In(non)credible power ratings

[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.

[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.

[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.