Product Review - Martin Logan SL3 Electrostatic Loudspeakers - March, 1998

By Stephen Slaughter

Martin Logan SL3 Speakers Electrostatic Hybrid 4' Line Source, 10" Cone Woofer Mfr. FR: 30 Hz - 22 kHz ± 3 dB Sensitivity: 89 dB/2.83 V/m Impedance: 4 Ohms Size: 64" H x 13" W x 14" D Weight: 65 Pounds Each Price: $3,200/Pair

For those who don't think that a loudspeaker should plug into a wall AC outlet, the Martin Logan SL3s may not be for you. For the rest, listen up. While electrostatic loudspeakers (ESLs) have always offered superb midrange, they often couldn't produce the bass like their coned counterparts. Adding a subwoofer introduces the problem of matching the transition from that speaker to the electrostatic panel. An easier way might be to let the manufacturers do the matching. Thus, the hybrid. Part ESL and part moving-coil woofer. Is this the best of both worlds? Maybe.

The elegant Martin Logan SL3 has a 10" cone woofer mounted to a 12" x 48" curved ESL. The crossover is specified at 250 Hz. Minimum recommended power is 80 watts, and maximum is 200 watts. With a 4 Ohm nominal impedance, and a minimum of 1.5 Ohms at 20 kHz, amplification is an important factor. Frequency response is reported to be 30Hz - 22 kHz ± 3 dB. Each speaker weighs 65 pounds and comes with spikes and leveling feet. Total height is 64" with a width of 13" and a depth of 14". A -3dB switch on the rear at the base of the speaker allows tailoring of the bass output. They are bi-wireable with high quality binding posts and have light oak trim pieces though other trim woods are available.

So how do the SL3s sound? Having mated the speakers to five different amps ranging from $300 to $5,000, I have found that they can illuminate the qualities of each combination. I used an Ayre V3 with ARC LS3B preamp and Theta Pro Prime IIa DAC, and the Martin Logans really sang. Bass is articulate, extended, and fast in typical solid-state fashion. The midrange is rich and as harmonically accurate as I've ever heard. The Audioquest Crystal cables I used for evaluation seemed to mate with the SL3s quite well. While the curved panels increase high frequency dispersion to 30⁰, there is still a sweet spot, but it is somewhat larger than with other ESL designs I have heard.

The SL3s can sound harsh if the amp/preamp combination is not up to the task, but given the right front end, they are both detailed and nonfatiguing during listening. There aren't enough letter "a"s in the word "fast" to describe the SL3s when I switched to a Fourier Components Triomphe OTL (Output Transformerless) Tube Amplifier. Transients unfolded at warp nine while maintaining a smoothness only heard with the best systems. The tubes produced that rich, involving midrange performance only select ESLs and tube amps can give. These speakers have an uncanny ability to portray the realism of a live performance.

A word about location. It has taken three rooms and six locations for me to find the right place to put these speakers. When placed in a sonically bright room, the SL3s can sound somewhat thin and etched. Electrostatic speakers are dipolar, meaning that when the electrically charged membrane moves back and forth between two perforated metal plates, air moves outward at the front while it moves inward at the rear. Not only is the sound transparent, but the speaker itself is transparent as well (see photo at right). The holes in the plates are critical to the sound, because diffraction can occur. So, the holes in the SL3s are round (see photo at left) and smooth along the edges to keep diffraction at a minimum.

Their dipole nature requires careful experimentation for optimal arrangements. Electrostatic speakers are notorious for "beaming", which means the dispersion is narrow. That's just the way it is with ESLs. In the case of the SL3s, they are curved across the front so that the dispersion is increased to 30⁰. Thin ribs maintain the proper curvature. ESLs also like a lot of space. In their current location, which is a 14' x 20' x 8' room with carpet and dry wall, they are 36" from the front wall and 47" from the side walls. I consider this to be a nearly ideal proportioned room, and the speakers really strut their stuff. They exhibit a solid 35 Hz bottom end. The sound staging is layered and deep. The Cleveland Orchestra recording of Beethoven Symphony No. 1 (Sony Essential Classics 46532) presented as much three dimensional staging as I've heard on any system. Imaging is impressive despite their dipole nature. Do they have the ultra precise performer placement capabilities of the best mini monitors? No, but they can come surprisingly close.

Some experimentation with diffusers/absorbers can dramatically enhance the soundstage accuracy. Yes, dipoles can image when set up properly. This further supports how important the installation can be. Just audition the excellent Keb' Mo' recording (Epic 57863) through these babies to hear first class imaging and sonics. When I listen in a near field type scenario, the SL3s are as transparent as can be. Martin Logan recommends, in their first class manual, that listening to the inner third of the panel is optimal. I used no toe-in for the evaluation setup, and this seemed to work well.

Are there any sonic downsides the the SL3s? Some CDs tended to manifest the difference in speed between the ESL panel and cone woofer. This was usually subtle, but nevertheless apparent, and only on some selections. The transition from the woofer to the panel was seamless on most material. Also, though not a downside (to me), the speakers do present a "wall of sound" which may not work for everyone (in other words, you may not like a 12' classical guitar). On full scale orchestras, the Martin Logans are startling in their realism. This is not to say that small ensemble performances are compromised. String instruments are rendered with a degree of accuracy that keeps you coming back for more. But some may prefer a point source (only theoretical, but small cone speakers are more like a point source than an ESL panel is) for certain types of music.

Now, about the dynamics. On the Reference Recording Stravinsky (Minnesota Orchestra Stravinsky's Firebird Suite - Reference Recordings RR70CD), one can be fooled for about 9 minutes into thinking that dynamics are limited. Then the system ignites with the fury of Zeus from Mt. Olympus. Rocking to the B52s sent me straight up the boogie scale. Martin Logan reports that these are capable of 105 dB, which is well past my listening pleasure zone.

ESLs are not for everyone, but if you are willing to go the extra mile to find the right speaker location, the payoff will be significant. Add a quality front end, and they will compete with any other speakers out there. The SL3s are very revealing of any other components in the system, and therefore require a commitment to quality throughout. But when you hear that "you are there" type reproduction, mark 'em sold. These hybrids offer a seamless bass driver/panel transition and are transparent with a capital "T". When set up properly, they involve you in the music in a way only the best transducers can. While $3,200 is a lot of money for a pair of speakers, they are a bargain considering the level of performance. A must audition for anyone considering speakers at this price point.

Stephen Slaughter

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