SPEAKERS OF THE HOUSE
For several months now, I have been evaluating two interesting new loudspeakers, the Meridian M10 and the Acoustat Model Eight. The Meridian is manufactured by Boothroyd Stuart, Ltd. of Huntingdon, England. In recent years, Meridian has specialized in what they call "interactive" loudspeaker systems: Simply put, this is a design wherein the driver elements are combined with dedicated amplifiers and crossovers, integrated in a common enclosure.
The M10 is the most advanced and most powerful of Meridian's line of interactive loudspeakers. One of the goals of the design is to create a virtual point source of sound, with symmetrical horizontal and vertical dispersion.
To this end, a unique enclosure is employed. On the front of the loudspeaker, 5-inch cone midrange drivers are mounted above and below a 2-inch dome tweeter. These drivers are in a heavily damped enclosure isolated from the woofers. The cabinet's width is just slightly larger than the 5-inch midrange units, thus presenting a very narrow frontal area said to reduce dif fraction distortion. On each side of this cabinet are mounted two directly driven, 5-inch bass drivers; a flat-diaphragm, 8 x 12-inch passive radiator is mounted behind the virtual source.
This slim enclosure is integrated into the top portion of a pedestal of the same width. Contained within the lower part of the pedestal are two 75-watt amplifiers for the bass system, another 75-watt amplifier for the midrange drivers, a 35-watt amplifier for the dome tweeter, an electronic crossover, and two power supplies. Quite an assemblage-and in spite of the close proximity of the various elements, very little heat is generated.
The M10 is thus a tri-amplified sys tem, and Meridian points out that the amplifiers and crossover are configured to match the characteristics of the drivers. Crossover from the bass section is at an unusually low 190 Hz, and a time-delay-compensated, fourth-order crossover directs high frequencies to the tweeter from 2 kHz on up.
Meridian claims an overall frequency response of-3 dB at 33 Hz and 24 kHz, with THD of the entire electronic system typically less than 0.01%. This slim pedestal design stands 39 inches high, with the upper enclosure 18 inches deep.
--------Meridian M10s
Since the M10 is an active system, the only other electronic component necessary is a preamplifier. Meridian recommends their own Model 101, but any high-quality preamplifier can be used. Each M10 is supplied with frequency-compensation plugs which can be inserted in the rear of the enclosure to tailor high-frequency response for variations in room acoustics.
To evaluate the Meridian M10, I teamed it up with a Levinson ML6A preamplifier which superbly complemented the fine performance of this unusual loudspeaker. With 270 watts of tri-amplified power per side, the M10s gave an impressive performance with large-scale symphonic works. I had the pleasure of a visit from Bob Stuart, the astute young designer of the M10, and we listened to digital discs on a prototype Sony CDP-101 digital audio disc player. It was obvious that the M10 could handle the great dynamic range of a number of recordings at high output levels, certainly approaching the 110 dB on program peaks claimed by Meridian. Bass response was very firm and solid: Bass drums had plenty of punch and weight, and contrabass had a most satisfying clean resonant "thrum." Only the extreme low organ pedals of Virgil Fox recordings indicated the need for a good subwoofer. Transient response of the M10 is exemplary. On the M & K Hot Stix drum recording, high percussion of cymbals and bells was very accurate, while the rim shots were positively explosive in their projection. Given the proper source material, high-frequency response of the M10 was very smooth, although there was a slight tendency to brightness. Judicious use of the frequency contouring plugs would be indicated in some rooms. As expected, because of the point-source emphasis in the design, imaging and depth projection were extraordinarily good. The image focus and instrument localization have to be considered among the top three or four loudspeakers which excel in this parameter. The overall sound of the M10 is accurate, very musical, and not fatiguing. A pair of M10s costs $4,450, but it must be remembered that this includes 270 watts of tri-amplification per side.
Acoustat now proudly proclaims that their line of electrostatic loudspeakers puts them in the category of the world's 10 best-selling loudspeakers. I have no reason to doubt this, as their speakers have garnered much ac claim and steadily increasing sales in the relatively short span of the company's existence.
---------Acoustat Model Eight
Some months ago, Acoustat updated their speakers and added several new models. The Model Eight, their state-of-the-art "flagship" electrostatic loudspeaker, costs $4,750 per pair. It is an imposing monolith, standing 7 feet, 10 inches high, 36 inches wide, 4 inches deep and weighing 220 pounds! The Model Eight is, in essence, two Model Four speakers stacked in a single unit. As with all current Acoustat ES loudspeakers, the Model Eights signal-carrying wire grids are made of high-purity copper, utilizing 47 strands of 40-gauge wire. This is claimed to produce high output with less mid range coloration. The wire grids are strung on a very rigid honeycomb plastic form, with the 0.0005-inch-thick, conductive mylar diaphragm sandwiched between the grids. Each panel of the Model Eight is equipped with a high-frequency balance control for frequencies above 10 kHz, and the system's frequency response is rated as 24 Hz to 20 kHz, ±2 dB.
Each Model Eight panel is also equipped with two Acoustat MK-121 input "biformers," since each side is meant to be driven by both channels of a stereo amplifier. (The MK-121 is said to permit a largely resistive load of 6 ohms.) The Model Eight requires a lot of amplifier power. I have used two Acoustat Trans Nova 200 watt/channel units very successfully, with the amplifiers providing a very clean, highly de tailed sound with plenty of punch. I currently use a Levinson ML-3 amplifier on each panel of the Model Eight. The huge voltage and current capabilities of the ML-3 amps provide a sound of unparalleled power and refinement.
Obviously, a speaker of such imposing size should be used in rooms of appropriate dimensions. Acoustat recommends rooms on the order of 20 x 30 feet, and their specification for sound pressure level is 125 dB at 25 feet in a room this size! However, an LEDE (live end-dead end) room can be much smaller since, with the absorption, the speaker is essentially in an "infinite" room. That is how I have the Model Eights set up, and it works perfectly, with excellent directivity and a large soundstage. Imaging is quite good, but not on the order of a B & W 801. On the other hand, depth perception is excellent. In spite of the speaker's height, I do not get disparate or elongated images or the sense of an orchestra performing above my head.
As to performance, the Model Eight has to be deemed one of the world's great loudspeakers. Transient response on everything from percussion to piano has a "right now" immediacy.
When fed signals from master analog tapes (and some digital tapes, too), string sound can be ultra-smooth and of ravishing tonal beauty. With 23 square feet of radiating diaphragm driven by two Levinson ML-3 amplifiers, bass response is awesome in its output, clarity and visceral impact.
Even with the Virgil Fox organ recordings, no subwoofer is necessary. In large-scale orchestral works like those of Mahler, Bruckner and Stravinsky, the dynamic range capability is enormous. No question whatever that digital sound can be handled. Given a recording of the requisite high quality, the Acoustat Model Eight can furnish some of the most accurate, wonderfully musical sound extant.
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(Adapted from: Audio magazine, Jun. 1983; Bert Whyte )
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