KLH Model Nine (1959–1979)

A floor-to-ceiling window into sound, so transparent it disappears - until the bass hits and you remember it's not magic, it's engineering.

Overview

The KLH Model Nine stands nearly six feet tall and is barely thicker than a hardcover book. You don't put these on stands. You position them like sentinels, one on each side of the listening chair. With a properly set up pair, the first thing you notice is the silence between them. Then they play, and the detail is fine enough that it feels like eavesdropping on the recording session. In 1959, the Model Nine was the first full-range electrostatic to deliver this without compromise.

Arthur Janszen, a pioneer in high-frequency electrostatic design, was behind the Model Nine. It was KLH's flagship at a time when most companies were still wrestling with cone distortion and box coloration. Janszen had already made waves with his Z-130 tweeter array, but the Nine was different. It wasn't a hybrid or an add-on. It was a complete, full-range electrostatic panel, the first to cover the entire audible spectrum without a conventional dynamic woofer. Each panel houses ten vertically stacked electrostatic "woofers" and a single 4-inch square electrostatic tweeter at the top. A single transformer-based network drives them all and handles the handoff around 800 Hz. There's no traditional crossover in the modern sense, just a passive, inductive divide.

The Nine doesn't "project" sound so much as "release" it. It's dipole radiation, with a wide, airy dispersion that avoids the forward glare of box speakers. The highs are famously smooth and extend well beyond 20 kHz without a hint of grain. The bass reaches down to 40 Hz, which is a lot for a design with no enclosure. It's taut, articulate and dynamic when fed with the right amplifier. Because the panels are so thin and wide, the soundstage seems to float in space, and the imaging is precise.

The Model Nine isn't for everyone. It demands space, both physical and electrical. These speakers are power-hungry, with a nominal 16-ohm load that climbs even higher at resonance. They need amplifiers with strong output transformers and solid current delivery. They also need outboard power supplies, one per panel, to generate the high voltage that charges the stators. The looks are striking, but the size and open-back design mean the panels have to sit well away from walls, often several feet, to breathe properly.

Specifications

Key Features

The Transformer-Coupled “Crossover-Less” Design

The Model Nine is technically a two-way system, but its crossover uses no traditional capacitors or inductors. Instead, a custom transformer with multiple windings on a shared core splits the signal between the woofer panels and the tweeter. Because the transformer couples the signals magnetically rather than electrically, it minimizes phase distortion and preserves transient detail. The handoff at 800 Hz is so clean that many listeners report hearing a single, unified source rather than two distinct drivers. That's rare even in modern high-end speakers, and in the 1960s, it was revolutionary.

Dipole Radiation and Room Integration

The Model Nine radiates sound from both the front and back of the panel. That makes a dipole pattern, and it interacts heavily with the room. You can't shove it into a corner or treat it like a conventional box. It needs space, especially behind it, so the rear wave can develop. Set up correctly, the dipole behavior eliminates cabinet resonances and reduces early reflections, which gives a more natural, open sound. Set up wrong, and you lose bass impact or get nulls at the listening position. Owners report that toe-in, distance from walls, and even carpet thickness can change performance a lot.

High-Voltage Outboard Power Supplies

Each speaker needs its own external power supply. It generates the 5,000+ volts needed to charge the stators and polarize the diaphragm. These supplies are integral to operation. They add complexity, but they also isolate the high-voltage circuitry from the audio signal path, which reduces noise and interference. The supplies are fairly simple inside: selenium rectifiers (in originals), step-up transformers, and filtering components. Over time these can fail, especially the selenium diodes, which degrade and can give off a rotten-egg smell when they go. Modern refurbishments typically replace them with silicon diodes, a critical upgrade for reliability.

Historical Context

The late 1950s were a golden age for electrostatic experimentation. Companies like Quad were pushing the boundaries with designs like the ESL-57, but those were limited to midrange and treble and relied on dynamic woofers for bass. The KLH Model Nine changed that. It was the first full-range electrostatic speaker to reach commercial production. Arthur Janszen, who had already proven his mastery of high-frequency electrostatics, joined KLH after the company acquired his lab, and the Nine became his magnum opus.

At a time when most hi-fi gear was shrinking into bookshelf cabinets, KLH went vertical. The Nine stood in stark contrast to the acoustic-suspension speakers Henry Kloss had made famous at Acoustic Research. The AR-3 was compact and self-contained, while the Nine was expansive and architectural. It was priced at $2,000 per pair in 1959, roughly $20,000 today, so it was never meant to be mass-market. It targeted serious audiophiles and design-conscious buyers who wanted sonic transparency and visual impact. Only about 5,000 pairs were ever made.

The Nine has been called one of the 12 most significant speakers of all time. Its influence shows in later electrostatics from Sound Lab, MartinLogan, and even modern reissues from KLH itself. When David Kelley relaunched the brand in the 2010s, one of his first moves was to reintroduce the Model Nine as a faithful recreation.

Collectibility & Value

A pair of original KLH Model Nines in working condition is a rare find and a serious investment. Prices vary widely with condition, completeness, and whether the electronics have been refurbished. Unrestored pairs with original power supplies and minor cosmetic wear typically sell between $2,500 and $4,000. Fully restored units, especially those serviced by specialists like JansZen Audio, can command $8,000 to $10,000 or more. A brand-new reissue from KLH retails for $12,499 per speaker.

The biggest concern for buyers is age-related failure. After 40 to 60 years, several components are prone to degradation. Selenium diodes in the power supplies are the most common point of failure. They can short, open, or leak toxic residue. Carbon composition resistors in the transformer network drift in value over time, which affects frequency balance. The original PVDC diaphragm material stiffens with age, reducing bass output and raising the low-frequency limit from 40 Hz to as high as 90-100 Hz in neglected units. Bakelite terminal boards develop leakage paths, and the original vinyl wiring loses insulation integrity.

A proper restoration is a full-system overhaul, not a simple refoam job. Reputable shops like JansZen Audio offer multi-tier refurbishments that include replacing diodes, resistors, and wiring; cleaning and re-membraning the panels; and upgrading terminal blocks. Some even apply protective, acoustically transparent films to prevent future contamination from dust and smoke. These services are expensive, at $7,000 to $10,000, but they restore the speaker to (or beyond) its original performance.

Never buy a pair without verifying that it works. Ask for sound tests, check for arcing or buzzing, and inspect the power supplies for corrosion or odor. If the seller can't demonstrate that they work, assume they don't. These are not "plug and play" speakers, so anyone not ready to pay for a full restoration should think hard about whether the looks are worth the cost.

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