ajsons
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Posts posted by ajsons
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I personally would only change the reflectors to optimize the response for upper bass bandpass in the Classic. Other than the throat reflector in the Dean, there is little or no enhancement needed.
DM
Dana,
I 'm still woking on the cad drawings for the Classic with the added reflectors, just like we talked about. I think I'll start a new thread on driver specs, construction details, and mods. I'll post the cad drawings for the reflector mods there.
Armando
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Quisitive,
I have limited space in my den too. I got rid of a stereo rack and a workout bench to make room for my stereo stuff, esp. the Classic. I take care of the WAF by playing Celine Dion and Fleetwood Mac cd's. She has a picture of the Classic ("that we picked up in Asheville, NC") at her work and she's showing it to her co-workers. She hasn't said anything negative about it, to my surprise!
Now, going back to the choice between a Classic and a La Scala, the answer is obvious if the decision has to be made depending on which one is a better bass reproducer. Between a Klipschorn copy and a Classic, I will still prefer the Classic or the Dean.
In my case, it is a choice between the Classic or the Dean.
Personally though, if space is really the determining factor, I will build the Belle instead, but it will stand on its side, so it's taller, then put a midrange horn on top (which is the other "side", now the top). I don't think it will have a noticeable effect on its dispersion or sound quality. I will also extend the bass section front depth so it is about 20-22 inches.
This ad for the Dean and the Classic summarizes University's approach to folded horn design.. ...
Self-contained horns, independent of walls or floors.
Single path, single mouth horns, unlike Klipsch's.
I think it makes sense. Most of the forum members will probably disagree.
Armando
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without the grille, but with EV mid & tweeter
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Bill,
I don't have a pair, but here's one with a grille.
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It's a little funny, but the 315c was in a Karlson enclosure I bought for $15.00 from an old woman. She had this "there is something about this speaker that is worth more than $15.00"-look on her face. I tried the Karlson (really old, probably as old as that woman and in bad shape ( the Karlson ) when I got home, and I was really impressed, it sounded as good as my SK. I was careless, dropped the woofer when I took it off, and put a big hole through the diaphragm. The enclosure would take a lot to restore, so I got rid of it and the woofer. At the time, about 5 years ago, I didn't know the value of that woofer.
No, I don't mind if you post it on the Karlson forum. What is the link, it changed its web address, didn't it?
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I myself prefer the Dean, and was going to build a pair, but was lucky to win a $30 Classic on ebay. Now I really am not sure what to do next. The logical thing to do is build a matching Classic to the one I already have. I tried to redesign the Dean so it is not as wide, but the height of the C15W gets in the way. An EV driver is shown on this rough plan, although an access cover can probably be made to follow the magnet cover of the C15W. The cobreflex horn is probably better on top so it doesn't restrict the mouth. The enclosure is 31-1/2 in wide, 34- 1/2 high and 27- 1/2 deep (so it can fit through a door). The folding eliminates half a turn. Flare = 50hz, throat = 6 x 13, mouth=1/8 size. (Ignore the reflector angle, I have to work on that.) Comments for improvements are welcome. The horn's length is about 47 inches.
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The Classic came after the Dean, if the Dean is what mine is called. My plans call it the Classic, but I'll call it the Dean here. I think the Classic was a compromise in sound for an easier build.
I was also intrigued with the Deans exterior shape. The 45 degree rear clipped corners make it easy to push into a room corner like the Klipschorn. This takes up a lot less floor space. The bass horn is wider then the Klipschorn allowing one to use a much larger midrange horn. A 200 to 250Hz horn is also very deep,( front to back). The rear of the horn and driver can hang over the back of the cabinet into the room corner.
Q-Man,
The Dean was erroneously called the Classic in Abraham Cohen's book. Thanks again for the plans by the way. It is not a wall type as the book calls it but a "cornerless corner horn".
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For a ported enclosure, Abraham Cohen's "Hi-fi Loudspeakers and Enclosures" recommends a 4.35 cu.ft. enclosure with a C8M mid, HF-206 tweeter and 4"dia port 4" long. I really like this woofer. I got 3, for a total of $180, plus shipping, all in excellent condition. Some had paid as much as $200 for one on ebay. Can Great Plains recone coaxials? I threw away a 315c thinking nobody can recone it.
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Here's another use for the C15W, using the same components used by the Classic.
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This is from Speaker Builder Journal. I hope it helps. I posted the plans for the University Classic a month ago. If anybody wants the full size plans, send me an e-mail.
armando_senson@amsec.com
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(I attached the wrong drawing to my last post, took it out and reattached the correct one).
Dana,
I get my emails at work, I'll read that first thing tomorrow a.m..
Armando
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I remember seeing those details in Speaker Builder, but the name Huygen didn't register. You mentioned that in a couple of other threads and I couldn't recall what that was.
It makes sense though, since it agrees with "the angle of incidence equals the reflected angle", i.e in a 90 degree turn you use a 45 degree reflector. If the turn is not 90 degrees, then the reflector angle needs to be adjusted.
I did the first drawing (and the second) ASSuming that the sound energy is travelling in the middle of the horn duct (reference line). To accomplish that, the reflector's angle must be positioned so that the angles are equal on each side of the reference line. I screwed up in the first drawing, but this second drawing is what I really intended. Now, I don't know if this is right, but my reasoning is, if this is what works for a lot of things....the angle the ball lands on a wall equals the bounce angle, reflected mirror image angle equals viewer's viewing angle, angle of incident ray equals angle of reflected ray, ...then it should work in a horn.
The angle of the throat reflector in my first drawing is a compromise, as things really will not lign up with the edges of the throat cutout as seen in this second drawing.
I did not use the same approach ("incident angle=reflectance angle") when I did the small corner reflector in the first drawing, I used another method to position that, and you're right, it is still a radius reflector. After adjusting it, it turned out to be less than 45 degrees.
Like I said, I don't know if this is the right approach to this angles, but this is the one that makes sense to me.
I think the same thing is accomplished when you draw a straight horn duct and fold it. The fold angle becomes the reflector angle.
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The University Classic seems to quite a bit like a 50 Hz Fc La Scala except that it does not bifurcate the channels. It has a mouth size conducive to single-planar element placement (allowing it to be free-standing). It employes a single expansion rate, but it has 1 problem that I can see (IMO). The same 90 degree untreated fold as seen in the La Scala. This should use a 45 deg. reflector instead to reduce reflections back into the throat channel.
In the old days, it was generally accepted that the use of full-radius turns be employed at folds. I think that hard reflective surfaces are better employed at horn folds. Edgar has also published this (see "The Monolith Horn" SB article) and I agree with his assessment (go figure!). Cohen got the reflection part right on the other fold of the Classic, which would lead me to believe that he also could have "fixed" the throat fold for being a less turbulant choke-point. Why he didn't who knows...
I suspect that it was generally accepted at the time (this is still a great rule of thimb) that if you are going to "get funny" with anything, do it close to the throat where the waveform is relatively small.
That makes me feel I'm going in the right direction with the Classic. On my drawing, I steepened the angle of the throat reflector, added the 45-degree one, and this I'm not quite sure, changed the angle of the large reflector, based on the "angle of incidence = the reflected angle". I don't know if that should apply here.
I also plan on adding a center divider starting at the throat section, like the Khorn, maybe it'll improve the high corner end.
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Second thing is that T/S parameters per Don Keele indicate that the driver can be further reactance "annulled" by achieving the appropriate amount of volume behind the driver to allow it to resonate at or SLIGHTLY below its normal Fs, in keeping with the PWK formula as described above. The K33E is not specifically annulled in the Khorn, for example; the theoretical annulled Vb would be 9343 cu inches vs. the nominal 4800+ cu.in in actual practice.
PWK tended to prefer to slightly undersize the Vb in his horns. This would raise the overall Fs of the driver slightly but increase upper-frequency corner response at the same time. The Keele T/S annulment formula is a technical refinement of the PWK approach and the mathematical results are more precise. It should be kept in mind that with lowering the Fs of the driver below a certain point, it also begins to increase IM distortion, of course, so there is the inevitable tradeoff.
The La Scala and Belle also use a multiple expansion rate and an undersized Vb. PWK horns (except the "Little Bastard") tend to display the following attributes: a) bifurcated at the throat,
radius folds, c) undersized Vb, d) front-loaded, sealed back chamber.How does the back chamber volume relate to F3, or does it relate at all? (This was another assumption on my part...Reactance annulling determines where F3 is going to be, and when done correctly will put it close to or at Fc).
Based on the above, and even the Classic, a horn can have the wrong back chamber and still be a very good horn.
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Whew!! I have to read that at least 5 times before things started sinking in.
Based on these things you said, I am drawing some conclusions related to the Classic, and maybe I'll ask questions on things I didn't quite understand."1) horns DO clearly operate below Fc".
The Classic goes down below the 50hz Fc, per Steve Schell and Q-mans observations/listening tests. And mine. I watched Fleetwood Mac's video the other night, John McVee was hitting the low E's and F's, with no problem on the Classic. I plan on doing more low end tests this weekend."for instance the -3db point of the Khorn's nominal 40Hz horn is 33Hz. This is the "halfway down" or 1/2 as loud as it was at Fc. Definitely "usable" output."
Earlier in the thread, you mentioned, "The -3db point (half down) is approx. 43Hz for the 50Hz Fc."Are those numbers formula based or rough approximations? I had always ASSumed that the final F3, when the horn is finished, will tell you if you did your homework correctly in designing the horn, and can end up higher than, lower than or at Fc.
"2) The Fs of the horn driver should be below the respective horn's Fc."
I was right then in thinking that the EVm15L (Fs = 43hz) is the better driver, specs-wise, for the Classic and not the C15W (Fs = 58hz), but the latter works well with it. (It puzzles me that Cohen used a high Fs driver when he himself ties Fs closer to Fc, well he has a (lower) theoretical Fc and a (desired) target Fc). I have to do more listening tests to figure out which one I really like. I wish I have another Classic so I can I do an A/B test. But that's coming."It might even be said that you would be safe using a driver with an Fs below the F3 of the horn."
Now, Qman also says use a low Fs driver, quoting John (Warren).
How does this then relate to the mass roll-off freq formula, which calls for a high Fs?
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(I know, Al, one of these days, I'm gonna pay for these!)
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Ours is not to question why or else, you can Klap your *** good-bye!
I can't help it , I'm KOL (Klapping out loud!)
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LOL for reasons I won't discuss!!
Ours is not to question why or else get whacked by the Klappenstick.
Dean,
IKMAO! (I'm Klapping My *** Off!)
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Thanks, Neil. That's a very good idea. I got lost there too with all the pictures, plans, sidetracks, etc. I'll do a part two.
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With an Fs of 25.7hz, and Qes of .38, it dosn't meet satisfactorily Keele's figure of merit for bass horns.
Fhm = 2Qts/Fs (mass roll-off frequency, must be around 300hz and above).
Like the K33, it is not a good match for the Khorn, according to Keele. But they both work well with a 3 x 13 throat.
http://forums.klipsch.com/forums/627507/ShowPost.aspx
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Here's a very good find for you, DrewB,
The SK's woofer driver, the W1508S.
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Last. The bolt pattern, I believe is the same as the K-33, I'm not sure.
radius folds, c) undersized Vb, d) front-loaded, sealed back chamber.
Should I build University Classic or La Scalas?
in Technical/Restorations
Posted
Dana,
I like that light/mirror analogy you have. I thought for a long time that horns can be like reflector telescopes in reverse. If all the reflectors in a folded horn are changed to mirrors, and they are set up in the proper angles, and you're standing in front of the folded horn looking through the mouth, then you should see the image of the throat.