Listening #5

Moderation, like a natural death, is what most thinking people roll toward, if only because extremism requires too much energy: Extreme points of view are hard to hold without a certain amount of self-delusion, and the brighter you are, the harder your self-deluder has to work.

I've told myself a few whoppers during my years as an audiophile. Chief among these is the lie that loudspeakers are the least important link in the audio-system chain. I confess: As many times as I've repeated that one, I never quite bought it.

I still think those nutty Flat-Earthers were right about lots of things. Until they came along, people didn't really appreciate the importance of source components in a hi-fi system—especially the poor, misunderstood turntable motor unit. And before the Flat-Earthers came along, most people didn't stop to think about the distinction between sound and music in home audio, or the need for the latter's primacy over the former. (They still don't, of course, but that's another column.)

But loudspeakers the least important components of all? Nonsense. You can't review gear for a living and embrace a notion like that, because in time you'll hear dozens, if not hundreds, of loudspeakers that really play music well, yet that interact with the rest of the system differently, or interact with the room differently, or just plain sound different. Wildly different.

Case in point: Elsewhere in this issue I have some nice things to say about the Quad ESL-989, an electrostatic speaker that stands 4½' tall, extends deep enough into the lowest octave to be considered full-range, and has an efficiency rating that is middling at best. On the other hand, right now I'm enjoying the latest loudspeaker from a company called Rethm: a 3'-tall rear-wave horn built around a single Lowther driver. The Third Rethm, as it's called, is supremely efficient, but its bass response disappears below 80Hz: Not only is the fundamental of an electric bass's low E-string beyond the capabilities of the Third Rethm, but the next E, one octave up, gives it some trouble, too. I know people who would love the Quad, and I know at least as many who would love the Rethm. I can't envision much in the way of overlap, but I suppose I could be wrong about that.

In any event, and more to the point: If you sneaked into a Quad guy's house and replaced his speakers with Rethms, or vice versa, that listener would know instantly, without having to open his eyes—much more easily and quickly than if you did the same things with his amp or CD player or cables. He would know because the change would screw up the sound of his previously enjoyable and presumably well-balanced system beyond all recognition. How unimportant does that sound?

Back to the Third Rethm: Most single-ended-triode (SET) enthusiasts would recognize its dual-cone driver as a Lowther, but few would recognize the specific Lowther model that designer Jacob George chose for this, his smallest speaker: an obscure 6" driver called the DX55. Apart from its size—the company's better-known products are 8" drivers—the DX55 is a Lowther in every respect, meaning that it combines two ultralight concentric paper cones and a relatively compliant foam-rubber surround with an unusually powerful magnet and minuscule flux gap. Here, as elsewhere, Lowther's goal is a speaker that can start and stop with great speed and efficiency, requiring little from an amplifier in terms of current or damping.

But these drivers have a limited excursion—just 1mm in either direction—meaning that low-frequency reproduction at realistic amplitudes is beyond them. The vast majority of Lowther enthusiasts have responded to this challenge by loading their drivers' rear waves with a horn of one sort or another, and so it goes with Jacob George and his Third Rethm, which employs a 9'-long hyperbolic horn.

That's a bit puzzling at first glance: a 9' horn in a speaker that stands only 3' tall and less than 20" deep? The fiberglass horn of the Third Rethm appears to be folded only once, but there's more to it than meets the eye: The first leg extends down from the back of the driver, then does a $wU-turn and goes straight back up—all the while expanding ever so gradually. Then the rear wave exits the top of the second section and travels back down toward the floor, via a chamber formed between the outer wall of the tube it just exited and the inner wall of the loudspeaker's main cylindrical structure. Thus a long horn is compressed into a relatively small volume and an ideal round cross-section is maintained throughout.

Another clever touch is the way Rethm modifies its Lowther drivers in order to banish their upper-mid/lower-high peakiness—something that's been driving Lowther enthusiasts slightly mad for as long as the company has existed. Most smart people—ie, people who agree with me (joke)—think this problem originates from the space between the drivers' main and high-frequency cones, where ringing and reflections cause the cancellation of certain frequencies and the reinforcement of others (which is the sort of thing a phase plug at the center of a driver helps take care of).

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Comments
Timbo in Oz's picture
I am surprised these image well at all Art!

Timbo in Oz's picture
Because the end of a cylinder is the worst place to put a driver

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