A Powerful Standard

Last month I wrote about parallels between the audio and watch industries, and finished with a mention of where those similarities end: in standards of measurement. The watch world has many objective standards, some loose, some quite strict, and every serious player in the watch business meets at least one of the well-established regimes that dictate how a watch must perform to be certified by the governmental body that established that regime. In the audio world, there are no such universally agreed-on standards of performance.

Who among us hasn’t browsed among what pass for audio electronics at big-box stores and been pitched by ill-informed saleschildren? Their stock in trade is to overwhelm the shopper with meaningless but impressive-sounding statistics, and would you like the extended warranty with that? Some homework for you: Visit your local electronics shop and ask the saleskid to define Root Mean Square. That’s what the letters tacked onto amplifier power claims stand far -- as in "100W RMS per channel." Wikipedia isn’t always the most trustworthy source of information, but it provides a great definition for RMS: "In mathematics, the root mean square (abbreviated RMS or rms), also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity." And gobbledygook to you, too.

For our purposes, what we need to know is that the RMS equation "allow[s] us to calculate the mean power delivered into a specified load." That’s where we get, say, "100W RMS into an 8-ohm load." In other words, sticking closely to this definition of RMS, the foregoing power measurement states that the amplifier is able to deliver a mean power of 100Wpc into an 8-ohm resistive load. Or does it?

Perhaps the best-known standard of the Swiss watch industry is the Contrôle Officiel Suisse des Chronomètres (COSC), an official Swiss body that certifies the time-measuring performance of watch movements. Any watch bearing the words "Officially Certified Chronometer" has met or exceeded the COSC standards, which are fairly elaborate and, just as important, universal. That’s because COSC set its parameters through international agreements with other timing bodies; whether a watch is certified by COSC, DIN (Germany), or ISO (International) doesn’t matter -- all of these bodies use the same criteria in measuring performance. Not so with audio electronics.

The problem with RMS power measurements is that they’re meaningless. The first problem is that there’s no such thing as "watts RMS" (it should be volts RMS). The second is that RMS power is typically measured using a 1kHz sinewave. If all you listen to is a 1kHz tone, then the RMS measure might be of some value, but most folks tend to listen to music that varies from 20Hz to 20kHz. That variation means that a simple 1kHz test tone reveals only what an amp may be capable of at that wafer-thin point in the audioband, while telling you nothing about what the amp can deliver at bass frequencies, where real power is most needed. A third problem is that the typical test of RMS power is conducted into an 8-ohm load. On the face of it, that seems reasonable: many speakers are rated at 8-ohms nominal impedance. But here, again, it’s the real world vs. the test bench: loudspeakers do not present an amplifier with a single, unified load. Instead, the impedance (load) varies with frequency; a speaker with a nominal impedance of 8 ohms might present a minimum 3-ohm load at one frequency and a maximum 9-ohm load at another. But if the test load is an unvarying 8-ohm resistor, well, that’s not much of a test at all.

It’s not hard to understand why many manufacturers have taken to using watts-RMS as a performance measure -- they had to, to meet a US standard of amplifier measurement (now defunct) called IHF A202, set by the FTC in 1978. This measure generates a numerical value that people can easily compare from product to product, since most performance stats are generated this way. There’s a bonus in that the numbers are generated at a less-than-taxing 1kHz into a steady load, which means that this test exaggerates the actual amount of power available to drive speaker loads. For marketing departments, that means consumers will believe they’re getting more performance than they really are. Doesn’t everyone like something for nothing?

For the vast majority of makers of audio electronics, the watts-RMS performance measure is the only one they care to provide to the buying public, and who can blame them? When companies A and B claim 100W RMS power for their amps using the 1kHz sinewave measure, but a more scrupulous company, C, claims for its comparable amp 60W of average continuous power but 110W of peak power, it’s not hard to see which firm is at a competitive disadvantage.

What might surprise some readers is that inflated claims of wattage are as decried within some parts of the audio industry (and by that I mean companies whose only line of business is audio gear) as they are, well, here. The best demonstration of this can be found at SoundStage! V, in the "Paradigm Sub 25 Technology" videos, Parts 1 through 3. The videos are the result of an extraordinary look inside the Paradigm Advance Technology Center, where PhDs are paid to dream up the future of speakers and amplifiers, and which is normally off-limits to the audio press. So when SoundStage! Network publisher Doug Schneider and I were invited by Dr. Marc Bonneville to see a unique demonstration of amplifier power, we could hardly say no.

Bonneville came to Paradigm from Canada’s National Research Council. As a professional scientist, he believes absolutely in honest research, and by extension, this applies to his work developing products for Paradigm. Like the rest of us, Paradigm noticed an ever-increasing number of subwoofer models entering the marketplace accompanied by extraordinary claims for their power output. The problem was that these output-power calculations were made using the old watts-RMS method, which tells you little about a full-range amplifier, and nothing at all about a subwoofer amp that may never be called on to amplify a 150Hz signal, let alone a 1kHz signal. The watts-RMS methodology is, at best, misleading; using it to calculate the power of a subwoofer amp seems little more than outright dishonesty.

It turned out that Bonneville’s demonstration didn’t involve a complete subwoofer, just the amplifier used in the Paradigm Reference Signature Sub 25. While he was determined to show us that this amp could indeed produce its claimed 3000W of power, he also wanted to demonstrate that it could produce enough current (amperage) to move a mountain. What better way to illustrate these capabilities than to use the amp to simultaneously power a hot-water kettle and a toaster oven, each drawing from the amp 1500W and 8-10 amps. Those might seem odd ducks to use for such a test, but think about what a successful outcome would mean: If nothing else, it would prove that the Sub 25’s amp can push 3000W and large current for minutes at a time. After all, it takes a lot longer than mere milliseconds -- or even seconds -- to boil water or toast bread. If the Sub 25’s amp can do both at once, it can deliver enough continuous, real-world power to simulate an earthquake or two.

The perturbing part of this story is that, on paper, Paradigm’s 3000W look the same as another company’s 3000W -- even though the former can produce that kind of power all day long, while the latter might be able to hit the mark for only milliseconds. And Paradigm’s watts are all there, available to power the sub’s massive 15" woofer; the other guy’s measurement might well reflect theoretical performance at a frequency no sub will ever be asked to reproduce.

Marc Bonneville shows the 3000W output that the Sub 25's amplifier is capable of producing.

The watts-RMS specification is as valid for subwoofers as depth capability is for bicycles. Therefore, no company should use it to misinform consumers about its products or how they compare to others. One way of eliminating from the marketplace such apples-and-oranges measurements would be to have every manufacturer conform to a valid, scientifically devised test regime tailored to the specific type of component. I don’t think we’ll see anything like the COSC watch certification in audio any time soon, but I do hold out hope that the European Union might force standards on any company wishing to do business in the world’s largest trading zone. After all, if the EU can ban banana plugs, imagine what it could do to deflate false or misleading claims of amplifier output power.

. . . Colin Smith
editor@goodsound.com