A fully passive hybrid floorstander, supplied as a pair: an XStat CLS electrostatic panel 23 cm wide sits above two 20.3 cm aluminium-cone woofers. It is aimed at two-channel listening in a domestic room.
Classic ESL 9: panel and bass section
The Classic ESL 9 belongs to MartinLogan's Masterpiece series and carries no built-in amplification: the whole signal comes from the system amplifier, for which the maker suggests between 20 and 400 W per channel. The curved panel stands 112 cm tall, offers 2,576 cm² of radiating surface and handles everything above 380 Hz; below that point the two woofers take over. Stated response runs from 34 Hz to 23,000 Hz within ±3 dB, and sensitivity is 90 dB.
MicroPerf stators use finer perforations and leave nearly twice as much of the diaphragm uncovered as a conventional panel of equal size, while transparent ClearSpar spacers hold the vacuum-bonded film at a constant tension. The AirFrame Blade frame, extruded from aluminium alloy, stiffens the panel and isolates it from the cabinet. Like every electrostatic, the panel is a dipole: it sends little energy sideways, so the side walls are excited less, and a good deal to the rear, which is where the sense of ambience comes from.
The two woofers are mounted back to back, one facing forwards and the other backwards, an arrangement that cuts cabinet vibration between 34 Hz and 100 Hz; a slot-shaped reflex port at the rear completes the loading and doubles as an internal brace. MartinLogan advises keeping at least 20 cm between the back of the cabinet and the wall, and roughly 75 cm between wall and panel. The Vojtko crossover is assembled by hand with air-core coils and film capacitors. There are two sets of terminals, for bi-wiring or bi-amping, and the panel is fed by a small low-voltage DC supply.
Specifications
- Frequency range: 34-23,000 Hz (±3 dB)
- Sensitivity: 90 dB (2.83 V at 1 m)
- Impedance: 4 ohms nominal, 0.8 ohms at 20 kHz
- Suggested amplifier: 20 to 400 W a channel
- Crossover point: 380 Hz
- Horizontal spread: 30°
- Electrostatic panel: XStat CLS, 112 x 23 cm, radiating area 2,576 cm²
- Woofers: two 20.3 cm aluminium units on cast baskets, one front and one rear
- Bass loading: reflex with a slot port at the rear
- Crossover: Vojtko with a dedicated audio transformer, air-core and laminate coils, polyester capacitors
- Terminals: two hand-tightened sets, ready for bi-wiring
- Panel supply: low-voltage DC unit drawing 2 W at most
- Size (H x W x D): 152 x 26.4 x 64.6 cm
- Weight: 35.4 kg each
- Supplied: sold as a pair
- Finishes: gloss black, cherry, walnut
