The future is rarely what anyone expects it to be. I still remember reading, as a child, predictions in Popular Science that everyone would have a personal helicopter by 1980. It never happened, though it sure seemed like a reasonable projection of events. Events, however, have their own agenda.
Until just recently, only companies known primarily for their surround-sound processors were producing the most advanced—and most expensive—Home Theater products. No longer. It was inevitable that traditional high-end audio manufacturers would begin producing equipment for this fast-growing market.
If Canada has emerged as a hotbed of loudspeaker production in the past few years, the folks at Audio Products International must be positively sizzling. Of their three lines—Mirage, Energy, and Sound Dynamics—Mirage is perhaps the best known in the US, with Energy running a distant second. Mirage, at least in their flagship M series, features rather esoteric bipolar designs, while Energy sticks to the more conservative, forward-radiating approach. Stereophile has had extensive exposure to the various Mirages (a review of one of the M-series babies, the M-7si, is scheduled for a future issue); our exposure to Energy has been virtually nil, save for the odd Hi-Fi Show and CES. And thereby hangs a tale.
You'd probably be surprised to learn that headphones are the most common means for listening to music. No, I didn't get that from a book, but from personal observation. I'm referring here to personal portable stereo listeningthe ubiquitous Jogman with which a whole generation has retreated into its own private world, isolated from traffic noise, muggers, and, at home, housemates or parents screaming "Turn it down!"
While headphone listening remains secondary to that of loudspeakers for most serious listeners, it's still an important alternative for many. And while good conventional headphones exist, electrostatics are usually considered first when the highest playback quality is required. As always, there are exceptions (Grado's headphones come immediately to mind), but most high-end headphones are electrostaticsuch designs offer the benefits of electrostatic loudspeakers without their dynamic limitations. Last year I reviewed the Koss ESP/950 electrostatics (Vol.15 No.12), a remarkable set of headphones from the company that practically invented headphones for serious home listening. Here I listen to examples from two other companies, each known for its headphones since Pluto was a pup.
Compared to the Krell KSA-300S power amplifier that I also review this month, the KRC preamp's design is, at first glance, almost conventional. But its thoroughly high-end internal design has been equally well thought-out and executed. Its main, four-layer, glass-epoxy circuit board is for the audio signal, DC power, and groundtwo layers for the latter are said to minimize noise. The gain stages are pure class-A and complementary. As in the amplifier, the circuit is direct-coupled, with servo circuits controlling the DC offset. The fully regulated power supply is housed in an external chassis. Seven inputs are provided: four single-ended, two balanced, and one single-ended tape. All inputs are line-level except for the optional, single-ended phono stage. (This review will address the line stages; a Follow-Up will discuss the phono stage's operation.) There are three outputs: balanced and single-ended main outputs, and a single-ended tape output.
That was the question asked by a reader who was perfectly happy with his CD-based system. He was using the gain control provided by the variable output of his CD player and was apparently in no need of phono playback or greater flexibility. He asked us to answer this question, ignoring for the moment the obvious functions of switching, volume and tone control, and phono preamplification. With those hardly trivial qualifiers—and bearing in mind the high output available from many of today's line sources, CD players in particular—do you really need the added expense and complexity of a preamplifier?
On a number of occasions we have commented on the effects of an amplifier's output impedance on a system's performance. A high output impedance—such as is found in many tube amplifiers—will interact with the loudspeaker's impedance in a way which directly affects the combination's frequency response. The Cary CAD-805, for example, has a lower output impedance than most tube amplifiers, and should be less prone to such interaction. Some months back—before the CAD-805 arrived—I investigated this phenomenon in conjunction with measurements for a forthcoming review of the Melos 400 monoblock amplifier. Since the Melos 400 also had a relatively low output impedance for a tube amplifier (at 0.43 ohms at low and mid frequencies, rising to 1.2 ohms at 20kHz, from its 8 ohm tap), I took that opportunity to run some frequency-response measurements using an actual loudspeaker as the load for the amplifier.
It was a dark and stormy night. A biting, cold wind cut through Sam's skimpy jacket; ice crystals clung tenaciously to his bushy moustache. As he approached his front door, visions of a toasty-warm, Krell-heated listening room softened the chill. He could feel the glow already; his Krell amp had been on all day, awaiting his return.
When Ken Kantor helped to found Now Hear This, Inc. (most commonly referred to by its initials, NHT) in 1986, he brought with him a wealth of design and production experience learned from stints with NAD and Acoustic Research. He also brought a desire to build and market products that a wide range of people could afford. NHT began by producing small, two-way designs distinguished by the angled front baffle which remains the company's trademark. The latter is no gimmick, but was designed to optimize the loudspeakers' radiation pattern, a matter of keen interest to Kantor ever since his undergraduate thesis work at MIT. This interest continued at AR, where he was responsible for the MGC-1 loudspeaker—probably his best known pre-NHT loudspeaker design.