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University Classic, Pictures & Drawing Plans


ajsons
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Internal schematic of the N3, if you are interested. This is from Cohen's book. I have a better drawing in my sketchbook, with actual part values used.

One more picture and I have to go, JC. Will check again when I come back.

Christmas party time. Merry Christmas to every body.

Armando

Good ole Abraham Cohen.

I dug in the attic until I found Hi-Fi Loudspeakers and Enclosures first printing in 1956.

My copy has many marks on the cover.....[;)] I cut my audio teeth on that old book in the late 60's. It was a great primer.

Regards,

Terry

EDIT: Looking at the book after 20 years; Old Abe displayed a degree respect for PWK. As a matter of fact, in my youth, I saw a pair of bastard Khorns at the Hope factory with a Cobra-flex and University tweeter. Must have been around '76-'78.

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Well, at least thats good - I know enough to know that Cohen designed the Classic!

I would like to read the book - where can I find one? Hopefully still in print?

DM

Dana,

Thanks for stopping by at my post. Now I feel like the thread just started. I sent you an e-mail.

I can only stay on line for a few minutes. (My son is in the hospital with a broken arm (skateboarding accident).

There is one book on ebay right now.

http://cgi.ebay.com/Hi-Fi-Loudspeakers-and-Enclosures-RARE-FIRST-ED-1956_W0QQitemZ5846527026QQcategoryZ50597QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Or you can try bookfinder.com, type the title or/and author. The price varies. Some places sell it for as much as $300.00 bucks. I was very lucky I got mine (first edition) from a bookstore in Ireland from the same website, they didn't know the US value of the book. $7.00 plus 12.00 for s/h. It is in like new condition. No tears, not a single pen or pencil mark.

There is also a second edition, laser copy being sold by torres1016@yahoo.com for about $19.00. I have both copies and there is lot of changes on the second.

Dana, I will post when I come home tonight.

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(I'm back from the hospital, my son will be ok.)

I'll reply to your first three posts in the reverse order. The easy ones first, then your horn design approach last .

Cohen's book covers a lot about horn theory and horn design, much more than "Building Loudspeakers and Enclosures" by Davis. About three months ago, bookfinder.com listed this book for $6.50. Now it is priced like Cohen's book. I have a torn copy and lost my chance to get a replacement for under ten bucks.

The Centurion has puzzled me. I can't find any plans for it. Twenty years ago I called EV and asked for a bunch of literature, spec sheets, plans, etc.they sent me a large package for free. At the time I didn't know much about their horns like the Patrician, Georgian, etc. I got the plans for those but not the Centurion. I found these pictures on ebay. Looks cool! But I can't figure out the folding. Maybe a forum member can explain it.

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Way TOO COOL, Armando!

The EVM 15B is going to suffer a bit by being in a too small back chamber which raises its Fs. I had a pair of them in some Klones in the 80's and same thing there too, but they are a great driver anyway.

The -3db point (half down) is approx. 43Hz for the 50Hz Fc.

I was looking some more at this pic (attached) which looks to me to be a modified Classic which is theoretically long enough to support a lower Fc than the stock one. It also looks to be ported, which I would be a little hesitant about in that the BC volume does not appear to me to be capable of supporting much of a low back chamber resonant frequency which would energize a low frequency tuned port. But if one was T/S+Keele designing around a particular driver with a low Fs and an extremely low Vas requirement (like a B&C), it could be fine as shown, of course.

However, as a front-loader (i.e., non-ported), it might be just the ticket to get the Classic legitimately down to the 40's with a couple of "adjustments" to the expansion rate... Something to think about.

Or is the University Classic "close enough" as it is without any additional fiddling? Would I love to hear one!

DM

What you mention here are exactly why I wanted to post this thread. I like the Classic very much, and have chosen to replace my SK's with them, but not quite sure which direction I will go.

I can build another one exactly just like what I have now, but beefed up (braces,etc). Or,

I can build the Dean, just like Q-mans, also beefed up (my original plan). Or,

I can build modifed versions of the above, (one) to reduce the size and (two) to improve the low end, if needed.

I haven't earned my horn design badge yet, and by picking your brain, and others on the forum, I like to come out of this thread with enough knowledge to improve on the Classic, or build a set of good horns. I know Andy and JC will be interested too, based on their posts.

I like the picture you posted. I was worried too about the volume of the back chamber of the EV's, but it looks like the driver end of the enclosure, (Classic and this picture) should be easy enough to extend to get more cubic inches.

How do you size the back chamber?

I am aware of Keele's formula for horns BC. Dr. Edgar has different volume recommendations based on whether the horn is eight-size, quarter-size, etc. I believe Bill Fitzmaurice uses the bass reflex formulas, I'm not sure. I don't understand his approach.

Abe Cohen has little info in his book. Dinsdale's formulas obsolete?

(I'll stop for now, I got more questions.)

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(I can't stop).

The more I look at that picture, the more I like it.

Referring to the factory plans, when braces were added to the Classic's doghouse, it reduced the back chamber into a little more than 1/3 of the original volume, but it looks like there was no concern for the volume in the first place anyway. As Steve Schell mentioned, gaskets were not used, and the hole for the driver wires was not sealed. The same is true with my Classic.

Here's MY understanding, or MISUNDERSTANDING of horns Fc. (This is a true or false test on my part).

Please tell me where I got it misconstrued.

Horns generally, do not go down to Fc (flare frequency cut-off).

Horns are designed with an Fc lower than the desired real cut-off (Cohen's approach..., if you want response down to 50hz, design a horn with a flare of 40hz)

The response down to Fc can be achieved by adjusting the back chamber (Edgar).

Drivers Fs must be close to Fc (Edgar..somewhat Cohen, too. Cohen looks at two numbers, the flare frequency, and the desired cut-off. Also, the mouth is terminated using the desired frequency cut-off, not the flare frequency).

The true cut-off is the -3db down point

Maybe when I fully understand this, I should be able to choose the best driver that fits the Classic, and maybe improve the low end.

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Ajsons wrote:

>Maybe when I fully understand this, I should be able to choose the best driver that fits the Classic, and maybe improve the low end.

Although I haven't digested everything in this thread, I think the Classic is a pretty cool beast. Is there a better bass driver for this application than the University C15W? I have a pair of those drivers and some other isolated Classic parts (Mid horn, crossover,etc) if anyone is looking for some of that stuff. At one point I thought I might build a pair of Classics, but as I've managed to acquire more big Klipsch than I can fit in the house (OK it's a small house) that'll never happen.

Best in horns,

Triceratops

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Tricertops,

I was trying to understand the relationship between driver's Fs, horn's Fc to come up with a driver that's best suited for the Classic. The C15W's Fs is 58hz, the Classic's Fc is 50hz . Maybe a driver with a lower Fs will be a better choice for it, I don't know. Right now I have an EVM-15B in it. I have to do more tests.

I personally believe that the C15w and the other components of the Classic are very good drivers, although I have not tested (don't have) the HF-206 tweeter. I have the Cobreflexes, but they're waiting for final sandblasting.

You may want to consider this University system. It doesn't take up as much space as the Classic. It uses the same components.

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Daddy Dee,

Yes, that's a cobreflex in a University Classic...That's the normal configuration of the Classic. Thanks for the interest on my avatar and this post. My cobreflexes are halfway thru the sandblasting process for a new paint job. I had to borrow the top from my SK for this thread. Here's the Classic with the grille off.

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DaddyDee,

There must be something interesting about your choice for an avatar.

Yes. This particular graphic is lifted from Disney's film production of C.S. Lewis' "The Lion, The Witch and the Wardrobe. Disney's production is titled "Narnia". IMO Disney does an excellent job of retelling a powerful story. I saw the film over the weekend and think it is worth the price of admission. As familiar as I am with the text of the book, I wasn't expecting to see the movie and think, "Wow, they did a great job!" Trying to communicate a book in the relatively few pages of a screenplay is often a task too difficult to achieve, IMO.

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I haven't seen it but I can tell it made a big impact on you.

These avatars really speak our minds in a silent but powerful way. It probably has been done before, but a thread on meanings of member's avatars and usernames will be really interesting and entertaining.

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A forum member has asked for the specs on the EVM-15L.

Drew, this and the EVM-15B are not really rare like you said. They were discontinued, but you can still find them. The C15W is older, but there is always one or two on ebay.

Here's the first sheet.

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