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"The Juliebee" (or Jubilating the Khorn)


ajsons

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From my understanding, there are two factors affecting the high frequency response for a folded bifurcated horn. First, the pathlength differences between the inside and outside of each bend are going to introduce larger phase rotations at higher frequencies than at lower frequencies, which will result in more phase cancellation at the higher frequencies - thus reducing the apparent high frequency corner.

The second issue is summing the two bifurcations back together into a single coherant wavefront. Basically, each mouth is going to behave like a separate speaker, so you need to take into account all of the line array theory that describes the interactions between two sources. Because the mouth is big compared to the wavelengths of high frequencies, the high frequencies are going to beam at the exit. If the separate beams never intersect, then you never get the acoustical summing. This is why angling in the mouths increases the high frequency extension - it's bringing the beams back together.

You've also got limitations from the mass and inductance rolloff from the drivers themeselves, but that's not specifically related to the horn design itself. However, that's likely the reason Klipsch went with two 12" drivers in the Jubilee instead of a single 15". There was talk once about Klipsch designing a Khorn that wasn't folded, and I believe it was good up to 1kHz? I forget. The most notable attribute was that the frequency response was ruler flat...basically an indication of all the craziness that folds impose on a horn's performance.

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AJ, Just a couple of quicck points because I think there is some confusion about the high frequency response and what limits it.

As pointed out in the JAES paper (Delgado & Klipsch, 2000), the splay angle was decreased since the separation between the two "mouths" (as a function of wavelength) would act as two separate sources. Two sources would create problems in the polar patterns since at some angles the two would sum and at other angles the two would subtract. Consequently the polar pattern would show "petals". At low frequencies the separation is well less than a wavelength (or half a length) so there is effectively a "single" mouth and no "petals".

The other issue about the high frequency response relates directly to the geometry of the path within the horn. As I understand it, if there were no folding then there would be great high frequency extension. However, with folding then each "side" of the flare has a different length as it bends around the folds. So it is possible that at a high frequency (short wavelength) one side (within a channel) could be anti-phasic to the other side in terms of pressure. This would trash the waveform (not a technical term) at that high frequency. One would need to go through and examine this possibility for your folding scheme. The authors in that paper also emphasized the desirability of limiting the folding to a single plane. One explanation was that it would ease construction, there may have been other reasons also. Your scheme has expansion in both planes over a considerable portion of the horn.

Good Luck,

-Tom

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"Look at ALK's suggested crossovers for the LaScala. It's higher on the Belle."

it is....on the LaScala after the first 90 degree turn...there is a section that does not expand...on the belle this non expanding section does not exists.

Inside the jubilee....the short non expanding section after the first 90 degree turn also exist. one could argue that using a Belle approach would raise the high end ceiling of the cabinet...but I think there are trade offs. Belle bass does not sound the same as LaScala bass.

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The Klipschorn though, based on the Jub papers, gets up to 500hz, if I recall correctly. This "cleaner" folding, hopefully, and the Jub-like exit, will bring the response higher. If I get to 700hz, even 600hz, I will be happy.  

There lies the problem...it starts to dip way before 500hz......way before.....

post-22082-13819354436794_thumb.jpg

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The non-expanding section on the LaScala, really doesn't contribute much, other than provide a 1:1 extension/coupling between two dissimilar flare rates,. and it also lengthens the horn to provide more rear chamber space for the driver.. Standing waves develop when the path between non-expanding 4 walls gets too long.

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So, looking at what I have versus the Jub, and the Khorn, excluding the driver count,

The folding schemes are proven foldings for two separate, ooops, THREE separate speakers, LaScala being the third one. Do you agree, Michael? The Klipsch folding is much cleaner on this, though.

the Juliebee still has a channel twist, or a flowpath in two planes (which works great for the Khorn), and the Jub in one plane..

The Jub has a bend, and the Juliebee doesn't, and has a more straighter path.

They are both bifurcated, so forget that in the equation.

The bifurcated soundwaves on both designs meet at the exit and everything becomes very similar from then on, between the Jub and the Juliebee..

I don't see a big reason not to do this design, do you?

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You seem quite interested in the high frequency extension. So have a look at what Dr Who (by implication) and I suggested regarding the path length differences (within a channel). Or you can simply cut up some plywood, which is the ultimate bottom line anyway.

There are a couple of other comments also.

Originally, you mentioned that you were not going to use a rubber throat design. What is the reasoning? PWK was a firm believer in their use.

Also there is another issue regarding the low frequency response. Have a look at the response for the octave(s) around 100Hz. The Jubilee is doing much better (and it also has lower distortion). The reason I bring this up is because the Jub may not be all that difficult to build compared to the modified K-Horn. The price of the drivers doubles, but there are some real performance benefits. I am not being a wet blanket and I appreciate the work & thinking you have put into this project.

Good Luck,

-Tom

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if you draw a straight horn, cut it in half, but reverse the position so that the top half is at the bottom, that's what is going on inside this enclosure design (like a LaScala, but side view), approaching the rear exit, still maintaining the shape of the exponential expansion. Not so simple on the Khorn. The path length differences will happen, on any horn, the best one can do is simplify the folding, and minimize the number of turns. . I stay away from foldings that look like [:D] the large intestine. I understand the advantages of rubber throating, but there is also no reason why I should not use a straight expansion. Many succesful horn designs use a single flare. It fits nicely on this one, like what I have stated earlier.

I drew the plans for the Jub, can do the Jub, like to have a Jub, but I have, I believe 6 15" EV's that are just waiting to be used. I don't want to spend the money on new woofers, when I have drivers I can use. I have also spare mids and tweeters, and the only expense on my part will be plywood and crossovers.

On top of that, if you can design one, why not build one that you designed yourself ? You know a lot about theory, you can do it too.....

I know about those things that you and Doc commented on. At the other end of all of this is...design freedom...

I'd rather do one of my designs. I wanted to do the Corner Belle, but it was stolen from me and was renamed something else.. And the worst part, there is a patent application for it. If you notice, "the man" is no longer posting on this forum.

This is not the number one design on my list, just want to prove that "it" can be done.

A larger Dean with double 15" woofers? Got the University drivers..

Thank you very much for your interest on this, Tom..

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On top of that, if you can design one, why not build one that you designed yourself ? You know a lot about theory, you can do it too.....

I know about those things that you and Doc commented on. At the other end of all of this is...design freedom...

I'd rather do one of my designs. This is not the number one on my list, just want to prove that "it" can be done.

That is a nice quote. Stick too it. YOU have a pile of plans to pick from......DIY and "known" results. Would love to see the finish of this one.

jc

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