In(non)credible power ratings

[Kevio]

I stopped into Best Buy the other day and saw a selection of home theater systems with very small speakers and very big power ratings (http://www.bestbuy.com/site//olspage.jsp?id=pcmcat167300050037&type=category). Doesn't seem likely that you would be able to get 1500 watts out of a system that would fit into a laundry basket.

Anyone know what's going on here?

[audio amateur]

Why do you care?

It's surely the credit crunch forcing them to push up the numbers and hope there will be more customers

[markw]

Actually, I think it's a very good question.

[sarcasm mode on]
The great unwashed, unlike us superior beings, have only a superficial understanding of audio and fall prey to a few well-placed superlatives that focus on the little terminology thsy seem to grasp.

Witness the sales of Bose. Surely their sales do not depend on the seasoned audiophile (like us) but on the ignorant folks with more money and ego than knowledge of audio.

Likewise, "watts" is the end-all and be-all to many of those, although the lower income masses seem to be more succeptable. Notice that Bose never mentions these.
[/sarcasm mode off]

As far as watts go, there are watts and there are watts, and it all depends on how they are measured, and home theatre manufacturers aren't mandated by law to state how they are measured.

For instance, take an amp that's made for sale in the audio domain that measures 5 watts, 20 - 20khz +- .5 decible, at .05 percent distortion, with all channels driven.

Now, (and I'm guestimating here), if we were to measure that amp at 1,000 hz only, and extend the distortion to, say, 10%, and we only drive one channel at a time, then that amp may well measure in the neighborhood of 50 watts. Now, if we just measure a high-level input burst for just a millisecond, it may more than double this figure.

Maybe this link will explain it better : http://sound.westhost.com/power.htm

[GMichael]

Actually, I think it's a very good question.

[sarcasm mode on]
The great unwashed, unlike us superior beings, have only a superficial understanding of audio and fall prey to a few well-placed superlatives that focus on the little terminology thsy seem to grasp.

Witness the sales of Bose. Surely their sales do not depend on the seasoned audiophile (like us) but on the ignorant folks with more money and ego than knowledge of audio.

Likewise, "watts" is the end-all and be-all to many of those, although the lower income masses seem to be more succeptable. Notice that Bose never mentions these.
[/sarcasm mode off]

As far as watts go, there are watts and there are watts, and it all depends on how they are measured, and home theatre manufacturers aren't mandated by law to state how they are measured.

For instance, take an amp that's made for sale in the audio domain that measures 5 watts, 20 - 20khz +- .5 decible, at .05 percent distortion, with all channels driven.

Now, (and I'm guestimating here), if we were to measure that amp at 1,000 hz only, and extend the distortion to, say, 10%, and we only drive one channel at a time, then that amp may well measure in the neighborhood of 50 watts. Now, if we just measure a high-level input burst for just a millisecond, it may more than double this figure.

Maybe this link will explain it better : http://sound.westhost.com/power.htm

Then, if the system has 5 speakers, they multiply that 50 by 5 to get 250. Then... add in the sub measured the same way and BAM! you get into the thousands.

[f0rge]

it's all "advertising", based on peak power. i'd wager the RMS power is much much much lower

[audio amateur]

I wonder what kind of wattage they would tag to a Krell multichannel amp..

[markw]

I wonder what kind of wattage they would tag to a Krell multichannel amp..Well, you read the article. Do the math

Those faks audio/boombox/car stereo/computer speaker manufacturers have always played fast and loose with specs. Here, "real" audio manufacturers are held to higher standards, by law, than mass-electronic/plastics manufacturers. Isn't it the same there?

[audio amateur]

Well, you read the article. Do the math

Those faks audio/boombox/car stereo/computer speaker manufacturers have always played fast and loose with specs. Here, "real" audio manufacturers are held to higher standards, by law, than mass-electronic/plastics manufacturers. Isn't it the same there?
Ok let's see., We'll take the Krell 'TAS'. 200 real per channel.
According to you, that's 20*200=4000 fake watts 'per channel'. We double it, that's 8000:ihih: watts (peak?) . Now, according to GMichael, we multiply that by 5 (after all, this is a multichannel amp). That's 40000 watts:skep:

This sucker does have a 4000VA PS. I bet if it was just one channel, 1KHz into 1 ohm load @ 10%THD, it could do it:cornut:

[GMichael]

And heat your house at the same time.

[markw]

Ok let's see., We'll take the Krell 'TAS'. 200 real per channel.
According to you, that's 20*200=4000 fake watts 'per channel'. We double it, that's 8000:ihih: watts (peak?) . Now, according to GMichael, we multiply that by 5 (after all, this is a multichannel amp). That's 40000 watts:skep:

This sucker does have a 4000VA PS. I bet if it was just one channel, 1KHz into 1 ohm load @ 10%THD, it could do it:cornut:I didn't even consider taking the measurements at an unrealistically low impedance.

[Kevio]

Maybe this link will explain it better : http://sound.westhost.com/power.htm

Thanks for the reference. Funny stuff.


As far as watts go, there are watts and there are watts, and it all depends on how they are measured, and home theatre manufacturers aren't mandated by law to state how they are measured.

Didn't the FTC stick their nose into this issue at one point? But that doesn't apply to home theaters?

[markw]

Thanks for the reference. Funny stuff.



Didn't the FTC stick their nose into this issue at one point? But that doesn't apply to home theaters?Yep, back in 1974 initially. It's been revisited more recently but basically remains the same. Ultimately, only "music" systems are subject to it but boombox/car stereo/computer speakers/HTIB's are excluded from the more stringint specs. HT receivers (not HTIB) do play somewhat fast and loose, but nowhere as bad as the others.

But, many of the more respected brands are pretty up front, although the all-channels driven power output is generally much less than the rated output when only one channel is driven.

Sound and Vision magazine does a pretty good job of illustrating this when they test stuff.

[JohnMichael]

Yes I remember when the turntable on top of the receiver with the two speakers claimed incredible power ratings. The FTC stepped in and all the stickers were removed from those "stereos". Then you could really compare receivers and amps. We are drifting into inflated wattage again. My Onkyo A-9555 is rated at 85 watts FTC. It is also rated at 100 watts into 8 ohms and 200 watts into 4 ohms by some rating system that I do not know. I think I have an 85 watt integrated amp.

[Florian]

Take a look at my new amps. They are huge and weigh 245lbs a piece. Consume about 2500 watts of electricity and give out only 200 watts but in pure class a. Now compare size and weight....and youll see how even Brands like Rotel, NAD etc... completely twist some facts

[E-Stat]

Consume about 2500 watts of electricity and give out only 200 watts but in pure class a.
That is a misleading statement. There is no question that class A designs are less efficient than AB or switching designs, but even then the efficiency typically runs about 30% - with some better than that. I think you'll find that maximum consumption for most Krell designs occurs at very low impedances like 2 ohms where the output is much higher than the nominal 8 ohm rating. Chances are the amp puts out closer to 800 watts under those circumstances. Take at look at their current SOTA product, the Evolution One (http://www.krellonline.com/new_pdfs/Evolution_One/0172_076_MAN.pdf). It is rated at 450 watts and has a maximum consumption of 3600 watts. But wait, that rating is at 8 ohms. At 2 ohms, it produces 1800 watts class A. If your design is truly only 8% efficient, then clearly D'Agostino has learned quite a bit in the past twenty years.


Now compare size and weight....and youll see how even Brands like Rotel, NAD etc... completely twist some facts
Would you provide an illustration? My NAD AV receiver is rated at 600 watts total and consumes 840 watts at maximum. 71% efficiency is quite typical for AB designs. And that is for all six channels - where in typical real world cases, the rear channels don't require full output. I would not, however, use this amp to drive challenging loads either of the extreme low impedance variety like yours or the equally brutal reactive load of my electrostats. :)

rw

[E-Stat]

Anyone know what's going on here?
Despite changes by the FTC for some components, the power inflation game really hasn't changed since 1970 when I bought an Electrophonic receiver with built in 8 track player. It was rated at 100 Instantaneous Peak Power watts. Translation: for a short duration of time (think particle collider brevity), it will generate that output at one mid band frequency. Today as then, such ratings are pure fantasy. On the other hand, switching amps have significantly changed the weight/efficiency equation. While I'm not a fan of those designs, one can truly have 20 lb kilowatt amps.

rw

[Florian]

Hi E-Stat,

i am talking about pure class A designs. The new EVO series is not pure class A. Actually none of the newer Krells are. The closest thing to the KRS200 Dan ever designed (according to his own words) is the MRA. The KRS, in IDLE (no connection) takes 2500 watts out of the socket and gives out 200watts (620 when measured)...... i am not a tech but this tells me that its got huge power reservers in it. It shows when you play at any level, the power consumtion does not increase as the socket. It all goes into heat..... The current Krells and EVO are in my opinion not state of the art and no match to the old pure class A designs. KRS.... or the new MRA.

Cheers

PS: It delivers 125A of current, not peak but always. Same as the power, it never draws from the socket to feed the outputs. Never switches to class B either.

[E-Stat]

The new EVO series is not pure class A. Actually none of the newer Krells are.
So what does he mean when he says of the Evo:

"All transistors operate in Class A mode."

rw

[Florian]

So what does he mean when he says of the Evo:

"All transistors operate in Class A mode."

rw

Its marketing i believe, i talked to Dan's son today on the phone and the KRS as well as the large KAS and MRA are the only amps that work 100% in class A at all loads. I believe that the Evo takes the input signal and only scales the transistors into class A for what the input signal needs.

[E-Stat]

Its marketing i believe...
Ok, so you need to include Krell with your indictment of companies with misleading information. Or else you are drawing a distinction they find irrelevant.


I believe that the Evo takes the input signal and only scales the transistors into class A for what the input signal needs.
I'll leave it to their better judgment as to what works best - unless you assume that the company has gone downhill over the intervening two decades in their commitment to delivering leading edge performance products. An amp with only 50% efficiency is clearly highly biased and not of the AB ilk.

Of course, none of this has anything to do with Kevio's topic about bogus watts. :)

rw

[audio amateur]

i don't think Rotel/NAD misspecifiy the wattage of their products. Simply, they are not class A neither are they meant to drive very low loads. Add that to the equation and you'd have much heavier Rotels and NADs..

[E-Stat]

i don't think Rotel/NAD misspecifiy the wattage of their products. Simply, they are not class A ...
There are two separate issues here, one irrelevant to the topic of inflated ratings. First of all, NAD doesn't claim to make class A amps. Who says they do? As for ratings, the figures for my T763 receiver aren't inflated as an AB design so long as you reference the FTC continuous rating for all channels driven. Yes you will also find the older and higher IHF rating as well. Flo has not provided any proof to the assertion they engage in "twisting facts". Measured performance of the two NAD products tested by Stereophile in the past five years show no such inflation.

You are correct regarding current capability. My '81 Stasis has one third the power of the NAD, yet it weighs a good bit more. It is designed to drive difficult loads and served that role very well for nearly twenty years driving full range electrostats. It also runs a much higher bias for class A operation up to about ten percent output. It uses a 1.2kVa transformer and thirty-two 150 watt output devices for simply 100 watts / channel. Consequently, it uses no active protection circuitry at all. But again, I see drive capability as a separate issue to the OP's topic!

http://home.cablelynx.com/~rhw/audio/stasis.jpg

If you want to view power inflation using absurd levels of distortion, follow SVI's latest entry in the computer audio section. :)

rw

edit: Sorry, I see we agree. I guess I'm still in fighting BS mode with one individual...

[pixelthis]

Its like car stereo, more fantasy than reality.
"regular " audio equipment bought by enthusiasts is under a lot more scrutiny.
People who buy these "HTIB" systems dont give a hoot.
And they will never get caught because the small speakers are highly efficent.
But there is always wiggle room.
Receivers used to be a certain power rating at "1,000" hz, which is great if all you listen to is music at 1,000 hz.
TODAY they advertise 20 to 20,000 hz, and its RMS.
What they dont tell you is that the power supply couldnt keep a clock radio going,
but they know that if you went to full power you would go deaf in short order.
So they dont worry that the receiver will melt down after ten seconds of "full" power.

Basically a HTIB is a P.O.S powered by car stereo amps if its a "higher line" model,
and by clock radio amps for the cheaper stuff.
KINDA like boom boxes.
They are like whiskey, in other words, made to sell, not use.:1:

[Woochifer]

Thanks for the reference. Funny stuff.



Didn't the FTC stick their nose into this issue at one point? But that doesn't apply to home theaters?

The loophole is one of the Mack truck-sized variety. During the wattage wars of the early 70s, the FTC standardized how the power output specs on amps must be reported. It had to use wideband frequency test, and the output had to be sustained. And for a while, you did have honest power ratings that routinely matched reviewers' benchmark tests. But, this only applied to monophonic and stereophonic amps/receivers.

With the advent of multichannel amps/receivers, manufacturers once again began playing fast and loose with the specs. They would often report the power output using a single channel or two channels driven. More and more, I'm now also seeing single-channel tests using a single-frequency test tone reported alongside the more demanding wideband test tone results.

But, what you almost never see in a manufacturer's specs is the all-channels driven output. On just about any monophonic and stereophonic amp/receiver, the all channels driven output will routinely exceed the rated output on a test bench. With multichannel receivers, I've seen some models output less than 25% of the rated output on an all-channels driven test.

A lot of the ads you see at Best Buy are not what the manufacturer reports, but something cooked up with BB's ad writers. A receiver or amp manufacturer might be truthful when specs a receiver at 100 watts/channel, but it does not mean that it will output 100 watts to all seven channels simultaneously. The wattage is a nonsensical way of comparing components to begin with (with most speakers, you're already going to be well above normal listening levels with just 1 watt of output), but consumers like to see big numbers and until someone comes in and clamps down on how these specs get reported, we'll continue to see these "700 watt" HTIBs.

[hermanv]

Ok, so you need to include Krell with your indictment of companies with misleading information. Or else you are drawing a distinction they find irrelevant.
<snip>
Of course, none of this has anything to do with Kevio's topic about bogus watts. :)

rwThe newer Krell design is not of a recognized class, that is to say it is not a traditional class A nor class AB.

One of the characteristics of class A is that the "push" stage current doesn't fall to zero when the "pull" stage is at maximum. This also true of the Krell design. In traditional class A the total current in the output stage does not vary from zero to full output, this is not true of the Krell design.

It is my understanding that Krell dynamically adjusts the bias current in the output stage, in this way none of the output devices ever turn fully "off". This gets you much if not all the benefit of a traditional class A design.

[Smokey]

I stopped into Best Buy the other day and saw a selection of home theater systems with very small speakers and very big power ratings. Doesn't seem likely that you would be able to get 1500 watts out of a system that would fit into a laundry basket.

Anyone know what's going on here?

Extremely high THD (Total Harmonic Distortion) 10% of those systems pretty much say what is going on here.

[Worf101]

I remember the first time I saw some crappy home computer speakers rated at 200 watts. Now I've been playing bass for pay with professional gear since Nixon was President, power to weight for bass reproduction I KNOW. They made me laugh. I laughed even harder when HTIB's started showing up. Ah... memeories.

Da Worfster

[audio amateur]

Nice amp E-Stat. What is it driving?

[E-Stat]

Nice amp E-Stat. What is it driving?
The Stasis drives double New Advents in the garage. Originally, I used it with Acoustat electostats for nearly twenty years before it was replaced with VTL monoblocks. Having 400 watts at 4 ohms is a bit overkill, but at the power levels it typically runs - usually peaks at -20db (4 watts) - it is still running class A.

rw