Martin Logan SL3

Martin Logan SL3


Author: Karsten Hein

Category: Gear & Review

Tag: Loudspeakers

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Gayle Martin Sanders and Ron Logan Sutherland had been interested in developing their own electrostatic loudspeakers ever since working together in a High End music store in Lawrence, Kansas in the late 1970s. Sanders was working as the store manager and had a background in architecture and advertising, and Sutherland was an electrical engineer. Both men were convinced that electrostatic loudspeakers had the greatest potential in providing High End audio performance, despite the fact that the electrostatic speakers that existed at that time still showed very limited performance in terms of frequency response and dispersion angle. Many of them became famous as amplifier killers, due to their troubling impedance curve nearing a shorted circuit. In addition to their lack of treble and bass response and the difficulty of finding a potent enough amplifier, electrostatic speakers produced a very narrow sweet spot for listening, sounding wrong or unbalanced in most places of the room. Among the few successful models of the time were the Quad ‘ELS’, mildly mimicking the design of an electric heater, and the huge KLH ‘Model 9’. While the Quad was able to reproduce chamber music in its fine and delicate tones, the limitations of its design became apparent when listening to louder performances, such as rock or classical music. The KLH on the other hand was very capable of producing all kinds of music, but its sheer size resulted in very low sales.

Sanders and Sutherland began constructing prototypes, some of which went up in flames when driven at higher volumes, until they found the materials composition that would enable them to play their speakers without fear of destroying them. Improvements included the development of an ultra-light Mylnar diaphragm and two horizontally curved stators made of perforated steel that would allow charges of up to 10.000 volts. According to the company website, Sanders and Sutherland exhibited their speaker concept at the 1982 Consumer Electronics Show in Chicago with only a mock-up and some photographs. The design was so radically new that it became an instant hit in the industry and was honoured with a CES Design and Engineering Award. While the ideas presented at the show were still in the design phase, Sanders and Sutherland had already developed their first working electrostatic speaker based on more conventional designs. It was called the ‘Monolith’, and dealers who heard it play during product demonstrations were more than eager to sell this to the public. Given the early acceptance of their ideas, the two men felt ready to start their own business. Having to come up with a brand name, they decided to combine their middle names to MartinLogan in 1983.

Despite many initial setbacks, including the departure of Ron Logan Sutherland from the company, the manufacturer managed to secure its foothold in the High End loudspeakers market. In the 1990s, MartinLogan created many now famous classics, such as the SL3, the smaller Aerius, and the Quest. The SL3 that is featured here is said to be the ‘rockiest’ of the 1990s range. It features a tall and slender stator panel that is flanked by blond oak rails. The Mylar membrane is almost completely translucent, inviting the application of soft back lighting to the front wall for optical effect. The SL3 is a hybrid speaker in the MartinLogan ‘Sequel’ series tradition and offers a 10” paper cone woofer for bass extension. The woofer is housed in a closed cabinet that also includes the 250 Hz 12 dB crossover and the high voltage transformer needed to generate the static electricity driving the Mylar membrane. The panel is open towards the front and the back of the speaker, and it is curved at the MartinLogan typical 30 degree angle to allow for optimum high frequency dispersion. The SL3 features dual binding posts for bi-wiring, as well as a Bass Control Switch to lessen bass response by -3 dB. This can be quite convenient, if the speakers are to be placed in smaller rooms in which bass response is accentuated. Although each speaker must be connected to a power source for high voltage generation, energy consumption is very low, and the speaker switches into standby if no signal current is detected on the binding posts. A small red light at the front of the speaker indicates when the speaker is switched on.

The MartinLogan SL3s is best driven with a strong amplifier that is built to handle high current feedback, because the impedance curve of the speaker shows some very low dips down to just 1,5 ohms at 20.000 Hz. Due to their bipolar panel design, placing the speakers can be a little more challenging than this would be the case with conventional designs. If placed well, the SL3 is perfectly capable of performing a disappearing act that is amazing to experience, in that the precise location of the speaker becomes difficult to trace and the music appears three-dimensional in the room. The sound is sonically balanced, and bass integration works very well on the hybrid design. At 0,37 sqm panel surface, the SL3 are capable of presenting a huge sound stage, both at low and high volumes. Bi-wiring is of the essence, as control over the woofer becomes sloppy when bridged. This may have to do with the hybrid design and the inherent electric characteristics of the drivers. When connected correctly, the SL3 is capable of lots of punch and a quick decay when needed. Because the panels themselves are of considerable size, listening to music at close distance can be quite overpowering. Some people have stated that they feel as if they are being grilled by them. To lessen this effect, but also to integrate the speakers more effectively into the room, the panels can be tilted backward. Overall, the SL3 provides a great basis for a high quality sound experience, as well as lots of room for experimentation.


  • Frequency response: 30-22.000 Hz +/3 dB
  • Dispersion angle: 30 degrees
  • Sensitivity: 89 dB
  • Impedance, average: 4 ohms
  • Impedance, minimum: 1,5 ohms at 20kHz
  • Power handling: 200 watts RMS
  • Weight: 29,5 kg, per speaker
  • Dimensions: (h) 163 cm x (w) 33 cm x (d) 36 cm
Martin Logan SL3
Martin Logan SL3
Martin Logan SL3