Martin Logan CLS Speakers

Description

MartinLogan CLS Electrostatic Loudspeakers

The MartinLogan CLS (Curvilinear Line Source) loudspeaker is one of the most iconic electrostatic speaker designs ever produced. First introduced in the mid-1980s, the CLS became famous among audiophiles for its remarkably transparent sound, wide soundstage, and highly detailed midrange reproduction. Unlike most loudspeakers that rely on dynamic cone drivers, the CLS uses a full-range electrostatic panel to reproduce nearly the entire audio spectrum, making it a purist design that prioritizes coherence and sonic realism.

At the heart of the CLS is a large electrostatic diaphragm suspended between two perforated stator panels. The diaphragm is extremely thin and lightweight—often only a few microns thick—and is charged with high voltage. When audio signals are applied to the stators, the electrostatic field moves the diaphragm back and forth, producing sound with exceptional speed and precision. Because the diaphragm has almost no mass compared to traditional drivers, the CLS can respond to subtle musical details with extraordinary accuracy. This results in the clarity and transparency for which electrostatic speakers are renowned.

The CLS differs from many later MartinLogan models in that it is a true full-range electrostatic speaker with no dynamic woofers or hybrid elements. Many modern electrostatic speakers combine a panel with conventional bass drivers, but the CLS uses a single electrostatic radiating surface to reproduce everything from bass through treble. This design eliminates crossover interactions between different driver types and helps maintain phase coherence throughout the frequency range.

Another distinctive feature is the curved panel geometry, which gives the CLS its name. The gently curved electrostatic panel helps disperse sound more evenly across the listening area, addressing one of the traditional limitations of flat electrostatic designs—narrow horizontal dispersion. The speaker operates as a dipole radiator, meaning sound is emitted from both the front and rear of the panel. This produces a spacious and open soundstage but also requires careful room placement to achieve optimal performance.

Standing nearly five feet tall with a broad electrostatic panel, the CLS is visually striking as well as sonically distinctive. The cabinet frame supports the large panel while keeping the structure rigid to minimize vibration. Because electrostatic panels require a high-voltage bias supply to operate, the speaker must also be connected to AC power in addition to the amplifier signal.

While the CLS is capable of impressive clarity and imaging, it can be demanding in terms of amplification. The speaker’s impedance varies significantly with frequency and can drop to extremely low values at high frequencies, meaning high-current amplifiers are typically recommended for the best performance.

Despite these requirements, the MartinLogan CLS has remained a beloved reference speaker for many audiophiles. Its ability to render vocals and acoustic instruments with lifelike realism helped establish MartinLogan as a leader in electrostatic loudspeaker technology and influenced many later designs in the company’s lineup.

Review Quotes

• “One of the most transparent loudspeakers ever made.” — Stereophile reviewer commentary

• “The CLS produces a startlingly real midrange.” — Stereophile listening impressions

• “A landmark electrostatic loudspeaker design.” — high-end audio press commentary

Product Specifications

• Type: Full-range electrostatic dipole loudspeaker

• Driver Configuration: Single electrostatic panel (no conventional drivers)

• Frequency Response: 45 Hz – 22 kHz ±2 dB

• Sensitivity: 86 dB (1 W / 1 m)

• Nominal Impedance: 6 Ω (early versions), 4 Ω (later versions)

• Minimum Impedance: approximately 1–1.6 Ω at high frequencies

• Recommended Amplifier Power: 80 – 200 watts per channel

• Horizontal Dispersion: approx. 30°

• Dimensions: 57.5″ H × 28″ W × 14.5″ D

• Weight: approx. 67 lb per speaker

Overall, the MartinLogan CLS remains one of the most respected electrostatic loudspeakers ever produced. Its full-range panel design, exceptional transparency, and immersive soundstage continue to make it a reference point for audiophiles interested in the unique sonic character of electrostatic speakers.