Article: Solving the Klipschorn Throat Riddle (Edgar)

[DrWho]

boink - just a friendly bump so that I don't forget to read this later when I have more time.

[boom3]

From a previous thread:

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D-MAN: (quoting)

boom3:

Corvette, re: wood wedges in the throat:

This refers to a thread about the "splitter" facing the woofer that is the first division of the two parts of the horn. I think this is the Type G Motorboard upgrade that appeared sometime in the 60s. Paul told me that the 'splitter" improved performance at the top end of the horns ranage, so the action is rather like a phase plug in a HF horn. I'd like to see that thread again myself and take the time to review current thought on it.

Dman:

Good heavens, NO! None of the above!

The throat splitting wedge existed well before the 60's. See attached 1957 Klipsch brochure showing a cut-through Khorn and note the splitting wedge in the (at the time 6x13") throat.

Also, it is a hard-surface 45 degree reflector, not a phase plug! No phase correction going on there - let me ask, how is it correcting phase issues? Well, it's doesn't and it never has and never will!

Also in 1962, when Klipsch switched to the from the EV woofer to the CTS, the throat cavity was experimented with, and ended up being narrowed to the 3x13" that we see today. Some Khorns left the factory with additional wedges (evidently experimental) in the throat area AS WELL AS the traditional splitting wedges. I want to say that forum member LarryC had a pair, if I remember correctly. He removed them - they sounded BAD.

DM

My reply:

Soooo...what was/is the Type G Motorboard ?...and what, pray tell was Paul talking about...I'd like to think he knew his own design...

***

Now: Does the current thread answer this question?

[sunnysal]

Thanks Gil for posting that article, I think it shows just how much we still have to learn about acoustics. The followup posts only emphasize this. Tony

[D-MAN]

Where is this famous PWK quote? Seems highly questionable to me. If he had actually talked about the Khorn throat, there would be no mystery, would there?!

The throat splitter in the Khorn is a 45 deg. radius-style reflector. As such it doesn't turn the entire waveform. It is better than not being there at all, but is not doing the whole job.

But there is ample historical evidence to support the fact that IT DOESN'T MATTER - most contemporary horns with the Khorn don't/didn't use ANY type of reflector at all (see the University Classic, Dean, JBL Hartsfield, EV Centurion, Jensen Imperial, L.E.E Catenoid, etc.). And they didn't seem to suffer from it, did they? The wavelengths involved for low frequencies don't particularily have any problem with confronting a turn. It all depends on where the upper frequency corner falls, and that is a factor determined by the driver, throat opening, and horn configuration. Most of these "old" horns tended to crossover around 300Hz. The Khorn (at 400Hz) was the exception.

The remaining question is to whether the design of the Khorn horn channels/folding technique tends to negate any attempt to enhance the upper frequency corner of the driver... So why mess with enhancing the throat when the intermediate folds effectively cancel out the highs? That is the crux of the Khorn design problem. Basically, it should be apparent to all that PWK knew that, and that's why he did the Jubilee design from SCRATCH, and not just modifying the Khorn itself. He understood the implications of the Khorn design and knew what it could do and more importantly, what it could not be made to do.

Nowdays, with advancements in drivers, the upper frequency corner can be somewhat higher, and that consideration is the most economically desirable, that is, mid-range drivers and horns that can effectively go down to 300/400Hz tend to be more expensive, due to the sizes of the horn, shipping, and the power handling capabilities of the driver in question. However, the trend is towards a higher crossover point for the bass horn itself, as most of you know, and THAT means that a radial-type splitting wedge is now out of favor.

For a really pathetic example of how to NOT implement a splitting wedge, see the La Scala splitter (again the driver, throat cavity opening and the throat cross-section is the SAME as the Khorn). Why the big difference between the two? Economy, kids.

Also, closing down the throat cavity opening as in the modern incarnation of the Khorn simply lowers the efficiency of the driver by increasing the throat reactance. The effect of this really cannot be predetermined ACCURATELY. The formulas do provide somewhat of a ballpark estimate, though. It depends almost entirely on the driver, not the horn, in this case. But for me, the Khorn throat is not a mystery, and DEFINITELY NOT A PHASE PLUG. That is just plain DUMB. Do not buy in to that blather.

I have tried the K33E in both slot sizes (6x13 and 3x13), and I can attest to the fact that it sounds worse in the wider slot, regardless of the horn employed. It LIKES higher reactance to work against.

Armando, I think the reason that the Khorn no longer sports a tailboard splitter, mitered tailboard, etc. is simply economics. It just didn't matter from a selling standpoint, and it was certainly cheaper to produce, being less parts and labor. That is not to say that you wouldn't HEAR a difference if they were there, only that it was good enough to sell without those "mods", thus increasing profitability.

Personally, it is JUST THESE types of changes that show PWK's true genius as a desingner/salesman/businessman. You "worshippers" need to remember that you are listening to the end-result of many years of production as a pared-down commercial product, NOT the best possible implementation of a given design! It is somewhat polished with time, but clearly shaved down a bit.

DM

[ajsons]

It makes perfect sense to me. PWK knew when to change hats. The 1945 construction plans were using 3/4" plywood. He changed that too. It's clearly "shaved down a bit".

[D-MAN]

PWK has much more to teach than simply just horn design. That's reason enough to respect his abilities, but the designs were only part of his success. He was one example of an inventor who was also a very astute and gifted businessman.

DM

[ajsons]

Nice to know.

[D-MAN]

I think that part of his formula was to "keep the mystery alive", that is, he specifically DIDN'T address certain issues directly, for example, the Khorn throat design. i.e., the "magic" that one hears bantered about. I guess that is the point I am trying to make.

That is a remarkable ability all by itself - knowing what to say and WHEN to say it (and more importantly, when to shut up)...

DM

[boom3]

Maybe we can bring this horse to the barn, I for one hope so since my original question has never been answered, even with some speculative, albeit entertaining, tangential commentary. If you look at DFH, Vol 2, No. 12, 10 Nov 1961, Paul said:

"A minor cause of loss at 400-500 cps was traced to driver unit variations within types and between types. This was minimized by a change in throat structure involving a multitude taper. This was investigated in 1953 but improvement was not then regarded as significant. Considering the driver variations and the minimizing of effect with the throat change, it was desired [sic] advisable to be put into production. Woofers with the change are designated "G" thus K-3-G means Klipschorn woofer unit, G modification"

In DFH Vol.12, No.5, 25 Oct 1972, revised (in price only) in June 1974, "Updating Klipschorn Loudspeakers", Paul said:

"There was a change in woofer horn throat structure about 1963...the "Type G motorboard" may be retrofitted to improve response in the 20-400 Hz range..."

In a 1970s letter (not extant) to me, Paul called this change a 'plug'- in his original quotes- that smoothed response at the upper end of the bass horn's range. I did not, nor do I now, take the 'plug' usage as phase plug in the classic sense.

One more time, does anyone actually know what the Type G is, and what it replaced? I have asked the factory...they don't know at this point.

[Guest " "]

Maybe we can bring this horse to the barn, I for one hope so since my original question has never been answered, even with some speculative, albeit entertaining, tangential commentary. If you look at DFH, Vol 2, No. 12, 10 Nov 1961, Paul said:

"A minor cause of loss at 400-500 cps was traced to driver unit variations within types and between types. This was minimized by a change in throat structure involving a multitude taper. This was investigated in 1953 but improvement was not then regarded as significant. Considering the driver variations and the minimizing of effect with the throat change, it was desired [sic] advisable to be put into production. Woofers with the change are designated "G" thus K-3-G means Klipschorn woofer unit, G modification"

In DFH Vol.12, No.5, 25 Oct 1972, revised (in price only) in June 1974, "Updating Klipschorn Loudspeakers", Paul said:

"There was a change in woofer horn throat structure about 1963...the "Type G motorboard" may be retrofitted to improve response in the 20-400 Hz range..."

In a 1970s letter (not extant) to me, Paul called this change a 'plug'- in his original quotes- that smoothed response at the upper end of the bass horn's range. I did not, nor do I now, take the 'plug' usage as phase plug in the classic sense.

One more time, does anyone actually know what the Type G is, and what it replaced? I have asked the factory...they don't know at this point.

I checked my various price list for any Type-g upgrades and found none.

[D-MAN]

The type G would have the 6x13" opening. The upgrade would have the 3x13" opening.

From your post I now understand that PWK would (correctly) refer to the restricted opening as a "plug", and as such he was not speaking about the throat splitting wedges being "phase plugs" as previously mentioned. Glad that got cleared up.

DM

[ajsons]

This may sound stupid, but the Georgian uses the same motorboard, with a 6 x 13 opening, and the Georgian plans I have calls the Klipschorn....... a type "K".

Which one had that kind of motorboard first?

[D-MAN]

Definitively, if the plans that you posted above are REALLY from 1946, then the Khorn certainly has it first, between the two. I don't know if it was the "first ever" removable motor board, that I would doubt.

The EV came along much later under license from Klipsch.

Gentlemen, it occurs to me that the "type-xxx" is just possibly a part number in the plans, sort of like "Area 51" came to be named.

DM

[ajsons]

It looks like it is a removable motoboard. The cutout though is a circle (piece 12), bolted to piece 8 with a cutout like a 6 x something.

[ajsons]

Here's piece 12.

[ajsons]

Here's piece 8.

This is most likely, a coincidence, but one of the Speakerlab plans calls the motorboard piece G.

[D-MAN]

It is definitely removable, except its for a 12" driver. If it wasn't there would be no reason to measure and align the mounting holes at the corners with the corresponding baffle holes! One reason (the only one I can see) of using a full circle cutout is to allow maximum extension of the cone to avoid slapping the baffle with the cone (reason 2 for removable motor board). This may be more necissary when using a 12" driver that is trying to do the job of a 15", at least IMO.

It is not shown in the 1945 patent, but like you said, neither is the tailboard splitter.

The Khorn patent does include a front compression chamber, too, but no details as to whether it was removable or not. Presumably, it was.

In doing patents, things that are in common usage (like removable motorboards and how they are attached) are usually left unmentioned and are not included in the drawings. So we are left to speculate...

DM

[ajsons]

Dana, I think you were posting while I was scanning.

Piece 12, the motorboard, is 1-1/2 thick, with a circle cutout. It looks like a compression chamber.

[D-MAN]

If it is that thick, i.e., has that much volume, it is definitely a compression chamber.

Dana

[ajsons]

Another solved mystery.