Preparing for Jubilee build

[bigdnfay]

Here we go. first time loading pics with new forum config. This setup has 2 throats with the 45 degree flare. If I had it to do again, I would move the woofers closer together to form 1 throat. Don't get me wrong, the current configuration sounds great. It's just after studying the plans a little closer, the 1 throat approach may be more efficient.

[bigdnfay]

I believe this is some of D-man's handy work(chime in). As you can see there is 1 flare instead of 2.

[D-MAN]

Yup, that was me.

The thing is that either way, you are ending up at the same cross-section in the same distance, so that means that they are essentially equivelent as a horn channel/expansion. The difference is that one is an easier build. True, it is not "exactly" symetrical, but the exceptionally short length of the channel is going to counter-act that to a degree. That is, there isn't enough literal time in that diatance for the soundwave to really get out of phase due to the difference in travel length.

The diffraction effects should also be minimal. Up to the builder which is "best".

DM

[Edgar]

Well, I've been playing with the CAD program. I haven't looked at this problem in several years, but finding this forum renewed my interest. Now that I know the shape of the Jubilee "skin" to pretty good accuracy, thanks to members of the forum, I can experiment with the internals.

I have found that creative application of internal "channels" can result in an expansion that is within a few percent of a perfect 39Hz tractrix characteristic over the entire length. See attached drawing.

Greg

[Guest " "]

Creative is an understatement.

Any idea if how the specs would change if you ran a senerio using a channel flare begining immediately at the throat and ending at the exit path while wraping around the turns as it expands.

[Edgar]

Creative is an understatement.

Any idea if how the specs would change if you ran a senerio using a channel flare begining immediately at the throat and ending at the exit path while wraping around the turns as it expands.

I'm not sure that I understand your question. If the rate of expansion is constant, then the horn is conical. If the horn is tractrix, exponential, or hyperbolic, then in each case the rate of expansion starts out slow and increases as you get farther away from the throat. If the horn is parabolic, then rate of expansion starts out fast and decreases as you get farther away from the throat. There are well-defined mathematical expressions for all of these shapes; anything not exactly following the math is still a horn, just not one of the named types.

Greg

[Guest " "]

Creative is an understatement.

Any idea if how the specs would change if you ran a senerio using a channel flare begining immediately at the throat and ending at the exit path while wraping around the turns as it expands.

I'm not sure that I understand your question. If the rate of expansion is constant, then the horn is conical. If the horn is tractrix, exponential, or hyperbolic, then in each case the rate of expansion starts out slow and increases as you get farther away from the throat. If the horn is parabolic, then rate of expansion starts out fast and decreases as you get farther away from the throat. There are well-defined mathematical expressions for all of these shapes; anything not exactly following the math is still a horn, just not one of the named types.

Greg

I understand. I was thinking 3-d. The drawing does show horizontal expansion as you indicate.

Different from previous renditions of the jubilee is the addtional vertical expansion you added close to the end. For the first two sections, there is no vertical expansion indicated at all, just horizontal expansion.

My question was simply to get an understanding of the pros and cons of doing the additional vertical expansion immediately rather than waiting til you got to the third section.

Are there any?

[Edgar]

Different from previous renditions of the jubilee is the addtional vertical expansion you added close to the end.

I'm assuming that the "beginning" of the horn is at the throat; the "end" is at the mouth. Under those definitions, I did NOTHING to the end, but constrained vertical expansion at the beginning.

My question was simply to get an understanding of the pros and cons of doing the additional vertical expansion immediately rather than waiting til you got to the third section.

Are there any?

Constraining the vertical expansion near the throat changes the horn contour from something resembling parabolic to tractrix. The advantage that a tractrix has over a parabolic is efficiency. The advantage that a parabolic has over a tractrix is lower throat pressure, reducing the chance of horn throat distortion. At the SPL most people use at home the pressure probably doesn't get high enough to be a problem. In a sound reinforcement situation, where the SPL is much higher, that might not be true.

Greg

[D-MAN]

Edgar, that looks fun - what CAD program is that?

My opinion is that the Jubilee is almost as simple as it can get, and doing anything else just complicates the heck out of it.

The problem that I see with what you are doing (an excellent excercise however) is alot of building work for virtually no gain - for me, a major drawback.

You don't want to use a tractrix expansion on a bass horn. That's why none exist out there already.

DM

[Edgar]

Edgar, that looks fun - what CAD program is that?

I use TurboCAD. Can't afford AutoCAD.

The problem that I see with what you are doing (an excellent excercise however) is alot of building work for virtually no gain - for me, a major drawback.

The gains, if any, would have to be quantified.

You don't want to use a tractrix expansion on a bass horn. That's why none exist out there already

For such a short section of horn, so near the throat, the tractrix, exponential, and hyperbolic contours are almost identical. As for lack of tractrix bass horns, I think that most bass horns were designed pretty long ago, when using a plane-wave approximation to an exponential characteristic was popular.

Greg

[DrWho]

I think mr. delgado confirmed 800hz as the crossover on the ones used in Klipsch demos HOWEVER my holy grail is to get something to cover 100-1000hz so that I can keep most of the fundemental ranges of the instruments I listen most often on one driver.

I thought that since the measurements PWK and Delgado showed in thier article should nice response from the bass bin from 35-1000hz that I could get away with it. I guess the concensus is that frequency amplitude measurements do not tell the whole story here and while it has output up to 1k it will not sound good up to 1k, am I hearing you guys right?

Guess I cross at 800 to a tractrix horn...or 300hz to altec 311? or simply buy the large format klipsch pro horn for the pro jubilee.

drats foiled again! tony

The bass bin is 10dB down at 1kHz...maybe this will help:

[D-MAN]

Edgar, that looks fun - what CAD program is that?

I use TurboCAD. Can't afford AutoCAD.

The problem that I see with what you are doing (an excellent excercise however) is alot of building work for virtually no gain - for me, a major drawback.

The gains, if any, would have to be quantified.

You don't want to use a tractrix expansion on a bass horn. That's why none exist out there already

For such a short section of horn, so near the throat, the tractrix, exponential, and hyperbolic contours are almost identical. As for lack of tractrix bass horns, I think that most bass horns were designed pretty long ago, when using a plane-wave approximation to an exponential characteristic was popular. Greg

Greg, Bruce Edgar has experimented with tractrix bass horns and he reports that they have trouble below 100Hz. But that's up to you to find out for yourself, if you want, of course.

Also, logically, if exponential/tractix are so close in short lengths, again, I have to ask, what is to be gained by all that "extra" work? However, I would agree with you that a single expansion rate is better than multiple flares but it would theoretically make the horn length longer by necessity. Perhaps that is enough to make it worth doing, I don't know.

I don't mean to be poo-pooing your idea(s), but I know it seems that way. But don't take it that way.

I think that experimentation is always a good thing. I just want to point out some of the problems that are already known about or published. Whether they can be regarded as gospel, I'll leave to you.

Dana

[Edgar]

Greg, Bruce Edgar has experimented with tractrix bass horns and he reports that they have trouble below 100Hz. But that's up to you to find out for yourself, if you want, of course.

You know, now that you mention it, I seem to recall reading that myself at some point in the past. But I never got around to pursuing the matter to try to find out why.

Also, logically, if exponential/tractix are so close in short lengths, again, I have to ask, what is to be gained by all that "extra" work?

I may have to eat my words on that, too. I just looked at the data -- this "thought experiment" tractrix Jubilee includes 59" of a 63.5" horn! That doesn't really qualify as a "short horn".

However, since nobody's cutting any wood at this point, the only cost is time. I happen to have an excess of that at the moment.

Thanks for your comments,

Greg

[Edgar]

Also, logically, if exponential/tractix are so close in short lengths, again, I have to ask, what is to be gained by all that "extra" work?

For the horn lengths that I'm talking about in this situation, I compared the tractrix contour with the exponential. I used the horn calculators at "http://melhuish.org/audio/horndesign.html". All values are in cm or cm^2 (I haven't figured out how to get this to format nicely; sorry):

(Dist) (Tractrix Radius) (Tractrix Area) (Exponential Radius) (Exponential Area)

0.0 31.6 3138.1 31.6 3138.1

20.0 36.6 4211.8 36.4 4172.6

40.0 42.5 5670.5 42.0 5548.2

60.0 49.4 7668.2 48.5 7377.3

80.0 57.6 10439.3 55.9 9809.4

100.0 67.6 14358.4 64.4 13043.4

120.0 79.9 20078.5 74.3 17343.5

140.0 96.0 28962.0 85.7 23061.2

160.0 120.1 45348.3 98.8 30663.9

The area of the tractrix is within 10% of that of the exponential up to 100cm, then starts diverging prettly rapidly beyond. In the Jubilee tractrix, the horn is about 150cm long.

I am skeptical that there will be a lot of difference between a tractrix horn and an exponential horn under these circumstances.

Greg

[bodcaw boy]

greg,

i am impressed by your drawings. for what it's worth, i think that you are on the right track. will you have a way to measure the lf cabinet when you are done?

thanks,

roy

[Edgar]

i am impressed by your drawings.  for what it's worth, i think that you are on the right track.  will you have a way to measure the lf cabinet when you are done?

Thank you, Roy. Coming from you that's quite an honor.

As for measuring the results ... unfortunately, at the moment I am not in a situation where I can even construct a cabinet, let alone measure its performance. I am willing to make the CAD drawings available to anyone who wants to give it a try.

Thanks,

Greg

[popbumper]

Greg:

If you can provide the CAD drawings, I can get these cut on CNC. Please let me know how I can get them, thanks!

Chris

[Edgar]

  If you can provide the CAD drawings, I can get these cut on CNC. Please let me know how I can get them, thanks!

OK; give me a couple of days to triple-check my work -- I hammered this out REALLY FAST -- and then I'll arrange to get them to you. I work in TurboCAD, but I am supposed to be able to export to AutoCAD .dwg file format. Will that work for you?

Greg

[popbumper]

Greg:

Excellent, ".dwg" works great, I appreciate the effort and look forward to the info. Much obliged!

Chris

[Coytee]

Can I ask what might come across as a rude question?

Before I do, I want to CLEARLY state that I do NOT intend for it to BE rude, that I'm genuinely wondering...

Why try to build a Jubilee?

I mean... haven't we all moped every now & then about Heritage not being easily available? Have we not every now & then, voiced our wishes that Klipsch would be more visible in the Heritage line? That perhaps, they might even produce a home version of the Jubilee?

They HAVE the Jubilee available and it can be ordered... yet instead, we now garner plans on how to make our own "on the cheap"?

Furthermore, these plans are discussed and fine tuned on the very forum of the people who's product you're copying?

I can understand someone wanting to make something like that "because you can", and happen to have the skillset & tools to do so. I can also understand wanting to save some greenbacks. I'm not beyond that comprehension.

Isn't that one of the problems with our country though, in that, we (as a society) are less and less willing to "pay the piper" for something if we can get same goods cheaper from China, or in this case, do it ourself?

I'm sorry, I am not trying to rain on a parade... I just think that Klipsch, PWK and Roy have put so much time into this project that it should be an "honor" (to use a corny word) to have their pinnacle achievement and frankly, to dissect their baby & make some home grown versions...well, is to me, a slap in their face. In my view, it implies those of you able to make a pair will make a pair. Will you make some for others? Will you share the plans with others so they can make or hire it out themselves?

Are these not some of the very reasons we might not ever see the Jubilee in producton?

Heck...I don't know, maybe I'm just mumbling at empty walls... it just strikes me as wrong to deny them the sale when it's the sale to them, that helps keep them going and MIGHT spur them to create a production run.

As someone who bought new LaScalas (2), Academy's (3), Promedieas (1) from Klipsch, I can stand fairly guilt free that some of my dollars helped them do that which they do. (I did buy my Khorns used, but back to the point...there is no local dealer here...I would have)

How would YOU feel, if you owned a business and had a forum for said business and your patrons went about making their own versions of your products because ostensibly, they didn't want to pay you for yours?

To finish off sounding corny... it frankly makes me a bit sad.