By Anthony H. Cordesman,The Absolute Sound
April-May 2001

The MartinLogan Prodigy is the best practical reference-quality electrostatic loudspeaker I've heard, and I don't say this casually. My experience with electrostatics goes back to the KLH-9s, the first generation of Quad electrostatics, the Acoustats, and the Quad ESL-63, and has always been something of a love-hate relationship. The midrange of those I've used has often been glorious, for its day. The treble, however, has generally been beamy and highly directive, and the bass and dynamics have always fallen short.

For all the potential of electrostatics, the limits in execution have consistently been a problem. Like ribbon drivers, cones, planars, and everything else in the speaker world, there is no right technology, simply a best available implementation. The issue is never which theory is best on paper, but always which mix of compromises sounds best in the listening room. The Quads ruled for many years.

Then, some years ago, MartinLogan seized the lead in electrostatic design at least to my ears with the CLS II. This speaker looked and sounded far better than the Quads. It had extended treble off-axis and a larger listening window of full-range sound. It was audibly more extended in the treble and more detailed, and it was truly transparent. With the right musical material chamber music, voice, solo instruments, and small jazz groups that do not rely too much on deep bass it could be superb. It was remarkably revealing, while remaining remarkably musical, and the soundstage detail and ambience were excellent.

"MartinLogan's use of a transparent electrostatic
panel and sculptured frame and woofer section
make it about as attractive a piece of modern
sculpture as any large speaker can be."

Yet power handling and bass remained major problems. The CLS II had the inherent dynamic limitations of most practically sized electrostatic panels. It could not accurately reproduce the loudest passages of full orchestral passages, loud jazz music, or power rock. Treble beaming also remained a problem, although the curved surface provided reasonably good dispersion up to 30 degrees. The beaming of flat planar electrostatics like the Acoustats and Stax eventually became too irritating to listen to. So did the beaming of the tweeter in the original Quad, which many listeners also disliked because of the limited listening area in which it produced its best sound. Getting deep bass from full-range electrostatics always seems to present insuperable problems. The CLS II could produce good bass only down to the edge of the lowest octaves and it relied heavily on unpredictable room reinforcement effects.

These problems led MartinLogan to hybrid designs. It produced a generation of mixes of its electrostatic panel and separate dynamic woofers. Each model reduced the problems in mixing two types of driver and moved toward a speaker that combined the advantages of an electrostatic in the midrange and treble with full dynamics and bass capabilities. The ultimate result was the Statement E2, which is unquestionably one of the most advanced speakers around. It sells for $70,000/pair and uses two dipolar towers, two sub-bass towers, and a complex, outboard electronic crossover called the EXOS. Each electrostatic tower in the Statement measures 82" h x 36" w x 28" d; the speaker also includes eight 7" cone drivers to cover the bandwidth from 60-200 Hz. In addition, each sub-bass tower measures 63" x 15" x 23" and has eight 12" cone drivers. If you have any illusions that electrostatics can easily become full-range references, consider these measurements and number of drivers.

Now, if you have the requisite space and money, by all means rush out to listen to the Statement E2. But if you don't, the MartinLogan Prodigy is a far more affordable product of this process of evolution and offers a practical way of getting the electrostatic treble and midrange without sacrificing dynamics and bass.

The Prodigy sells for $10,000/pair, depending on finish, and has some of the technical features of the Statement E2, including the advanced electrostatic transducer. The panel is a 4-foot line source in the new multi-transformer design, and its isolated high-pass/low-pass crossover results in increased efficiency, power handling, and bandwidth extension. An aluminum alloy head-piece and side plate and an extruded stator increase the rigidity of the frame of the panel and act to reduce resonance. The cabinet is a multi-laminate composite. The cone woofer/subwoofer system crosses over at 250 Hz.

"...there is a kind of magic that emerges from
the Prodigy, in direct proportion to the quality
of the recording and the system's front end,
electronics, interconnects, and speaker cables."

There is a difference in size between the Prodigy and the Statement E2, as well as a $60,000 difference in price. The Prodigy weighs only 133 pounds a side, less than a fifth the weight of the Statement, and it measures 67 x 16.5 x 28 inches. Scarcely petite, but it will fit in an average real-world listening room. MartinLogan's use of a transparent electrostatic panel and sculptured frame and woofer section make it about as attractive a piece of modern sculpture as any large speaker can be.

The electrostatic panel is the key to the overall sound quality of the Prodigy. It is curved to provide dispersion over 30 degrees and tall enough to act as an apparent line source to a seated listener. The design is quite reliable, given the fact that an electrostatic uses high voltages and requires excellent insulation over a wide surface area of very thin panels. I do not know of any cases of arcing in a MartinLogan or panel breakdown since its early models.

Furthermore, MartinLogan's transparent diaphragms and perforated metal plates eliminate the need for grill covers. The panel and frame are highly rigid. An electrostatic panel is inherently free of most cabinet resonances, but frames can still vibrate and MartinLogan has paid careful attention to this problem. The end result is a remarkable midrange and treble. The 30-degrees radiation pattern and modified line-source configuration make for a relatively narrow area in front of the speaker that accommodates two or three listeners, about as wide as the ideal listening area gets. The panel design also limits sidewall reflections. The dipole panel radiates almost the same signal to the rear and so adds apparent space, depth, and air particularly if the speaker is moved four to six feet from the rear wall.

What is most important, however, is the sheer transparency and dynamic clarity of the Prodigy's sound above 250-300 Hz. I don't want to exaggerate the magic of electrostatics. Today's best dynamic drivers are superb. So are ribbons, as manufacturers like Apogee, Magnepan, and VMPS have shown. Nevertheless, there is a kind of magic that emerges from the Prodigy, in direct proportion to the quality of the recording and the system's front end, electronics, interconnects, and speaker cables.

I'm not sure I can put this sonic quality into words. It is not dependent on a particular type of music or recording. We have used the word "veil" so often in reviewing that Salome now seems to have begun her dance several thousand veils short of the average reviewer. Yet this is really the, er, net effect. It becomes most apparent when you shift back to a speaker with less resolution and clarity, less ability to reproduce fine dynamic detail, and more coloration in timbre.

"The Prodigy has good, clean, tight, deep bass
by the standard of the best speakers in their price
category and have more than enough power
for music listening even on demanding organ,
rock, and full-orchestral spectaculars."

This superior sound quality is also apparent when you want to reveal the differences in electronics and cables. For example, the Prodigy did a superb job of differentiating the few good SACD recordings from the many mediocre ones. It revealed the differences between two superb speaker cables: the Kimber Select and the Transparent Audio Signature Reference XL. The Kimber was slightly softer, but more integrated in terms of overall frequency response; the Transparent Audio was extraordinarily detailed and revealing.

Another word to describe the midrange and treble of the Prodigy is "effortless." You really don't have the feeling of listening to a mechanical device; the music seems to flow naturally into the room, and once the Prodigy is properly set up, the imaging and soundstage width and depth are excellent and stable. The MartinLogans differ from many electrostatics in that they do not roll, soften, or romanticize the upper midrange and treble.

The Prodigy has more upper-octave energy than the Quads and most electrostatics I have heard in the past. This is typical of other MartinLogans and makes them more "ribbon-like." It gives them advantages with really clean recordings that are not miked too closely. Of course, you can hear every defect in lesser material. The Prodigy also has more lifelike dynamics than the Quads and other full-range electrostatics I have auditioned.

In short, the electrostatic panels in these speakers are very "flat" with extended and revealing upper octaves whose timbre and dynamic energy are revealing of both the strengths of a good recording and system and the weaknesses of bad ones. If you want reference quality, the midrange and treble of the Prodigy are excellent. If you want soft, forgiving sound, look elsewhere.

Let me note that the manufacturer's set-up instructions must to be followed to get the best kind of midrange and treble response and an equally good soundstage. I had to move the furniture in my room to give the speakers more distance from the rear wall; I experimented with the spacing between the speakers and with their angle toward the listening position to minimize a vestigial upper-midrange and treble beaming and to lock in the soundstage. I ended up with a slightly wider position than is normally recommended, and with the speakers angled so their on-axis response crossed in front of the listening position. If you hear a hole-in-the-middle effect or major changes in sound with minor head movements, the problem is in your set-up. Experiment!

The bass section of the Prodigy is the key to its ability to provide better dynamics than a pure electrostatic and far better bass at real-world listening levels. It is also both a great strength and the limited weakness of this speaker. MartinLogan uses what it calls its ForceForward configuration of the two 10" woofers in the bass section. This makes a quite audible contribution to creating a cone woofer system that can match the speed of an electrostatic and create a more seamless hybrid system. Non-ForceForward speakers radiate bass equally in all directions, including toward the wall behind the speaker. The sound radiated toward the wall is then reflected back toward the listener. The reflected energy will add and subtract, depending on the wavelength, from the forward-radiated sound, creating high and low amplitude response anomalies when the low-frequency response is measured from the front of the speaker or at the listening position. Typically, these anomalies are a suck-out at 50 Hz and a peak at 100 Hz.

"I'm not kidding when I say the ESL-subwoofer match
is very good, and some aspects of it are excellent."

MartinLogan says that the ForceForward configuration ensures that the low-frequency energy from the Prodigy is not radiated behind the speaker, thereby eliminating the reflected energy from the rear wall. As a result, it reduces the in-room response anomalies and allows easy room placement and creates smooth, powerful bass throughout the listening area, and optimum, smooth bass response at listening position. In practice, ForceForward means that the woofers have some distance between them in the direction of the wave launch. Electrical filters on each driver control phase in a rather complex mathematical model. In the end, of course, what's important is that the Prodigy's bass proves to be good to excellent even in listening comparisons with the Revel Salons, which have some of the best deep bass around.

The Prodigy system was relatively free of placement and room problems from 200 Hz to below 30 Hz. It allows the user exceptional freedom in placing the speakers in the best location for imaging, soundstage, and midrange/treble response without sacrificing bass performance. Most speakers with true, deep bass response require far more serious trade-offs between the best bass and the rest of speaker performance.

Performance with test tones was quite good for a speaker this size, and so was sweep performance. Most speakers excite more room resonances and lose more detail at some point in the sweep. The ForceForward section of the Prodigy worked well, but it did not perform miracles. I still got some standing waves and room effects, and the usual "mountain-range" of peaks and valleys in bass response that I have measured with every speaker in every listening room I've tested.

If you judge the Prodigy in terms of practical music listening, however, its bass performance was very good even at the kind of levels (100 dB+) more suitable for home-theater applications. I can easily see this speaker doing dual service in a stereo and home-theater system, although I would not attempt to use its bass section as effects channel. The Prodigy has good, clean, tight, deep bass by the standard of the best speakers in their price category and have more than enough power for music listening even on demanding organ, rock, and full-orchestral spectaculars. It had no problems reproducing a demanding recording like the Oue/Minnesota Orchestra version of Aaron Copland's Fanfare for the Common Man [Reference Recordings RR-93CD] to levels beyond those I would ever need for music listening.

One key to measuring the Prodigy's overall success is the extent to which the sound of the electrostatic panel and bass section form a seamless whole. Here I would give the speaker a "very good" mark the highest I've so far given a hybrid design but not "excellent." Properly set up, the Prodigy provides an excellent match in timbre between the treble/midrange and the bass.

In dynamic contrasts, the apparent speed of musical changes is also very good, but not excellent. The midrange and treble speed and definition are better than in the bass, and this is sometimes audible in the transition area about 300 to 80 Hz. You will notice this with clean solo piano or guitar recordings or a natural-sounding disc of small jazz, rock, or chamber groups where you can place each instrument in space and hear how it performs over the entire frequency range. You can also hear it with bass warble tones and sweeps.

Don't let this put you off the Prodigy. It is still the most seamless electrostatic-dynamic hybrid I know in its price range. It is better than the Apogee or VMPS ribbon-dynamic woofer hybrids I've reviewed, and clearly outperforms any combination of Quad-subwoofer I've heard. I'm not kidding when I say the ESL-subwoofer match is very good, and some aspects of it are excellent. I would also hazard the guess that there is only so much you can do with speakers with crossovers much above 60 Hz. Certainly, I hear more serious mismatches between dynamic speakers and dynamic subwoofers every time I review a home-theater system, and often hear them in full-range dynamic speakers.