Should I build University Classic or La Scalas?

[ajsons]

Bill,

I don't have a pair, but here's one with a grille.

[ajsons]

without the grille, but with EV mid & tweeter

[ajsons]

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

[Duke Spinner]

other than the obvious K.H. ...

I wonder why PWK chose to use the "W" design, or dual throats for most speakers

[Quisitive]

other than the obvious K.H. ...

I wonder why PWK chose to use the "W" design, or dual throats for most speakers

Ummm . . . obsession with his middle initial? . . . symmetry of design?

This is actually an intriguing question, but my knowledge is so limited in this area that I have no idea.

Would love to learn more, though.

[TRiv]

Could it be to keep the horn cabinets to a more WAF acceptable size? I have been following several of the posts on the University Classic, and after loosing ebay auction last night for 1954 Khorn bass bin ($285 + $140 shipping) then reading this post, the Classic cabinet looks like a better alternative. Have EV KD-2 plans and was going to go that route but considering Classic design. Question, I would like to build Classic cabinets and transfer 1977 Cornwall components (cabinets are in fair cond. parts like new), all stock except for 511B horn, any problem here? The Khorn using the K33E woofer uses 3"x 13" slit on compression chamber, would this be used in the Classic design (opposed to the 6"x13"). Would also use the Cornwall type B crossover, then upgrade to type AA crossover, thoughts?

[Q-Man]

Question, I would like to build Classic cabinets and transfer 1977 Cornwall components (cabinets are in fair cond. parts like new), all stock except for 511B horn, any problem here? The Khorn using the K33E woofer uses 3"x 13" slit on compression chamber, would this be used in the Classic design (opposed to the 6"x13"). Would also use the Cornwall type B crossover, then upgrade to type AA crossover, thoughts?

Slow down.

The Classic bass horn is only good to around 350Hz. I measured it once, but I don't remember the exact number. That information is with my old notes. I also believe that the University crossover is also at 350Hz. The Cornwall midrange horn won't go that low. I think the Cornwall had a 700 Hz. crossover point. The Corbreflex midrange horn in the Classic is a 250Hz. horn.

The K-33 can be used in the Classic, but I think the C-15W sounds a little better. Again, I did this a while ago and I don't remember why I like the C-15W better.

You guys are going to make me want to get into this project again. I left it with knowing that the Classic suffers from an inferior midrange and tweeter just like the Klipschorn and LaScala. I took my Klipschorns to another level by changing the midrange horn and driver along with the tweeter and network. It may be time to pick up where I left off. I would also want to find a current woofer close to the C-15W so people could buy them.

I would still suggest building the Classic with all the original drivers and network. They were cheap on ebay when I was buying them. You should listen to the speaker the way it was designed to sound before you decide to change it.

I once sold a guy a pair of LaScalas, and before he left he asked to hear the Classic.

I thought that he was going to cry, and also be angry with me for not letting him hear the Classic first before he bought the LaScalas.

[D-MAN]

Yes, the Dean is a very interesting design. But its as wide as the Khorn bass horn is tall - it's only drawback for me!

Some thought about the hard full-channel ("Huygen") reflectors vs. none or radius (partial channel) wedges.

The Classic, in particular (the rectangular one) and the LS (and the Jubilee) have 90 degree untreated corners in the horn path (the Jubilee uses radius type reflectors there!). This is fine for bass horns that do not go much above 200Hz, like a subwoofer as long bass wavelengths do not particularily care. As notes on another forum, that was fine THEN for Abe Cohen & University who was limited to the University 15" driver which fell off rapidly at 300Hz. Crossover at 250 and call it good - but now we have new drivers available, and we would all prefer a higher crossover point.

However, for frequencies above 200Hz, the use of reflectors is manditory in my book, and I mean full-channel hard surface reflectors, not radius-types, which produce 180 deg. reflections back to the source, not at all a good thing.

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

[ajsons]

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

[ajsons]

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.

[D-MAN]

other than the obvious K.H. ...

I wonder why PWK chose to use the "W" design, or dual throats for most speakers

He definitely had a marked preference for symetrical bifurcated-at-the- throat horns, with the standout being the "Little Bas***d" in the 70's, the only PWK design that is an entirely unitary channel horn from start to finish. Better known as a bifurcated-throat horn (or butterfly throat). The "W" pattern of folding is perhaps better applied to the LS rather than the Khorn, mainly because the Khorn is reentrant (folds in 2 directions opposite to each other) and the LS is not a reentrant horn pathway.

The University Dean and Classic are not reentrant, have 90 degree turns (at most) and unitary horn channels which reduces the number of folds to 3 total (the Dean is perhaps the best design for its Fc) as it reduces the number folds to 1 and that is in the throat.

There are some very sound ideas behind bifurcation, though. The first being that the horn folds have to occur BEFORE the horn channels cross-section reaches 0.6 of a wavelength to avoid 180 degree reflections, and of course, smaller channel dimensions means a longer distance before this comes into play.

The second is that the respective channels are small(er) and that makes for a reduced footprint size and a throat configuration of narrow dimensions.

The third is that folds themselves work best when the dimensions across the fold is small.

All of the above reasons are very sound physical solutions and allow for a relatively long horn length in a relatively small space.

If any of you are thinking that the University horns MAY be the cat's meow, it should be noted that they are at best 50Hz Fc horns, good to 43 Hz F3 (-3db) at the most under the best of conditions. Also note their great size, they each take up more floorspace than a Khorn, and don't go as low (an OCTAVE!). There are certainly some tradeoffs to be considered.

Where they could outperform a Khorn is in the apparent speed of transients (drums, mid-bass, vocals) with the attendant "punch" and convincing authority of an A7. I would expect the efficiency to be on par with the Khorn, but that depends on the driver employed. Perhaps it was performance-to-size ratio (and visa-versa) for why they went extinct in the first place. The point being, that if you are willing to sacrifice some floorspace, how about an extra octave of LF to go with it (i.e., a Khorn)?

However, I have no doubt that they could be very delicious to listen to if one can live with their size and crosses them over properly.

DM

[ajsons]

Where they could outperform a Khorn is in the apparent speed of transients (drums, mid-bass, vocals) with the attendant "punch" and convincing authority of an A7. I would expect the efficiency to be on par with the Khorn, but that depends on the driver employed. Perhaps it was performance-to-size ratio (and visa-versa) for why they went extinct in the first place. The point being, that if you are willing to sacrifice some floorspace, how about an extra octave of LF to go with it (i.e., a Khorn)?

However, I have no doubt that they could be very delicious to listen to if one can live with their size and crosses them over properly.

DM

Tasty!

[ajsons]

There are some very sound ideas behind bifurcation, though. The first being that the horn folds have to occur BEFORE the horn channels cross-section reaches 0.6 of a wavelength to avoid 180 degree reflections, and of course, smaller channel dimensions means a longer distance before this comes into play.

The second is that the respective channels are small(er) and that makes for a reduced footprint size and a throat configuration of narrow dimensions.

The third is that folds themselves work best when the dimensions across the fold is small.

All of the above reasons are very sound physical solutions and allow for a relatively long horn length in a relatively small space.

DM

Sound solutions that are very sound, indeed! Bifurcation, inside the horn based on the above, is ok then.

The La Scala, like the Klipschorn, is bifurcated, with a single mouth. The Klipschorn has two separate smaller mouths, separated by the enclosure. What happens to the wavefront here at exit time?

[D-MAN]

We are getting into the idea that "bass notes" are not particularily directional, aren't we? It depends on the circumstances.

The splay angles of the Khorn mouth influences the high frequencies that can be transmitted, but at the relatively low frequency crossover point of 400Hz, it is not as critical. The higher the upper frequency passed, the more instance of comb-filtering becomes apparent being that the normal 6db slope allows the midrange to produce the same frequencies in the overlap, and the different angles of pathway dispersion becomes apparent as the two pathways intersect at least once somewhere between the horns and the listener.

Note that the Jubilee was designed for higher frequency crossover, so it has more "direct" bass horn mouth splay angles, and even so, I would suggest that 6db first order crossovers would also not be appropriate as a guess, based on my experience with the Khorn-style splay angles (my horns have Khorn splay angles).

Bottom line is, bass-wise, the mouth splay angle(s) is sourced as 2/pi solid angle and is not considered to be reflected sound. That is, the incident angle is the same as the corner walls and there are no reflections in that case. The alternate example is that if a LS (having a single mouth), placed in a corner as far as possible would entertain some cabinet diffraction and wall reflections to a noticable degree because of the angle of incidence.

However, it could conceivably use a higher crossover point, and produce better mid-and-upper bass with less coloration due to the more-direct path from the horn mouth to the listener, at the expense of the lower frequecies due to diffraction and reflections exactly like the Jubilee, the Jubilee being the better compromise between the two horn mouth examples.

Here is an example of the Gately "Super Horn" rear-loaded corner horn that entails perhaps the best of both worlds as far as using the 2/pi steradians placement to greatest effect.

DM

[D-MAN]

Here is another one of my favorites. This is Rice's rear-loaded corner horn patent #1 (he did 2 different corner horn patents) that exhausts upwards in the corner. Pretty unique and has its points...

However, it remains that the upper-frequency response provided by a more-direct pathway is not part of the intention of the design.

One of the things to remember is that most bass horn designs rarely every attempt more than 3 octaves from the Fc of the horn. Occasionally 4, but usually only 3, which means a crossover point of between 300-400 Hz is pretty much typical.

DM

[ajsons]

We are getting into the idea that "bass notes" are not particularily directional, aren't we? It depends on the circumstances.

DM

No, I was still in bifurcation versus single path thoughts.

For a while there, after reading the University ad I posted earlier, I was asking myself what kind of tradeoffs are there when you bifurcate the path? Do you mess up the wavefront? If you do, how do you get it back together? Shall I stay away from bifurcating the horn path?

Now, I understand. It seems like the more I learn about horn design, the more I find out that there is very little I know.

[D-MAN]

I do not particularily see a reason for bifurcating the throat of the Classic. What are you seeking to do? Does this have anything to do with the horizontal brace that we talked about? It won't harm anything at all, if that's a worry. It actually is not bifurcating the throat per se, anyway. The axial length is the same as the center of the throat channel, and the two halves of the throat channel divided by the brace are exactly the same.

BY the term bifurcated, I am implying that it becomes 2 separate exponential channels, such as in the butterfly-style throat. In the case of the brace, it is simply there to prevent channel wall vibration. It performs no baffling purpose in the horn channel itself and does not alter the waveform whatsoever. This is because both of the "sides" of the dividing brace are equal, as is the throat cavity opening "feeding" them. Therefore, the waveform is equal - as if the brace wasn't there at all. No effect on the waveform whatsoever.

For example, the Khorn has a center-of-throat brace running vertically from top to bottom. It is technically NOT part of the horn itself, although it sort of looks like it creates 4 HYPERBOLIC horns out of the throat's 2 exponential ones - but it doesn't!

So, employing an axially oriented brace across a horn cross-section is not the same thing as bifurcating the horn channel (even though it is two distinct sections) - both sections are mirror images (opposites) of each other, and are therefore STILL A SINGLE UNITARY CHANNEL because the size of the waveform in the braced channel is unchanged and is an image of the original waveform.

On bifurcation, Harry F. Olson was referenced by PWK in the 1945 KHorn patent as stating that two of more channels of equal cross-section and expansion can be effectively "split" and put back together without any discontinuities, providing everything adds up to a single "correct" horn channel.

In general use, it depends on where you want to bifurcate the horn channel - for example, the JBL Hartsfield uses a unitary throat and pathway until it bifurcates at the tailboard into two Khorn-style terminal horn sections.

The large Tannoy rear-loaded corner horns also follow this approach, although they bifurcate somewhere closer to the throat. But it has to do with the exit channels forming the mouth rather than the throat design.

DM

[ajsons]

I do not particularily see a reason for bifurcating the throat of the Classic. What are you seeking to do? Does this have anything to do with the horizontal brace that we talked about?

DM

No, I have something else in mind. I was trying to see the possibilties of reducing the size of the Classic, especially the depth. I can live with the 30 inch width, and 40 or higher height, but 24 inches sticking out into my den takes up a lot of space. There is nothing you can really do to reduce that if the initial path is shooting to the rear of the enclosure but if I shoot it to the side, like a Belle then I can reduce the depth.

See the attached picture. Imagine the Classic with La Scala doghouse on its back tilted 14+ degrees, with the rest of the path of the Classic. The drawing is on its rough stage, I have not shown the other pieces of the bifurcated section. I think it will work. The name BTW, brings back memories of my college years.

[ajsons]

Woffer access will be to the rear, (I have not shown that), unused space around the throat area will be sealed and opened to become a part of the woofer rear chamber. Dimensions, especially the path expansion will be kept identical to the Classic, what I lose in depth I can regain in height, if there's any.

[ajsons]

Is it a bad idea?