KLH Cabinet Construction

[Guest Droog]

I wanted to supply some history and invite any other details from readers. Henry Kloss, besides being the amazing innovator of speaker and electroncs design was a first a wood working man. He spent much of his early childhood on a farm in Sebastopol, California and became very handy in wood working, later moving back to his birthplace of Tyrone, Pennsylvania, living in a log cabin. Henry soon ndeveloped a reputation for being able to fix or build almost anything in construction. While at MIT he worked for a Harvard Square contractor rebuilding houses into apartments for students. At this time (1950-52 ?) Jordan Baruch, an MIT professor, and Henry Lang, a graduate student hired Kloss to build a loudspeaker box for the Baruch-Lang speaker. According to H. Kloss the speaker was later sold under the name Kloss Industries, employing a hand full of people for production. (I've never seen one of these, but I'm looking!).

Jumping ahead to KLH cabinets, It's clear Henry cared about not only proper acoustic design of his enclosures, but also materials and construction were A-1 quality as well. My 1958 model six's are 12-ply furniture grade plywood with rebated joints. The eight speaker was solid walnut, very nice. I recently saw a pair of # six's made of solid wood, (spruce ?) with walnut veneer, serial #'s 31,000 about 1961. My 1965 model nineteen's are plywood with 1/8" walnut veneer. About this time fiberboard came in (MDF). this was used until the end of Cambridge made KLH in the mid 70s. The end wasn't pretty, the model fifty six cabinet was made of thin MDF covered in vinyl, having the 10" cloth woofer this unit was the size of the model twenty but the weight was much less. of course Kloss had been gone for many years so he didn't have anything to do with this product.

A side note about inconsistent construction, my circa 1965 model six's, serial numbers only 7 apart, one back panel is plywood and the other is MDF ? Also, my circa 1968 model twenty two's, again very close serial numbers, one has solid walnut trim around grill cloth, the other is veneered, plus the cabinets have very different types of MDF used, from behind they look like mis-matched speakers. This seems odd since these speakers must have been sold as pairs with #'s so close!

If reader's have any other details about early KLH cabinets......would like to hear.

[Guest russwollman]

Interesting bits, Droog. Kloss was a man of another era, with a versatile intelligence the likes of which we don't see much today.

What are the "rebated" joints you mention? I have never heard that term applied to woodwork. I'll head for the dictionary first.

Regarding plywood vs. mdf, I noticed the AR3a's I had were made of plywood while my Advents are made of mdf. When I rap the side, the ARs sounded solid but the Advents sound hollow. Seems to me the plywood is superior. And the 3a cabinets had nice internal bracing.

Thanks for a worthwhile item.

[Guest russwollman]

Merriam Webster's Collegiate Dictionary says "rebate" is "chiefly Brit var of" RABBET.

[Guest Droog]

Yes, a rabbet joint, I got the "rebated " term from a furniture book which had a similar joint. In my early KLH joint, the corners are joined with a cut that looks like a number 7. Early AR speakers looked very much the same but used plywood with 5 or 6 layers. My KLH have this 12 ply, each layer about 1/16" thick (pretty sure there spruce) making for a incredibly solid cabinet and when knocking on it, it sounds like no other speaker I've owned. I have them hooked up A, B with a mid 60's pair of MDF model six's and I think the early pair sound better. I showed them to Modernist furniture guy and he said this multi-ply was used in the 50s for high end designer furniture and was costly. I've not seen any other speakers using this type of plywood. KLH must not have made many speakers with it, mine are very early, serial numbers 684 and 711. The factory blonde finish make for a great Cold War looking pair of loudspeakers!

[soundminded]

My very early KLH sixes were made out of solid wood and the drivers were epoxied into the front baffleboard as mentioned in a previous posting. The grillcolths were not removable either. This made servicing a nightmare even at the factory and virtually impossible anywhere else. You can still see where a crowbar was apparantly used to remove the front baffleboard to repair a failed tweeter (possibly due to a crossover failure.) Other times, the woofer cone had to be removed to repair the crossover network and the woofer reconed. Later production units had the woofers screwed in like every other manufacturer did. Good engineering design considers many aspects of a product including performance and reliability but also repairability as well. In this important regard, the early KLH model six is a total failure. The next time it fails, I'm sorry to say will probably be the end of them. 40 years later, They will no longer be repairable in all likelihood. That will be tragic so they are never pushed to anything like extremes.

[tysontom]

>I wanted to supply some history and invite any other details

>from readers. Henry Kloss, besides being the amazing

>innovator of speaker and electroncs design was a first a wood

>working man. He spent much of his early childhood on a farm

>in Sebastopol, California and became very handy in wood

>working, later moving back to his birthplace of Tyrone,

>Pennsylvania, living in a log cabin. Henry soon ndeveloped a

>reputation for being able to fix or build almost anything in

>construction. While at MIT he worked for a Harvard Square

>contractor rebuilding houses into apartments for students. At

>this time (1950-52 ?) Jordan Baruch, an MIT professor, and

>Henry Lang, a graduate student hired Kloss to build a

>loudspeaker box for the Baruch-Lang speaker. According to H.

>Kloss the speaker was later sold under the name Kloss

>Industries, employing a hand full of people for production.

>(I've never seen one of these, but I'm looking!).

> Jumping ahead to KLH cabinets, It's clear Henry cared about

>not only proper acoustic design of his enclosures, but also

>materials and construction were A-1 quality as well. My 1958

>model six's are 12-ply furniture grade plywood with rebated

>joints. The eight speaker was solid walnut, very nice. I

>recently saw a pair of # six's made of solid wood, (spruce ?)

>with walnut veneer, serial #'s 31,000 about 1961. My 1965

>model nineteen's are plywood with 1/8" walnut veneer. About

>this time fiberboard came in (MDF). this was used until the

>end of Cambridge made KLH in the mid 70s. The end wasn't

>pretty, the model fifty six cabinet was made of thin MDF

>covered in vinyl, having the 10" cloth woofer this unit was

>the size of the model twenty but the weight was much less. of

>course Kloss had been gone for many years so he didn't have

>anything to do with this product.

> A side note about inconsistent construction, my circa 1965

>model six's, serial numbers only 7 apart, one back panel is

>plywood and the other is MDF ? Also, my circa 1968 model

>twenty two's, again very close serial numbers, one has solid

>walnut trim around grill cloth, the other is veneered, plus

>the cabinets have very different types of MDF used, from

>behind they look like mis-matched speakers. This seems odd

>since these speakers must have been sold as pairs with #'s so

>close!

> If reader's have any other details about early KLH

>cabinets......would like to hear.

Droog, that's some great history on Henry Kloss. He did indeed know how to build good cabinets -- and good speakers.

The Model Sixes you refer to above that were on eBay (and were described by the seller to have solid-wood cabinets) do *not* in fact have solid-wood cabints, despite the seller's insistance. I questioned him about it, he had it burned into his sensibilities that they were solid wood, and he would not back down. But he was mistaken. I hope that the buyer of those KLH Sixes didn't buy them based on that misleading notion.

First of all, solid-wood cabinet sides would ring like a bell, and would likely warp unless they were 2" thick or more, and would probably split or crack terribly as well. You couldn't brace them well enough; besides, KLH did not use much bracing in any of their speakers. Consider a plank of solid walnut or birch, 3/4-inches thick, that is 14 or 15" deep by 23 or 24" long. It is not half as strong as multi-ply marine-grade plywood or MDF; it would warp in no time, and likely crack soon thereafter. It would also be prohibitively expensive, and although the Six was a high-quality speaker, it was not a "high-end" speaker by any means. Also think about moisture changes and the shrinkage factor of solid wood. The person listing that KLH was mislead because he could not see an edge mark where the so-called "edge molding" on the KLH Six was separate from the rest of the cabinet (a la AR), and he looked at the back of the cabinet and saw what appeared to be solid lumber. What he saw was this: (1) KLH veneered from the back of the cabinet all the way to the front leading edge, covering the edge molding (usually in solid birch or poplar), banding around the front edge, and into the inner lip of the molding close to the front baffle board and grill cloth, making it look like one piece of solid wood; (2) by the time this speaker was being made, KLH had gone away from plywood and was using a form of MDF known as NovaPly, a material that AR pioneered in the AR-3 and also used on their bigger speakers until the early 1970s. The material is dense and relatively expensive, and looks like solid core wood from the back, with no flakes showing, etc.

--Tom Tyson

[tysontom]

>Interesting bits, Droog. Kloss was a man of another era, with

>a versatile intelligence the likes of which we don't see much

>today.

>

>What are the "rebated" joints you mention? I have never heard

>that term applied to woodwork. I'll head for the dictionary

>first.

>

>Regarding plywood vs. mdf, I noticed the AR3a's I had were

>made of plywood while my Advents are made of mdf. When I rap

>the side, the ARs sounded solid but the Advents sound hollow.

>Seems to me the plywood is superior. And the 3a cabinets had

>nice internal bracing.

>

>Thanks for a worthwhile item.

The reason the AR's have a more solid, rather than hollow sound when you rap your fingers, is just what you described: bracing in the cabinet. Kloss didn't believe that the improved deadening of bracing was audible enough to warrant the added cost. Villchur of AR did believe it made a difference. It was just like the "Tee-nuts" and machine screws that AR used to mount their drivers: Kloss always used the less-expensive wood screws.

The only AR-3as to have all-plywood cabinets were the utility or unfinished-pine cabinets with the birch cabinet molding. The fronts and backs were plywood on some AR-3as up until the early 70s, but the sides were *always* MDF or NovaPly on the finished-wood finishes. Only the earliest AR-1s and AR-2s had all-plywood boxes, (with the exception of the utility finishes on the later models).

--Tom Tyson

[Guest Droog]

That sounds correct Tom......The only exception would be that great little model eight of KLH's in solid walnut . Of course it's only 6"x6"x 11". Every example I've seen has kept it's corner joints tight and stayed crack free. This proved to be to be costly even for KLH, so the later production model eight's were veneer covered plywood. An interesting story about the model eight....The acoustic consultants Bolt-Baranek and Newman had a project to equip the Senate chambers with individual speakers for each Senator, needing a high quality reproducer small in size, so they went to KLH, That project never happened so Kloss used the concept for the Model eight radio. The World had never seen a table model radio with such good sound!

[tysontom]

>That sounds correct Tom......The only exception would be that

>great little model eight of KLH's in solid walnut . Of course

>it's only 6"x6"x 11". Every example I've seen has kept it's

>corner joints tight and stayed crack free. This proved to be

>to be costly even for KLH, so the later production model

>eight's were veneer covered plywood. An interesting story

>about the model eight....The acoustic consultants Bolt-Baranek

>and Newman had a project to equip the Senate chambers with

>individual speakers for each Senator, needing a high quality

>reproducer small in size, so they went to KLH, That project

>never happened so Kloss used the concept for the Model eight

>radio. The World had never seen a table model radio with such

>good sound!

I had the KLH Model Eight radio. It was a wonderful table radio, very beautifully crafted, and it had very clean and full sound, primarily because Kloss developed a way to equalize the speaker very nicely. My Model Eight was in mint condition when I sold it, and it had the original shipping box and all the accessories, etc. I regret having parted with it. Since then I have owned table radios by Advent, Cambridge Sound, Tivoli and even the excellent new "Receptor" by Boston Acoustics, and all have equalization for outstanding sound.

--Tom Tyson

[Guest russwollman]

Would adding bracing contribute to speaker performance? I recently read a tip about gluing a hardwood broom handle, inside the enclosure, from side to side.

But inside the 3a's I had, the bracing was more elaborate than that.

I suppose I could just play with various ideas and hear what happens.

[Guest Droog]

In my opinion that would be a waste of time unless you're experinced at bracing & woodwork, but if you have old speakers and want to experiment , why not. The vintage Wharfdale speakers from England had sand in the cabinets to deaden vibration and it worked! I recently saw a pair of massive Bozak's at a flea market, the inside looked like my attic, it had so much bracing....they must have weighed 200 LBS. each ! But thats off the KLH topic.............any KLH should be solid enough as it is.