MartinLogan Impression ESL 11A Hybrid Electrostatic Loudspeaker

What’s in a Name?

Equipment report
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Floorstanding
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Products:
Martin Logan ESL 11A
MartinLogan Impression ESL 11A Hybrid Electrostatic Loudspeaker

MartinLogan’s new Impression ESL 11A is a direct replacement for the company’s Montis that I reviewed so enthusiastically almost three years ago. Like the earlier model, which is priced identically to the new one at $9995 a pair, the Impression is the third from the top of the company’s floorstanding Masterpiece line and consists of one of ML’s proprietary CLS electrostatic panels affixed to an enclosed dynamic subwoofer. Inasmuch as both my colleague Dick Olsher and I have written extensively about MartinLogan speakers in the past few years, I refer readers to our respective reviews of the Montis (Issue 244) and the Summit X (Issue 209) for technical and historical background, and to Dick’s chapter on the company in TAS’ Illustrated History of High-End Audio, Volume One: Loudspeakers.

The main talking points are two: First is ML’s electrostatic panel, which it designates CLS for “Curvilinear Line Source,” owing to the mild horizontal convex curve designed to overcome the typical narrow high-frequency dispersion of flat panels. Second is the use of powered dynamic woofers to surmount the usual bass and dynamic limitations of most ESLs. Owing to the superior transparency of electrostatics and flat panels’ dipole radiation pattern, matching ESL panels to dynamic woofers has proved vexing both for designers and for audiophiles who prefer to add aftermarket woofers. In recent years and models, however, MartinLogan has managed to solve the integration problem virtually to perfection. Since then, however, evidently feeling that “virtually” is not close enough, ML’s engineers—largely Joe Vojtko, whom his colleagues often refer to as their resident genius—have completely redesigned the woofer section for all-around superior performance, which shall be the focus of this review.

Glance at a single Impression from the front and you’d be forgiven for thinking it’s identical to the Montis. Look at it from the side and the back and you see that the compact, almost square woofer housing of the earlier model and its ten-inch driver have given way to a cabinet extending almost two feet back that houses a pair of eight-inch woofers, one front-mounted, the other rear-mounted. (A friend of my wife’s inquired if they were some kind of contemporary chair.) At first I assumed the cabinet was to allow the woofers to mimic the panel’s dipole radiation. In fact, with help from the digital circuitry, the two woofers, crossed over at 300Hz, are made to work in a kind of sliding phase arrangement whereby the phase shifts with frequency in order to suppress the backwave and also to prevent frequency-specific cancellations that may result from woofers arranged to mimic dipole radiation. According to Vojtko, digital manipulation of phasing directs most of the two woofers’ output forward, not toward the back wall, an arrangement claimed to facilitate setup and speaker placement: “The sliding phasing is weighted toward the frequencies where directionality is more critical, where the manipulation of the phasing is taking place, and the woofers come into phase together at the lower frequencies.” This does address what has always been one of the thornier problems with ESL/dynamic hybrids, namely, that optimal placement of the panels does not necessarily correspond to optimal placement of the woofers, hence the preference among many audiophiles for the positional flexibility of stand-alone woofers.


But the ace up ML’s sleeve in the Impression is the provision for Anthem Room Correction (ARC), a highly effective digital-signal-processing program designed to cope with typical bass response anomalies of most listening rooms. I say “provision” because while the speaker comes equipped with the circuitry, it can’t be activated without purchasing the ARC microphone, which is an optional accessory priced at $100. In other words, if you don’t purchase the microphone, then the Impression can be used as-is without DSP, just like previous ML speakers. But, as I’ll come to, the Anthem feature is so effective it’s hard to for me to believe that any user, once committed to ten grand, wouldn’t spring for the extra hundred bucks.

Using ARC is quite easy once you get it to lock onto the online program that allows it to work. Unfortunately, if you’re an Apple-man like me and are PC-phobic to boot (me again), this is easier said than done. I eventually got it to work properly thanks in no small part to my wife, who is ambidextrous when it comes to computers and has a PC laptop. But if you’re an Apple-only household, you might want to ask your dealer to do it or else enlist the help of a PC-savvy friend.

As I say, once you’re hooked up and online, it’s a snap: Set up the microphone according to the instructions, then sit back for the few minutes it takes for the application to do its work. (A before-and-after curve is displayed on the screen.) Once it’s done, it’s done, though of course if you change your listening location or move the speakers, then you must redo the procedure. It should go without saying but I’ll say it anyhow: Prior to engaging ARC, you are advised to make every effort to place the speakers optimally in your room. As remarkable as digital room correction is when it works—and this Anthem system certainly works a treat—it’s most effective when it corrects speakers that have already been set up to good or better advantage.

Before I get into the sound, let me take you on a tour of the signal path and the woofer cabinet’s back panel. From the binding posts, the full-range signal goes through two filters, an analog 300Hz high-pass filter to the ESL panels and a digital low-pass filter to the woofers. The low-pass signal is digitized, filtered, and then passed through the ARC circuit. The corrected signal is next sent to a switching amplifier and to the woofers (back in analog). If you’re a digi-phobe—in my opinion, a really silly prejudice in this day and age—then know that if you opt for the ARC feature, at least part of the signal will have undergone A-to-D and D-to-A conversion.