WMcD Posted November 4, 2004 Share Posted November 4, 2004 Your weekend reading assignment is being given early this week. Enjoy. Gil Link to comment Share on other sites More sharing options...
WMcD Posted November 4, 2004 Author Share Posted November 4, 2004 The quality of the image is a bit poor. This came off microfilm. Best, Gil Design of Compact Two-Horn Loudspeaker.pdf Link to comment Share on other sites More sharing options...
WMcD Posted November 4, 2004 Author Share Posted November 4, 2004 Looking at it closely, it probably didn't come off microfilm after all. Link to comment Share on other sites More sharing options...
J.4knee Posted November 4, 2004 Share Posted November 4, 2004 Gil, Thanks for posting this article, I just did a quick review and will do as you suggest and read it this weekend. Since you assigned it as weekend homework we aren't going to have any quizzes on Monday are we? Link to comment Share on other sites More sharing options...
WMcD Posted November 4, 2004 Author Share Posted November 4, 2004 Nope, this is a no credit, no tuition seminar. However I actually was a college professor for one year. Gil Link to comment Share on other sites More sharing options...
JohnA Posted November 5, 2004 Share Posted November 5, 2004 Gil, Where do you GET this stuff?! Thanks! Link to comment Share on other sites More sharing options...
D-MAN Posted November 9, 2004 Share Posted November 9, 2004 Interesting that in '46 PWK was seemingly happy with the 2-way approach, which he later (1998) decided that the Khorn bass horn itself was not appropriate for a modern 2-way lashup (giving impetus to the Jubilee bass horn) due to it having a tendency to cutoff and/or hammer the upper "mid-bass" frequencies. Of course, I think that he was right in his assessment, due to the physics of a single mid-range/tweeter driver which demands a higher low-frequency cutoff/crossover point, and the nature of the Klipschorn horn folding which (somewhat) "twists" the waveform to a degree and renders a somewhat distorted, peaky version of upper bass response above 400Hz. I think he was a big man to "abandon" the best-known object of his life's work and explore other solutions to the same problem. The more I read about PWK, the more I respect this remarkable man. DM Link to comment Share on other sites More sharing options...
Q-Man Posted November 9, 2004 Share Posted November 9, 2004 Gil, I've been meaning to tell you thanks for posting this stuff over the last few weeks. They are articles that I have read before and may even have some of them tucked away somewhere. I think that it's good for the young pups on this forum to read them and learn what Paul was all about. The Articles may also help these younger Klipsch fans to understand why us old timers got so involved with the Klipschorn in the first place. Link to comment Share on other sites More sharing options...
WMcD Posted November 9, 2004 Author Share Posted November 9, 2004 Thanks guys. I'll try to keep them coming. I've toyed with the idea of setting up a website with a collection. A lot of work. So right now I'm doing the weekend serial entertainment thing. In my view, PWK's works, and approach, can't be fully appreciated without knowing the times. Certainly Bell Labs had done the work for theaters, and he brought it into the home. Others were doing this too. Jensen, EV, JBL. I'd like to think he was at the front of the pack. I'd like to think that the huckterism of those days was out of ignorance and lack of technical data; and he confronted it with facts and science. To the extent there is more hucksterism today, perhaps it is worse in that it is out of disregard for facts. The little yellow button will always be needed. = = = = = I'm not quite decided on what is "wrong" with the K-Horn, if anything. As a starting point, Don Keele's analysis of the driver shows that the high end of the K-33 does roll off just below 300 Hz. So we're relying on beaming by the horn mouth to keep things right. It seems to me that the LS and Belle does just that. If you look at the specs for the drivers in the Jubilee, the high end rolloff should be compromised too. I'm not quite sure how the back chamber increasing the Fs of the system figures in. Some of my calulations show it should not make a difference. (You can increase the system resonance by adding a spring, but then the system Q goes down. Fh doesn't change.) One issue is whether the second section of expansion of the K-Horn is causing a problem. This is indeed were there is a twist from a horizontal cross section to vertical. However, look at the Jubilee article. The first prototype does not have this twist, yet HF response is still poor. This prototype has widely splayed final flares. So lack of beaming might be the issue. In the final prototype, the Jubilee, the mouths are facing forward and more closely spaced. And the HF response is indeed improved. The other odd thing is driving the K-Horn at below cutoff. My guess is that the K-33 has parameters so that it becomes more like an efficent direct radiator with minimal horn loading. I.e. you need a driver which is not overdamped (not a very low Q). I've seen some articles saying that reactance annuling occurs when the system resonance is at Fc of the horn or maybe even higher. In the K-Horn the Fc is at 48 Hz. Yet system resonance is down around 35. Someday, all will be revealed. Best, Gil Link to comment Share on other sites More sharing options...
D-MAN Posted November 10, 2004 Share Posted November 10, 2004 Hi, Gil. Some further thoughts... What was I thinking?! It makes sense that PWK would be satisfied in '46 with the 2-way, as it only went to 12k at the top-end. As technology progressed and the requirement for high frequencies went up, the laws of physics kicked in, making the 400 Hz to 18+KHz driver either unavailable or overly expensive. Note that the Jubilee is a rather expensive little number today for the same reasons. The requirements of a crossover is still there, although with a slightly reduced number of parts, and the design is still relatively complicated and labor-intensive. The net gain is one-less crossover "notch". Is it worth it? I don't know. I am guessing that PWK was more interested in the project than the product, as it is in a more expensive market niche, which becomes more restrictive as one moves up in price, as with the Jubilee being almost twice as expensive as the Klipschorn. I think he was unconcerned with the marketability, just the thing itself. I look at it as a no-holds-barred all-out solution, regardless of the cost. I think that an important key to the Jubilee having a greater ability to produce mid-bass (compared to the Khorn) is due to the use of dual 12" drivers. Less total cone mass results in a tendency to more easily produce higher frequencies, but the combined throat area is consistant with the 78" Khorn throat (although the Jubilee has reputedly a slightly larger throat area). The twisting fold actually occurs twice in the Khorn. Essentially the first being "inside" )the horizontal to vertical) and then (at the tail) from vertical to horizontal again. I think that this is what PWK decided to "replace" with a single vertical expansion followed by horizontal in the Jubilee. My home-made corner horn design is related to the prototype described in the Jubilee paper, except that it stays with vertical expansion all the way to the tail. It then becomes horizontal from there, so it also has a single "twist". The point of that is that I find no trouble in putting out a convincing 500Hz through the bass horn using a K33E driver. So I know from experience that PWK was certainly on the right track in his approach to the Jubilee. I also would guess that the nominally 4 Ohm K33E acts as a 16 Ohm driver when placed in the horn, due to the resistance of the air in the horn throat (more than atmospheric due to wall drag), and the counter-balance of the sealed back chamber which is sized appropriately for the air volume in the horn channels. This is mentioned somewhat to in "How to Build Speaker Enclosures", by Badmaiff and Davis (our buddy), 13th reprint, 1978, where (I paraphrase) "the driver becomes a 16 Ohm equivelent due to the excellent loading of the horn", however, it is mentioned in a passing manner so that it appears that the authors assume that the reader already understands the ramifications of horn loading, which I do not fully grasp. The application of the resistance to cone movement actually increases the resistance that the amplifier "sees", and reduces the tendency of the impedance to vary widely with frequency as it would in free air. This means that the driver when placed in the horn presents a more stable load to the amplifier. If one uses a woofer of 8 Ohms in the horn, the throat reactance must be reduced (usually by widening the throat opening) to gain the same efficiency, as it will tend to make the driver appear as a 32 Ohm (or higher) load to the amp. The narrow throat opening (3x13") of the modern Khorn is used to reduce the upper bass frequencies from broadcasting through the horn as the slot itself is a high-pass limiting filter, in order to prevent the bass horn from inducing some peakiness to those frequencies above 400Hz due to its folding design. I agree that there is nothing inherently "wrong" with the classic Khorn design. It is very clear that PWK's design is specifically intended to be the most compact folded 40Hz fc. corner horn there is and with that goal in mind, it cannot be bettered and still maintain the response on the bass end. The Jubilee has a different goal in mind, so I guess PWK didn't really "abandon" the Khorn, he just had a new goal to pursue. While I think that he still strove for compactness, it was a secondary consideration to a wider low-end frequency response while remaining competetively sized. In the case of the Jubilee, I suspect that 8 Ohm drivers are used in proportionally wider throat cavity openings, but I am guessing here. At least, that's what I would do if I were going to build one. The "splay" of the Jubilee horn "mouths" is a subject whose benefit I will rely on PWK for, but for the life of me, I cannot see how that would make a difference, except in providing an easier sensitivity measurement due to a "direct" path (which mid-range frequencies "prefer") to the microphone or listener's ears. Another point which I think needs mentioning is that in the article above, one of the footnotes mentions the famous Klipschorn patent, but then PWK not only states that he would allow DIY'ers to build one as long as they ask permission, AND also invites suggestions and/or critique. That's a CLASS ACT. That's what I've been thinking... what do you guys think? DM Link to comment Share on other sites More sharing options...
WMcD Posted November 10, 2004 Author Share Posted November 10, 2004 Okay, now I remember where I got the article. I was visiting the Klipsch Museum in the telephone building and the article was just sitting there. It was on a K-Horn to the right as you enter the main room. I'd not been aware of it at all. The folks in the office made me a photocopy. I did thereafter write to PWK asking for retroactive permission. I never got a reply. He was having health problems at the time and it was quite understandable. It would have been a treasured letter. One observation is that it seems to me the Jubilee has about the same footprint as the K-Horn, except that the mouth(s) extends to being almost planar with the front. So the Jubilee is wider, but not if you consider the room walls to be the extension of the K-Horn. It may have been his whim to make a better product of the same size. Naturally this is pure guesswork on my part. OTOH, it is difficult to believe such things are accidents. It is worth looking at the plan view in the Jubilee article. If you want a wider mouth (important), the same single orientation wrap of the sound path (important), and have to keep the footprint the same (a given), you've got a problem. There is only room for 12 inch drivers. Best, Gil Link to comment Share on other sites More sharing options...
boom3 Posted November 11, 2004 Share Posted November 11, 2004 Hey Gil, Do you have PWK's original paper on the Cornwall? I have it, but it's deeply buried in my paper archives right now. Thanks! Link to comment Share on other sites More sharing options...
D-MAN Posted November 11, 2004 Share Posted November 11, 2004 ---------------- On 11/10/2004 10:12:08 PM William F. Gil McDermott wrote: It may have been his whim to make a better product of the same size. Naturally this is pure guesswork on my part. OTOH, it is difficult to believe such things are accidents. ---------------- Some more analysis on the Jubilee vs. Klipschorn. I think that PWK just "let things be" in the Jubilee, but he had some well-worked notions concerning certain variables in mind. The overall size is dictated by the chosen Fc and related size of the back chamber, A=(v*2.9)/R where a=throat area in sq in, v=back chamber volume in cu in, R=expansion rate area doubling point in linear inches (derived from his original Khorn patent). PWK mentioned that the overall mouth area of the Khorn worked out to approx. 4 sq. feet, appropriate to act as a 16 sq ft horn mouth when corner loaded (that is broadcasting into a 2pi/r solid radians which gives the effect of multiplication of 4x). I'm doing this from memory, so please bear with me, I may be off a bit). I would assume that this would also be what he kept in mind for the Jubilee (supposition here) as the throat area is relatively close in both. Granted, the Jubilee uses a "rubber throat" and changes its expansion rate 3 times in the course of its length, but at the end of the day, the mouth is still going to be a specific size in order to "work" properly, as calculated using an averaging of the expansion rates involved. Probably resolves to the area of about 4 sq. ft. The results will provide the "sizes" needed, and then one has to work out the most economical way to get it all into a corner. The point being that the size is relatively fixed. The variables of height, and depth are the basic things that can be changed, since the corner itself provides an unalterable factor. PWK mentioned that he felt that the best height of the midrange/high freq horns was between 36 and 44 inches, so I would assume that he kept that in mind. Therefore, the size of the Jubilee is basically constrained by the desired height and the "fixed" corner, more or less. The relationship of the Jubilee's size and the Khorn is circumstantial, I think. If either was reconfigured for a lower Fc, it would be larger in either depth and/or height, and I feel that PWK would try to retian his preferred height in the design. This is all just a guess. DM Link to comment Share on other sites More sharing options...
WMcD Posted November 13, 2004 Author Share Posted November 13, 2004 Boom3, Yes I've got it. I'll use it for next weekend's reading. Best, Gil Link to comment Share on other sites More sharing options...
Recommended Posts