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. 


    Level 1 comprises fully restoring the twenty woofers and two tweeters, giving the walnut frames a light sanding and a new coat of linseed oil, rebuilding the supplies, including replacing the selenium diodes with silicon diodes and upgrading the transformer damping network, repairing any broken or faulty but repairable parts, tightening the walnut frame corner joinery, etc.. The speakers will perform somewhat better than new, but appear completely stock. $7930/pair.

    The Level 2 refurbishment is really an upgrade to the original. It adds the following improvements to the Level 1 refurbishment: completely dismantling the speakers right down to the sticks, and then rebuilding them to better than original condition, repairing of scratches and gouges, substituting better joinery and finishing with multiple coats of Rubio Monocoat Oil Plus finish, new wiring and terminals in the speaker panels, new epoxy/fiberglass terminal blocks to replace the leaky Bakelite originals, coating of the woofer electrodes to reduce the chance of arcing when run with oversized amplifiers, cutting of windows in the front perforated metal grills and welding of wire mesh ahead of the tweeters to eliminate interference effects, addition of acoustically transparent membranes to prevent the incursion of particulates, replacement of the grill cloth with off-white linen or the color of your choice, replacement of the supply binding posts with WBT nextGen, replacement of the power inlets with IDC C14 inlets that work with standard IDC power cords, refinishing of the supply enclosures with a durable post-catalyzed lacquer, revision of the ground connections to the rear grill, refinishing of the rear grill, and more. $9690/pair.

    If any parts require replacement, and replacements are available. there will be an extra charge, but only if you approve the additional repairs. The speakers will thereafter not age appreciably for decades. JansZen-restored KLH Nines carry a full, transferable, two-year warranty.

    Turnkey. We maintain a stock of original KLH Nines, and make them available refurbished to Level 1 for $10,000/ pair, which is half the inflation-adjusted original 1959 price of $2000, or Level 2 for $14,290/pair. We feel this is a bargain, considering they will have been brought up to modern standards.

    Note: If your pair has been worked on by others, there may be a reduced charge if that work has been done correctly, which FWIW we've not seen yet. On the other hand, there may be an additional charge to rectify erroneously undertaken modifications or repairs, which we have seen. We once received a pair with thirty-one extra problems to correct, yet we had not thought this could happen and thus did not think to warn the owner, and so didn't feel entitled to charge for the extra work.

    Lead times vary depending on our back order queue, which includes orders for our new products. It's generally at least four weeks, and can be as long as sixteen weeks. 

    Refurbishment with upgrade

    In addition to what's entailed in the Level 2 refurbishment service, the upgrade also includes replacement of the original tweeters with our new ones, which have twice the membrane area and work down to 500 Hz, rather than 800 Hz. This requires supply modifications and changes to the wiring. The price for the service is $11,490/pair, and the price for those built from our stock of original pairs is $14,380/pair.


    One owner of a double pair of fully upgraded Nines went to the trouble of posting a very thorough account of his rebuild project adventure to PS Audio's forum. I was quite touched to read it, and am sure you'll find it very informative.

    To inquire about KLH Nines, please refer to the contact page.


     October 1960 Audio Magazine cover, showing a pair of KLH Nines

    October 1960 Audio Magazine cover, showing a pair of KLH Nines, and at the center, also the Model Eight table radio. Although the Nine was entirely Arthur A. Janszen's development, he also developed the EQ network for the drivers in the Eight's matching speaker enclosure (not shown).


    Upgraded pair of KLH Nines

      Upgraded pair in David Janszen's office