University Classic, Pictures & Drawing Plans

[ajsons]

Schematic Diagram N-3 crossover hookup

[ajsons]

A shot of the N-3 crossover, without the pots. First reaction......Where's the beef?

[mungkiman]

plans for the rectangular box:

[mungkiman]

and the corner version:

[ajsons]

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

[mungkiman]

another interesting animal:

[ajsons]

Mungkiman,

I redrew the corner version in AutoCAD to check for accuracy. There's a lot of errors on that one. The compound cuts don't line up. I promised Qman I'll send him a corrected copy, but can't find the time right now.

Well, right now , I got to go to a party. Will post more pictures tomorrow, hopefully I'll find the spec sheet for the C15W.

Armando

[mungkiman]

good to know.

there is a lot of helpful info at www.hifilit.com

[jwc]

guys thanks. i can read them fine. Will try and print them out tonite.

jc

[Klipschguy]

Those plans will be quite helpful. Thank you for taking the time to post. I seem to recall Q-man saying he really liked the University Classic.

Andy

[DizRotus]

Andy-

Would you build one of these?

BTW, I enjoy those RS-40-1197s daily. Someday I hope to return the favor. Thanks and Happy New Year!

[ajsons]

I believe there is a third sheet to this. Drawings normally come with a materials list, and somewhere on these plans, a finish table is mentioned. So I think we're all missing a third sheet. We do have enough information though.
My Classic does not have the braces these plans are showing. Three braces were added to the drawing revision in 1969. (The ebay seller (a nice lady, BTW) told me my Classic was built in the late 50's). The drawing shows two triangular braces in the doghouse, dividing the doghouse into three sections. The third brace is behind the doghouse.

The braces are a must! There is too much panel vibration (panels are 3/4 plywood) due to the bass energy! The SK's built out of 1/2 plywood do not vibrate like this one. The three added braces I don't think will be enough. And if I build them they will probably be 2 x 4's in the doghouse. I will add braces to the side panels, or double up the plywood material.

Rather than me blabber about the rest of its construction, here is a quote from the Audio Asylum from Steve Schell.

http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=4519&highlight=This+past+Friday+I+hauled+one+cabinet+with+bass+driver+University+C15W&r=&session=

Posted by Steve Schell on October 30, 2000 at 00:15:13:
In Reply to: Abaham Cohen's University Classic Basshorn - Anyone here built or heard one?
posted by freddyi on October 29, 2000 at 08:37:15:

Recently I purchased a pair on ebay from a seller in Idaho. These and several others had
been pulled from a dumpster after being placed there as part of an auditorium remodelling.
Anyway, these were built in 1974, had unfinished birch cabinets, and contained all the
original drivers and crossovers. The seller has sold all that he had; many cabinets were
badly smashed, so he parted them out and sold the drivers.

They were impressive on first listen, after correcting some driver phasing problems. Very
lively, dynamic bass, more extended than I would have expected. Everything present except
the extreme, below 30 hz. shuddering pipe organ fundamentals. I then stripped them apart,
patched, sanded, and finished the cabinets a medium walnut (in part to hide the remaining
flaws).

This past Friday I hauled one cabinet with bass driver (University C15W) installed over
to Dr. Bruce Edgar, as we both wanted to measure this design. Nearfield frequency response
was quite good, remaining within a 5dB window (plus or minus 2.5dB) from 55hz. to 300hz.
and sloping off fairly rapidly from those points. Not bad at all for a front loaded horn
of this size. I believe Dr. Edgar had previously calculated the design to be an exponential
50hz. flare.

Today I hauled the completed Universitys to my brother's house, to upgrade his hi-fi/video
system. We began listening after they had been installed on either side of his new big
screen TV. His room is quite a bit larger than mine, and built on a concrete slab, whereas
mine is not. I was not prepared for the fabulous bass they provide in his room. After
working through a few CDs, we put on his laserdisc of the film "Backdraft". The speakers
handled all the explosions, elevated trains passing through the living room, and other
heart pounding sound effects with effortless ease. This quality of natural, lifelike,
realistic low frequency reproduction seems to be available only from front-loaded bass
horns in my experience, and these speakers confirm my belief even more. I believe that
Mr. Cohen's grand design is a real sleeper and due for a comeback.

A few details: the construction of these cabinets was sloppy in some respects. Nothing had
been done to properly seal the rear chamber. Particle board dividers on either side of the
driver divided the cabinet's central triangular section into three sections, the larger
center section containing the woofer. These dividers were improperly cut, allowing unsealed
gaps of as large as 1/4" to the side, waste sections. I sealed the rear chamber carefully.
The board allowing access to the woofer had not been gasketted, and the boards in contact
with it were uneven and did not permit a tight fit. I planed these down as necessary and
added a gasket.The board had been installed with an inadequate number of too - short
screws. I added more, and longer, deck screws.

The Cobreflex midrange horns and drivers look like they should be installed at the airport,
but they perform well. I'm going to stick with my RCA theatre drivers and multicellular
horns, but these Cobreflexes are not bad. Ditto for the tweeters (forget the model number),
which look and sound a lot like EV T35s. The stock crossover contains two iron core inductors
for mid and high frequency level. After adjusting driver levels, the system blended together
very well.

The strongest attribute of these systems is...that bass! Hope this info helps.

----------------------------------------------------------------------------------------------------------------------------------
Armando

steve schell on classic.txt

[ajsons]

I have a copy of Q-man's post about the University speaker he built, but I'll wait before I post it, he might chime in.

Q-man,

I'm sorry I haven't redrawn the plans. Recovering from the hard drive crash was just too much for me, I lost a lot of AutoCAD files. I learned the lesson, though. Back them up!

[Klipschguy]

Neil,

Yes I do plan to build some type of bass horn in the future. I have a recycled M&K subwoofer amp (I replaced the electrolyitcs in it) and a lovely square magnet K33 in my shop. The K33 and M&K amp have been begging me to drop them in a folded bass horn to go with a rather dynamic pair of stand mounted satellites I built about a year ago. The Unversity classic design looks pretty good. "The scoop" is another. Armando's experience with U. Classic is pretty compelling.

I would like to retrofit the folded horn design to a modified furniture cabinet so it will blend into the room without drawing attention to itself, visually. An antique radio console cabinet might fit the bill.

The design/idea really needs to be tested before building it. I was planning to hook the M&K amp up to my friend's La Scala bass horn and then run my satellites on the L+R channels of his amp to see if the sound is what I'm looking for. Better to bail early if the idea is flawed.

I've never heard of hooking up a sub amp to a bass horn - it might be a terrible idea. Anyone?

An additional sub could also be used to pick up where the U. Classic leaves off.

Andy

P.S. I'm glad your backloaders are still giving you listening enjoyment.

[ajsons]

The day after Christmas, I took the C15W out and replaced it with an EVM 15B, the "brother" of the 15L which is in the other channel. The 15L has a brighter sound, the 15B has a traditional bass guitar sound (honestly I can't tell the difference) and the specs are almost the same. The bolt patterns of both EV's are the same as the C15W. Now, the drivers are nearly identical between left and right channels, leaving the horn enclosures as the uncommon denominator.

It didn't change the order of things!

The C15W has an Fs of 58hz, Qes of .22. I think the EV's (Fs=43hz) are more suited for the Classic which has an Fc of 50hz (per D-man and Egar's estimates.

I need to ask D-man's opinion on this.

Armando

[formica]

Armando...

Glad you posted a pointer in DMan's thread i almost missed this

post. University Classics have intrigued me for quite some

time... []

ROb

[ajsons]

It looks like everyone else had stopped by to take a peek, except Dana.

[D-MAN]

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

[D-MAN]

I also was thinking that the EV Centurion also has some relation to the University Classic. I haven't run across any plans for it per se, but the drawing in this brochure leads me to beleive that it could be closely related... It is somewhat like a Classic sitting vertically, in essence, albiet with a corner-style cabinet.

DM

[D-MAN]

Armando, what is "Cohen's book"? Looks interesting. I want one. Where and/or how can I find it?

DM