December 2003

MartinLogan Clarity Electrostatic Hybrid Loudspeaker
Review by Alvin Gold
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  There are few true audiophiles who have not lusted after MartinLogan speakers. Well perhaps they're not for everyone. On the plus side, MartinLogan is one of the few manufacturers worldwide of electrostatic loudspeakers, and in recent decades by far the most successful. Electrostatics have always been held in a very special esteem, mainly because their large, ultra light diaphragms are perceived as capable of resolving the complexities of a fast changing musical waveform in a manner that the stiff, heavy cones of moving coil speakers are generally incapable of matching. The perception doesn't always coincide with reality, which is that electrostatics and moving coils come in many different flavors, and that although sometimes electrostatics are often objectively better in this respect, this is always not the case.

But there are other differences that are inherent to the two technologies. Because electrostatic diaphragms are large and acoustically relatively transparent, it doesn't usually pay to build them into sealed boxes as the sound will certainly be dominated by the sound of a hollow box reflected through the diaphragm. What is not always realized is it that open back electrostatics also suffer from box type colorations. Flat panel frames are inherently lacking in torsional stiffness, and the open box sections used by others, including MartinLogan, in an attempt to address this problem, suffer similar problems to some extent as sound is reflected off the structural wings that stiffen the main baffle. Getting this part of the design right is one of those black arts, but it is one where the unusual geometry of MartinLogan loudspeakers has an edge.

The geometry referred to is the co-called curvilinear diaphragm, which was designed initially to address a quite different problem intrinsic to panel speakers, namely their very limited horizontal dispersion. Large flat panels act as line sources, projecting sound perpendicular to the panel, and reducing off axis dispersion so that if you don't sit almost exactly on axis, the treble content of the music drops alarmingly. Not only does the direct response suffer from off axis, so does the spectral response of the sound reflected from room boundaries, and the result is a loudspeaker that interfaces poorly with rooms, and which becomes very fussy both about where it is positioned and where the listener sits. Partly for this reason, traditional electrostatics tend to recommend themselves mainly for solitary listening, as only one person at a time will hear music as the designer intended.

The curvilinear diaphragm works quite simply by curving the diaphragm and the perforated electrostatic plates that surround it, over a 30-degree arc, which gives a listening widow that in practice is a little greater than 30 degrees, enough for several listeners in most rooms. But there is still a problem on the vertical axis, because the output in also beamed narrowly in this plane, which means that the treble almost disappears when standing. Again this has implication for early room reflections. The normal answer for this is a tall diaphragm which provides a listening window comparable to (actually slightly greater) than the length of the diaphragm in the listening plane, but this is clearly a far from complete solution, especially with less expensive, more compact electrostatics.

The subject of this review, witch is also MartinLogan's entry level stereo floor standing model, has an answer for this too, but at first sight it is not one that will please purists. You can see it by looking at the top surface of the bass unit enclosure, just behind where the electrostatic panel is attached. It is a moving coil unit, called the NAC (Natural Ambience Compensation) tweeter, which faces upwards towards the ceiling. Moving coil tweeters are directional too, with a dispersion pattern that narrows progressively with increasing frequency, but this is turned to the Clarity's advantage by the way it is used. Sit directly in front of the speaker in a normal listening position, and the tweeter will be edge on, masked by the panel, and is virtually inaudible to the listener. Stand up, and the tweeter becomes audible, to a degree depending on the angle it is heard from. The arrangement is calculated so that the moving coil tweeter becomes progressively more audible as the output of the main panels falls away, but the balancing act is fairly conservative, and in practice you are rarely conscious of the moving coil tweeter.

There is no direct answer to the purist's objection, which is that the speaker is no longer a pure electrostatic. MartinLogan designs are not pure electrostatics anyway. They are hybrids with the bass generated by a moving coil drive unit. reflex loaded in this case. Except at the very high end, it virtually impossible to design a pure electrostatic that is practical and useable with all music types. And although there are real difficulties stitching moving coil and electrostatics elements together, MartinLogan is well practiced in the black arts required, and has been getting progressively better at it over the ears. The more specific answer however is that MartinLogan has never been adverse to using whatever technology comes to hand to achieve their desired end result. Moving coil tweeters have long featured in their centre dialogue speakers to help focus the stereo image, and the Clarity is simply another example of a design which does precisely this, albeit with a slightly different end result in view. But if you really don't like the idea, an off switch has been included.

The Clarity is intended to be an affordable path to electrostatic nirvana, and this is reflected in the way it is built, as you can see from the key numbers from the spec sheet, namely weight at an modest 31lbs each, and size which is 53 x 10.2 x 12.25 (HxWxD in inches). With a footprint of well under a square foot, these are not space consuming loudspeakers, but being dipolar the rear radiation reflected from the back of the room meshes destructively with the forward output to produce a wavy frequency response. The solution as usual is to allow plenty of room behind the speaker - ideally at least three feet, but more is better. Impedance is a moderate 6 Ohms overall, but dips to 1.1 Ohm at 20kHz, but with most music types there is relatively little energy at such frequencies and most amplifiers won't object. Sensitivity is 89dB, and referred to the 6 Ohms nominal impedance means that power demands are modest enough, but the 200-Watt power rating is surely optimistic in the extreme, and indeed would result in extremely high maximum volume levels if it was true. The 8 inch aluminum cone bass driver, loaded by a rear facing port, runs up to 450Hz, and so operates well outside the subwoofer zone, which is where moving coil units are used with senior MartinLogans.

One final design point remains to be covered. This is the first of the new generation models from the MartinLogan stable, and it introduces the so-called Generation 2 electrostatic drivers. The key change is to a new plasma bonded conductive coating, which according to the manufacturer is more consistent in its behavior, for example under different climatic regimes, and which in particular is less affected by humidity levels than the older, hygroscopic vapor deposited coatings. The change in diaphragm has also allowed some other changes, notably smaller and more closely packed perforations in the electrode plates that sandwich the diaphragm. The spars which control the spacing of the diaphragms from the electrodes have been redesigned to improve control and overall driver performance. Being transparent, they are all but invisible in practice.

Sound Quality
To handle, the electrostatic panels feel a little creaky, but they're not intended to be handled directly, and the bass enclosure are solid and well built. As usual with this marquee, fit and finish are of a very exacting standard. The Clarity may be the cheapest free standing model in a range that goes all the way to the stratosphere, but the only obvious signs are its lack of physical stature and the relatively modest volume ceiling.

The Clarity is described by the maker as a home theatre model, but the only obvious justification for this is that there are matching specialized speakers which produce a full multichannel system. I can hear nothing in the way the Clarity has been designed or voiced to suggest any special empathy with home theatre material. Just the opposite. Although I can see it being a very effective main speaker in a home cinema system, for many it will not have the weight and immediacy for the job, though it certainly has the transparency (literally as well as figuratively of course) as well as the refinement.

But transparency and refinement are the kind of qualities that count most with music, not home theatre, and the Clarity is most impressive in this traditional role. The bass appears to extend to around 45Hz in room, which is roughly comparable to a small floor standing speaker, or a large stand mount, so this is not a speaker that can be used to generate full scale organ music, and even with orchestral material it tends to sound relatively lightweight and small in scale. Classical piano, for example the tremendously powerful opening section of the Beethoven Opus 111 Sonata, lacks the almost electric sense and dynamism that is available from larger designs. Conversely however it is an extremely agile and transparent loudspeaker, which responds easily and fully to the varying timbral demands of different types of music. In that same piano example while it may not have quite the muscle to fully display the extraordinary architecture and statue of the music, the very distinctive metallic ringing quality and attack of the Steinway grand used in the test recording was captured beautifully, as was the subtle modulation of dynamics in the more restrained second movement.

Voice was also handed extremely well by the Clarity that lacks the rather wooden quality of most speakers, which as discussed earlier is a natural consequence of the way they are constructed. The midband and treble, which is the remit of the electrostatic panel, starts and stops in the head of a pin. The bass is qualitatively slightly different, a little warmer in balance and more diffuse by the standards of the mid and treble, but it remains sharp and precise by normal box speaker standards, and despite the high crossover frequency to the panel, there is little obvious sense of discontinuity between the two that can be detected with broadband music material. Similarly, the contribution made by the NAC tweeter is genuinely discreet, and helps deliver a livelier, more open result for people who are standing and moving around. This doesn't quite make the Clarity a party animal, but it's certainly a less demanding, and better-balanced design than most of its type.

Conclusions
The Clarity is an excellent loudspeaker, one that provides a taste of the high end for those without the kind of spending power or hi-fi system normally needed to support an electrostatic habit. It is not the best of its type. Larger models in the range sound more muscular (though MartinLogan has never been the most muscular range of loudspeakers), and they use the moving coil bass section more discreetly than is possible with this model. But the Clarity remains a well balanced and highly capable loudspeaker which is fast, fluid, highly detailed and refined. It works well enough with most types of music, though it is really in its element with small-scale acoustic material, and the whole effect is less clinical and more relaxed than you might expect from an electrostatic.

Specifications
Type: Full range hybrid electrostatic/moving coil loudspeaker

Frequency Response: 46Hz to 22kHz (±3dB)

Dispersion
Horizontal dispersion: 30 degrees
Vertical: 26" (66cm) line source with a NAC™ enhanced sound field

Sensitivity: 89dB/W/m

Impedance: 6 ohms, 1.1 at 20kHz

Crossover Frequency: 450Hz

Components: Custom-wound audio transformer, air core coils

NAC Driver: 1" (2.5cm) soft dome

Woofer: 8" (20.3cm) high excursion, high rigidity aluminum cone with extended throw driver assembly, non-resonance asymmetrical chamber format; bass reflex

Power Handling: 200 watts

Weight: 31 lbs.

Dimensions: 53 x 10.2 x 12.25 (HxWxD in inches)

Price: $2,695

Company Information
MartinLogan
2101 Delaware Street
Lawrence, KS 66046 USA 

Voice: 785) 749-0133
Fax: (785) 749-5320
Website: www.martinlogan.com