 run hot

[DaveOCP]

It may not be perfect, but it is a way to compare one amp to another. Just as EPA mpg tests are impossible to replicate in the real world, but they are useful because you can directly compare one car to another. I'm not sure of any receivers that list how many kVA the transformer has, or how many microfarads of power supply filter capacitance there is. Reviews dont list that either. All you generally get is a very ambigious THD rating, and rated power for one channel. Using the all channels driven test as a comparison is better than say, how much they weigh.

[Pyrrho]

Hello:
I'm in the process of setting up my dedicated home theater/music room. The room is 18' X 12', so of mid size. I've read with great interest the entries on this forum for several months and have a feel for which components I'd like to purchase.

My question concerns Amp Wattage.... If I buy a 130 watt per channel A/V reciever, is this enough to produce quality sound for a room of this size. Or should I buy a 200 Watt per channel Amp and use my reciever as a pre/pro. How much audible difference is there between 130W and 200W?

My speakers are Anthony Gallo Ref3s, plus Anthony Gallo Dues used for surround. I listen 50/50 to music/movies. My budget for receiver is about $3500.


Any help appreciated!!

With 8-ohm speakers with a sensitivity of 88 dB/1 Watt/1 metre, and rear speakers rated at 8 ohms with a sensitivity of 89 dB/w 2.8v (1m), 130 watts should be more than enough. The actual results will vary by room (and speaker placement and seating location), but you can subtract 3 dB per extra meter you are from the speaker, and then calculate the sound level to get a rough idea of what you are likely to get. Assuming you are 2 meters from the speakers, you should get about 95 dB at 10 watts, which is quite loud. You should get about 105 dB with 100 watts (keeping in mind that we are talking about only one channel; each additional channel would add 3 dB to the figure, assuming the same efficiency speakers, and assuming that the sound from each speaker does not cancel out the other speakers due to being out of phase, etc.). If you were 3 meters from the speakers (you could not be that far from all of them in your room), we would be talking about approximately 82 dB at 1 watt, 92 dB at 10 watts, and 102 dB at 100 watts, with only one channel driven. As we are also talking about continuous power, your peaks should be able to be louder.

However, if you want to go deaf very quickly, then you might want more power (though you should be able to go deaf quickly enough with the 130 watts).

I have less power in a larger room, with speakers rated the same* impedance and sensitivity, and I can play it louder than I ever want, maintaining great clarity as loud as I can stand it. But if you are someone who listens to rock music at rock concert levels (which causes hearing loss, by the way), then you may require more power.

For more information on hearing loss and loud sounds, see:

http://www.howstuffworks.com/question124.htm



*That is, rated the same as your front channel speakers, although, as we are talking about "nominal" impedance, and impedance varies with frequency, it may be that our speakers will not be capable of the exact same loudness with the same amplifier in the same room. Still, assuming that Gallo has not mislabeled their speakers, it should be close.

[gene]

Using the all channels driven test as a comparison is better than say, how much they weigh.

Ok its obvious you care not to read why this is a flawed test, especially since the conditions in which they are conducted aren't realistic, not to mention that many receivers deliberately self limit full cycle power tests like this.

[DaveOCP]

What is a better way to compare what different amps can do? HT mag, for example, tests all amplifiers the same way, therefore all of their all channels driven tests are directly to comparable to at least each other, if not tests done by other reviewers.

With Pioneer's 70 series of receivers, the weight is way down, which probably means a big reduction in the transformer and power supply. How do we know what effect that will have if Pioneer lists the same wattage driving one channel as the 50 series and lists no other information regarding transformer capability?

Personally I dont get what the problem is. The fact that inexpensive receivers must use power steering to deal with the stress of the test does not make the test "unfair".

A somewhat similar situation is testing a CPU under 100% load conditions. The P4 3.8Ghz must throttle itself in this situation because it exceeds the safe thermal envelope. An Athlon64 FX-57 is able to run under 100% load for hours and hours without requiring any speed throttling because its simply designed better. That doesnt make an 8 hour, 100% load test "unfair" to the P4 because it cant handle it.