KLH speakers reference thread (original models/Henry Kloss era) 1957-1977

[RxDx]

Henry Kloss left Acoustic Research in 1957, as the AR-2 was being finalized. He started KLH in 1957,
designing or directing the design of the original series of speakers. KLH was bought by Singer in 1964,
though several* of the original models were sold until about 1977.

*Models Five, Six, Nine, Seventeen, Thirty One, and Thirty Two

Index

My web page listing all the classic KLH systems and components
http://www.aphenos.net/electronics/speakers/klh/all_klh.htm
or http://tinyurl.com/vintageKLH

Systems
Model One, Two, Three, Four, and Five (this post)
Model Six (early), Seven, Nine, and Ten.
10" and 12" systems after 1963
8" systems
Smallest systems

Identifying drivers

Crossover diagrams
Model Five
Model Six
Model Seven

Minutia​

Model One, Two, Three, Four, and Five company sales brochure
Model One, Two, and Three operating instructions
Model Five, Six, and Seven crossover diagrams.
Model Five woofer variations
Model Six table of model changes (switching from epoxied drivers, etc)
Model Six epoxied woofers and screw-in tweeters
Model Six video a la Glenn
Model Seven epoxied woofer and screw-in tweeters

Epoxied vs. removable drivers
Surround sealer service bulletin.
Capacitors that definitely need changing out.
_________________________________________________________________________

Model Evolution
The first three models were woofer-only systems, some with provision for mounting additional
drivers in built-in compartments. They were available in Mahogany, Birch, Walnut, and
unfinished (the Model Two was apparently not available unfinished). A tweeter/mid-range
system, the original Model Five, was offered for the Model One and Two, in addition to the
more expensive Janszen 1-30 super tweeter.

The fourth, the Model Four, was KLH's first full-range system. It used the same in-house
woofer as the Model Two and Three (and early Six and Seven), but a GE phenolic tweeter
(also used in the early Six and Seven). The company's own phenolic (with a screen) would
appear in 1962.

Ads appeared in May 1957 announcing the line, the Model One being announced a month
later in June. Of these first five systems, only the Model Four survived past 1960.

KLH also made component tuners, amps, and receivers in this time period. Turntables were
supplied by Garrard and Dual, tape decks built in house and by Advent (Forty), and by
Nakamichi (Forty One).

The original era lasted until 1977, when new models began to be introduced. The Five, Six,
Nine, Seventeen, Thirty One, and Thirty Two were the last models available. (HiFi-Stereo
Review buyers guide)

Model One
The first system (at least in numerical order) was the Model One. It had two 32 ohm 12"
woofers in a 4.5 cubic foot cabinet. It had a compartment at the top for either the Janszen 1-30
or the Model Five, except for the unfinished utility version.

The woofer housing was divided into two equal chambers, separated from each other. Wiring
was direct from the terminal plates to the woofers- no caps, coils, or resistors.

The earliest KLH woofers had conventional aluminum cast frames and were massive affairs.
They were also massively inefficient. Epoxied drivers came at an indeterminate time later,
once original casting equipment began to wear out. It was less expensive to switch to the
conduit-and-epoxy driver than replace equipment.

Here's the thread on restoration of the pair I own.

Model Two
The second model was a single 12" in a smaller cabinet (21.5" x 25" x 12"), but it still had
a shelf for a midrange and/or tweeter.

The woofer enclosure for Models Two, Three, and Four is the same size for all, and the woofer
itself is the same.





Model Three
The Three was essentially the same woofer and cabinet as the Model Two, minus the provision
for additional drivers.



Model Four
The Four was the first full-range system, using either one or two GE tweeters. It was a
competitor to the AR-3, though it was generally thought to have a bit less low end in comparison.
It is, however, brighter at the top end. Observed examples generally have the epoxied drivers,
though at least one of the cast aluminum woofers was on auction for months.

Claimed specifications (from a Radio Shack catalog) are +/- 1.5 db, 30-20khz, It is a 16 ohm
speaker and was available in Birch, Mahogany, Walnut, Oiled Walnut, and unfinished.







Here's the thread on a pair I restored.

Model Five
The original KLH Model Five was a midrange/tweeter combination for use with the first
three models as a lower-cost alternative to the Janszen 1-30. It had two tweeters and a mid, as
far as is known. It lasted until about 1960.

[to be continued]

 

[joelongwood]

Great info! Thanks for sharing.

 

[GD70]

^^^ Totally agree! I've got a link somewhere that has the KLH lineup dates, driver complements etc... But these pics are a terrific reference! Thanks RxDx for taking the time to put this together, and I'll be watching for the next installments!

Glenn

 

[RxDx]

Model Six, early style
The Model Six was KLH's breakout seller. At almost half the price of the
otherwise-equivalent Model Four, it became quite popular. Introduced in
early 1958, it also had the 12" epoxied woofer and GE-style tweeter*. I'm
saying this from observation, not hands-on experience. Pictures look
similar enough; KLH never identified drivers in early systems, which
makes verification more difficult.

*Andy Kotsatos, involved in KLH at this time, says it's not GE as far as he
knows.

In 1960, the Model Six was available in mahogany, walnut, birch, oiled
walnut, unfinished walnut, and unfinished birch.









Model Seven
The Model Seven uses the same epoxied driver set as the Model Four in a larger box-
21.5" x 11.9" x 26.25" and 2.6 cubic feet. It lasted from 1959 to ~1961. There are a few
reports of screwed in tweeters. This was a fairly low production system.



(from pabs911's restoration thread)

Model Nine
The Model Nine wasn't a KLH speaker at all. It was built by Janszen, a connection
between companies that started when KLH promoted (and one presumes sold) the
Janszen 1-30 to mate with the woofer-only systems. It is an electrostatic and was
sold from 1961 to 1977 (according to Stereo Review buyer's guides). Janszen still
offers service for these spectacular systems.

Retrovert provides schematices and various details on handling and rebuilding the
power supplies, here, and on.







Model Ten
Also introduced in 1961 was the short-lived Model Ten. It was a rare 10" KLH ported
system and only lasted a year or two, but it marked the change from epoxied to
removable drivers. It sported the only phenolic tweeter without a screen.

Radio Shack rebranded the Model Ten as the Solo-10.

 

[Tim D]

Really loving this history. I especially love the Six baffle where it shows the PIO cap. I hadn't actually seen the fabled oil caps before now.

 

[RxDx]

Expoxied vs. removable drivers
The transition to removable woofers and tweeters included a change in the
crossover and the grille cloth. The crossover changed from a potted assembly
right behind the flush-mounted terminal plate to a recessed plate with point-
to-point assembly. The early style grille was wrapped around the baffle before
being glued into the cabinet, while the late style had a removable grille frame
and cloth.

Said transition was gradually phased in. Removable tweeters were first, one
presumes accompanied by removable grilles and crossovers, though the grilles
might have been upgraded before any drivers. There are also examples of
systems with removable drivers and the early style crossover. These changes
happened in the 1963-65 time period.

Model Six, late style
The later style Model Six (and apparently the Model Seven) bridged the transition.
It performed almost identically to the early style. Woofer excursion is longer on
the epoxied drivers, and they dig a bit deeper at the low end. This version sold
from ~1963 to 1977. The first removable drivers were installed on serial number
93000, according to a KLH employee. The recessed terminal plate came along
at approximately serial number 134000.





Model Seventeen and Model Twenty
Virtually identical aside from amplifier load (the first was 8 ohms, and the
second was 4), they were also hugely successful sellers for KLH. Essentially
a 10" woofer and the common 1.75" phenolic tweeter with a grille, they were
introduced in 1965 and sold until 1977 (at least the Seventeen).

one of urizen's nice examples from specialidiot's thorough Model Seventeen renovation thread

Model Twelve
What looks like the third iteration of a big-box sound (after the Model One and Model Seven),
the Model Twelve is one of only two early three-way KLH systems. Introduced in 1967, it used
the same drivers as that other system (the Model Five), but was unusual in its four-way
outboard crossover controller. The box was an early EQ, which was not a widely available
option at the time. It lasted until 1972.

from amarjr's renovation thread

Model Five
Arguably the best medium-sized KLH speaker, the Model Five was also a
competitor to the AR-3a, though most accounts give the AR an edge in sound.
The Model Five was sold from 1968 to 1977.

salb203's fine pair

Model Twenty Three
Another fine system from the 1960s time period, some have commented this is their
favorite early KLH. It is a more traditional, for KLH, two way. It sold from ~1968 to
at least 1974 (hornbostel, post 163).





Model Thirty
KLH's last 12" system, the Model Thirty uses the same drivers as the Model
Six in a cabinet about 2/3 as deep. It didn't sell well, apparently, and is rarely
mentioned on AK. The date of introduction is unclear.



Model Twenty Eight
KLH's last full-on, all-hands-on-deck system from this era was the Model
Twenty Eight, which had three 10" drivers (probably from the Model
Seventeen or Model Twenty) in a odd triangle-shaped cabinet. The date
of introduction is not clear, but it was sold until 1976.











not pictured: Model Thirty Three and Model Thirty Eight, both 10" woofer systems.

 

[GD70]

This is terrifific!
One note on the Six's. It's my understanding the "later" model was more around 1965 when the screw mounted woofers were introduced. 1963 still had epoxy mounted woofers and tweeters, glued grill cloth and caps in the epoxy tub behind the terminal plate. 1963 was when screw mounted tweeters were phased in. My 63's have an epoxy mounted tweeter, and screw mounted tweeter, and I got them from the original owner.

 

[RxDx]

Thanks for the detail. I knew some of it, but it didn't surface at the time of writing.

Looking at the whole timeline, I wonder if the changeover was that late. A bunch of
models came out before 1965 with removable drivers- Ten, Eleven, Thirteen, Fourteen...
Of course, KLH could have had old stock they needed to use, etc. Also, the Model Four
looks like it was sold until 66. I don't have serial numbers/years for the two styles of
woofers.

 

[RxDx]

Identifying Drivers

Woofers
Woofers sometimes had the cone weight marked on the cone. From
a KLH service bulletin. Otherwise, it's typically difficult to distinguish
similar-sized woofers from one another. The Twelve is unitque; the
Five and Twenty Three appear to be identical.



Midranges
The Model Five and Twelve used the same driver, and it's likely the same
for the Model 21 radios, as well as the speakers in the Model Eight extension
speaker, the Model Eleven, Fourteen, Fifteen, and Nineteen.

Tweeters
There are ~six basic style tweeters, three of them the removable type.

Original "Non-removable" tweeters
There are four early style tweeters. Two are unique to the original Model Five
supertweeter system. One is a cone type; the middle one has yet to be
identified.

T1
The other two were the GE (original?) phenolic tweeter used in the Model
Four and Model Seven and what appears to be a unique driver in the
Model Six- similar to the GE but not sourced from them, according to
Andy Kotsatos.

Removable Tweeters
There are three different style tweeters for the later systems:
• (T2/T3) a 1.75" phenolic unit with a screen. It looks like the generic phenolic used
in a lot of other brands of speakers.
• (T4) a 3.75" standard cone type, no screen. Called a 3" tweeter in KLH literature.
• (T5) a 2.5" standard cone type, covered with fiberglass

T2/T3
T2 and T3 were installed on the higher-end systems, 10" and 12" woofers
They look very similar, but sound a little different, apparently owing to a
difference in damping between them.

T2: The tweeter on the left fits the Five, Twelve, and Twenty Three. It has
a thin plate between the basket and the magnet.

T3: The tweeter on the right fits the Six, Seventeen, Twenty, Twenty Eight, Thirty,
and Thirty Three. It has a thick plate.

More information and original photo courtesy of audiojones here.



T4
T4 was paired with 8" woofer systems, at least the Twenty Two, Twenty Four,
Twenty Five, and Twenty Six.



T5
This tweeter was used in Models Thirty One, Thirty Two, and Thirty Eight, as
well as some sightings in late manufacture date Seventeens.

from saunadog in this thread.

 

[GD70]

Identifying Drivers
Woofers sometimes had the model number marked on the cone. From
a KLH service bulletin.

There are two different style tweeters for the late style (removable driver)
systems, apparently owing to a difference in damping between them.

The tweeter on the left fits the Five, Twelve, and Twenty Three. It has
a thin plate between the basket and the magnet.

The tweeter on the right fits the Six, Seventeen, Twenty, Thirty, and
Thirty Three. It has a thick plate.

More information and photo courtesy of audiojones here.

Good reference pic with noted usage. These tweeters are very confusing for which one is for which model, as they look the same from the front.

 

[Tim D]

What about the tweeters in the 22 and 24? Aren't they yet another type? Seems to be the same size as the ones in the 17, 6, etc, but it doesn't have a screen and the magnet is round instead of square.

 

[gbroot]

I believe the production dates on the 5's and 23's were 68-70 rather than 72. Thanks for a great thread! Fabulous pic's of the 28's by the way.

 

[g..v]

5s were a current item when I left the store in Boston in 1973. As were 6, 17, & 12. About 2 years later the Research Ten line was there.

 

[RxDx]

What about the tweeters in the 22 and 24? Aren't they yet another type? Seems to be the same size as the ones in the 17, 6, etc, but it doesn't have a screen and the magnet is round instead of square.

Yes, it's another type. I revised the write-up. There's a third style tweeter, too.

edit 03/12/21: There are actually five different types.

 

[Drugolf]

Great stuff, thanks.

 

[ra.ra]

Yep, still using this thread as a reliable reference.
Thx, RxDx.

 

[Tim D]

It would be nice to split the type 1 tweeter into two different tweeters - even if it is only to type 1a and type 1b. There is apparently a difference in how they sound between the two types/subtypes. Many are asking about the differences where it impacts their search for replacement tweeters.

Gosh this is a good reference. It should be stickied.

It would be nice if there was a database with serial numbers, characteristics and any date information. I know that a lot of people are asking w.r.t the KLH Six and some of the manufacturing changes throughout its long life. Oil caps, wood veneer types, epoxied tweeters, epoxied woofers, epoxied crossovers, removable grills, etc.

EDIT: And also the Model Six Lattice grills; and backside in plywood or particle board too.

 

[RxDx]

Oh, okay

Model Six Driver and Design Changes

 

[jlovda]

My Model 15 speakers had two of the midranges in series in a ported box. The drivers were 4 ohms each. I believe all the other midranges were 8 ohms (I could be wrong). One side note. I believe there were two versions; one with much better cabinet construction (Isaw pictures on ebay). Mine had absolutely terrible, cheap internal wood construction with the worst performance I have heard from a small system. I did only pay $5 for the pair.

 

[Tim D]

wow. Wow. WOW. WOWWWW!!!!!! Thanks RxDx!

BTW, I was just about to edit my post to add the lattice grills for the Sixes too. It would be cool to list whether the backs are plywood or MDF. It would be nice to add veneer type too. They were offered in at least 3 or 4 different woods.

For your list:

I have two basket case KLH Sixes in the queue the serial numbers are:
8058 (Unknown date. With Oil Caps. plywood backs, sealed tweeters, sealed woofers and outside mounted terminal plate without the zip code for KLH's address.)
8135 (Unknown date - No date stamp inside the cabinet. With Oil Caps. plywood backs, sealed tweeters, sealed woofers and outside mounted terminal plate without the zip code for KLH's address.)

My other two KLH Sixes that are refurbished and in main rotation have the following serial numbers:
61759 (Date stamped inside with 1963. With Electrolytic Caps, plywood backs, sealed tweeters, sealed woofers and outside mounted terminal plate without the zip code for KLH's address.)
61114 (Date stamped inside with 1963. With Electrolytic Caps, plywood backs, sealed tweeters, sealed woofers and outside mounted terminal plate without the zip code for KLH's address.)
* This set had the original sealed tweeters removed by the previous owner and replaced with some Radio Shack tweeters. I replaced them with KLH 22 tweets that actually sound terrific in the Sixes. Don't know if someday I will put in the later KLH Six tweeters. It sounds so good as-is that I don't have much incentive to change them right now.