Floorstanding loudspeakers — Martin Logan Classic ESL 9

The Classic ESL 9 is a passive hybrid electrostatic floorstanding loudspeaker from MartinLogan, placed by the company in its Masterpiece Series. It combines an XStat CLS electrostatic panel with a pair of 8-inch aluminium cone woofers in a sculpted enclosure. MartinLogan lists it at USD 7,499.98 per pair.

Key specs that matter

The Classic ESL 9 covers 34 Hz to 23,000 Hz within 3 dB. Sensitivity is 90 dB at 2.83 V and 1 m, and nominal impedance is 4 ohms, falling to 0.8 ohm at 20 kHz. The recommended amplifier power range is 20 to 400 W per channel. The crossover point sits at 380 Hz. The panel measures 112 x 23 cm and offers a radiating area of 2,576 cm2, forming a 112 cm line source vertically, with horizontal dispersion of 30 degrees. Each speaker weighs 35.4 kg and measures 152 x 26.4 x 64.6 cm.

Engineering and use context

MicroPerf stator technology exposes almost twice the diaphragm surface of a traditional electrostatic panel of the same size, and ClearSpar spacers hold the vacuum-bonded diaphragm at a fixed tension. The panel carries a built-in horizontal curvature, the Curvilinear Line Source principle MartinLogan applies to all of its electrostatic designs. It attaches to the cabinet through an AirFrame Blade made from extruded aerospace-grade aluminium alloy, which also isolates the panel electrically and acoustically. The two woofers were custom designed by MartinLogan's in-house engineers, use cast baskets with an extended throw drive assembly and a non-resonance asymmetrical chamber format, and work in an opposing array, one firing forward and one to the rear, to cut cabinet vibration in the 34 to 100 Hz band. The rear-firing woofer is tuned to minimise near-wall interaction. A flared, slotted rear port adds a layer of rigid internal bracing to the enclosure. The hand-built Vojtko crossover uses metallised film capacitors, air-core inductors, steel laminate coils with low DC resistance and a custom-wound audio transformer. A low-voltage DC supply replaces a standard IEC mains cord, with a maximum draw of 2 W per channel.

Pairing

The manufacturer lists the model as compatible with 4, 6 or 8 ohm rated amplifiers and says it is engineered to work with practically any type of electronics. Two sets of custom tool-less 5-way binding posts feed the panel and the woofer section separately, so the Classic ESL 9 can be bi-wired, bi-amped vertically or horizontally, or driven over a single run of cable using the supplied jumpers.

Alternatives

Within the same Masterpiece Series, MartinLogan offers the Impression ESL 11A, which moves to a 28 cm wide panel and adds dual 275 W amplifiers for its woofers.