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If anyone can be said to be the guru of the transmission line, that would have to be Irving M. "Bud" Fried. He has been promoting the design for years now, first with the made-in-England IMF designs, later with the designs of Fried Products, made right here in the US of A. He has long been convinced of the basic superiority of the design, and still uses it in his top-of-the-line systems. But true transmission lines are invariably big, heavy, hard to build, and, for all of those reasons, expensive. Essentially, they involve a long, convoluted, heavily damped tunnel behind the bass driver which channels the back wave to the outside world. The length and cross-sectional area of the tunnel are of some importance, although the technical basis for the transmission line, as applied to a loudspeaker enclosure, has never been firmly nailed down. Certainly there is no mathematical model for the transmission line as complete as that developed over the past two decades for the sealed or ported box (footnote 1).

But Bud Fried has clung to the transmission line, for all of its complexities. In order to bring at least some of its touted advantages to a lower price point, he had to come up with a variation which would work in a smaller enclosure. That variation was the "line tunnel," which, according to Fried, originated in an early-1970s Ferrograph (a British company specializing in tape recorders) monitor which was later adapted by IMF. Basically it consists of a short (compared with a transmission line) duct from the inside to the outside of the heavily damped enclosure. The duct is designed with approximately the same cross-sectional area as the loudspeaker cone.

How would you feel after paying $2000 for super-stereo system, you learned that genuinely high-fidelity recordings of many excellent classical musical performances were not available to you? Could you excuse it with a shrug and the philosophical observation that nothing's perfect but things will get better as the state of the recording art improves? Okay then, what if you learned that truly high-fidelity recordings of these performances, that would sound very much like the real thing if reproduced through your super system, are available to millions of other people but not to you? Would you begin to feel just a little bit slighted, or maybe even irritated?

In the May 2015 issue, I fairly raved about Simaudio's Moon Evolution 740P line-stage preamplifier, and now here I am confronting its Moon Evolution 860A power amp. The two are companion models of sorts, with prices of $9500 for the 740P, $15,000 for the 860A—and for much of the time I spent listening to the 740P it was hooked up to the 860A, so some of the descriptions of sound in this review will seem familiar. The two components are both products of the same design shop—Simaudio, Ltd., of Quebec, which has been a prominent brand in high-end audio for 35 years—and are often marketed as a pair, so it should be no surprise if they have a common sound.