Preparing for Jubilee build

[Daddy Dee]

One thing I'm wondering, from trying to imagine what the folded horn would look like in 3D...

Would this be an easier build, in terms of wood working than the Khorn bass bin?

[bigdnfay]

When I built my k-horns there were several compound cut. From what I can tell there are none in jubilee since all the folds are on one plain. This ,to me, would seem to be an easier build, but I think it will take just slightly more plywood.

Big D

[Parrot]

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On 1/29/2005 1:13:03 PM Daddy Dee wrote:

Would this be an easier build, in terms of wood working than the Khorn bass bin?

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Yes, definitely.

[tigerwoodKhorns]

This looks much easier to build.

The Jubilee is designed to be placed in a corner, but I assume that "perfect K-Horn corners" are not necessary as teh corner will serve as a "megaphone effect."

This leads me to a K-Horn question. All of my corners have windows, thus I have never heard the true potential of my K-horns. I have one good wall around each speaker and one window wall. If I seal the one side of the cabinet where the window is I am assuming that I will get an improvement. However, other threads concerning false walls mention that the K-horn fals off rapidly below 100 hz when it is sealed as I am suggesting.

The AES paper shows the K-Horn design as extending to the front edge of the cabinet at 45 degrees to the inner surface of the horn (the outer surface intended to be the wall). (See figure 1.) If I build extensiosn out at a 45 degree angle as depicted in the AES paper (look closely at teh top of the cabinet and compare to a production K-horn), and locate the k-Horns in the non-perfect corner, it seems that the equation for fc in section 3.1.1 would be satisfied as moving out further increases the area (m) and thus increases fc (the cutoff frequency). This would suggest that this equation only works "inside of the horn" and when past the enclosure, the corner is fuunctioning as a "megaphone effect."

Trey, you were the person who posted that the K-horn rolls off rapidly at 100 hz when the sides are merely sealed. What were the lab results of the configuration in Figure 1??

Thanks,

Chris

[Q-Man]

This speaker would be a piece of cake to build. If you built a K-Horn, this will be a snap.

[Dylanl]

Tiger, I saw that post and wondered the same thing you did. Yes, Trey was the one that posted on that thread.

So, I guess we ned an answer from him.

[tigerwoodKhorns]

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On 1/29/2005 6:57:04 PM Dylanl wrote:

Tiger, I saw that post and wondered the same thing you did. Yes, Trey was the one that posted on that thread.

So, I guess we ned an answer from him.

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This could make a big difference to K-horn owners that do not have proper corners. If the AES Paper Figure 1 configuration will get the response down somewhere between 100 and 40 hz, hopefully close to 60, this would be an ideal alternative to those without good corners. Just add a sub and you are there (I already use an SW 15).

The Figure 1 "bell" looks easy to fabricate and grill cloth can be added to the side exits to give a jubilee look. This would seriously help the WAF and the MAF (Me acceptance factor). I already have some extra Tigerwood to cap the top.

My fear is that although the equation appears to quit at the end of the effective horn, I am probably missing some other factor.

The next mod that I want to look at is mounting the squaker and tweeter on a swivel base. This would allow corner placement and the ability to adjust the sweet spot forward or backward. The only problem is that with the K-horn pushed against a wall, there is not adequate clearance for the two foot long mid to swing, even if the pivot is skewed to the side of the horn's front.

However, and here is the real beauty, if the AES Paper Figure 1 configuration will work, then the speaker can be placed a few inches from the wall and the squaker and tweeter will have room to swivel.

Chris

[IB Slammin]

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On 1/29/2005 8:08:23 AM Klewless wrote:

Terry,

I plan to cross at 500. Will look for the Altec 902 drivers.

I have a pair or RCF drivers to try first (actually I have the horns for them also). I don't know anything about these drivers except that I made a ridiculos offer for them and ...

Don't know which crossover to use.

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Klew, Just a couple of points. I understand that two forum members tested the 511b and found it to work well down to 400hz. I think that the 902s are very sweet, but I have been told that, without the phase plug, there is a "fry factor" at 500hz. I cross at 600 in CWs, so they work super for me. Just FYI from what I have been told.

Terry

[djk]

"but I have been told that, without the phase plug,"

I think you meant to say 'loading cap', which bolts on the the diaphragm under the driver back cover. A 902 will only handle about 5W at 500hz without the loading cap. The main reason people remove the loading cap is that it boots output in the 3Khz range about 3dB (which it really doesn't need for home use).

[D-MAN]

I count at least 35 pieces of wood, and that does not include that parts required for a flush-mount access panel lip, and only one access panel, that is, not from the top AND the bottom, which might be useful since it is 39" high and there are 2 woofers in it.

I don't think that there is much labor to be saved in the building, and it takes more wood in the long run than a Khorn. The only diff is I don't see any compound miters.

Now I can see why Klipsch would want to charge so much for a pair... and considering that an all-new high frequency setup need to be included to keep up with the bass horn output.

{edit} but it looks like most of it could be cut with a panel saw and a router, not too shabby by any means.

DM

[bigdnfay]

I think 2 woofer doors is the way to go. I have another question...Are there 2 air chambers or is the air chamber one open area(top to bottom)?

Big D

[WMcD]

I realize now that I may have presented some incorrect data.

I'd said that during 2001 Pilgrimage to Hope we heard a pair of Jubilee. True. At least one was made of ordinary plywood and there was a facade of finished plywood. The facade was shown to us by, in recall, Trey. The grills were detachable too. I assume the other of the pair had the same construction.

Now I have some second thoughts. I can't say for sure whether what we heard was an off the shelf theater unit which was then in production, or the type describe above with an additional passive.

During the factory tour we passed by a collection of Jubilee's which were not quite completed. No drivers. The top and bottom hatches were missing. I saw one continuous back chamber. Mr. Hunter asked me to keep up with the tour group (rather than me do any serious investigation).

For the life of me, I can't see how one could be made without a hatch on the top and bottom if one is to have access to the woofers after they are assembled.

I'd say that there is no reason to bifurcate the back chamber of a two-driver unit, it would work the same anyway. If there is a passive in the center, it would certainly have to be in communication with the pressure off the driven units.

Gil

[bigdnfay]

This is how I envisioned the internal workings(from back to front). This rendering has 2 air chambers. To me, in order to have a passive, there would have to be alot of changes. 3 slots or openings would be needed. would it not change the first flare outside the mouth of the motorboard? Does the passive need a flare as well?

[Q-Man]

Gil is correct. The passive is shared by the two drivers. One back chamber, two woofer doors.

[D-MAN]

Forgive my drawing but perhaps it can make a point, I don;t know. I'm speculating at this stage. I agree that the back chamber is a single undivided unit. The actual horn throat can also be a single undivided unit, too, depends on how elaborate you want to get. There are many possibilities.

DM

[D-MAN]

Here is another possibility which is the easiest to build, but may not be the jubilee's approach as it depends on the specified expansion rate indicated in the paper. Just a thought...

DM

[D-MAN]

In thinking about it, the cross-sectional area at the corners (the first fold(s)) is fixed, so that ANY expansion rate used to get there is also quite valid as the throat cavity opening(s) are also fixed in size, and is stated in the paper.

I would therefore go with the last picture that I uploaded, as it entails the least amount of work and accomplishes EXACTLY the same task in the mathematical sense.

No need to get more elaborate as it will amount to naught in the end. The actual horizontal travel is less than 6" to clear the baffle board, so not alot of worry there.

I am wondering if, in reality, if ANY throat baffling is actually REQUIRED, that is perhaps only straight horizontal bracing could be used. I am thinking that it may not be, as long as there are no restrictions at the throat.

One reason that I am leaning in this direction is that PWK actually uses that in the LS design, that is after the first fold, there is a short area of horn that is "columnar", that is, no expansion at all, evidently for expanding the back chamber area of the LS. It is known that a columnar channel of relatively short length has virtually no effect on the passage of soundwaves through it when used as a intermediate passage inside of a horn.

That's sort of where I'm heading with this, due to the extremely short passage from the throat opening to the first fold in the Jubilee. Food for thought, alright.

DM

[bigdnfay]

Thanks D-man.....Lots to think about.

Big D

[tigerwoodKhorns]

I would stick to the Klipsck design except for one thing. Per the design paper, the dimensions of the horn are critical and the best compromise has been obtained. This is the case in every engineering design. Klipsch has built several prototypes and I would imagine uses sophisticated modeling analysis in the design that we shade tree mechanics do not have access to.

That being said, there is one limitation that I noticed that was a production cost/benefit compromise (that a home builder certainly can build around). The size of the woofer chamber is 37 L (I am going from memory) and I think that the ideal size was 39 L. The woofer bin can be extended above the top of the horn to achieve the ideal volume. This will result in a more complicated design, but not that difficult.

The top can then be removeable to access the woofers. If the board that the woofers are mounted to is designed to be removed in one piece from the top, access and service will be easy as to get to the woofers, you would remove the lid (and probably the bottom too), unscrew the woofer mounting board, and remove, then you can remove the woofers from the board.

Just some design food for thought.

Chris

[D-MAN]

Some guesswork and extrapolations based on PWK's horn designs...

PWK had a preference to slightly undersize the back chambers by as much as 15-20% as discussed in his 1970's patent for the "Little Bastard" (Horn of Small Dimensions with a Unitary Sound Path), where he explains his decisions and the ramifications involved.

I would expect that he would apply the same to the Jubilee, although I have not run the equations.

He also stated a preference that the optimum height of his horns bass cabinets to be between 38-44 inches (as I remember) as the upper-frequency horns propagated best in his opinion at that height, so he would probably stay within those parameters, IMO. Basically, the Khorn at 37-1/2" tall (inside horn channel measurement).

The height of the Jubilee bass cabinet can be determined more exactly if unknown by the cross-sectional area at the "sides". We know the throat size, and the respective exponential rates of the different sections, so the correct height of the horn sections can be determined from that based on horizontal distance travelled along with the width of the front motor board which appears to be about 12-1/2" wide. Where this gets "fishy" is that there appears to be areas within the horn channels where there is no expansion applied at all. The precedent for this can be seen in the La Scala.

PWK also has a tendency to stay with front-loaded horns (the exception being the REBEL/SHORTHORN, which he later abandoned). He promoted the sealed and "properly sized" back chamber as a reactance nullifying mechanism in as much as possible within the design, however, he did (as noted above) make certain allowances towards the overall size, quite application specific as in the case of the LS/Belle and "Little Bastard" designs.

He also preferred a symetrical bifurcated horn design over others, this is really his "trademark" for the front-loaded Heritage horns. Therefore, I would assume a symetrical approach to the Jubilee throat baffle arrangement.

I would expect the Jubilee throat to be symetrical, with the drivers and respective throats to be evenly spaced apart, as in your diagragm. It takes more wood and work, and that leads me to my final conclusion:

The Jubilee is not designed with ease of building in mind, it looks to me that it is a no-holds-barred design to accomplish the design goals, and therefore, I conclude that the throat baffles would be arranged and consists of several parts very much like the LS/BELLE throat channels with a center horizontal brace. Your basic 2- LS throat channel designs evenly spaced sitting "on top of each other". Evenly spacing the driver/throats will make the access from both "ends" more of a necessity.

I would personally try to simplify it, but that's just me.

DM