THE ALL CHANNELS DRIVEN FALLACY

Advice needed: RE A/V Wattage

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!!

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?

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

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

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.

Denon and Yamaha

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.

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.

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Dave you may wish to read this post to learn more about this topic:
http://forums.audioholics.com/forums/showpost.php?p=102050&postcount=26

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.

MrMezz said:

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!!

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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.

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

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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.

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.

DaveOCP said:

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.

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Neither the EPA or all channel measurements reflect real world conditions. Not sure how useful it is to use it as a tool.

EPA mileage is a yardstick, and based on a modality calculation of 30 years ago. A few cars do exceed the EPA ratings today. This EPA business is all about politics so as not to burden the auto industry in meeting real world mileage.

Just read Consumers Report, especially their latest issue that explains all this. Not sure if they know what they are doing though.

DaveOCP said:

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

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What idiot would rate a receiver by weight? cough cough...33+lbs... cough cough.

OH, sure, now you bring up the weight issue.

"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?"

DaveOCP said:

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.

Click to expand...

DaveOCP said:

You just don't get it. Not rocket science. Just because HT does this doesn't make it useful. One would reject a perfectl;y good amp beacuse of a flawed protocol. But, if you want to base your choices on their data, be my guest.

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It does level the playing field in that all the units are tested the same way, however, it is not a good representation of what each is actually capable of when driving speakers. Even with a movie with active surrounds, the receiver will generally not be driving every speaker at full wattage for any length of time, if ever. That being said, the speakers and room will have a huge impact on how that power is put to use.

IMO, for the system described, the 4806 is overkill for those particular speakers, but it certainly isn't going to hurt anything to have that kind of power.

Weight isn't a scientific way to get an idea of a receiver's capability, but it isn't entirely off the mark, as there is a good chance a heavier receiver will have a more stout power supply. I like to just look into the holes in the top of the receiver and actually SEE the PS and the capacitors to see how much power this thing really looks like it will provide, then LISTEN to it.

Weight will not tell you how well a receiver will perform but it may tell you a little about the "build quality". As was stated, if you can see into the case it might tell you that the power transformer is large and the capacitors are big. Might even be able to tell that the case is made out of heavy gauge steel. But none of this will tell you how well an item will perform. Bigger doesn't always mean better.

Now back to the original questions, you said you wanted to run the system 50/50 theater music. Did you want a 5.1 , a 6.1 or a 7.1 system?

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.

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Um let me see, how about measurements like we do such as SNR at 1 watt and full power, output impedance at 1 watt and full power, frequency response uniformity at various power levels, damping factor, FFT distortion analysis at various power levels, etc. Oh I forgot it takes a few pages of data to look at rather than an instant gratification #.

You also fail to realize even their ALL CHANNELS DRIVEN test aren't always consistant. S&V Magazine for example forgot to regulate power on a Yamaha RX-V1 review but subsequently did on a cheaper Denon AVR-4802 in the same issue which made the latter appear more powerful. In their next issue they made a very small mention of this in their feedback letters, but the damage was already done. Readers lost interest in the Yammie b/c it looked less powerful. I am not picking on S&V Mag, just using them as an example that I have seen. Many magazines fall victim of this. In fact, I would question power #'s if they don't list the line voltage conditions and whether or not they are regulating power. I have also seen some magazine reviewers bypass the power fuse in the receiver to run this test. IMO that is absurd.

Again if a receiver is designed to produce alot of dynamic power in this price range such as the Yammie RX-V2500 then it has to employ a limiter so it doesn't dissipate too much heat in this type of test scenario. If you notice, some of the other brands in this price range that will deliver more power in this test scenario will not produce the same #'s as the Yammie would with 1 or 2 channels driven. Personally, I would take the amp that has more dynamic range with just 1 channel driven than the one that has less headroom but can deliver a few more watts in a test case that will never occur in real life.

gene said:

If you notice, some of the other brands in this price range that will deliver more power in this test scenario will not produce the same #'s as the Yammie would with 1 or 2 channels driven. Personally, I would take the amp that has more dynamic range with just 1 channel driven than the one that has less headroom but can deliver a few more watts in a test case that will never occur in real life.

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Buck/Dave:

I have to agree with Gene, if you look at the HTMag tests on the Yammie 2400, Denon 3805, Pioneer 52TX, HK630, you can rank them as follow:

By weight: HK(41 lb), Denon(37.5 lb), Pioneer/Yammie (34.2 lb)

By 5 channel output: Pioneer (115.3W), Denon (114.9W), HK (79.7W), Yammie (43.5W)

By 2 channel output into 8 ohms at 0.1% THD:
Denon (132.2W), Pioneer (121.2W), Yammie (102.9W), HK (84.6W)

By 2 channel output into 4 ohms at 0.1% THD:
Denon (218.4W), Pioneer (197W), Yammie (158.4W), HK (146.9W)

So the heaviest HKAVR630 actually came in last in the 2 channel tests. Except for the Pioneer, all tests were done by Mark Fleischmann.


Following are more details taken from http://www.hometheatermag.com/receivers/


HT Labs Measures: Harman/Kardon AVR 630
Five channels driven into 8-ohm loads: 0.1% distortion at 79.7 watts; 1% distortion at 93.3 watts

Analog frequency response in direct mode: –0.35 dB at 10 Hz; –0.12 dB at 20 Hz; –0.13 dB at 20 kHz; –0.72 dB at 50 kHz.

Analog frequency response with signal processing: –0.85 dB at 10 Hz; –0.27 dB at 20 Hz; –0.45 dB at 20 kHz; –28.64 dB at 50 kHz.

This graph shows that the AVR 630's left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1% distortion at 84.6 watts and 1% distortion at 100.6 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at 146.9 watts and 1% distortion at 170.8 watts.


HT Labs Measures: Yamaha RX-V2400 A/V Receiver

This graph shows that the RX-V2400's left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1% distortion at 102.9 watts and 1% distortion at 130.5 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at 158.4 watts and 1% distortion at 195.3 watts. With five channels driving 8-ohm loads, the amplifier reaches 0.1% distortion at 43.5 watts and 1% distortion at 44.1 watts. With seven channels driving 8-ohm loads, the amplifier reaches 0.1% distortion at 32.3 watts and 1% distortion at 36.9 watts.


HT Labs Measures: Denon AVR-3805

Five channels driven into 8-ohm loads: 0.1% distortion at 114.9 watts; 1% distortion at 125.0 watts

Analog frequency response in pure direct mode: –0.11 dB at 10 Hz; –0.03 dB at 20 Hz; –0.16 dB at 20 kHz; –0.89 dB at 50 kHz.

Analog frequency response with signal processing: –0.71 dB at 10 Hz; –0.20 dB at 20 Hz; –0.19 dB at 20 kHz; –24.96 dB at 50 kHz.

This graph shows that the AVR-3805's left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1% distortion at 132.2 watts and 1% distortion at 162.3 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at 218.4 watts and 1% distortion at 243.0 watts.


HT Labs Measures: Pioneer Elite VSX-52TX A/V Receiver

• Five channels driven into 8-ohm loads: 0.1% distortion at 115.3 watts; 1% distortion at 129.7 watts

• Analog frequency response in direct mode: –0.17 dB at 10 Hz; –0.06 dB at 20 Hz; –0.21 dB at 20 kHz; –1.21 dB at 50 kHz.

• Analog frequency response with signal processing: –0.17 dB at 10 Hz; –0.06 dB at 20 Hz; –0.21 dB at 20 kHz; –1.21 dB at 50 kHz.

This graph shows that the VSX-52TX's left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1% distortion at 121.2 watts and 1% distortion at 143.1 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at 197.0 watts and 1% distortion at 231.4 watts.

Buck/Dave:
I have to agree with Gene, if you look at the HTMag tests on the Yammie 2400, Denon 3805, Pioneer 52TX, HK630, you can rank them as follow:

By weight: HK(41 lb), Denon(37.5 lb), Pioneer/Yammie (34.2 lb)

By 5 channel output: Pioneer (115.3W), Denon (114.9W), HK (79.7W), Yammie (43.5W)

By 2 channel output into 8 ohms at 0.1% THD:
Denon (132.2W), Pioneer (121.2W), Yammie (102.9W), HK (84.6W)

By 2 channel output into 4 ohms at 0.1% THD:
Denon (218.4W), Pioneer (197W), Yammie (158.4W), HK (146.9W)

So the heaviest HKAVR630 actually came in last in the 2 channel tests. Except for the Pioneer, all tests were done by Mark Fleischmann.

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Fair enough. It appears the HK is the loser at first sight. But is it?

It's the only receiver to claim 75 watts per channel, when in reality, is putting out a bit more (in all 5 channels). Kudos for honesty to HK.

Secondly, weight is a good parameter, but not an end all. By being the heaviest unit, it may simply have a larger heat sink. While that may not add more power, it most likely will go longer without the negative effects of excess heat (distortion, clipping, and protection mode).

That still doesn't relieve the Yamaha for it's pathetic results in 5 channel mode, the mode and reason people buy surround sound receivers. It may be capable of outputting similar specs into 5 channel mode, but for whatever reason (protection, etc), Yamaha chose to limit it's current when needed most. 2 channel output - not an issue. 5+ channel output, you've got the chart. That spec alone should at least raise some eyebrows.

By 5 channel output: Pioneer (115.3W), Denon (114.9W), HK (79.7W), Yammie (43.5W)

gene said:

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.

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Wouldn't one think that a better amp design wouldn't "self limit" this kind of abuse?

Gene, I read your entire article a while back and I'd have to partially dissagree with you. The "all channels driven" test is often a good indicator of the pedigree of power supply. Typically a ginormous power supply will have no problems driving all channels simultaneously. Generally speaking, better amps have better power supplies. Quoting a review from another online publication, the Yamaha RX-V4600, with 5 channels driven simultaneously barely put out 40 watts each.(!) I am one to know that most consumers won't ever see that much power at the same time, but it does help to separate that from say, a Krell amp which would be able to deliver 5 channels at rated power simultaneously. So it does help to differentiate when you can't actually open the cover and look. That's what your reviews are for. In the grand scheme of things watts are a terrible spec to compare amp quality,(1000Watt HTIB? yeah right) but all channels driven is a spec on paper for those who have nothing else to compare and it serves as an indication of what's underneath. Whether the tests are conducted under similar conditions.....

As to the original question, I ran my system off of a Denon 5700 receiver with 140 watts per channel for about 4 years and I recently upgraded to a Parasound amp with 125/ch, and the difference was amazing. Even still using the Denon as a Pre/Pro, my system took an incredible leap forward in sound quality. Spend your money on quality of amp and consider upgrading the pre-pro in the future and you will not be sorry. Trust me.

Buckeyefan 1 said:

Fair enough. It appears the HK is the loser at first sight. But is it?
It's the only receiver to claim 75 watts per channel, when in reality, is putting out a bit more (in all 5 channels). Kudos for honesty to HK.

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Yes, but in 2 channel it is barely above its 5 channel rating. So much for being a better amp when those conditions would never come.