The quest for a full-range electrostatic loudspeaker has occupied many engineers' minds for many years. The problems are manifold: large physical size (which can lead to room placement problems and poor dispersion), the difficulty of achieving high sound pressure levels, the need for a potentially sound-degrading step-up transformer, and the unsuitability for production-line manufacture. Even so, the potential rewards are so great that one can understand why loudspeaker designers keep on attempting the apparently impossible. Epoch-making models do appear at infrequent intervals, keeping the flame burning since the appearance of the original Quad in 1955: Acoustat, Sound Lab, and Beveridge in the US, Stax in Japan, Audiostatic in Holland, Quad, of course, in England, and now MartinLogan.
Not only does the venerable vacuum tube refuse to lie down and die, as everyone predicted when audio went solid-state; it continues to deliver better performance than anyone had imagined it could. Only a few years ago, we could characterize "the tube sound" as being sweet but soft at the high end, rich but loose in the midbass, deficient in deep bass, and bright and forward, usually with excellent reproduction of depth. Since then, we've seen the introduction of what might almost be called a new generation of tube amplifiers, which rival solid-state units in those areas where tubes used to have weaknesses, but have given up little of the tube's sonic strengths.
Warning to Purists: Despite certain qualities about the ESL-63 speakers which you will probably like, Quad equipment is not designed primarily for audiophiles, but for serious-music (call that "classical") listeners who play records more for musical enjoyment than for the sound. Quad's loudspeakers do not reproduce very deep bass and will not play at aurally traumatizing volume levels, and Quad's preamplifier is compromised through the addition of tone controls and filters, all for the purpose of making old, mediocre, and/or worn recordings sound as listenable as possible.
Americans might be forgiven if they haven't heard of Epos. A small, British specialist loudspeaker manufacturer, it was founded in 1983 by its designer, Robin Marshall—an ex-BBC engineer and a onetime consultant to Monitor Audio, according to Roy Hall of Epos's US importer, Music Hall. Their first model, the ES 20, didn't make it to the US, and was apparently a bit too pricey in the UK to make much of a splash there (about £700, $1300 at the current rate of exchange—a mint in a country with the patent on sub-$500/pair (UK prices!) two-ways). In 1986 or thereabouts, the new, smaller ES 14 was introduced, using updated versions of the same drivers in a smaller, ported cabinet. Music Hall only recently began importing the Epos into the US.
I must admit that even before I connected up this amplifier I was put off by the accompanying literature. B&K makes some persuasive points about the validity (or rather the lack thereof) of some traditional amplifier tests, but the literature was so loaded with flagrant grammaticides, syntactical ineptitudes, and outright errors that I could not help but wonder if the same lack of concern had gone into the product itself (eg, the term "infrasonic" is used throughout to mean "ultrasonic"). Good copy editors aren't that hard to find; B&K should have found one.
I am reluctant to call any given transistor power amplifier a "best buy" or "breakthrough." From my talks with designers and other audiophiles, it is clear that the state of the art in power amplifiers is about to change. From where I stand, the Adcom GFA-555 is the first sample of this new wave. It is so clearly superior to past amplifiers in the low- to mid-priced range—not to mention most amplifiers two to three times its pric—that I can unhesitatingly recommend it for even the most demanding high end system.
I am puzzled. No, really. I know you find it hard to believe that we sacerdotes of the golden-eared persuasion could ever be perplexed, but I have been pondering the imponderables of ports. Ever since the classic work of Richard Small and Neville Thiele in the early '70s showed how the low-frequency response of any box loudspeaker can be modeled as an electrical high-pass filter of some kind, with the relevant equations and data made available to all, there would seem to be very little reason why all loudspeakers with the same extension should not sound alike (or at least very similar) below 100Hz. Yet after reviewing 20 dynamic loudspeakers (and using 24) in the same room over the last seven months, I am led to the conclusion that speakers vary as much in the quality of their mid-to-upper bass as they do in any other region. A few are dry, more are exaggerated in this region; some are detailed and "fast," most are blurred, with the upper bass "slow" (by which I mean that the weight of bass tone seems to lag behind the leading edges of the sound).
Lee de Forest filed for a US patent on his "Audion"—the first triode—on October 25, 1906, but never could explain why it worked (footnote 1). It was up to Armstrong and Langmuir, in their pioneering work, to place the hard-vacuum triode on firm scientific ground. When the US entered World War I in April 1917, the Army had to rely on French tubes. Six months later, Western Electric was mass-producing the VT-1 receiving tube and the VT-2 transmitting tube. However, it was only in the decade following World War I, as designers became conversant with the triode amplifier, that many of the crucial elements of tube amplification were nailed down. Technical issues such as coupling two gain stages and selection of optimal coupling impedance were already resolved by the mid-1920s. The triode ruled supreme until the tetrode came along in 1926, followed in 1929 by the pentode from Philips's research laboratories in Holland.