Edgar

Everybody; do not overlook the use of a PC and a good sound card as a (fairly) inexpensive digital crossover. Sound cards like the LynxTWO (http://www.lynxstudio.com/compare.html) and others have outstanding audio performance for reasonable prices. (Of course, "outstanding" and "reasonable" are in the eyes of the beholder.) I have a fair amount of experience programming audio processing under ASIO 2.0, so I can help with that if anyone wants. Greg

Roy, I cannot begin to tell you how relieved I am to read your post. As the literal "new kid on the block" who jumped-in feet-first and started splashing around in the water, only to have Coytee ask the very proper and necessary question, "Should we be doing this?", I felt AWFUL. I would NEVER dream of stepping on anyone's toes at Klipsch or anywhere else. As you pointed out, the design changes that I proposed would be purely experimental. At the moment I have no way to construct an enclosure and no way to test one once it was constructed. I am an engineer myself, so it is in my nature to experiment with numbers and design alternatives. There are no guarantees that what looks good on paper (or on the computer screen) will be good in reality. At this point I do not know what to do. Having an idea for a design, or even a crude sketch, is one thing. Having a full 3-D CAD drawing is yet another. I certainly don't want to enable anyone to pirate your design. Greg

Oh, no; this is terrible. I honestly did not know that the Jubilee was still in production. When I searched for "Jubilee" on the Klipsch site, it sent me to the "Discontinued" section. This is difficult, but under the circumstances I don't think that I can offer the CAD drawings without approval from Klipsch. I am sorry, but I have to respect their right to earn a living. Coytee, thank you for bringing this to my attention. Greg

I understand, and generally agree. However, according to the Klipsch website the Jubilee is discontinued. I discovered this forum less than a week ago because I was browsing the Klipsch site to find out what ever became of the bass horn that was described in that old issue of JAES. Thinking that it had probably been made into a product, I was hoping to someday be able to purchase one. One thing led to another, and here I am not only hoping to someday be able to build one, suddenly I'm modifying it as well. My head is spinning. Greg

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

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

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

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. 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

I use TurboCAD. Can't afford AutoCAD. The gains, if any, would have to be quantified. 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

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. 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

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

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

See section 11.20 of http://www.gatago.com/news/answers/16950855.html Also http://www.avahifi.com/root/equipment/bridge/index.htm Also search for "bridge" at http://www.nleindex.com/index.php?pID=HTDI&sID=BrowseIndex&tID=E/891 Great American Sound made a transformer-coupled bridge in the late 70s, but I've never actually seen one.

How did you determine the shape? It looks like this has a conical initial expansion across the front panel, followed by a linear section along the sides, followed by a slight expansion across the back, followed by much more rapid expansion once it turns around and comes forward again. While that's a pretty coarse approximation to a tractrix, perhaps it's close enough to still be effective. You can get away with a surprising lot of "close-enoughs" in speaker construction. Thanks, Edgar

I have almost exactly what you have. I entered it in TurboCAD yesterday. If I could figure out how to attach a file I'd include it. My question is, what's on the inside? There must be some internal channels, but nobody has talked about them. Edgar

I believe that the main focus of the product is the transformer, not the cable. If I remember correctly, Paul originally sold just the transformer, then added cables to it in response to demand. Being transformers, they do exactly what transformers do: transform the impedance. This is a particularly effective with OTL tube designs because they REALLY don't like low impedance speakers -- I believe that Paul's original motivation for designing the ZEROs was his love of Atma-Sphere OTLs. The big difference between the ZERO transformers and standard output transformers on most tube amps is the impedance ratio. Most tube amps match a primary (source) of perhaps a couple of thousand Ohms down to a secondary (load) of 16 or 8 or 4 Ohms; the ZEROs maybe go from a primary of ~16 Ohms down to a secondary of 4 Ohms or even less. But the load seen by the amp at the primary is always directly proportional to the actual load connected to the secondary. Edgar

I know Paul Speltz from my previous association with the Audio Society of Minnesota. While I have never heard his autotransformers in action, Paul knows his way around electronics pretty well, and is very active in the Atma-Sphere User's Group. http://www.zeroimpedance.com/ Edgar

By the way, according to the TS numbers that I have, the JBL G135 (not G135A) would be a good substitute for the K33E, at least in terms of the required back-volume, throat area, and fHM. I have no idea about availability. Edgar

Ah, that's better. That puts fHM at 177 Hz, as indicated by D-MAN in post 753043. Is there a complete list of TS parameters for Klipsch woofers available anywhere? Thanks, Edgar

From Keele; fHM = 2fs/Qts. It is possible that I have the wrong numbers for the TS parameters, but I found most of them in this forum. Edgar

But the tide lifts all boats. Raising the efficiency should just raise the entire response curve. My numbers show fHM for the K-33-E to be 88 Hz, based upon fs=28 Hz and Qts=0.633. There is obviously more going on here than meets the eye. Thanks, Edgar

Thank you. It's tough to argue with reality. "When reality disagrees with theory, get a new theory." Edgar

Thanks. That's actually a Speakerlab K that I brought into TurboCAD. I bought the plans way back in 1979, but never got around to building it. Edgar

Greetings! I have been interested in building a dual-12" horn bass enclosure since the Klipsch/Delgado article in JAES several years ago. I just discovered these forums the other day, so I've spent the past couple of days catching-up on everyone's posts about building a Jubilee clone. I have a question about the upper frequency limit of the bass cabinet. People report Jubilee crossovers of 600, 800, even 1000 Hz. But according to the Thiele/Small parameters I've been able to find for various Klipsch 12" drivers, along with Don Keele's horn parameter equations, the woofers themselves run into mass-rolloff well below that: K-1242 384 Hz K-22-E 189 Hz K-22-K 170 Hz K-23-K 195 Hz K-24-K 149 Hz K-25-K 221 Hz Does Klipsch EQ the Jubilee woofers to extend the HF response? Thanks, Edgar