Was K400 a rejected or modified Jensen design?

[garyrc]

PWK wrote an article in 1963* about the design and testing of the Klipschorn's K400 midrange horn.  It discusses 3 possible designs, one without a flange, one with a flange, and one with a flange and also with a decreased taper rate for improved low end response.  There is also a story about PWK visiting a Jensen factory, finding a rejected horn in the garbage, asking about it, and taking it home to become the K400.  What is the truth of the matter?  Was the Jensen horn the one without the flange?  If the story is true, what didn't Jensen like about the horn?

 

The article mentioned that whether the new horn alone, or the new horn in a three way design was better was yet to be decided.  Can you tell us how PWK decided to use the three way design?

 

Thanks.

 

* IEEE Transactions on Audio AU-11, November-December 1963 Number 6, A New High-Frequency Horn

[JRH]

It was not the K-400.  Unfortunately I cannot say with certainty which model "came out of the trash can at Jensen".  I think it was John Eargle's trash can when he was working at Jensen.  There is documentation, but it's currently a needle in a haystack.  If I had to bet, it would be the K-700.  Eventually I will come across that documentation, but not today!

[WMcD]

FWIW: During the first pilgrimage I was observing the contents of a closet. (Not snooping, mind you, the door was open!)  There was a sheet of thick masonite or the like about 10" x 10" and on it a structure made of modeling clay.  It made me think it was the interior plug of half a K-700.  You could cover it with fiberglass or something and get the top half of a horn and then do it again to get the bottom half.  It looked clean though.  Perhaps there were other, similar molds and this was a survivor.

 

I've looked at Allied Radio catalogs from 1960 and see that the general geometry of the K-700, etc., was used with tweeters going down to 2000 Hz at best.  There is something to the aspect ratio of the mouth.  They were getting away from the diffraction type.  

 

Please also recall that mid-range horns were of the multi-cell WE type and the K-5 variation.  Therefore, Eargle - Jensen may have been breaking ground in adapting the tweeter to a larger midrange.  That might have been new.  PWK adopted the logic to a mid-horn for the Heresy and then extended it to the K-400.

 

As far as the diagrams. To me they show a progression of thought. (Imagination being very important for explaining basic principles rather than complicated math.)  If you start with a horn with a high fc and mouth size loading for free space , you can lower the fc by stretching it..  Then the mouth is too small for mouth loading.  But if a baffle-flange is added the mouth loading is improved.  Generally, the last three inches of length of an exponential horn at the mouth for these frequencies is almost like a flat board.  We are putting these in a flat board at the front of the speaker box or top hat.

 

WMcD 

[HDBRbuilder]

On Thursday, November 03, 2016 at 8:14 PM, WMcD said:

FWIW: During the first pilgrimage I was observing the contents of a closet. (Not snooping, mind you, the door was open!)  There was a sheet of thick masonite or the like about 10" x 10" and on it a structure made of modeling clay.  It made me think it was the interior plug of half a K-700.  You could cover it with fiberglass or something and get the top half of a horn and then do it again to get the bottom half.  It looked clean though.  Perhaps there were other, similar molds and this was a survivor.

That is called a master pattern.  The master pattern itself is used to create a production pattern, a core box, or both. These items are used to make a sand mold for the metal object being cast using molten metal, in this case aluminum. The production pattern would be FURTHER modified by adding what is called rigging, which creates in the sand mold the pathway for the metal to follow to fill the cavity for the part.  Rigging and the production pattern itself will be modified as necessary to ensure less scrap is produced and more usable parts are made, in addition to ensuring that the final product is exactly what the customer ordered.

 

The aluminum mid-range horns were sand-cast items back in those days.  AND, they were cast in two halves, which were brazed together for a number of years at "Wounded Buffalo", just behind the plant, in the building that became the Lab at Klipsch after it was moved from the old telephone exchange across the street.  The pattern you actually saw was not for the horn's outside, but for its inside.

 

And when the inside must be SMOOTH, and not left rough, like on cast-iron skillets, a CORE is used...the core is made of extremely fine sand that has a proper moisture contend and it is packed into a core-box made of iron and baked at high temperature, to make it hard.  It will be hard and smooth and the molten metal will not be able to erode it as the metal flows into the sand mold.  BUT the core is still just baked sand, so when the part is removed from the sand mold, any part of the core which STUCK to the metal will be easy to remove.  Cores are not reusable, but the sand from them can be recycled to make more cores.

 

Rigging is what people who build plastic model kits often call the "trees" which one must remove the parts from.  Making proper rigging adjustments to get the parts to run right, in addition to making production pattern modifications for the mold itself for the same reason, comprise the so-called "ART" side of pattern-making, which is part art and part science....the "ART" part is learned from EXPERIENCE.  Good pattern-makers generally have very good wood-working skills, can apply those same skills to plastics and resins, and are highly capable of doing custom machine-work with tolerances down to and under 0.001 inch.  And pattern-making is a constant decision-making process for which one, or which COMBINATION of any of these is needed to get the job done for each stage of the operation in order to make patterns, rig them, and make them run correctly, with or without cores (according to the need), with the least amount of scrap produced and the highest quality of part produced, all in an efficient manner.

 

You folks DID know that a number of years after I left Klipsch, I became a pattern-rigger and pattern-maker, didn't you?  I spent twelve years at foundries (one was grey and ductile iron foundry, where I began and completed my apprenticeship and moved up to the pattern-maker slot after the 70-year-old pattern-maker retired two years after I got there (spent 10 years there, until it shut down).  The other was a brass, aluminum, and bronze foundry.  So, when my former boss asked me to "come down to Paris, Texas to help me fix this mess down here" after he went there as its new sales manager/pattern-shop supervisor, He made me a deal I couldn't refuse, so I got some experience with those metals.

 

I have acquired a "few" blue-collar skill-sets in my 63 years on this planet....LOL!  NONE of which I am currently using at the moment.

[WMcD]

Well, I think I indicated that the clay model was what I thought was the interior plug -- but perhaps I did not use the correct terminology in the art of casting.  Of course HDRB's knowledge is wonderful to hear.

 

Dang.  I should have made notes over the years.  I did visit Hope to take a look at an old RCA two-way horn they had, probably still in the museum.  The folks were gracious.  I didn't find the interior of the horn to be remarkable.

 

The attached shows a mold for the K-400 which was at the plant.  My recall is that the hinges were too rusty to move.  Of course it would have been used at a foundry.  My thought is that it was saved when the 401 was made in resin.

 

Perhaps HDRB can comment on when and how this was used.  Was the wooden throat piece something which was sacrificed?

 

A few folks investigating their 400's complain of discontinuities or flashings and perhaps this is the origin.

 

 

[WMcD]

whoops, error

[HDBRbuilder]

52 minutes ago, WMcD said:

Well, I think I indicated that the clay model was what I thought was the interior plug -- but perhaps I did not use the correct terminology in the art of casting.  Of course HDRB's knowledge is wonderful to hear.

 

Dang.  I should have made notes over the years.  I did visit Hope to take a look at an old RCA two-way horn they had, probably still in the museum.  The folks were gracious.  I didn't find the interior of the horn to be remarkable.

 

The attached shows a mold for the K-400 which was at the plant.  My recall is that the hinges were too rusty to move.  Of course it would have been used at a foundry.  My thought is that it was saved when the 401 was made in resin.

 

Perhaps HDRB can comment on when and how this was used.  Was the wooden throat piece something which was sacrificed?

 

A few folks investigating their 400's complain of discontinuities or flashings and perhaps this is the origin.

 

 

This is a steel mould for hand pouring a metal horn out of aluminum (or brass, or bronze).  The section in the center has a dark upper portion, probably the pattern for a sand core, which replicated what part of the horn (the throat section) would actually be what is called a core.  For this horn lens, it is cast in one piece and the only thing added is a hard sand core for the throat section in the center prior to the mold being closed for its pour.  The throat section required a core because it was too tiny of an opening to be able to get anything into to remove any seam flashing so that the sound pathway of that throat section ended up with no flashing to be removed by using that core.  This same horn could easily have been made on an automatic Hunter match-plate machine...such as the Hunter 30 or larger machine...using sand-casting...and with a core that would be used for the ENTIRE inside of the horn (although it might require a two piece core, each section made of a different core sand than the other...one for the mouth portion and one for the throat portion).

 

As it is, what is there would work fine, but take lots of time to make a large order of horns.  A hunter would vastly speed up production of that same horn...and with advances already made decades ago, investment casting would speed it up even more.

 

Hunter machines are likely what was used to make the two-piece smaller aluminum mid-range horns, using a one-piece full-length core.  This would allow for TWO or more halves to be produced from each sand mould, depending upon how large the match-plate is and how small the horn body is.

 

They, too, could easily be made nowadays on investment casting equipment...and as complete lens, instead of in halves.

 

See pics below...two mold hunter machine pattern rigged for first pic.  Single mold hunter pattern rigged and set up for core use, with core-locks easily seen on pattern for second pic

[WMcD]

BTW, who is this?  You?

 

 

[DizRotus]

I wonder who made the aluminum H 350 aluminum squawker horns used in my 70s Speakerlab SKhorns.  They looked like K400s.  The process seems more expensive than a small outfit like Speakerlab could have undertaken.

 

[garyrc]

10 hours ago, DizRotus said:

I wonder who made the aluminum H 350 aluminum squawker horns used in my 70s Speakerlab SKhorns.  They looked like K400s.  The process seems more expensive than a small outfit like Speakerlab could have undertaken.

 

How close are they to the K 400 in slope, size, etc.? 

Also, did PWK ever complain about Speakerlab?  Test their SK?  Sue?  Was there a case?  How did the sound compare?

Did PWK ever consider replacing the design of the K400/K401?  Did he feel it could be improved, while still fitting in the Khorn or La Scala Top Hat? 

[HDBRbuilder]

21 hours ago, WMcD said:

BTW, who is this?  You?

That is a pic from shipping, and it's not me....this is me (but not at work; but, instead, a few minutes before going to see Willy Nelson and Leon Russell at Hirsch Memorial Colosseum in Shreveport, LA...1977 or 1978)...note the PWK belt buckle:

[WMcD]

That's good.  You look better than the guy in shipping.  Did you crop out the lady on your arm?  (Maybe that is too personal.)

 

The tee should be reissued.

 

WMcD

[HDBRbuilder]

34 minutes ago, WMcD said:

Did you crop out the lady on your arm?  (Maybe that is too personal.)

 

The tee should be reissued.

 

Yes, the T SHOULD be re-issued...it was one of the most popular ones Klipsch ever had in those days!

 

Wanda, the lady on my arm, is deceased, as are at least two more in the original pic: one of which is her older sister, Marlene (far right), and the other is Gary (to my immediate left), who at the time of this pic was one of the Klipsch Sales Reps.  The lady on Gary's Arm (Linda Kaye) is one of my facebook friends.  As for the others, I have totally lost touch with them over the years, I am sad to say.

 

Many of the Klipsch employees back then hung around with each other...and/or made plans to link up somewhere on the way to concerts.  We also held parties together...which included a large satellite of friends.

[WMcD]

I'm sorry to hear about the passing. 

 

It was nice of you to post the entire gang.

 

WMcD

[Don Richard]

On ‎11‎/‎12‎/‎2016 at 6:30 AM, DizRotus said:

I wonder who made the aluminum H 350 aluminum squawker horns used in my 70s Speakerlab SKhorns.  They looked like K400s.  The process seems more expensive than a small outfit like Speakerlab could have undertaken.

 

 

Probably went to a foundry with the design and had them do the castings there.

[JRH]

The only example of a SpeakerLab "K-400" that I have seen was a fiberglass version which would be pretty simple to come up with.  Take an aluminum original, fill it with "mud", and create a pattern on which to lay up fiberglass.  If they made an aluminum version the simplest route would be a sand-casting arrived at in a similar fashion.

 

PWK and Bob Moers were well-aware of SpeakerLab.  As patents on the K-horn had long-since expired, and there were no patents on the K-400, the only recourse was to prevent SpeakerLab from using trademarks, which they did enforce. 

[filmofreddy]

David Grabner, one of Speakerlabs founders, told Me that they had a surprise Visit from Mr.Klipsch in the Flesh! He said the meeting was cordial but, you could have cut the tension with a knife!-LoL