Behind The Scenes "Speaker To Spec" (March 1985)

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The well-known British loudspeaker manufacturer, B & W, has always had a research-oriented approach to the design and development of transducers. In recent years, B & W has placed even greater emphasis on research, and has expanded their laboratory facilities considerably. They have equipped their laboratories with the most exotic and sophisticated devices of modern audio technology: Fast Fourier Transform analyzers, computer design modeling, and the manufacturer's pride and joy, a laser interferometer.

All this apparatus and many other devices were used in the design of B & W's Model 801 loudspeaker. This transducer aimed to meet record companies' stringent performance requirements for a monitor speaker suitable for classical music recording.

While the Model 801 was well received, ongoing research provided an important refinement to the design.

Special fiber-reinforced concrete known as fibercrete, a very inert high density material, was used to fabricate the midrange and tweeter enclosures.

This virtually eliminated panel flexure of the enclosures and the coloration by spurious resonances. Now known as the Model 801F, this speaker has been widely acclaimed for its accuracy of frequency response, very low distortion, smooth spectral balance and, above all, its superlative, almost palpable three-dimensional imaging. The Model 801F is now the "official" classical recording monitor speaker for EMI, London/Decca, Philips, Deutsche Grammophon, CBS, and many others.

In fact, I noted that in a recent recording, Telarc too is using the Model 801F. Needless to say, thousands of audiophiles and music lovers all over the world have also acquired the Model 801F.

---B & W Model 808

This sounds like a success story, and it is. However, a new chapter has recently been added. While the Model 801F was widely used to monitor the recording of classical music, there were pop/rock recording engineers who liked the characteristics of the 801F but wanted to monitor at very high levels. Because of the widespread use of synthesizers, with their very high-energy output at extended low-frequency response, these engineers wanted a speaker that could reproduce such huge signals without distress. Hearing about the requirements of their pop-music colleagues, the classical recording engineers declared that, with the wider dynamic range and very low-frequency response of digital recording, such a king-size monitor would be advantageous to them, as well. As I understand it, some EMI recording engineers finally approached B & W, and asked them if they could design a sort of "super 801F" that would afford a very high-quality sound at very high listening levels.

Feeling that with present-day recording technology there was a need for such a no-holds-barred monitor speaker, B & W took up the challenge and, after much research, introduced the Model 808 "super monitor" at the 1984 Summer CES in Chicago. At the show, I asked the ever-genial John Bowers if I might try out a pair of his Model 808s in my home. He graciously consented, but at the time I had no idea what this would eventually entail! Finally, in early November, a huge truck pulled up in front of my house to deliver the very first pair of Model 808s in the United States. Now, I've had all kinds and sizes of audio gear delivered to me over the years-but I wasn't prepared for what was emerging from the rear of that truck! The Model 808 is shipped in a big wooden case, which (probably by clever foresight) just managed to squeeze through my front doorway. Believe me, B&W is making certain the 808 reaches you intact! Unpacking is a bit of a chore, but once uncrated, the 808 rolls out nicely on its ball casters. Each 808 weighs 185 pounds, so the casters are much appreciated.

The Model 808 is an imposing and beautifully crafted loudspeaker. Available in walnut, black ash, rosewood and natural oak, the 808 is 44 1/4 in. H x 25 3/4 in. W x 21 1/4 in. D. Unlike the 801F with its separate, external midrange and tweeter enclosures, all five drivers are totally within the Model 808 enclosure.

The B & W engineers set three principal design goals for the 808: First, the 808 had to achieve frequency linearity and freedom from coloration and distortion, similar to that of the Model 801F. Second, sensitivity of the 808 was to be 91 dB at 1 watt/meter at 8 ohms, double that of the Model 801F. And third, the 808 had to achieve 120 dB SPL in typical recording/listening environments.

This was quite a tall order, and it necessitated the design of entirely new driver units. The claimed frequency response of the 808 is ±2 dB from 30 Hz to 20 kHz. Couple the obviously extended bass response with the requirement of a 120-dB output, and the necessity of a large enclosure (220 liters) is apparent. The 808 employs two 300-mm (1178-inch) drive units with thermoplastic cones and PVA compound coating. Voice-coils are 2 inches and are wound on special, high temperature Kapton formers, permitting safe operation up to 250° C (over 480° F)! Each bass driver has a magnet system weighing almost 10 pounds. The drivers feature ultra-long throw suspensions. Computer predictions indicated that achieving an efficiency of 91 dB at the desired low frequencies would require a fourth-order vented system. This was constructed, and the box has a system resonance of 22 Hz. There is a special design for the internal bracing, and measurement of enclosure panels with laser interferometer and accelerometers gave readouts 60 dB below directionally radiated signals. In other words, resonant coloration from enclosure panels is almost nil. Power handling of the 808 bass section is an enormous 200 continuous watts below 400 Hz! The two midrange drivers are new high-power units, employing the same special Kevlar cones used in the 801F. The voice-coils are once again wound on high-temperature Kapton formers.

The specially developed tweeter uses a 32-mm (1 1/4-inch) polyamide diaphragm, whose contour was determined by laser interferometer studies.

High-temperature aluminum formers are used for the voice-coil, and use of Ferrofluid restricts operating temperature to a safe 100° C (212° F). Both midrange drivers and the tweeter are in a vertical in-line configuration, housed in an extremely rigid enclosure completely separate from the bass enclosure. The midrange/tweeter enclosure is a rear-loaded, quarter-wave transmission-line system of tapered construction. It is damped with special fibrous material and tuned to ensure flat impedance and linear absorption.

This three-way speaker uses fourth order Butterworth-squared configuration crossovers at 400 Hz and 3 kHz, and delay-line correction between midrange and tweeter is provided. The Model 808 can be bi- or tri-amplified, and there are internal protection circuits to place limits on the power input to midranges and tweeters. Input impedance is 8 ohms nominal. At 100 dB, second-harmonic distortion is only 1% from 100 Hz to 20 kHz, with third harmonic distortion a mere 0.64% at the same frequencies. Obviously, the 808 is designed and constructed to a new and very high standard.

What you folks probably want to know is what this sophisticated, high-technology loudspeaker sounds like.

First off, it must be noted that the Model 808 is an incredibly revealing speaker. Good or bad, it accurately reproduces what you put into it. To really appreciate the fabulous performance of the 808, it should be teamed with the best equipment available. The 808 sounded quite good with a number of high-quality amplifiers and preamplifiers, but the cleanest, most musical, most impressive sound from the 808s was produced by driving them with the new Krell KMA-200 Class-A amplifiers.

(Krell's Dan D'Agostino tells me that these mono amplifiers have new "inverse drive" circuit topology, that they are internally wired with Sal DeMicco's Discrete Technology cable, and that they are capable of extremely high current output.) For the preamplifier I used the new Gamma version of the Spectral DMC-10, a unit I find increasingly impressive for its cleanness, quietness and very musical qualities. I also used the Meridian CD player, and the Sony PCM-F1 and JVC 6400 professional VCR for playback of my own and other digital tape recordings.

With the setup described, listening to the Model 808 is an impressive sonic experience. There simply is no comparison with conventional speakers.

Knowing you have 120 dB of output might offer temptations to those who like their music larger than life. Needless to say, some exploratory listening, including forays into ultra-high levels (just to see if the loud levels stay clean), is in order.

It was soon apparent that the 808 has many of the desirable characteristics of the 801F. Spectral balance is extremely smooth unless distortion is present in the source material; I've heard no distortion produced by the 808. Bass response is flat within a few dB to below 30 Hz. Above all, there is utter clarity and cleanness to the sound, no matter what the listening level. Coloration is very low, and the stereo imaging is precise and stable, although it must be said that the 808 doesn't quite match the three-dimensionality of the 801F. Quite apart from all this is the sheer emotional impact that the 808 uniquely imparts to music. Because it can handle the very wide dynamic range and extended bass response of some digital tapes and Compact Discs, you no longer have to play them with trepidation. There is no longer any fearful "walking on eggshells" feeling that is engendered when playing digital material through loudspeakers that simply are not designed to handle high levels.

On certain uncompressed digital recordings, you can set the pianissimos just above the ambient noise floor of your listening room, and feel secure that, when you reach the triple fortissimos, nothing will blow up. In such situations, the impact of the 808 is startling. Bass response is ultra-clean, awesome and visceral in its unbridled power.

Classical music played on this 808 system becomes a new experience. It is difficult to describe how one gets caught up in the music, how the climaxes of a Mahler symphony, for instance, afford an emotional impact that can truly be described as uplifting.

For devotees of pop and rock music, this is a dream speaker. All the high-level sounds are produced without strain. Transient response and power are shattering. On some Compact Discs with percussion, especially rim shots on drums, you feel someone is in the speaker shooting at you with a .357 magnum.

There is no doubt that the B & W 808 is a major achievement in advanced speaker design. There are other speakers having excellent qualities, but for sheer, gutsy, and emotional musical excitement, the 808 will be hard to beat. There is but one little drawback-you'll need $7,500 for a pair of Model 808s.

(adapted from Audio magazine, Mar. 1985; Bert Whyte)

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