early KLH model six

[Guest Droog]

While driving away from a flea market after looking all morning for KLH I thought I wouldn't find anything, then I spotted

a late arrival, pair of model six's in mint condition, blond finish, all plywood cabinet, serial numbers 684 & 711

What years did KLH use this 12-ply plywood. These must be first year if not first week speakers with such low serial numbers.

I'm interested in any info on early KLH. When did production start on the model six?

[soundminded]

Production ran from 1958 to 1972. It was an extremely successful model, a benchmark of value and performance. Early production units such as mine had the woofer frame epoxy cast into the baffle board. Nothing could be removed, not the baffle, the drivers, or even the grill cloth. When they had to be serviced, it was big trouble meaning they had to go back to the factory in Cambridge Mass. Mine were serviced several times, invariably for tweeter or crossover failure. The first time, they apparantly had to pry the front baffle board out with a crowbar. You can still see where the mark was left on the inside of the side wall of the cabinet. Other times, they apparantly removed the woofer cone, worked through the basket, and then reconed the woofer. Later models were much more practical having velcro detachable grill cloths and screws holding the woofer basket to the baffleboard. The tweeters are the same ones used on KLH 17 so if you ever need replacements, you can hunt down a pair of those to canabalize or they are sometimes available by themselves on e-bay. Since their last repair probably about 25 or 30 years ago, they have worked perfectly and still sound excellent. Except for the deepest bass, I preferred them to AR3 and AR3a. They sound even better with three 3/8 inch indirect firing Audax polycarbonate tweeters paralleled and crossed over at 6Khz, the same enhancement I use for my AR9s.

How much did you pay for them and what kind of condition were they in? They usually sell for cheap even in excellent condition and unlike AR speakers, the surrounds on the woofers were cloth, not foam and didn't rot.

[Guest Droog]

I paid $20. for the pair in near mint condition and luckily they are in fine working order. It's a shame it's so hard to get inside these early speakers. Having to take a crowbar to them just doesn't seem right, was it that they were trying to ensure a air tight enclosure? Doesn't seem like something Henry Kloss would do. I like these because it's an early example of KLH. Also, as I write this post there is a pair of model one's with electrostatic high freq. unit on ebay. A great piece of KLH history, but I sume these are sealed cabinets as well.

[tysontom]

>Production ran from 1958 to 1972. It was an extremely

>successful model, a benchmark of value and performance. Early

>production units such as mine had the woofer frame epoxy cast

>into the baffle board. Nothing could be removed, not the

>baffle, the drivers, or even the grill cloth. When they had

>to be serviced, it was big trouble meaning they had to go back

>to the factory in Cambridge Mass. Mine were serviced several

>times, invariably for tweeter or crossover failure. The first

>time, they apparantly had to pry the front baffle board out

>with a crowbar. You can still see where the mark was left on

>the inside of the side wall of the cabinet. Other times, they

>apparantly removed the woofer cone, worked through the basket,

>and then reconed the woofer.

This is a great reply to the question regarding the early KLH Model Sixes. Henry Kloss, after departing AR in 1957, co-founded KLH and actually had a patent on the epoxied-in woofer and tweeter. Kloss, who had a penchent for breaking things down to their simplest form, avoiding complication (such as 3-way speakers) could be at other times amazingly convoluted in his engineering. Due to a lack of tooling funds, he was forced to design the in-house, aluminum-tube woofer frame, epoxy and the "epoxied-coffee-can" magnet assembly. Crude hardly describes it. No one ever paid one penny to KLH for patent rights; no one was ever interested in it, but Kloss patented the epoxy design to give it a hint of dignity. If a failure occurred, just as you say, the speakers had to be returned to KLH to be repaired (KLH also did not have as generous a warranty as AR, and did not pay for shipment to and from the factory). The grill and its black-linen baffle ticking underneath would have be cut out and destroyed, the woofer cone ripped out, and hands would pass through the hole in an attempt to repair broken parts. A new cone and voice coil was then put in place and a new grill cloth tucked into the edge-molding crevice and glued. God knows that had to be labor-intensive. The KLH-6, KLH-4 and KLH-7 of the more popular models, all had the epoxied driver, and this continued well into the 1960s. Strangely, KLH had a lot of crossover capacitor problems, despite the fact that oil-filled surplus caps were widely used. The KLH Model Fours were the most notorious for this failure.

> Later models were much more

>practical having velcro detachable grill cloths and screws

>holding the woofer basket to the baffleboard. The tweeters

>are the same ones used on KLH 17 so if you ever need

>replacements, you can hunt down a pair of those to canabalize

>or they are sometimes available by themselves on e-bay. Since

>their last repair probably about 25 or 30 years ago, they have

>worked perfectly and still sound excellent. Except for the

>deepest bass, I preferred them to AR3 and AR3a.

Many people preferred the KLH (and subsequently Advent) sound to that of ARs. The principle reason for this was the much more forward sound quality of the KLHs -- all of them. Kloss knew that nearly all ARs had a reticent sound quality, and as a new competitor, he intended to capitalize on that AR characteristic, despite the fact that AR-2axs, AR-3s and AR-3as were more sonically accurate and would easily outperform the KLH-6. But the KLH-6 sold extremely well and had a great following, not to mention a fantastic dealer network to sell these speakers.

They usually sell for cheap even in excellent

>condition and unlike AR speakers, the surrounds on the woofers

>were cloth, not foam and didn't rot.

Incidentally, I sold an early, mint-condition pair of Mahogany KLH Model Sixes on eBay last year for $300, so they don't do badly if described properly. I went into great detail describing the history and performance of the Sixes I had, and had an amazing number of inquiries. KLHs don't bring as much as ARs, however. Also, all of the early AR speakers, such as the AR-1, AR-3, first AR-3as, AR-2, AR-2a, first-generation AR-2axs, AR-4, AR-4x all had cloth surrounds that don't deteriorate. The foam didn't come until the 1968 AR-5.

--Tom Tyson

[soundminded]

"Crude hardly describes it."

In some ways yes, they were very crude. But in other ways they were remarkably advanced. It was amazing that a two way system could achieve such a wide overall frequency response. Published independent measurements by CBS labs in High Fidelity Magazine showed it extended out to 16KHZ yet with a crossover frequency around 1KHZ the tweeter covered an amazing 4 octaves. It had a long throw and was made from what KLH described as a hard shell like material. I'd heard other people say it was made from phenolic and a nylon mesh stocking was used to mold the cone??? KLH claimed that all production models would match the prototype within +/- 1 db which as I recall was about what AR achieved, those probably being the only two manufacturers who could justifiably make such a claim in those days. This was long before ISO 9000 was ever dreamt of. (more about AR's fantastic quality control at another time.) KLH said that they had taken great care with "the octave to octave balance" of the six which Kloss also claimed in an interview had been equalized through the crossover design. He also said that he had heard another equalized speaker (I forget the manufacture and model) which sounded more like the model six than the model six and after that he never neglected to build in equalization in his loudspeakers. Could this have been the thinking behind the model 12 which for some inexplicable reason never seemed to sell very well.? (What an uncanny resemblance between the equalizer controls on the KLH 12 and AR9.) Apparantly a resistor was inserted in series with the model six woofer to limt the effective amplifier damping factor to no more than 8. Bass extended to 40 hz, not quite the reach of AR3 but certainly in a class with AR2. CBS also said that tone burst tests showed near perfect transient response. Perhaps this in part was responsible for the speaker's clarity of sound. Given that this speaker appeared in 1958 some 45 years ago and was relatively modestly priced, it is small wonder it was so popular. It was also slightly more efficient than AR3, irrelavent by today's standards but back then, amplifier power was expensive.

Best of all, after owning these for 43 years and having heard thousands of other speakers, I still enjoy listening to music through them, not because of nostalgia but because I still like the way they sound.

BTW, even though I bought mine used from a previous owner in 1964, KLH repaired one for free and shipped free one way. They also apologized for the tweeter failure. That was remarkable and would be remarkable today as well.

[tysontom]

>It was amazing that a two way

>system could achieve such a wide overall frequency response.

>Published independent measurements by CBS labs in High

>Fidelity Magazine showed it extended out to 16KHZ yet with a

>crossover frequency around 1KHZ the tweeter covered an amazing

>4 octaves.

This was, I think, the genius of Henry Kloss. He designed this novel tweeter that peformed really quite well over much of its bandwidth, and he never to my knowledge used an anechoic chamber or measured the response other than impedance and free-field on-axis frequency response. Yet he and his fellow KLH people (Hoffman & Lowe I believe, and later Andy Kotsados) would sit and listen and "voice" the speaker's sound, ultimately adjusting the crossover and drivers to do what was needed. Where the tweeter was lacking was in off-axis extension and uniformity (smoothness) compared to AR tweeters. Therefore, the acoustic-power response was not as good as any of the AR's; but on axis, and under most circumstances, the Sixes would sound brighter and more "alive" than a comparable AR speaker. Julian Hirsch noted this in his review and stated that the KLH 6 showed "a noticeably more solid midrange" than their reference, which happened to be the AR-3. It was equal to the AR-3 down to about 40 Hz, but the 6 also had a tendancy towards heaviness or "chestiness" in the mid-bass that was not noticed on the AR-3. This was the result of underdamping. Both the AR-3 and the AR-2 had lower harmonic distortion at the very lowest octaves than the KLH 6, but the differences in the 6 and the AR-2 were relatively slight. Also, the 6 had a slightly lower system resonance than the AR-2, but not as low as the AR-3.

It had a long throw and was made from what KLH

>described as a hard shell like material.

KLH claimed the tweeter had a 1/16-inch excursion, quite exception for a tweeter. This also allowed it to extend down to the 1500 Hz crossover, but this was a high crossover nontheless for a woofer that size. The woofer is getting rough and has poor off-axis response at that frequency.

>KLH claimed that all production

>models would match the prototype within +/- 1 db which as I

>recall was about what AR achieved, those probably being the

>only two manufacturers who could justifiably make such a claim

>in those days. This was long before ISO 9000 was ever dreamt

>of.

This is amazing since these speakers were completely hand-built. The way AR maintained tolerances was through Ed Villchur's insistance that each production model be tested to insure that it fell withing the prototype's anechoic response. KLH did something similar to this, but they did not have an anechoic chamber.

>never neglected to build in equalization in his loudspeakers.

Actually, the AR-2 had equilization in the crossover, and this was originally designed by Ed Villchur, but implemented by Henry Kloss before he left AR in 1957. So Kloss had experimented with equilization in the crossover before he started at KLH.

>Could this have been the thinking behind the model 12 which

>for some inexplicable reason never seemed to sell very well.?

>(What an uncanny resemblance between the equalizer controls on

>the KLH 12 and AR9.) Apparantly a resistor was inserted in

>series with the model six woofer to limt the effective

>amplifier damping factor to no more than 8. Bass extended to

>40 hz, not quite the reach of AR3 but certainly in a class

>with AR2.

I have not seen the resistor in series with the woofer, but the woofer was certainlly underdamed at certain frequencies. Was it in later crossovers? There is a choke in series with it, but nothing else that I have seen, but I have only the original crossover for the Six, not the later one. If I remember, KLH cheapened the crossover considerably by the time they went to conventional mounting of the drivers.

CBS also said that tone burst tests showed near

>perfect transient response. Perhaps this in part was

>responsible for the speaker's clarity of sound. Given that

>this speaker appeared in 1958 some 45 years ago and was

>relatively modestly priced, it is small wonder it was so

>popular. It was also slightly more efficient than AR3,

>irrelavent by today's standards but back then, amplifier power

>was expensive.

>

I think it did perform well to impulse testing, as did the AR-3, considered by many to have the best transient performance of any of the dynamic speakers of that period. Julian Hirsch was big on impulse testing. The KLH-6 was at least 3-4dB more efficient than the AR-3, perhaps even more so. It was less noticeable by the time solid-state amplifiers came out, as during A-B testing the less-than-4-ohm AR-3 would injest at least twice the power of a 8-ohm KLH-Six speaker at the same voltage gain.

--Tom Tyson

[soundminded]

Unfortunately, AR3 was beyond my means at the time and even if I had the money to purchase a pair, I wouldn't have had the money to buy a sufficiently powerful amplifier to do it justice. One big mistake I made was to buy a Harman Kardon A500 and F500X instead of the Dynaco PAS3X, Stereo 70, and FM3. With only 20WPC RMS, this was marginal for KLH6 and inadequate for AR3.

For 14 years, my father was the Quality Control Manager of Hazeltine Electronics, a manufacturer of state of the art military electronics on Long Island. He once flew to Cambridge to audit AR for a military contract they were to be awarded. When I asked what possible military hardware AR could supply, he said that some engineer had specified an AR driver for an intercom built into an electronics control console. He said that he had seen enormous piles of destroyed speaker drivers. When he asked about them, he was told that they had been rejected as being out of spec and by destroying them they were assured that they would never see the light of day on the market. Now that's what I call quality control.

[tysontom]

>Unfortunately, AR3 was beyond my means at the time and even

>if I had the money to purchase a pair, I wouldn't have had the

>money to buy a sufficiently powerful amplifier to do it

>justice. One big mistake I made was to buy a Harman Kardon

>A500 and F500X instead of the Dynaco PAS3X, Stereo 70, and

>FM3. With only 20WPC RMS, this was marginal for KLH6 and

>inadequate for AR3.

After I got out of the Air Force in 1965s, I took my one-and-only AR-3 off to college with me, and I powered it with a Heathkit 20WPC Williamson amp. It was marginal, but with the speaker mounted in the corner of my dorm room, it actually did fairly well in the bass up to a point. It never ceased to amaze people who came in to listen to it, especially the deep bass on organ pedals, etc. By the time I got the second AR-3, I had acquired a pair of Dynaco Mark IIIs, two PAM-1s with the DSC (whatever) stereo control, and the AR Turntable. I was in good shape by then.

>

>For 14 years, my father was the Quality Control Manager of

>Hazeltine Electronics, a manufacturer of state of the art

>military electronics on Long Island. He once flew to

>Cambridge to audit AR for a military contract they were to be

>awarded. When I asked what possible military hardware AR

>could supply, he said that some engineer had specified an AR

>driver for an intercom built into an electronics control

>console. He said that he had seen enormous piles of destroyed

>speaker drivers. When he asked about them, he was told that

>they had been rejected as being out of spec and by destroying

>them they were assured that they would never see the light of

>day on the market. Now that's what I call quality control.

Thas is an interesting story. I have an image of one of "reject" piles, and I will try to attach it here. Give me your e-mail address and I will send it the usual way if this doesn't go through.

--Tom Tyson

P.S., I can't see that it went through, even though it said the upload was successful. Maybe I have to start a new message to send a file, I don't know. Send me your e-mail address and I will attach it in a message.