Article by PWK: A New High-Frequency Horn (K-400)

[WMcD]

I'm pleased to provide you with an article about the K-400 midrange horn. Naturally it is still in use in the K-Horn and LS in the form of the K-401.

Please see the attachment to the following.

Gil

keyword gilarticle K-400

[WMcD]

There you go. I use this second post because the BB seems to not like attachments to the first.

Gil

K-400 Article.pdf

[WMcD]

I'm bumping this up from eleven years ago.  It is PWK's article on the K-400 horn - - and drivers.

 

It comes to mind because there is thread going about the SK and possible substitution of midrange horns.   SpeakerLab was using its near copy of the K-400.

 

The graphs in the article show that the K-400 has remarkably good response in the lower regions.  In Fig. 7 it looks to be good to 250 Hz.  Its predecessor, the K-5 is very good down below 400 Hz too.  If someone thinks they've got a substitute, they should check for performance in that region.

 

There is room for discussion on whether the K-400 should be used above 4000 Hz, but that is another issue.

 

WMcD

Edited May 9, 2015 by William F. Gil McDermott

[dubai2000]

Thx. for bumping this up - it certainly confirms what my ears suggest - that on a Khorn bass bin the K-400 can be pretty good indeed .

 

Wolfram

[Mike 585]

Gil,

Is it known what the unnamed "wide range driver" was that he that he graphed in the two way?

Mike

[OO1]

I'm bumping this up from eleven years ago.  It is PWK's article on the K-400 horn - - and drivers.

 

It comes to mind because there is thread going about the SK and possible substitution of midrange horns.   SpeakerLab was using its near copy of the K-400.

 

The graphs in the article show that the K-400 has remarkably good response in the lower regions.  In Fig. 7 it looks to be good to 250 Hz.  Its predecessor, the K-5 is very good down below 400 Hz too.  If someone things they've got a substitute, they should check for performance in that region.

 

There is room for discussion on whether the K-400 should be used above 4000 Hz, but that is another issue.

 

WMcD

I wonder how SpeakerLab was able to copy the k400 - wasn;t the K400 patent protected or is the SpeakerLab version very different

[OO1]

 

I'm bumping this up from eleven years ago.  It is PWK's article on the K-400 horn - - and drivers.

 

It comes to mind because there is thread going about the SK and possible substitution of midrange horns.   SpeakerLab was using its near copy of the K-400.

 

The graphs in the article show that the K-400 has remarkably good response in the lower regions.  In Fig. 7 it looks to be good to 250 Hz.  Its predecessor, the K-5 is very good down below 400 Hz too.  If someone things they've got a substitute, they should check for performance in that region.

 

There is room for discussion on whether the K-400 should be used above 4000 Hz, but that is another issue.

 

WMcD

I wonder how SpeakerLab was able to copy the k400 - wasn;t the K400 patent protected or is the SpeakerLab version very different

 

the  ,SpeakerLab gorn was rated at 350hz , that should explain the difference - some even called that horn an upgrade to the k400 -

[WMcD]

I don't know the identity of the wide range driver.  It occurs to me that there are some drivers in the Klipsch museum and there is a long video of Jim Hunter giving a tour.  Maybe there is a hint in there, or maybe Jim knows.

 

There was no patent on the K-400.  PWK wrote that it was based on a Jensen design and maybe that it why.  I think there was one on the K-5.

 

Don Keele has written that the K-5 was the first constant directivity horn (or like that).

 

I can't see the SpeakerLab being better than the K-400.  They are certainly close, if not identical, in dimensions.  Probably SL could copy it because there was no patent.  The patent on the bass bin had expired.

 

WMcD

Edited March 8, 2015 by William F. Gil McDermott

[minermark]

There you go. I use this second post because the BB seems to not like attachments to the first.

Gil

Great, i will print this up as these K400s are what woke-up my EAW stacks, (Wife's comment) now i have the Data     

[BeFuddledinMn]

This is the kind of wonderful and rare information that makes this site stand out. Great analysis of the early K-5-J wood horn by PWK himself! Much thanks to Gil McDermott for sharing this.

[BeFuddledinMn]

The Klipschorn timeline suggests that the K500-5000 crossover used with the K-5-J mid horn was phased out in the late 50's in favor of the "a" network. Interestingly, this article and horn analysis shows that the k55 produces higher sensitivity with the k400 horn - across nearly the entire frequency range, and significantly on both low and high ends. The "a" network uses 3db attenuation for the k55/k400 combination. It would seem that perhaps no attenuation would have been necessary with the k55/ K-5-J horn combination. I wonder what attenuation settings were used with the k500 - 5000 crossover as well as the early "a" networks used in combination with the k55 driver / K-5-J horn combination. This also raises the question of possible bass bin sensitivity changes in the early years - and if so, corresponding changes in sensitivity matching between the bass and mid sections. Any information on this would be fascinating.

For what it's worth, I currently have a 1956 Klipschorn that came with the k-5-j and k500-5000 crossover. I now run it with two top hats - one with the k55/k-5-j horn combination with a crites a/4500 network, and the other with a k55/k401 horn combination with a crites "a" network. Perhaps I should be running the k55/k-5-j horn with the "a" network and 0 db attenuation on the mid section?

In terms of my contemporary listening experience, I don't have golden ears - yet to me the sound contrast is clearly recognizeable - the k55/k-5-j combination sounds much more transparent, open and realistic to my ears - yet a bit softer with less punch, than the k55/k400 combination. I could easily see many opting for either flavor based upon preference.

Thanks in advance.

[djk]

_{"Is it known what the unnamed "wide range driver" was that he that he graphed in the two way?"}

 

_{Altec 802.}

 

[WMcD]

Thanks for info djk. It certainly makes sense to try the Altec. It is a heck of driver, but maybe it did not go as low as needed.

As for the question by BefuddledinMn. It is interesting to ponder.

Looking at the schematic for the K-500-5000, it shows there is no attenuation by autotransformer or resistors.

And looking at the timeline for the K-Horn it seems to say the replacement for the K-500-5000, the 1-RC, was first used in 1955 but the designation to A was made until 1966. A reasonable assumption is that the 1-RC had 3 dB of attenuation by means of the autotransformer and they are equivalent.

It is at least interesting to note that PWK published his article “The Trouble with Attenuators” in 1958 and the schematic for the new crossover is shown in Figure 2. It has an inductor in series with the mid, which makes it a passband design. To my understanding the A as we know it does not have this. But, on the other hand, the text by PWK in the article speaks of the Shorthorn and Rebel, not Klipschorn. There is mention of the K-1000-5000 in connection with the Rebel. The attenuation caused by the step-down function of the autotransformer is said to be 6 dB. Therefore the schematic shows what is used in the Rebel and not K-Horn, most likely.

https://community.klipsch.com/index.php?/topic/59451-article-the-trouble-with-attenuators-by-pwk/?hl=%22trouble+with+attenuators%22

I do understand your observation that the K-400 is a bit more efficient (or less lossy, probably) than the K-5. I agree that the replacement of the K-5 with the K-400 would be a good time to redesign the crossover autotransformer to knock down the mid a bit. But I expect you see in the timeline, as I have, that this is not described.

We do see in the timeline that many drivers were used. We see the K-55 Atlas was brought in, in 1961 as a replacement for the University SAHF, whereas the switch to the K-400 didn’t occur until two or three years later.

There are related issues. Was the SAHF as sensitive as the K-55? Also, the switch to the throat restrictor on the bass horn brought up response at 400 Hz but knocked it down elsewhere.

Overall, it seems to me that as these many changes were made, the crossover was not altered at the same time. Maybe the philosophy was to not make too many changes at once.

WMcD

[Deang]

I've worked on networks labeled "K500/5000" that did have an autoformer. We know from pasts posts here from Bob that were more than one of those networks carrying the same designation.

The horn choice: PWK would always choose the thing which produced the most efficiency, and so in his mind, the least distortion. The K-5-J might in fact sound better, but I can almost hear him saying, "Just because it sounds better doesn't mean it's right."

Edited May 14, 2015 by Crankysoldermeister

[BeFuddledinMn]

This is a fascinating discussion and thanks to all of you for sharing your knowledge and experience. Below are several pics of k500-5000 crossovers , the first one is mine from Sept, 1956. The others are from 1952-1954, then one from 1957 or later I believe.

I have now installed a modified "a" network with 1db attenuation for the k55/k-5-j mid section rather than 3db. I'll share my unqualified listening experiences and thoughts when I get a chance later this week to test against the standard A and a/4500 networks. I guess I could also throw the k500-5000 back in - might be interesting to listen for the higher woofer crossover at 500hz with the k-5-j. If anyone can recommend a good software package and equipment to measure frequency response it might be fun to test each option and then post the results.

Thanks again gentlemen!

Best,

Michael

[BeFuddledinMn]

FYI - the order of those pics in my prior post is all screwed up. Lower right is my 1956 k500-5000, lower left pic is 1957+, upper left is a very early model ~ 1952 or 1953??? and the top right is I believe a 1954-1955.

[ClaudeJ1]

I'm bumping this up from eleven years ago.  It is PWK's article on the K-400 horn - - and drivers.

 

It comes to mind because there is thread going about the SK and possible substitution of midrange horns.   SpeakerLab was using its near copy of the K-400.

 

The graphs in the article show that the K-400 has remarkably good response in the lower regions.  In Fig. 7 it looks to be good to 250 Hz.  Its predecessor, the K-5 is very good down below 400 Hz too.  If someone thinks they've got a substitute, they should check for performance in that region.

 

There is room for discussion on whether the K-400 should be used above 4000 Hz, but that is another issue.

 

WMcD

PWK told me that after designing the K-500 for the Belle he felt that the K-400 was a lot longer than it needed to be. But hey, what is one to do after spending all that money on tooling and production!!

[ClaudeJ1]

Looking at the schematic for the K-500-5000, it shows there is no attenuation by autotransformer or resistors.

 

Looks like he used air core chokes, which, with the right wire gauge, would have DC Resistance necessary to "knock things down a bit."

 

Just a thought.