Axiom Home Page Forums General Discussion Home Theater How much power do I need - m60 measurements

I measured the power consumption by a m60 speaker.

I’ve done these measurements for two reasons: (a) to satisfy my curiosity, (b) to understand whether I need extra power for quality listening. You know this gnawing feeling - I don’t have enough power, the speakers suck all the power from my receiver, I need a power amp...

My audio: Front – m60(2), Center – VP150, Surrounds – QS8(2), Rear – Klipsch 2.0 (4 Ohms each), Sub – EP500. Receiver – Onkyo 703, rated 100W+100W, 2 channels driven.

My room – 16’x28’x9’, the listening distance 12.5 feet.

What I did: played different tones and tunes and measured the voltage on the m60 with a very accurate Fluke 189 True RMS voltmeter. The power was calculated as Vrms^2/8Ohm. The sound level at the listening position was measured by a RS sound meter, slow response, C-scale.

Ok, now to the measurements.

First, I played 1 kHz sinusoidal wave tone on an audio test CD through the receiver connected to a single m60. I varied the receiver volume and here are the results:

Vrms (V) -- Power (W) --Sound Level (dB)
1.53 //0.29 //72 Pretty quite
2.8 //0.98 //78 Getting louder
6.0 //4.5 //85 Really loud
17.1 //36.7 //93 Piercingly loud

If you plot these results (in log scale) the points pretty much will lie on a straight line, as it’s supposed to be. The sound level corresponding to 1W is 78dB. Now, I’m sitting at 4 meters from the speaker, so to convert this to the standard distance of 1 m I will have to add 12dB. Remember, doubling the distance reduces the sound level by 6dB. So the speaker sensitivity is 78+12=90dB/1W/1m. It’s somewhere between the in-room spec value 92db/1W/1m and the anechoic sensitivity of 89 db/1W/1m. This makes sense since my room is pretty big.

So, from these measurements at about 1/3 of rated power I’m getting the sound level that I can not possibly stand for more than a few minutes!

Now move to some real music. For this I put Floyd’s ‘Time’ in an excellent 5.1 Dolby edition and this time I turned all the speakers and the sub back on as I would listen to a 5.1 material. All the speakers were crossed at 80 kHz.

At the receiver volume of -10dB the sound level was 85dB – this was the maximum I can listen to for some extended time. The average voltage on the speaker was about 2V – this is 0.5W of rms power and the peaks were up but never higher than 10V – this is 12W of power. So even the peak power at this level was only 10% of the receiver rated power! No signs of distortion or receiver strain were observed.

Hope it would help others to make their choice. I’ve made mine

This is all very interesting but jeeze... I'm sure glad I'm right brained.
oz

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I'm sure glad I'm right brained
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Me too

You must be ambi the way you throw those numbers and measurements around.
oz

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I'm sure glad I'm right brained.

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Alas! I'm wrong brained!

Leave it to you! I love it!!!

oz

Good one Jack, but we all know you have a wealth of knowledge.

Excellent methodology and test.

I am going to print and save your experiment.

I think Axiom should hire you! I'm picturing you in a white lab coat and a clipboard doing all these experiments!

Nice of you to say so, Dennis. But, when it comes to what Gena is talking about, there is a paucity of plenitude in the purse, and I much admire those, like Gena, who know what they're doing with all those numbers.

Good test for volume level's, I don't think anyone would disagree that more power louder sound. But as Alan wrote
"Specifications (distortion, noise, etc.) of preamp-processors and power amps are usually a bit superior to an A/V receiver, since there is better internal physical separation of wiring pathways (more room), hence less chance of interference (and resulting noise) from nearby hum-causing component parts."
Can that be measured?

And I thought I was good at math.

Oh no, and female JohnK

Very good, Gena. Keep in mind that in addition to the direct sound, which falls off at a rate of 6dB per doubling of distance, assuming omnidirectional dispersion as a sphere(the area of the surface of the sphere being 4pi[r(squared)],doubling the radius quadruples the area, leading to a SPL 6dB lower), the reverberant sound must also be taken into account. See this analysis , especially fig.10.4.1, for an application of combined direct and reverberent sound. Linkwitz also has an excellent discussion of room acoustics on his site . The information found by scrolling down to "Reverberation distance" and "Amplifier Power to Obtain Reference Level" is particularly in point. At the "critical distance"(aka "reverberation distance"), which is about 3-4' in typical home listening rooms, the reverberant sound is equal to the direct sound and the combined level is therefore 3dB higher. At longer distances, as the direct sound falls off, the reverberant sound remains relatively constant at the critical distance level in typical home listening rooms.

This may seem somewhat technical, but the practical effect is that far less power is used than is sometimes assumed if the combined sound fields aren't taken into account.

"Specifications (distortion, noise, etc.) of preamp-processors and power amps are usually a bit superior to an A/V receiver

Good point and if I start from scratch it would make sense. However, many people think about adding an amp to already existing receiver. Even it's a very good amp it sill has distortions that will be added to whatever the receiver has. So one can end up it with the power that only a very small fraction is used AND more distortions.

Good point John.

I am not an acoustic specialist, so I thought it was loosely called the room gain.

You don't think it would grossly change the result, do you?

Thanks for the info,

Gena

You must be ambi ...

Yes, it's called bi amping

I'm picturing you in a white lab coat and a clipboard doing all these experiments

Well, this what I do. Sort of. Sans the lab coat

I do have to say Gena, I am very impressed with your knowledge, you have probably forgotten more than I'll ever know about this stuff

Michael, of course lower noise and distortion levels are measurable and are made part of a unit's specs. The point is, however, that once these levels are inaudible to humans, reducing them still further(either in a different receiver or a separate amplifier), while showing good engineering, results in no audible benefit(note of course that Alan doesn't say that it does, and his past posts show that he certainly isn't into amplifier "sound").

Only carefully controlled blind listening tests can accurately examine these factors. The classic amplifier listening tests from Stereo Review , which enraged some audiophiles(but opened the eyes and ears of others who were able to get their heads up out of the sand)illustrate the unreliability of open listening. Differences which were lavishly described before the blind tests began disappeared once the name plates and price tags also disappeared. Among the notable results was that the $12,000 pair of tube amplifiers(correctly designed without a flawed "tube sound")were indistinguishable from the $220 Pioneer receiver. So, we can't follow the old "Just trust your ears" mantra unless we make sure that we aren't allowing other influences to mislead us.

Excellent analysis, Gena. Thanks so much for taking the time to document your experience.

Thanks John, great article, once again I'm amazed by your ability to get relevant advice on any subject. It makes me wonder if you and Gena had offspring what the results would be

I've always been curious what speakers JohnK actually owns? I heard a nasty rumor he was a BOSE guy.

Hey Gena!
Very cool post! I'm mostly ignorant about such things but have a few questions (mostly to prove that I didn't just skim your post!!!):

--I assume the fluke connects between the amps' outputs and the speakers themselves? Does the resistance/Ohm rating figure into this as to what a speaker actually draws?

--How fast does the Fluke respond to peaks? I'm curious about those very fast, very short transients.

--Did you re-meter the Floyd music tests with the RatShack SPL meter or base the peak levels on the previous sine-wave readings?

--In another post, you alluded that adding an external amp to a receiver would double the possibility of distortion (I'm paraphrasing). Why would that be the case? The signal is still going through one preamp (the receiver's) and one final amp stage (auxiliary amp).

I don't know enough to agree/disagree on this topic. Mostly, I have a tendency to agree that there wouldn't be a difference in well-designed, reasonably-powered amps. I'm 90% committed to that.

But......
For years, I did own a NAD 2200PE, which (according to the marketing) was designed as a 100 WPC amp in continuous mode but with high power (if I remember correctly, 400 watts for short-term of 10 seconds or so) and enormous capability for short peaks and transients in the area of 1200 watts. Maybe I succumbed to the marketing, but I would swear that a good, dynamic recording such as a Billy Cobham drum solo just sounded much more "real", which I wholly attributed to the reproduction of the transients. Of course, that was 15-20 years ago, and I sold them to buy a cheap Technics surround receiver (because I didn't spend any time listening to music anymore) and wanted multi-channel capability for my video collection. So maybe I just remember the whole thing as going from "separates to a Circuit City special" and was so biased as to not really hear the differences….

God, I DO miss that "Pride of Ownership" of those three NAD separates though. Much as I like my Denon 3805, it's really not the same!

If the M60s where 8 ohm across the board this test would seem correct. As we all know there is not a speaker made that has a straight across the board omh rating. Not to invailidate the test but how can it be accurrate when the fluctuatoin of resistance is not takin into affect.

I must admit that until recently, 'upgraditus' had been starting to take hold regarding the purchase of an additional 2-channel amp/seperates to hopefully 'improve' SQ even at lower volume levels (especially bass), as a majority of people who have upgraded have stated.

After extensively reading posts regarding this very subjective issue, I found myself gradually shifting to a more pragmatic approach, leaving myself open to the possibility that my mind may play a large role in SQ perception in terms of possible improvement upon what I already own.

After reading JohnK's posted article, it just plain makes more sense to me. In my opinion, the only reason to upgrade to a more powerful (at least twice the power) amplifier is to fill a much larger room with louder sound. I won't get better imaging, clearer mids, more dynamics, or better bass at low volume levels. I've got an EP500 helping out down there anyway! Speaker selection and room acoustics play the largest role in sound reproduction. It isn't my intention to upset anyone who believes otherwise... I'm just sharing my own conclusion.

While what Alan says about the specifications between a receiver and a pre/ pro may be true in some cases, I have to wonder if anyone can hear the differences???? When you are talking about THD numbers (differences) of less than .01-.04%, who can hear the difference. Same goes for other specifications.

We have discussed, on other threads, that the MAIN difference between receivers and most pre/pros with seperate amps is the design of the power supplies. So, once again, we are back to how much power do you really need on a per channel basis for your listening pleasure in your home?

I just don't think that we will get a consistent answer to that question.

Mark, thanks for time reading the post.

About the Fluke meter. It allows to capture short peaks, down to 250 microseconds (it’s one period of 4 kHz tone). While by no means it is as fast as a scope, I thought it was good enough for practical purposes. The Fluke was connected right to the speaker’s posts, and the 8 Ohms constant resistance was assumed for power calculation. The SPL was measured for both single tone and music tests.

By no means a 100% accurate test, I think it correctly captures some very practical moments. One of which is it takes less than 1W of average power per main channel to listen at my threshold of loudness. I agree, it’s personal, and some people might like it much louder. At the same level the peaks reach at about 10W or so which is still much less than the dynamic power of the receiver.

As far as comparing the sound quality from a distant memory…. I think JohnK already alluded that only a carefully designed double blind test can prove or disprove that. Other than that it’s only on the personal level of perception.

But, here is a thing. There are trade-offs. My other hobby is photography. You’d be surprised how many people buy ten’s of thousand dollars worth of equipment and then spend all their time taking pictures of brick walls, comparing the sharpness of this to that, resolution of this to that… No money left over to make good prints or travel to photographic locations.

I can afford a $2,000 amp. But the same money can get me a bunch of DVDs and CD’s and a few tickets to good concerts. I’d rather do that then succumbing to a questionable sound improvement. But, it’s me, everybody’s mileage is different.

Nice post......I have a question.
I don't recall seeing a mention, about THD specs in the thread. ( I hope I didn't miss it).
For me, the THD info tells one if the "amp" can indeed, provide clean power...especially at higher listening levels...(if the figure is legit. of course).
Where am I going wrong?........perhaps someone could address this for me, even the ever enigmatic John K.

I agree. First of all, I know nothing about what Gena was talking about...waaay over my head! However, I know what I hear. I had a cheap Sony AVR which was rated with over 3x the power of my first Denon. The sound didn't even compare. Regardless of volume, I couldn't believe the amount of hiss that was removed with the Denon. I didn't even have to put my ear up to the speakers to notice it.

I had the same experience when I upgraded to the Denon 3805, there was no comparison between my old receiver and my new one in terms of music and movies. Mabey that was due to better processing, I'm not sure.

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I don't recall seeing a mention, about THD specs in the thread
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I don't have any instruments handy to measure the THD. However, Onkyo specs are 0.08%, power rated. I think that since I'm way under the power limit that number should be correct.

Terrific experiment Gena! I have the same kind of curiousity about this as you do, but never did anything about it. Now I don't have too I thank you for your efforts.

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My other hobby is photography. You’d be surprised how many people buy ten’s of thousand dollars worth of equipment and then spend all their time taking pictures of brick walls, comparing the sharpness of this to that, resolution of this to that… No money left over to make good prints or travel to photographic locations.

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So...which lens is sharper? Leica or Zeiss? I used to read those photo forums quite religiously. I know exactly what you're talking about. Made me chuckle a bit.

Gena,

Thanks for this post, I was wondering how a separate multi-channel amp would affect my sound as I hear some strain in some loud(not wake the dead ear splitting) vocals. But I am way to stupid and lazy to do measurements.

With 1kHz tone

“Vrms (V) -- Power (W) --Sound Level (dB)
6.0 //4.5 //85 Really loud “

With 5.1 music
“At the receiver volume of -10dB the sound level was 85dB – this was the maximum I can listen to for some extended time. The average voltage on the speaker was about 2V – this is 0.5W of rms power and the peaks were up but never higher than 10V – this is 12W of power.”

These power measurements are 1 channel then 1 of the 5 channels for music ? Amazing how much power the powered subwoofer saves the channel amps.

JohnK,

That article is fantastic, makes a good case for BLIND testing.


Looks like an amplifier does not have much effect on signal quality and buys only undistorted volume, which is what I need if I want to crank it up. I would not go further than something like the 200 Watt Outlaw. My receiver(Yamaha RX-V2400) spec., is 120 Watt rms per channel. Even if that’s shared between the front 3, the Outlaw buys me 200 W rms vs. 40 W rms only half again as loud ? Am I looking at this correctly ?

I agree with the numbers as presented but do find my sentiments follow this line of thought.

As I have said before, "It all may be between my ears".

Bug

Another good article, I think more than a few of us have the same thing between our ears

These power measurements are 1 channel then 1 of the 5 channels for music ? Amazing how much power the powered subwoofer saves the channel amps

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Right. These measurements are for one channel with all the rest 5.1 (or 7.1) ON including the sub. So they all kick in. The mains are relieved from the bass duties and the 500W of EP500 are doing all the hard work.

So...which lens is sharper? Leica or Zeiss?
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Oh, don't get me started . Besides, I'm content with Canon 20D and my 135L. The lens is a marvel

A WATT is a mathematical sum of voltage and current. (One watt equals the production or use of one joule of energy per second)

What is missing with the synopsis that “a power amp” only requires X Watt’s to effectively drive a set of speakers, does not take into consideration that while ONE WATT may be ample to drive a set at some deafening SPL, that ONE WATT may require 60 amperes of current. 120 VAC @ 60 amperes is roughly 7200 Watts.

This is where low end (low current capable) amplifiers can not supply the required current (amperes) to drive those speakers. IE: highly efficient 4 ohm speakers such as the M80.

For example, I have a POS AVR that I picked up at Costco a few years back for a HTIB system that was “rated” at 120 watts per channel. As an experiment, I hookep up my M80’s to it, and it would immediately go into overload protection and shut down when I would try to power it up. I then hooked up a set of M3’s to it and it would power up, but would shut down at half volume.

I’m far from being anywhere close to an EE and would be interested in your thoughts in regards to this (Gena / John).

Interesting stuff. I just want to know where can i get a 5 watt HT receiver with all the options i want.

Gena,

This was an interesting test and it certainly continues to show how at average to moderately high volumes, consumers still only require relatively small amounts of power. However something is still missing from the equation (in practice) which may only be tested at the risk of damaging your system, something a friend of mine tried some time ago.
If i understand your measuring correctly, you hooked up a single M60 to test the power consumption at limited frequencies, then turned on all other speakers plus a sub and set the speakers back to 'small' before testing music (some inherent holes in the measuring by doing this, but easily rectified). Ayway, with all channels running, the amount of power consumed will actually be x times the wattage per each speaker. In your example of peaks ( and assuming the setup consisted of 4-M60s), 12W peaks times a 4 speaker setup brings the total consumption into a 48W range, well below the rated output for a receiver but about 50% of its rating, not 10% (and these numbers use the subwoofer "on", mains set to "small" power values).
Next take that 4 speaker setup and turn the receiver up to 100% (or maybe even less) and measure the output as it drives the speakers once distortion begins.
You may find that the total wattage consumed is still not beyond the rated output of the receiver (a guy i knew tested something similar). So if this is the case, how is it possible that distortion is present if the measured consumption 'should' be under the rated receiver power output?
Here's where capacitors and power supplies (size, quality) comes into play for energy storage/flow during sound playback and power consumption (rates vs. capacity). This is usually where receivers fall short of separate components...but again only at higher SPL, varying with room size, amount of low frequency energy being played, speaker size, impedance or the other usual suspects as to why a receiver drops out before separate SS amps.

I wish i could provide more details on the experiment but it was done quite some time ago and my memory is faded. I don't know the guy anymore.
Food for thought.

Incidentally, my listening preference for movies is often lower than for music. When i'm playing pool in the room next to the media room, my Axiom system can average 94-98dB at the seating location (about 11'). I only have a receiver at this point but will likely add an external amp for the mains to give me a bit more overhead as the 100dB point is approached, distortion can begin (on my system).
My larger Tannoys upstairs typically average 104dB (also at about 11') when i'm listening to them while cooking in the kitchen. I'm planning on getting a larger amp since the one driving them is incapable of overdriving them. I would rather have an overpowered rather than an underpowered amp for those pricey dickens.

A WATT is a mathematical sum of voltage and current.

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Power=Voltage x Current. Using the Ohms low U=IR that can be written as W=U*I=U^2/R=I^2R.

In your example, 1W into 4 Ohms requires only 0.5 A. That is an easy task for your amp. However, if you want to drive a 100W into 4 Ohms that would require 5A and may be your amp was not rated for that, I don't know. May be it was hitting the rail voltage limit.

These numbers are the power into the load. The power from the wall can be higher, by a factor of 2, so the amp was trying to draw a high current from the wall and was hitting the fuse limit. It's hard to say.

But, again, 1 W into 4Ohm requires only 0.5A of current and it should be a peace of cake for any decent amplifier.

...brings the total consumption into a 48W range, well below the rated output for a receiver but about 50% of its rating...

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Small correction. The receiver is rated 100W+100W, 2 channels driven, so it's at worst 25% . Plus there there is power in all other channels as well, may be 50Wpc, so over all the figure would be closer to 48W/300W = 16%. Still plenty of headroom

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12W peaks times a 4 speaker setup brings the total consumption into a 48W range, well below the rated output for a receiver but about 50% of its rating, not 10%

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You make some good points, but typical amps are rated at X Watts per channel, not total. Certainly depends on the amp. There are many different ways of expressing the ratings that can me misleading to some.

A decent amp usually denotes the Watts per channel rating with "all channels driven simultaneously into 8 Ohms at 20Hz-20kHz". Less desirable is the "driven with 1 kHz".

The other thing I've seen recently is an amp rated at 110 WPC driven into only 6 Ohms, which works out to be about 80 WPC into 8 Ohms. I think it is the manufacturers way of inflating their specs to the consumer.

Gena and Others:

This has been a most interesting and stimulating thread and has stimulated me to do some "deep" thinking!!

Let me try to make a case for requiring more than 100 Watts of Peak Power. This may answer, at least in part, why some folks report better sounding music with the higher power amps.

Lets use some of Gina's data (and maybe I will take a little liberty with an "assumption" or two).

1. 5 Watts for 85 dB SPL (some board members report listening at 90 -100 dB SPL)

2. Factor of 24 between Peak and Average (.5 W average versus 12 W peak)

3. Speaker impedance is not fixed across the spectrum (may dip from 8 ohms to 4 ohms or lower)

Ok, lets take some of you folks who like to listen at 85 dB SPL, no louder. That's 5 watts. Multiply that by 24 is 120 watts (consider just a single channel). Lets "assume" that the impedance dips, at the same time to 4 ohms, then we have 240 W of peak power.

Now, if you want to listen at 95 dB SPL, that equates to 2400 Watts of peak power.

I don't know how realistic this hypothetical case is, but it does demonstrate that you may need much, much more than 100 W of peak power to accurately reproduce your music at moderate to loud listening levels.

I think that this analysis would apply to fronts and center channels. Rears and surrounds probably an order of magnitude or two less.

Alright, what say the tribe?

Ratpack,

I am not really an expert in loud listening:)

You have shown very convincingly that by applying certain numbers and assumptions one can arrive to an absurdly high number - 2400 W per channel. That's the SuperDome class acoustic.

I see you have the same Onkyo 703 as I do. I think it's a very capable and powerful receiver. However it might be not so for you.

Here's what I would suggest. Pick an inexpensive multi-meter and measure the average power coming into your speaker. You can measure the voltage if you connect it to the speaker's posts or the current if you connect it in series with the speaker. Then you will have an idea how much power the receiver puts out into the speaker at your listening level.

Now, granted it will be the average power. If you have a scope, you can make the same measurements for the instantaneous power. If not, well, you can apply some reasonable multipliers. At the end, I believe, it will make the decision of whether upgrade just a bit more sound

Secrets of Amplifier and Speaker Power Requirements Revealed

Lots of points raised, I'll make some brief comments.

Larry, blind listening tests have shown that THD has to be more than about 1% to be detectible when listening to music rather than pure test tones. The THD numbers for any of the units which we would seriously consider are far below audibility when operated within their designed limits.

Speakerchooser, the 120 watts of your Yamaha are measured according to the FTC regulations with two channels simultaneously driven at full rated power for at least five consecutive minutes. The three front speakers don't "share" this. The difference between 120 watts and 200 watts is 2.22dB in maximum sound output; e.g. if a peak could be played at 110dB with 120 watts, it could be played at 112.22dB with 200 watts. Both figures are higher than likely to be needed for home use.

Mike, the controlling element is voltage, not current. For 1 watt into 8 ohms a bit under 3 volts is required(V[squared]/R)and about a third of an ampere(P/V)rather than 60 amperes.

Bernard, the calculation of power required has to take into account both the reverberent and direct sound fields. This is as was described in the Voelker and Linkwitz material that was linked in my first reply here. They should be studied carefully(especially the Linkwitz power calculation) to understand why less power is used than is sometimes thought.

Gena: I'm not really interested in doing any experiments. I think that you did an excellent job.

My point was that you could take a lot of liberty with my numbers and still come up with peak power requirements of more than 100 Watts.

One other thing to consider is that solid state amplifiers are not very forgiving to peaks (spikes) that exceed their maximum ratings. They can be destroyed very easily by fast spikes containig very little energy.

In the course of all of this discussion, I think that I have convinced myself that if I get a seperate amplifier, I want at least a 3 channel unit (RCL).

This is a most interesting thread.

By the way, what color is your 703? I bought silver.

Wid: an interesting article by Alan. In so many words, I think that he agrees to my analysis.

Rat one thing is for sure this thread has not convinced me to trade in my amp .

Your reply reminded me of Alans article, that's the reason for the link. I don't think you were to far off base.

John: my bottom line was that you could take a lot of liberty with my numbers and assumptions and easily come up with peak power requirements far in excess of 100 watts.

This is especially true for those who listen at levels at or above 90 dB SPL.

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Small correction. The receiver is rated 100W+100W, 2 channels driven

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Yes i slipped back into a thought on my own receiver which is rated at 100w/ch, but as all channels are driven, the reality is more like 70w+ per ch.
In your case, 100W + 100W would be a split.
Dual power supplies?
Dual mono design?
Or just a spec?

It seems like plenty of headroom, but push those dB into the 90+ range and watts consumed still fall under the max. rated spec yet distortion is created.
The paradox of it all!!

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3. Speaker impedance is not fixed across the spectrum (may dip from 8 ohms to 4 ohms or lower)

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Rat, this is something i briefly noted earlier as a variable unaccounted.
Gena measured the individual situation with the originally described setup so the numbers apply properly in this case. When deriving 'what ifs' for other situations then the idea is expanded just as you did and obviously an argument can be made in the second instance.
In Gena's example (or rather real world situation) this newly derived situation is moot.
However, it would apply to me since i own speakers (6ohm) that do dip to 4ohm, in a large room, and as such, i need a beefier amp for the SPL i use with this specific setup.
All i use is a receiver in my 5.1 media room though. The area is small enough (and speakers less demanding, more efficient) to attain the SPL i require. I've already setup my receiver to stop its volume increase before its distortion point is hit, plus a small safety margin.

How did you set up your receiver to prevent clipping?

By the way, what color is your 703? I bought silver.
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It's silver too

The receiver has a max volume setting to limit anyone from cranking up the knob to 100%. I set that limiter to 83% or 83 on an absolute scale of 100 which incidentally is the units' reference point. The receiver also has a limiter for subwoofer output as well but i leave that off/unlimited.
I've done some testing in the past and usually above the 90 mark distortion begins with my M60s (playback material dependant). As such, setting the unit to max at 83 means i always know it is well below a clipping point.

We tried a similar test with a friend's Tannoy S6s and an Anthem amp (225w/ch). We had the speakers hitting their excursion limits (only very briefly) w/o detectable distortion and at relatively low gain %s so we knew that his amp had more power than the speakers could consume. Hence, he really doesn't have to worry about distortion blowing his drivers (electrically caused damage), but he does have to worry about more direct physical damage to the drivers if he pushes them too hard.

I probably should have also asked what receiver do you have and is the setting internal or something that you can so external with your remote?

Ratpack,

If you're asking about Onkyo 703 it's done via remote control Setup==>Pereferences==>VolumeSetup==>MaximumVolume. By default it's set to OFF but you can set any level.

It also has another useful setting - the turn On level. By default it is set to LAST, and if the last night you're listening at 0dB and turn it back on at 6 in the morning... Well, your family is not going to be happy I set mine at -45 to provide a smooth start.

Regards,
Gena

I find this thread fascinating. I wonder what I am missing without separate amps, but I have no desire to pay for something that doesn’t do much for me.

Gena,

Unfortunately it seems like test equipment is specified just as aggressively as audio equipment. 250 us acquisition time is for repetitive peaks, 2.5 ms for single events, which is 1 cycle at 400 Hz. This is, of course, buried in a foot note of the extended specs. of the Flukemeter. It seems likely that musical peaks typically last longer than 2.5 ms anyway, so it does not matter. I have no idea, maybe someone who knows about the duration of musical peaks can comment ?

My receiver claims to handle 7, 120 W rms each channel 20 Hz to 20 kHz, with 0.04 % THD into 8 Ohms. Max. of 175 W with 10 % THD. Dynamic power 8/6/4/2 Ohms of 155/195/250/330 Watts (no distortion rating). It is not clear on how many channels this is for at the same time. I think it cannot be more than 2 since the unit consumes 500 W. Outlaw states “all channels driven at the same time”.

If my peaks are 24 X like what you have measured with Floyd, average could be 120/24 = 5 watts. If 240 is shared between 3 fronts then 3.2 W. I don’t believe it is playing at 95 dB undistorted. My room is a bit smaller than yours and fairly reflective.

As mentioned above things are material dependent, but I can play most things at a loud (rock the house or almost but not quite orchestra seat level for the other half) without distortion, but not extremely loud, approaching concert or live music in a small venue level. I am not an audiophile who listens to minute differences.

It gets down to personal preference and how much you want to pay but I definitely understand the case for more power, more so for an efficient speaker. But if for $ 1500.00 I get 600 W instead of 200 or 250 W across the front 3 I’m thinking it’s not worth it. That is only 4 or 5 dB, which is not even twice as loud.

Gena: thanks for input about the 703 setup. I have read the manual several times and just did not pick up that capability.

It never hurts to have a second or third set of eyes/ brains.

speaker: remember that the bottom line issue is not absolute dB or power. The bottom line is how much peak power do you require to accurately reproduce the music at your desired listening level (SPL) in your home theater.

I just don't think that there is a universal answer for this question.

Chooser, the basic 7 channel, 120 watt, 20-20KHz, 0.04% THD, 8 ohms rating of your 2400 can be relied upon as accurate since it's governed by the FTC power regulations and a manufacturer would be foolish to violate the regs with bad numbers. Under the regs the rating for a multi-channel unit has to be taken with at least two channels driven at the full rated power for at least five consecutive minutes. If nothing is specifically said, the rating is to be understood as being with two channels driven; manufacturers have the option to test with more than two channels driven(e.g. "all", although this isn't a realistic scenario for home, rather than laboratory, use)and will state that as part of the spec. However, the 500 watt power consumption figure has no connection with the maximum power rating. Unless the power consumption rating is specifically described as e.g. "maximum", it's an average figure derived during a UL required test for overheating with all channels driven at 1/8th power(considered to be roughly the average power consumed over the course of playing an entire CD). Although class AB amplifiers are roughly 50% efficient at full power, efficiency falls steeply at lower power levels and is roughly 20% at 1/8th power. 1/8th of 840 watts(7x120)is 105 watts, and at about 20% efficiency will require about 500 watts of consumption. So, there's no inconsistency between the seven 120 watt channels and the 500 watt consumption figure, although we read comments to the contrary by those uninformed on the matter

A little on power peaks. The IHF Dynamic Power rating is derived by using 20 millisecond tone bursts repeated every 500 milliseconds. Although this varies somewhat with the instrument involved, 20 milliseconds was adopted by the IHF as being a typical number.

Note again that if you'd like to know the requirements for power, that the two sources from Voelker and Linkwitz which were given earlier are very useful, since the entire sound pressure level from combined direct and reverberent sound has to be taken into account to get a realistic number. Since over half of the sound reaching a listener in a typical seating position comes from reverberent, rather than direct, sound, considering only the 6dB decrease of the direct sound for each doubling of distance doesn't describe the total situation.

John,
Thanks for the wealth of information. I really enjoy reading it.

This really has been an excellent thread!!!

Of course there are those who have measured receiver amplifier section output and found a substantial variance between actual output and rated output.

http://www.geocities.com/Area51/Hollow/3401/ratevsac.htm

2x6, note that the linked site, whether done intentionally or not, is misleading and has been a cause of unwarranted suspicion. The manufacturer's ratings are in the majority of cases with the FTC reg required two-channels driven, yet the site doesn't show that, but rather a five-channels driven number. The tests(including Stereo Review/S&V) have confirmed the accuracy of the ratings and any "variance" has been to the upside.

Your post moved me to google ratesvac to see if there were any posts which suggested that the site's tests raised "unwarranted suspicions," or are regarded by the audio community as misleading. I only went through 3 pages, but I did not see any discussions which would support your contention. To the contrary, several respected audio sites, and discussions refer to ratesvac test results as authoritative.

Your suggestion that it is misleading to test multichannel receivers for output with all channels driven confuses me. Seems to me that it is misleading for manufacturers to rate a 7 channel receiver at 100 watts per channel (or 7x100 watts) when the receiver is not able to produce even half that output with all channels driven.

I had a Sony STDB1070 receiver which Sony rated at 6x100 watts. Although I liked the receiver, and thought its processing section was pretty darn good for the money, I always thought its power output was seriously overrated. Sure enough, ratesvac tested the 1070 and found that it was putting out only 31 watts per channel. Now, it is difficult for me to understand how you can say that Sony's rating of 6x100watts (that was what the sticker on the receiver said) is proper, while ratesvac publication of the true 'all channels driven' output of 31 wpc is misleading. Perhaps you can explain that to me.

Read the law, counsellor.

Thanks for the explanation. Very helpful. Seems to me that if the law permits manufacturers to mislead the public, there's a law that should be changed. Also seems to me that such smarmy regulations which permit manufacturers to mislead the audio consumer should be criticized rather than embraced by folks who are interested in audio and in truth in advertising. But, hey, there are lawyers who live for the loopholes. I guess you think that's how it should be.

2X6: if you will read the FTC Regulation that John referenced, you will see that he is correct in what he says.

I'm not saying that the FTC Regulation is right, wrong, or indifferent, but it was an ATTEMPT to force manufacturers to more accurately specify their gear. Read some of the FTC commentary leading to the Regulation. You may find it quite interesting.

I'd really like to see the FTC do the same sort of thing with speaker wire/ cables. If such a thing were to happen, watch all the charlatans cry foul!!!!

Back to the “how much power do I really need question”.

My M80’s driven by a HK 7300. A pretty respectable AVR by anyone’s standards for power capabilities. I have a set of M22’s in parallel as my center. QS-8’s, and an EP 600. All this is an area that is 10’ X 10’. According to your calcs and the hard line that John has always taken here about the “how much power do I need” topic, any ol’ AVR rated at 50 watts per channel or less would be more than adequate. Right??

I don't think so.........

Last night the little lady was out so my son and I watched a movie the way we like them, “movie theater loud”. (great kid, takes after his old man)…….We watched Spawn (his pick this time). I bumped the volume up to what sounded about right, which just happened to be -10 on the AVR. The AVR goes from a -80 to +8. (It was roughly 85%). Out of curiosity, I pulled out the RS meter just to see how loud things were getting. On the C setting, slow response, normal dialog was around 75 db. Gun fights and action scenes would get up to 95 db with an occasional spike over 100 db. Just for the hell of it, I ran the volume to max, and guess what; it didn’t get all that much louder. (the EP 600’s volume is just about ¼ up).

That was watching a movie………………..

Listening to stereo is completely different. I don’t know how loud it’ll play. Well over 100 db’s at 12’. That’s as far as I’ve had it.

You can’t just say “a 50 watt AVR will be just fine”. It very well may be just fine for YOU and at YOUR listening levels. But it sure in the hell wouldn’t cut it for ME. And it may not cut it for half the folks asking the question either.

mdrew: I think that you just verified my above analysis that seems to indicate that for loud listening, you need more capability than 100 watts of peak power, at least for the fronts and center. It may be that the peak power capability is far more important than the average power capability. At least, that is what I am currently thinking.

I, too, was playing around last night with the SPL meter. I find that anything averaging 91-94 dB SPL on the meter is just too loud for me to enjoy. 87-90 dB SPL is about as loud as I would like to listen. But, that is just me.

Boy, I'm glad I skipped this thread...

This has been a great thread. What don't you like about it?

I agree with you fellas. I usually listen to movies at 72db. Music, a bit less. Most of the music I listen to is jazz or female vocals, so it tends not to be too taxing on the amps. My Thiel CS 3.6 fronts are 4 ohm power hungry monsters, so I use the Yamaha Monster M-80s which are rated at 330 wpc, continuous 4ohms, at 0.02% distortion, Dynamic power (1KHz/4ohms) 640 wpc; Signal to Noise ratio 127db!!!; Damping Factor (1KHz/8ohms) 250. I figure they deserve some headroom. Great combination with the Yamaha brutes - power for the power hungry. Axioms are efficient. and the 8 ohm speakers at less than ear-splitting volumes don't need much power, but if you have a high quality amp (sounds good), then the more the better.

As to the FCC regs which permit manufacturers to rate multichannel amps on a per channel basis when the output is only accurate when 2 channels are driven is simply a license to proliferate false and misleading advertising. If a mfgr rates a 6 channel receiver's amp sections at 100 wpc, and when 6 channels are driven it only puts out 31 wpc, then anyone who relied on the 6x100w rating has been deceived. Simple.

Johnk,

Thanks great info. So is the blind listening comparison of amps. This stuff is just gold when trying to decide how to spend your A/V money.

My room is a little smaller than Gena's and probably a lot more reflective, so I would expect to get to ear splitting without strain or distortion.

I am beginning to think the "strain" I am hearing at loud but not exceeding loud volumes in some material may be due to the material. When I turn down the volume I think I am hearing it when near the speaker but not in the listening position. Maybe just a hot mic, close mic, or saturated mic on some of my recordings. They are modern recordings and otherwise well done so I did not notice. Nora Jones "Come Away with Me" is the CD I heard this on most. Not sure if there are any fans with amps in their system. Wish I had an amp. to compare.

Mike, you may have confused me with another poster; nothing like that was said.

A short course for the technically challenged like myself.
Link

As luck would have it I did get a loan of an Anthem 5 ch 225 W rms amplifier to compare to my integrated Yamaha RX2400-V 125 W x 7ch receiver's amps.

In each case the "distortion" or harshness I heard was on the recordings. Both the Yamaha and the amp play to, FOR ME(and others listening), painful levels with no discernable distortions or differences. I am not claiming there wasn't any, there obviously is if you look at the specifications or measure, just reporting that I could not hear them. I am not an "expert listener" or an audiophile just posting my experience in case it is of use to someone.

I would still go with separates if it was in the budget, but my next purchase will be rear channel backs if I start getting 7.1 DVDs or an HD DVD player.

My setup
M60ti
VP150
QS8
Velodyne DLS-4000 Sub
Yamaha RX-V2400
Room is 15 x 18" open at one corner and part of one side. Carpet but wall surfaces are fairly reflective. Listening position if 12'.

Speaker,

Thanks for the great input. Indeed, it backs up my conclusions from the power measurements and hearing observations.

Your input is very valuable since you've had an option to compare the amp and the AVR side by side. Too many anecdotal evidences from childhood memories are floating around

Regards,

gena

For me it absolutely does back your conlsusions. Glad you experimented. Really helped me make useful A/V spending decisions.