Jubilee Alternate Folding

[Edgar]

For comparison, here's the HORNRESP response for the standard Jubilee. Numbers directly from the Klipsch/Delgado JAES article. Again, woofers are EVM-12L; I don't have model parameters for the Klipsch drivers.

[jwc]

Here...K31

jc

[Edgar]

Thank you, jc. Here is the HORNRESP modeled response using the Klipsch K31 (previous EVM-12L model in gray), and the HORNRESP.DAT parameters so that you can check for yourself.

Greg

0.5 x Pi 2.83 0.00 14.99 580.00 816.00 23.53 0.00 816.00 1727.40 59.75 0.00 1727.40 2817.66 29.45 0.00 2817.66 5527.15 44.81 0.00 530.009.69E-04 71.00 5.70 15.90 1.96 1.34 2P 80.00 40.00 0.00 20.00 4.00 376.00Two Klipsch K31; Alternate Jubilee 3 ConConConCon

[ajsons]

Edgar

You and I have some things in common. I play a lot too with AutoCAd, and try to come up with new horn foldings and use the EV's that I have (15's).

As far as the Jubilee, i don't think there is much anyone can do to improve that design.. There is not a lot of folded bass horn that can get that freq coverage. It's a simple folding, practically no wasted space, and easy to build (no compound cuts). I thought of a couple of mods, but they're probably not worth a dime.

The 3 flare rates were not the design goal (a single one was) but were trade offs. Roy and Paul knew exactly were compromises can be made. Designing your own folding and trying to match the Jubilee flares, or any horn, will not guarantee that it will perform like the original. I stick to one flare if I can.

I thought of Jubilizing the Hartsfield, since the footprints are close, and two-driver Hartsfields had been done, but it's going to use more wood panels (more complicated) to accomplish the same. Forget that idea.

I haven't listened nor seen a Jub in person, I envy those who have and own a set.

Here's one autocad idea, though.

The Jub uses 3/4 plywood. If you have a set of plans in autocad, you can scale it down 0.8333333, and use 10-inch woofers (if you can find 10-inch woofers with good T/S parameters for horns. There is not a lot.) The flare rate Fc will go up, and so will the low end response, and will be a smaller version.

If you scale it down to .6666666666666, then you can use two 8-inch woofers (they're easier to get), and use 1/2 plywood. Again, it'll be smaller, with a higher Fc, probably around 70hz.

(For non-autocad people, scaling an entire drawing in autocad only takes about 5 seconds).

The height is easily adjustable if you want a specific flare freq, and the non-expanding channels can be lengthened or shortened if needed, to adjust the throat/throat initial section.

The folding remains the same.

I do have an alternative folding for the Khorn and Jub though, that I will post one of these days, that may qualify. It is also, unfortunately....plug ugly!

AJ

[Edgar]

You and I have some things in common. I play a lot too with AutoCAd, and try to come up with new horn foldings and use the EV's that I have (15's).

It's a great way to kill a boring day ... at work.

As far as the Jubilee, i don't think there is much anyone can do to improve that design.. There is not a lot of folded bass horn that can get that freq coverage. It's a simple folding, practically no wasted space, and easy to build (no compound cuts). I thought of a couple of mods, but they're probably not worth a dime.

I agree. However, there may be ways to improve it for specific circumstances. I cannot say this with certainty, but it looks to me like the Jubilee was designed as a corner horn that doesn't HAVE to be placed in a corner. In a theater or club there is no guarantee that there will be a good corner available.

If that is true, then redesigning it to both be more attractive and as a dedicated corner horn, for use in the home, may be a worthwhile pursuit that just might bring some improvement.

The 3 flare rates were not the design goal (a single one was) but were trade offs. Roy and Paul knew exactly were compromises can be made. Designing your own folding and trying to match the Jubilee flares, or any horn, will not guarantee that it will perform like the original. I stick to one flare if I can.

Again, I agree. However, given that the Jubilee is an already proven design, it makes a good starting point.

... use 10-inch woofers (if you can find 10-inch woofers with good T/S parameters for horns. There is not a lot.) 

Electro-Voice EVM-10M and DL-10X are very good. But I don't know if they're still available. However, just scaling everything in a horn by a constant generally doesn't work very well.

I do have an alternative folding for the Khorn and Jub though, that I will post one of these days, that may qualify. It is also, unfortunately....plug ugly!

Thought experiments are fun. I wish that I could build some of the designs I've come up with, but time and skill prevent it.

Thanks,

Greg

[PrestonTom]

Just a few quick comments.

Multiple flares; I am not sure that a single flare rate would be best. According to the JAES article, it seems that the rapid initial flare rate was chosen quite deliberately. This is the "rubber throat" issue and I assume was done in order to minimize throat overload distortion. Although it may be the case that in a home system the levels would never get that large and this may not be necessary. But I am guessing on this.

Also if you look at the article you will see a couple of things that suggest some design issues that might not be easily juggled. One is the throat size and the initial flare. The throat is actually different size from the recommended (by equation). If you plot out the flare for the first 20 cm or so, you will see that it is not strictly exponential, rather it appears to be more of a conical flare. Tthis is assuming that there are simple ramps in the vertical (between the baffle and the motorboard). This is how it appears on some photos displayed from the factory build (you can search for this thread). I suspect these two features (and others) are not easily dis-entangled. That is why I would be concerned about "messing with success" regarding changes at or near the throat).

I am quite curious about what changes you guys might be thinking about at or near the mouth. One constraint already mentioned is the issue of keeping the splay angle small.

Good Luck,

-Tom

[Edgar]

Multiple flares; I am not sure that a single flare rate would be best. According to the JAES article, it seems that the rapid initial flare rate was chosen quite deliberately. This is the "rubber throat" issue and I assume was done in order to minimize throat overload distortion.

Yes, now that you mention it I recall either reading that somewhere or concluding it myself at some point in the past. For the home, where the SPL is nowhere near what it is in a theater, that issue may very well disappear.

I am quite curious about what changes you guys might be thinking about at or near the mouth. One constraint already mentioned is the issue of keeping the splay angle small.

That was exactly my objective in the design I called Alternate Jubilee 3; see previous posts.

Thanks,

Greg

[Guest " "]

""The Jub uses 3/4 plywood. If you have a set of plans in autocad, you
can scale it down 0.8333333, and use 10-inch woofers (if you can find
10-inch woofers with good T/S parameters for horns. There is not a
lot.) The flare rate Fc will go up, and so will the low end response,
and will be a smaller version.

If you scale it down to
.6666666666666, then you can use two 8-inch woofers (they're easier to
get), and use 1/2 plywood. Again, it'll be smaller, with a higher Fc,
probably around 70hz."

I like the idea...but we are probally re-inventing the mouse trap. As a flip side to all this scaling down....all you need is a LaScala Bass Bin and a sub woofer and you would have a higher upper frequency....smaller foot print...and bass covered by the sub. A Jubilee cab is basically a LaScala with an additional fold.

[ajsons]

good point.

a good reason not to []waste those 5 seconds to downscale it.

[DrWho]

I cannot say this with certainty, but it looks to me like the Jubilee was designed as a corner horn that doesn't HAVE to be placed in a corner. In a theater or club there is no guarantee that there will be a good corner available.

I don't mean this harshly in any way, but the KHorn Jubilee LF was designed for the home, period. It comes up all the time on the forum because people get thrown off by the aesthetics. It's migration to the pro-cinema world was a move by Roy to keep the design alive when he realized it wouldn't be marketed to the home audio market.

In the JAES article, it was stated that the Jubilee was originally designed for an identical footprint to the Khorn (read, being a corner horn), but it was determined that by tilting in the splay on the sides increased the high frequency extension.

I also bring this up because it indicates that a rubber throat is advantageous for the home (in other words, not just for the high SPL's of the pro audio world). Doesn't the Khorn have a rubber throat too?

[Edgar]

(Hopefully not a double-reply; the Website coughed while I was previewing my original response and it disappeared completely.)

I don't mean this harshly in any way, but the KHorn Jubilee LF was designed for the home, period. It comes up all the time on the forum because people get thrown off by the aesthetics. It's migration to the pro-cinema world was a move by Roy to keep the design alive when he realized it wouldn't be marketed to the home audio market.

No "harsh" intent taken from your words. I'll defer to your knowledge on this subject.

In the JAES article, it was stated that the Jubilee was originally designed for an identical footprint to the Khorn (read, being a corner horn), but it was determined that by tilting in the splay on the sides increased the high frequency extension.

I also bring this up because it indicates that a rubber throat is advantageous for the home (in other words, not just for the high SPL's of the pro audio world). Doesn't the Khorn have a rubber throat too?

I'm still skeptical about the rubber throat. Though I know that PWK liked it, simulation models indicate that it leads to a very rough frequency response. If it really does result in audibly lower throat distortion, though, then perhaps that's a worthwhile trade.

Thanks,

Greg

[DrWho]

PWK's design philosophy put distortion as second priority followed by efficiency. Third was polar response and Fourth was the frequency response. As such, I would not be surprised if he chose solutions that sacrificed frequency response for lower distortion. [] There's nothing wrong, though, with pursuing a different design approach if it ends up sounding better.

I've noticed that the newest version of HornResp will provide distortion predictions. I have no clue how accurate they are, but I would be interested to see if they indicate lower distortion for the rubber throats you're modeling. Since so many measurements have been provided for the Jub LF, it would be interesting to start comparing the model against the real world. I almost wonder if the frequency response abberations induced by the rubber throat don't get squished by the frequency response abberations induced by folding the horn...

[Edgar]

I've noticed that the newest version of HornResp will provide distortion predictions. I have no clue how accurate they are, but I would be interested to see if they indicate lower distortion for the rubber throats you're modeling.

Which version of HornResp does that? I'm running v17. Perhaps there's a newer version.

If I can find some time, I might try the rubber throat distortion analysis.

Greg

[DrWho]

I think v17 is the latest? When you're looking at the predicted frequency response, just hit <F3> and type in a frequency and it will give you all sorts of info, like the system efficiency and distortion and whatnot.

[Edgar]

I just tried that. It offers SPL, electrical input power, acoustical output power, and system efficiency. Unfortunately no distortion.

[DrWho]

Interesting, this is what I get:

[Edgar]

Mine is missing the distortion field. Here's the version info:

[DrWho]

Maybe download it again? The nice thing is you don't lose any of your projects when you reinstall [Y]

[Marvel]

Notice the Product Number? The first four digits are the version - the next digits are probably the build number. Dr. Who's is a later build, which probably has included the extra feature.

[Edgar]

 Notice the Product Number? The first four digits are the version - the next digits are probably the build number. Dr. Who's is a later build, which probably has included the extra feature.

I suspect that the product number is the date of download.