KLH Nine

The KLH Nine is the superb sounding and history making, full-range electrostatic loudspeaker that Arthur A. Janszen (AAJ) created at JansZen Laboratory and put into field tests in 1957. This design was then taken on by KLH and put into production at the end of the 1950's, with AAJ as V.P. Engineering.

The KLH Nine was the first truly full range electrostatic speaker. Even fairly recently, it was declared one of the 12 most significant speakers of all time, and has been written about repeatedly (example). Production began in late 1959 and continued for nearly twenty years. The list price was initially about $2,000/pair, which translates to about $20,000 in 2023 dollars (https://www.usinflationcalculator.com/). 

Each 6' x 2' x 3" thick speaker panel comprises ten woofers and a single 4" x 4" square tweeter. The treble back wave, being emitted from such a small area, does not intersect itself, and thus does not create the prominent, artificial sounding comb-filtering artifacts that large, wide range panels do.The 800 Hz hand-off from woofers to tweeter is accomplished by way of a single transformer's innovative design, having different windings on a common core, with different inductive characteristics for the woofer and tweeter output signals. The Nine might thus be considered crossover-less, despite being 2-way.

The bass response is flat to 40 Hz, at least when they were new or once they've been refurbished, and the treble extends to 30 kHz. They were also durable, and could handle 60W amplifiers without damage. Neither aspect could be expected of its contemporaries from QUAD. Of course, with the advent of solid state amplifiers and the ensuing power wars, people did try connecting oversized amplifiers, and were able to melt the wax out of the supplies and punch pinholes in the woofer diaphragms that eventually caused failures.

Over the past decade or so, we've accumulated a fair number of pairs for refurbishment or upgrade to your specifications. We can also receive your pairs for refurbishment or upgrade, or take them in partial trade for pairs we may have already serviced.

Although there are pairs still in operation without having required repair, there are several things that can go wrong with this model after 40 to 60 years:

• Selenium diodes were the only high voltage, solid state rectification devices available in the 1960's. After 40 - 60 years, they're prone to failure. This causes reduced or missing sound from tweeters, woofers, or both. This will not happen to the modern silicon diodes that we replace them with.
  
• Carbon composition resistors were the only type available in those days, and after decades of exposure to high voltage, they can change their value and even fail. Failure of these devices also causes reduced output. We replace them with metal film resistors that do not age.
  
• Soot and other particles can become electrostatically precipitated onto the woofer panels and high voltage wiring. This can cause leakage paths for the high voltage. Leakage can cause reduced output and popping sounds. Our rebuilds include a thorough dismantling and cleaning. We then add a low density, acoustically transparent barrier membrane that's only three microns thick, which prevents particles from reaching the high voltage areas. (Human hair averages about ninety microns thick.)
• The Bakelite (phenolic) terminal boards develop leakage paths over long periods of time. This can cause reduced output or popping sounds. We replace them with new ones made from circuit-board grade epoxy/fiberglass material. 
• The original vinyl-insulated wire loses its insulating properties, unlike the mPPE-insulated wire that we replace it with.
• The PVDC membrane film used for the woofers, which was the only thin film available with appropriate tensile properties, becomes stiffer and tighter over the decades. This typically causes a reduction in bass depth, which on the oldest pairs roll off at 90 to 100 Hz, instead of the 40 Hz original design spec.
     We'd been replacing it with a special PET to prevent aging, but a material that's similar to the original works better for a number of reasons, so that's what we use now. We can't predict whether it will age similarly to the original, but we feel confident that it will remain substantially the same for at least 20 years, as did the original. 
  
• The connection to the tweeter membrane coating can fail inside the tweeters, which causes the treble to be reduced or disappear. The coating and coating connection that we apply during panel rebuilds is far more robust. 

We're uniquely qualified to address these issues.

We offer a refurbishment service as well as an upgrade service. You can order pairs that start out as one of our original vintage pairs, or you can send us your own pair for refurbishment or upgrading.