I’ve just read a review of two ultraluxurious sedans, from Rolls- Royce and Bentley. At one time the two car brands were made by the same company, though today they belong to BMW and VW respectively. Back then, the literature included no information on engine power, or even the number of cylinders (an urban legend of the day claimed <strong>that</strong> the hood was welded shut, and the company would fly in an engineer if your car ever broke down). You needed to know only <strong>that</strong> the power was “sufficient to exceed any speed limit in the world.” Today, Bentley says its Mulsanne touring car’s V8 engine develops 512 PS (505 bhp/377 kW), while the “massive torque” (1020 Nm/712 lb ft) is delivered at 1750 rpm. Got <strong>that</strong>? I’m a little surprised <strong>that</strong> no amplifier manufacturer has ever been as reticent to advertise available power. Of course if your amplifier will put out a kilowatt you’d be silly not to feature the fact prominently in your ads, but what about those very expensive amplifiers with available power of maybe 10 watts? Or even less? Has no one ever been tempted to say merely <strong>that</strong> an amplifier has “sufficient power to drive any speaker made today beyond concert levels?” True, <strong>that</strong> could be dangerous, because out there somewhere is, no doubt, a speaker <strong>that</strong> requires energy from a small substation to produce more than a pitiful squeak. Still, just as the power race in the auto world overshadowed more significant technical virtues, so the question of amplifier power has often taken on an exaggerated importance. This is all the more evident today, when efficient speakers are so much in vogue, making smaller amplifiers an interesting choice. Though it’s not impossible to design a high-powered amp <strong>that</strong> sounds transparent, the challenge grows with every additional amplifying device you add. Besides, does anyone remember when a 25 watt amplifier was a muscle amp? But do those power ratings matter, and do they even mean what they appear 82 ULTRA HIGH FIDELITY Magazine State of the Art by Gerard Rejskind to mean? Let me return to the automobile analogy again. Consider an engine promising 450 horsepower. By any standard short of Formula One <strong>that</strong>’s a lot of power, or is it? Put <strong>that</strong> engine into a two-seater sports car and, sure enough, you’ve got yourself a mean machine. Put the same engine into a giant SUV, like a Cadillac Escalade or a Lincoln Navigator, and you won’t be getting more than leisurely performance. That’s because those horses have a lot of steel and plastic to haul. Put the motor into one of those pickup trucks with the double rear wheels, meant to pull a small yacht, and you’ll find yourself struggling to make it up a steep incline. And so it is with amplifiers. Pick up antique AR2 acoustic suspension speakers, and your muscle amp may seem barely adequate. Listen to uncompressed recordings of large musical ensembles, and suddenly you’ll be glad you set your amplifier choice to “overkill.” Then again, with a different speaker, with other music choices, you may be content with a tiny amount of power. STATE OF THE ART: THE BOOK Get the 258-page book containing the State of the Art columns from the first 60 issues of UHF, with all-new introductions. See page 6. And, as with cars, raw power doesn’t tell the whole story. Power is voltage multiplied by current, but some “powerful” amplifiers can’t deliver adequate current into real-life loudspeakers. Similarly, some small but “powerful” car engines have low torque, or can deliver adequate torque only at high engine speeds. It’s the torque <strong>that</strong> gets you to cruising speed, and it’s the current <strong>that</strong> drives the loudspeaker. But there’s one more problem with power ratings. Watts are a linear measure, but loudness is logarithmic. Double the power, from 50 watts to 100 watts, say, and the increase is only 3 dB (supposedly the smallest audible increment, though we know <strong>that</strong>’s not true). Some listening tests seem to indicate <strong>that</strong> most listeners will judge a 10 dB increase to be subjectively a doubling of loudness, but in fact it’s a tenfold increase. That’s right…increasing output from 10 watts to 100 watts sounds subjectively like a mere doubling of loudness. Some years ago there was an attempt to develop a logarithmic scale for amplifiers, and perhaps we should return to <strong>that</strong>. Let us call the new unit the dBl (“l” for loudness), and <strong>let</strong> us arbitrarily set 0 dBl to correspond to an output of 1 watt. Then 10 watts would be 10 dBl, and 100 watts would be 20 dBl. A monster amplifier with an output of a kilowatt would be rated at 30 dBl. The advantage of such a rating would be <strong>that</strong> the numbers would correspond, subjectively, to what you could expect to hear. I don’t expect to see the dBl adopted by the <strong>audio</strong> industry, if only because of the damage it would do to bragging rights. Anyway, even a logarithmic rating wouldn’t tell the whole story. Many amplifiers appear to deliver twice the lower into a 4 ohm load as they do into an 8 ohm load, and some amplifiers can sustain more current draw than others. The interaction of amplifier and loudspeaker shape the listening experience. But don’t be overimpressed with those power ratings. Perhaps Rolls Royce had it right all along.
Why do UHF readers start reading their magazines at the back? Countless readers have confirmed it over the years: when they get their hands on the latest issue of UHF, they open it to the last page. The reason all of them mention: Gerard Rejskind’s last-page column, State of the Art. Since the magazine’s founding, the column has grappled with the major questions of high end <strong>audio</strong>. It has been acclaimed by readers around the world. Now, the columns from the first 60 issues of UHF are brought together into one book. Each is exactly as it was originally published, and each is accompanied by a new introduction. Order your copy today: $18.95 in Canada or the US, C$32 elsewhere in the world, air mail included.
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No. 92 CAN $6.49 / US $7.69 USB DON
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