KLH Nine Refubishment and Upgrades
JansZen Nine-J -- call for price
If your Nines work fine, then there's no need for a rebuild nor an increased reason to worry about damaging them.
Still, in nearly every case, servicing will improve them in two ways.
1) Woofer membrane tension. A prime difficulty we discovered in our rebuilding operation is that the woofer diaphragm tension is too high. I don't know how to attribute this, but it causes the low frequency extension to be lost below about 70 or 80 Hz. This must be how these speakers got a reputation of having poor bass response. After we replace the diaphragms with a modern and lighter material, and tension it properly, we are seeing the frequency response running flat to 40 Hz in our warehouse, which I'd consider a worst case environment.
2) Bias voltage. In most cases, the selenium stack diodes, which were the only solid state, high voltage diodes available in the old days, have degraded over time. Surfaces in the speakers have ofttimes attracted soot, and the Bakelite terminal block has ofttimes degraded, and these conditions form high voltage leakage paths that draw current from the bias supply and thus reduce its voltage. This will reduce the sound level and in severe cases also cause the speakers to hum at 60 and 120 Hz.
Here's a list of the service options for pairs in basically good condition, along with what to expect as outcomes:
Straight refurbishment -- $2500/pair
Twenty woofers: Disassemble, remove membranes, clean stators, mount new membranes, apply new inks and coatings -- ensures that there are no leakage paths for the bias charge, and ensures that the membrane resonance is at its correct value, which will restore deep bass response (40 Hz) if it had been lost due to membrane tension self-increase or other reason
Two tweeters: rebuild -- restores performance
Replace selenium diodes with silicon -- ensures that time will not eventually cause a loss of membrane bias charge due to diode failure
Upgrade original tweeter compensation network -- decreases THD and flattens the upper midrange bump
Replace phenolic (Bakelite) terminal block with one made from fiberglass circuit board material -- eliminates leakage paths
Upgrade I -- $6250/pair
Same as above plus
Modify internal mounts and wiring to accept our z87 tweeters
Modify supply/crossover accordingly (add notch network to remove upper bass hump, raise tweeter bias voltage, add rolloff network for tweeter split)
Replace original tweeters with z87 tweeters -- wider dispersion, smoother response, lower crossover frequency
Cut window in frontal perforated metal grill and weld in an area of wire mesh ahead of tweeters -- smoother tweeter response
Add rear damping and rear radiation absorption -- better imaging, especially obvious in smaller rooms; better transient response; smoother tweeter response
Add acoustically transparent particulate barriers to grills (3µ, low density film) -- increased durability
Replace grill cloth with fine, open weave linen (relatively convenient to do while grills are off for modifications) -- cosmetic
Furniture grade refinishing of wood and repainting of rear grill available for additional $585.
Upgrade II -- $9900/pair
Same as Upgrade I plus/except
New woofers that are arc-proof, 3 dB more sensitive, and produce 3 dB higher maximum SPL (double the sound power)
Modify internal mounts and wiring to accept two z87 tweeters in each speaker
Replace each original tweeter with two z87 tweeters -- 3 dB higher sensitivity and SPL; wider dispersion than single tweeter
Cut two windows in both frontal grills and weld in areas of wire mesh ahead of tweeters
Packing/shipping cost is a significant factor, generally running in the range of $500 inbound to us, and $300 outbound.
We have been using spare technician time to rebuild pairs of KLH Nines that we have in stock here.
The first pairs are being refurbished to the Upgrade I level as described to the left (full details). The result is substantially better than new.
A pair of these was shown at the 2018 CES. Jonathan Valin of The Absolute Sounds wrote in his Best of Show category:
"Best Sound (For the Money): In my category of speakers $20k and up, that would have to be the reborn KLH Model 9, driven by Rogers Sound integrated amps and an Oppo disc player—perhaps the most completely natural sound at CES."
One person who's heard them in my office wrote (PS Audio Forum 8 Jan 2017): "I recently heard a pair of refurbished KLH Janszen Nine-J speakers and I am now lusting after them. I have truly been smitten by these electrostatic speakers both by their historic lineage, and their tall and wide sound staging, yet exact placement of the smallest of instruments, with the most natural tones. I do not typically listen to Opera. However, David Janszen played Jonas Kaufman’s Turandot, Atto III Nessun Dorma from the Puccina Album. Through the Janszen Nines for the first time in my life I felt like I was truly transported to a venue with no veil or distance between me and the performer. I could visualize the singer’s true height, see his shoes, pants, suit coat, and face in actual size. I felt like I could peer into his mouth and see the wobble of his tonsils. But at the same volume I could hear the most delicate and discrete symbol to the far right of the soundstage. I have never been transported like that before. I had never heard such transparency from a driver speaker, although now I know more why people like the size imagery of tall line array conical driver speakers. I have never been moved so much by an electrostatic speaker for under a $15.000. I want the KLH Nines so bad I’m now looking to sell some of my gear to afford them."
That person has now been able to fulfill his wishes, and is the proud owner of a double pair of upgraded Nines. He has posted in detail about his system (PS Audio forum, March 24, 2019).
Here are some snapshots of the first pair we upgraded.
I just finished rebuilding a set of Nines that exhibited some hum on a couple of bass panels. De-potted the wax to replaced the selenium , found out they were replaced already. Upon reassembling had lost high voltage somehow, Found out I wired one of the rectifiers backwards. Had to depot the wax again and redo the rectifier array. Still no high voltage. Changed a transformer, checked all caps, checked rectifiers again and reassembled. The hum remained. Cleaning the bass panels to "reduce leakage" solved the problem. Now both work well with no hum. Thanks to David Janszen for pointing me in the right direction! How simple that turned out to be! Despite all the negative comments I've read and heard from people over the years about these units (maybe because they really haven't heard or owned them and they just perpetuate negative comments they have read elsewhere), these speakers are very musical. Ive owned SL A-3, Maggie's, ML CLS-z and currently zA2.1 (air-layer). I just love the Janszen designs. tonight I'm going to run the KLH-Nines with a Futterman H-3a amp (the original Julius Futterman design, not a NYAL design). Should be fun!"
Miscellaneous comments about KLH Nines: