Classics of the Golden Age of Speaker Design (TAS 205)

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Classics of the  Golden Age of  Speaker Design (TAS 205)

TAS Founder Harry Pearson was so inspired by The 12 Most Significant Loudspeakers of All Time that he wrote an extended, in-depth look back on some of the most significant loudspeaker designs. HP, who lived with each of these classic loudspeakers, is uniquely qualified to weigh in on how these landmark designs changed high-end audio. His essay also creates a historical framework for understanding how the modern high-end loudspeaker industry came to be.

Robert Harley

________

This article is intended to be an evolutionary guide to the way we, as searchers after the truth of music, got from the early days of the high-end movement to where we are today in loudspeaker design.

Not so long ago Robert Harley suggested that TAS writers compile a list of their dozen favorite speakers; I (as you might easily guess) jumped. In minutes (a record for me) I dashed off a list of the golden dozen.

Then mulling over my choices and fondly recalling the magazine’s early inter-commentaries, I sent the list around to a few friends (including Dr. John W. Cooledge who helped me found the magazine back in 1973), some audio enthusiasts, and a designer or two. As the list then evolved, so did my thinking. Harley suggested that I might make an article out of this; I jumped at that, too. But who knew how much digging around would lie ahead?

I decided against listing those speakers I had liked and liked living with over time. (These were three KLH models [4, 5, and 12], the Sound Dynamics 300ti, several big Alon/Nola systems, and the Henry Kloss-designed Advents [doubled, of course].) At the same time, I also included several speaker systems that I either didn’t much like (the Dayton Wright) or had little firsthand experience with (the Acoustic Research AR-3 series).

Ultimately, I assembled a list, however imperfect, of the systems that had, over those years, deeply influenced the art of loudspeaker design. I say “imperfect” because many a product of considerable fascination (if not widespread influence) isn’t on the list (this could be a book, you know). And because we don’t yet have a perspective on recent advances in the field, I omitted most contemporary designs of considerable fascination that have not yet stood the test of time, such as the Reference 3a Grand Veenas (see Review, Issue 178] and the Mark Porzilli Pipedreams and Scaenas.

I also curtailed an in-depth technical discussion of many of the intricacies, particularly those of the earliest “full-range” electrostatics, assuming, maybe mistakenly, their operating principles to be well understood by veteran audiophiles. (If I am wrong, you can find a plethora of info on the Web.)

<h1>Electrostatic Speakers</h1>

 

The Quad 57

At the time of its introduction at the dawn of the stereo era, the original Quad was said to be a full-range electrostatic and was not. It was limited in its high-frequency extension, innocent of anything like real lows, and had a quite narrow dynamic range, more suited for chamber music than any full-scaled symphonic works or the popular music of the day. Many of the (mostly) mono speakers were behemoths (Klipschorn, ElectroVoice Patrician, and the like) and quite capable of dynamically outclassing the Quad, and with energy at both frequency extremes, though far from the same octave-to-octave coherency, given the extremely poor crossover designs of the day and the sometimes slapdash matching of individual drivers.

What the Quad did have, and what made it an overnight sensation (particularly in Britain where listening in the home was a much more subdued and “refined” sort of experience), was its seamlessness, quite low coloration, and, compared against the rest of the field, incredibly low distortion in its range. Many reviewers compared the experience to one akin to listening to the original sound as if through a partially opened window and it is an apt analogy, right down to the narrowness of that window and compression of loudness and sense of “air” and attendant life. But the purity, unheard of in designs of its day, was addictive, and the frustrations resulting from its limitations maddening.

Given the context of the time, the Quad seemed, to its fans, to represent the future of the art. But there were problems, many inherent in the nature of an electrostatic per se: crazy impedance variations, a tendency toward electrical arcing (between its sandwich-like layers), the limitations of dynamics and out-of-midrange frequencies. What also went unmentioned, then, was a kind of “sheen” (maybe lent by the tube amps used to drive it) that some considered a “transparency” instead of a coloration.

The KLH Model Nine(s)

What the Quads were to the British, the KLH Model Nine was to the American, but without many of the same limitations. Let’s get those out of the way first: A single pair of the Nines (circa $900 some 50 years ago, an audio fortune then) wouldn’t play very loudly (indeed they were fused to prevent damage to the speaker itself); the quite small and bright tweeter beamed and was itself audibly discontinuous with the superb mid and low-range panels below. By doubling up and going for double Nines, as J. Gordon Holt did in his famous review for High Fidelity magazine, the speaker could reach deeper into the bass, and the listener could angle the narrow beaming tweeters to create a less distracting and more cohesive top octave. Doubling up also allowed a more reasonable (though not fully symphonic) playback level. The sound was so clean you wanted to keep turning the volume up (and thus discovered the virtue of buying fuses by the lot) to get even greater aliveness.

Part of the secret here lay in the bass panels’ refusal to “double”—a feature of nearly every moving-coil dynamic speaker of the day. Doubling is measurable second-order harmonic distortion, and it lends bloom (sometimes boom) and thickness to the critical midbass region, where the fundamentals of the orchestra are concentrated and, thus, to the “realism” of the sound. (If it were an odd-order distortion, harsh and ugly to Western ears, it would never have been tolerated. Many began to think of this kind of lower midrange and upper bass sound as attractive in a “want-to-have-it” way, and it is a trick still used today by some highly profitable compact systems.)

This refusal to double in itself set the standard high for those designers looking for a closer approximation of the real thing. You can’t make an electrostatic panel double; it simply quits when its excursive capacity is exceeded. In practical terms, the Nines had a midrange much like that of the Quad and a low bass response down to about 40Hz in the right room and with a stiff wind behind it (the dipolar effect). Even as such, this “sound” became a virtual reference standard for astute (and well-off) listeners, and designers as well.

The Dayton-Wright XG-8

Not all of the technologically impressive speakers during the first 38 years of this magazine’s existence have sired offspring that remain on the market today. One of the most daring of the designs, by Canadian William Michael Dayton Wright, was his XG-8 electrostatic, which, for most intents and purposes, was a true full-range transducer, capable of volumes sufficient to fill a big hall (that is, if you could find an amp powerful enough to drive it). Each of these large dipolar speakers consisted of eight cells inside a large bin filled with sulfur hexafluoride, an electrically insulating gas that permitted somewhat greater efficiency than the usual ’stat’s and, as our reviewer, John W. Cooledge put it, “a marked advantage in attainable volume levels.” [See, if you can find it, JWC’s elegant review in Issue One of TAS. One of the best reviews in this magazine’s earliest days, maybe the best.]

Ah, but the problems: Although individual cells did not spring leaks (except to the extent that they might start “leaking” electrical charges by arcing, which was the usual reason that one or more might have to be replaced), the bin in which they were freely bathed in the sulfur hexafluoride had to be sealed and regularly refilled with gas, and that was just for starters. The price: $1800, the transformer included. It was big, almost 40" tall and wide, and 9" deep. All this excluding the several hundred watt amp needed to make the things go.

To conclude, I will quote from Cooledge’s original review: “To summarize…filling the speaker system with a heavier-than-air gas produced great mass-loading of the speaker diaphragms; raised its low-frequency efficiency and permitted a crossoverless design unique in commercially available electrostatics, permitted the use of greater-than-usual voltages on the speaker elements thanks to the electrical insulating properties of the gas and this, in turn, permitted much greater volume levels than are possible with other full-range electrostatics.”

It was, in a sense, the sought-after electrostatic dream realized.

And by a novice designer in his first commercial outing. Is that dream yet alive? The answer would seem to be a definitive “No!”

The Acoustic Research Model 3a

The coincidental arrival of stereophonic playback in the home, and the perceived need for more “decorator-friendly” listening rooms, along with the not inconsiderable weight of Consumer Reports (in its wilder and less conventional younger days), led to the quick ascension of the bookshelf-sized air-suspension (or acoustic-suspension) speaker, particularly those from AR—and later, KLH. The selling point of this design was that the designers were able to use that air as a linear restoring force to correct for the displacement of the woofer caused by the audio signal and thus to restore a large cone driver to its resting position. (Put, perhaps, more clearly, this they did by sealing that speaker in an airtight box and relying upon the compression of the air itself [air has linearity] to act as a spring.) The problem, in JWC’s words “was what to do with the sound wave from the rear of the speaker cone, which was 180 degrees out of phase with the front wave and thus powerfully inclined to cancel it. Prior to AR’s introduction of the acoustic-suspension method there were three principal kinds of (bass) speaker enclosure: infinite baffle, which isolated the rear wave so that it couldn’t interfere with the front wave (see Bozak); folded horn, which inverted the phase of the rear wave so that it could augment rather than cancel the front wave (see Klipsch etc.); and bass reflex, which tuned the resonant frequency of the air within the box to that of the speaker cone, thus loading the speaker cone acoustically and extending its low-frequency response. These all worked on principles different from each other; none of them, except to some extent bass reflex, relied on the principle of a spring. The innovation of the AR design was that it did indeed turn the air within the box, finally and unequivocally, into a spring.”

A lesson learned, perhaps, from the ascendancy of the electrostatics?

Even better was the fact that dispensing with the normal enclosure approaches allowed, for a bookshelf design, a far deeper low bass response, one exceeding even some of the Big Boy designs of the day. But this was achieved at a price, and that price really did change the future of amplification. The JBLs, Altecs, Patricians, and Klipsches then could be driven to ear-melting levels with extremely low-powered amplifiers (such as Class A designs, then in their prime). But the ARs didn’t come to life until the associated amps passed the 60-watt mark (per channel).

AR was roundly toasted by the critics in its original design for its unremarkable midrange and high-frequency units. (The company even came out with a woofer-only version for those seeking a super woofer.) The AR-1 became the AR-2 (less expensive) with a better tweeter, and bass that was almost shocking considering that it came from such a reasonably sized box. Many of the AR-2’s initial owners, including this one who was fond, fond of it, opted for an electrostatic midrange/tweeter (guess why?). In my case, it was an import called the AH!

The “a” of the Model 3, was the version that introduced the dome tweeter, a breakthrough and this quieted the tweeter-tiques, and led to a host of imitators, down to this very day.

The BBC/Rogers LS3/5a “Monitor” speaker

I shall not tarry long here, partially because the BBC-approved “monitor” design has been through as many incarnations as Shirley McLaine. The most famous of these was, and still is, the semi-official Rogers version, though there have been a host of revisions and variations on the BBC theme from companies like Spendor (a better-sounding unit then), Audiomaster, and Chartwell, etc.

The significance? This speaker set off the so-called mini-monitor craze, both abroad and here in American circles, with the purist segment of the community infuriated by the oxymoronic conjunction of “mini” and “monitor” (pace, the late Irving M. [Bud] Fried).

Some of the historic details are, putting it mildly, a bit murky. But what is clear is that the British Broadcasting Company audio people wanted a small enough speaker to use in their mobile recording trucks and get a good approximation of what they were recording. To this end, specifications were devised (there in-house or by an outside engineering team), and audio manufacturers invited to submit proposals for the fulfillment of the design. The original units were manufactured by Jim Rogers (and his company), and soon thereafter the troubles—or complications—began. Through a series of maneuvers too baroque for a short comment, one Willi Ling bought the rights, made changes in the original design, and, still later, sold the rights to Swisstone, which (by coincidence?) owned the rights to the Rogers name. Eventually others, most notably Spendor, were licensed to build the monitors.

The reviews of the day, including those published here [in Issue 11], bordered on ecstasy, given the clarity and glory of the original KEF five-inch midrange driver (the speaker really didn’t go below 90Hz, except in the smallest of rooms, and even then, several bumps in its response created a satisfactory illusion of there being more—it, too, doubled, so that and a couple of bumps in response made it sound more evenly balanced than it was in fact). It set off a race to see who could get the most articulate sound out of the smallest box (a box which was, for its time, solidly built and unusually free of resonances). Check out the LS3/5a (on Google, preferably) to see how after all these years the BBC-approved design still sells and has developed a cult-like following and how many lives it has led.

The Dahlquist DQ-10

This, the first speaker design by Jon Dahlquist, despite some rookie errors, has had an effect on the art of speaker design still being felt today. Some of his accomplishments are well known even now, but there is one for which he may not have gotten sufficient credit. Before discussing that one, the “phased array,” let’s quickly review what was unusual, even novel, in 1973.

The DQ-10, which bore a deliberate physical resemblance to the original Quad electrostatic (a speaker that heavily influenced Dahlquist), dispensed with enclosures for the speaker’s four individual drivers that operated in cardioid fashion above 400Hz (but not for its woofer) and, further, aligned those units physically so that their drivers were time-coherent. But time-coherent in the physical sense did not mean they were coherent in phase. What Dahlquist, (who designed computer programs for Bendix corporation and the NASA Lunar Landing Module) built was a quite complex crossover, electrically uniting all the individual drivers and thus insuring the signals, respectively, would be in phase as they left the individual drivers.

This meant, audibly, that the speaker had much of the coherency of the vaunted electrostatic and provided a kind of window onto the sound that was quite possibly nearly unique for designs featuring mostly ordinary drivers. (The exception in this case was a horn-loaded piezo-electric super-tweeter, operating above 12kHz, which beamed, thus adding a degree of incoherency, but at such a high frequency that it was way less obvious than the discontinuity of the enclosed and quite slow response of the subwoofer. I mean, how many people could hear that high? Even if, off-axis, the piezo could sound as if it were “ringing”?) In trying to extend his speaker beyond the range of a Quad 57, he invited sonic disparities that the Quad’s midrange units didn’t have.

It is ironic, given his short career as a revolutionary designer that his two follow-up projects never saw the light of day: His own version of a full-range electrostatic (with the elements arranged in circular fashion), and, to these ears, an absolutely remarkable bookshelf speaker whose single prototype was stolen from the back of a rental car he and his partner Saul Marantz were using while visiting California dealers. It was the best bookshelf, at that point, I’d heard, and by a mile. Dahlquist hadn’t kept his working notes (not his intuitive style) and could not exactly duplicate the magic of that design. The commercial success of the DQ-10 made Dahlquist (and Marantz?) put the electrostat on hold.

2 One other contribution Dahlquist made to the world of speaker design was in hiring Carl Marchisotto, who has gone on, in his Alon and Nola models, to make speakers that never, ever sounded less than musical, but not in the same way as that first Dahlquist. Carl is his own man.

Hybrids: Planar and Other Exotica from Magnepan and Infinity

Upon reviewing our back issues, I am reminded how intertwined (interleaved?) the developments at Magnepan and Infinity were over the years. Putting it succinctly, you could fairly say that Arnie Nudell in his many speaker designs at Infinity was working his way from the top down.

On the other hand, Jim Winey, at Magnepan, started with the most musically natural bass and midbass producer ever and worked his way up to a true ribbon loudspeaker (for which he has a patent) and, which is, inarguably, the best ribbon transducer since the fabled Decca design of pre-high-end days.

Both men were specializing in line-array designs (mostly dipolar designs radiating front and rear) and would, in a hybrid version of some of their best work, create a loudspeaker system that helped this writer redefine audio by establishing a vocabulary for the soundspace, i.e., the creation of a three-dimensional sound field that could exactly reproduce that found in the concert (if the recordings were made with the absolute in mind). That was our melding of Infinity’s QRS mid- and high-frequency drivers with the bass panels of Winey’s Tympani I-D (about which, more in a bit).

The basic construction of the first (and succeeding Tympani’s) used a three-quarter inch composite board material, sawed away to leave the supporting frame for the speaker elements. A sheet of steel, perforated for 22 percent openness (like the holes, say, in the tile of a bathroom ceiling), was bonded to the front of the front. Behind it, 5/16th" strips of Mylar were suspended in sections to achieve progressively lower frequency. It basically worked like a drum, hence the name tympanic device. Attached to the steel (interleaved ) were bar magnets. Result: a flat impedance curve, no arcing or many of the other ills afflicting a purely electrostatic design. (Reviewing that first product, I note that “from time to time, the Magneplanars sounded frighteningly life like.” And that because of the resolution and truth in its mid and low bass (to about 32Hz) reproduction. The fundamentals of the orchestra, in other words. It took power to drive the Tympani’s, and the sound as the frequencies extended into the middle of the orchestra and top octave became progressively duller and more veiled—the very problems Winey immediately sought to address through a cornucopia of new designs. This, in time, would culminate in the 20.1 speaker, with its ribbon tweeter (absolutely not a planar-magnetic unit). Students of irony or those who haven’t heard the original Tympani’s ought to know that the sleek and sexy-looking panel of the 20.1 does not have the musical authenticity, definition, or impact of the massive Tympanic screens (yes, each of the two for the lows that were six feet tall and 16 inches wide but only one inch deep). One of the tricks behind the speaker’s performance is not push-pull operation, as some have reported, but what the company calls “opposing magnetic fields.”

At the other end of the country, in California, Nudell was proving himself to be one of the most innovative and futuristic designers in the business. Maybe it has been forgotten that his forces put out two pickup arms (the Black Widows), the first Field Effect Transistor (FET) preamp, a hybrid Class A tube amp, and a pair of electrostatic headphones. He couldn’t make a Class D switching amp sound like music no matter what he and his design team did, so that project was aborted.

His spectacular debut in audiophile circles in the pre-high-end era was a full-range speaker he called the Servo-Statik One (there was an update), which contained six RTR tweeters (descendants of the JansZen design), two electrostatic midrange panels, which had the unfortunate characteristic of going up in smoke when looked at cross-eyed, and a bass commode (the right word sonically) that sounded nothing at all like the rest of the system.

His next venture into the highlands came with the development of the samarium-cobalt EMIT tweeter, a planar design, not a true ribbon. This was incorporated in a short-lived Model, the QLS, which had multiple dome units for the midrange, and a now-forgotten curiosity, the dual-coned Watkins woofer (thought to be the breakthrough, it wasn’t—it was a transitional device). The next version was the transitional QRS, which had improved versions of the EMIT (developed in conjunction with KLH, at that time also owned by the same company that had bought Infinity). The QRS also included something new: What Infinity called a true ribbon speaker, the elaborately named EMiRM, the electromagnetic induction midrange driver (from an Irish company, now long gone, named Straitharn). There were three of these and they operated in true dipolar fashion, which the EMITs did not—so Infinity placed a number of EMIT units, seven on the rear panel (thirteen up front). The sound from these units, in combo, was spectacular. Oh yes, attached to the vertical columns were boxes with folding wings no less, containing the Watkins woofers, even less convincing in this assemblage than before.

I began thinking about marrying the Tympani woofer panels to the midrange/tweeter panels of the QRS—I wanted a coherent and full-range speaker system. One night, Wendell Diller came to town and, thinking that the QRS/Maggie might be a marriage made in heaven, helped figure out a way to make it work. We spent the rest of the night (in what is now called Music Room 2), until dawn’s early light, listening to something new in my experience—a full-range system of unsurpassed tonal neutrality and low distortion that could, for the first time in my experience, recreate a three-dimensional soundfield of an orchestra playing in a hall. Part of this occurred because there were no diffractions from the raised edges of cabinets; thus, the full width of the stage could be replicated, along with the precise placement of instruments where they were supposed to be. (The Maggies had no baffles and we had them placed so there were no dipolar cancellations.)

I know this “mating” aggravated Nudell into the Infinity Reference System (which we jokingly called at first, the IRS—$20,000 it cost, and Infinity promised an Infinity engineer’s personal supervision of the setup). Shipping weight: 1200 pounds. The IRS put deeply arced panels to the side of the strips of 36 EMIT tweeters (24 up front, 12 behind) and 12 coupled midrange units, now called the EMIMs (but whose provenance and exact operating character I couldn’t pry out of Nudell). One more thing, Nudell had finally given up on the Watkins—there were six conventional woofers per side, enclosed in tall sand-lined boxes (line arrays), replete with a servo-controlled 1.5-kilowatt amp driving them. And, to my surprise, it all spoke with one highly convincing voice.

The speaker was a triumph of Nudell’s audio wizardry, the high-water mark. It also initiated the age of the ultra-expensive “statement” speaker system, which we have to live with today.

If you have your own suggestions about the most influential speakers (or comments on my list), be sure to write a Letter to the Editor.  The Absolute Sound, 4544 S. Lamar, G-300, Austin, TX 78745 or e-mail rharley@nextscreen.com

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