Jump to content

University Classic Part 2 Driver Specs & Mods


Recommended Posts

(That last post you did only shows a square with an x for a picture. Your room layout too on the other thread shows up the same way. It might be my pc, because others have seen your pictures. )

I've seen that "corrected" drawing, and a big thank you. I'm not sure yet what were corrected.

That hifilit website sure has a lot of good stuff.

Here's a 4401 tweeter, some Classics came with it. The HF-206 is a better tweeter.


Link to comment
Share on other sites

  • Replies 40
  • Created
  • Last Reply

Top Posters In This Topic

While ajsons is busy drawing his plans, I thought I would introduce the topic of material for the enclosure.

I believe early Klipsch products were built using domestic 7-ply birch plywood. I notice that the new La Scalas have 1" MDF walls, I suppose the sides but maybe the back as well, while keeping the internal walls at 3/4" plywood.

In talking to different people across the forums, the consensus seems to be 13-ply baltic birch. It's certainly the densest of the available plywoods, but today's samples invariably have "cats eye" patches on both sides, so it's quite difficult to find a nice face. Another factor is it comes in (roughly) 5'x5' sheets instead of 4'x8'.

I've used some 11-ply, 3/4" "birch" plywood that's made in China. Early samples from Home Depot rivaled some of the best 7-ply, cabinet-grade domestic birch I've seen. Lately though, all the samples I've seen are made from "mystery" wood, warped all over the place and not very usable in general.

A couple of days ago I was able to visit a local hardwood and plywood distributor that has a small retail operation for hobbyists. The selection they had available was astounding. It wasn't on display, either. It was only when I brought up my impending project that I got an impromptu tour of the warehouse. Unbelievable. You would have never known what all was available.

They had about 300 sheets of the 5x5 Baltic birch. Dead flat and good structure, but the faces weren't very pretty and they had plugs on both sides. So unless you're going to use paint as a finish, or veneer, it wasn't too appealing. Especially with the potentially low yield of 5x5 sheets depending on the eventual dimensions of the enclosure.

As we were walking around, he pointed out some other interesting stacks, including 4'x8', 11-ply goods from China. There was the usual birch, but he also had flat cut, book-matched beech. Talk about nice! He also had oak, alder and Honduras mahogany. This was definitely *not* the stuff you would find in the big boxes. their main clientele are cabinet shops and custom contractors. They ship out three 18 wheelers of goods every day.

So long story short, here are the prices I found here in Texas:

Big Box, bad 4'x8' 11-ply "birch" $32.00

Distributor-sourced, "good" 4'x8' 11-ply "birch" $34.00

Distributor-sourced, 5'x5' 13-ply Baltic birch $35.00

Distributor-sourced, 4'x8' 11-ply Oak, Beech, Mahogany $54 - 60.00

So if you do the math, the local, big box stuff runs about $1.00 per foot, The good stuff will cost just a bit more, but it will be less convenient for you to get it. Good grade Baltic birch will cost you about $1.50 a foot, and the really nice face wood, which is 11-ply, will set you back as much as $2.00 per foot. If you go to 7-ply you can get even more choices, but then you need to worry about voids in the laminations and a lot of times, the interior plys will be "hadrwood", but generic, so the density may not be that great.

There's a reason so many speakers are made of MDF these days. It has high machinability, especially if you use CNC machinery, it's available in all kinds of thicknesses, it's engineered to be flat, and it also has incredible density. The density leads to damping. Some people think the damping sounds "dead". I think it depends on the design of the enclosure and the matching of drivers. It's also a wonderful surface to veneer, but it sure is heavy! Especially if you're a one-man shop!

We never got around to the "sound" of the enclosue, which I 'm sure can be a lively debate based on similar threads I've seen before. What would be more interesting is taking a look a density as it relates to damping and structural flex. Sometimes those aspects don't seem to get brought up, at least on other forums. Since this is more of a horn-oriented forum, this may be a subject that's beat to death. Since the search function doesn't seem to go back very far, it's hard for me to tell.

I haven't even thought about cutting schedules yet. We'll leave that for later, at which time we'll have a better idea as to how many sheets will be required.

Hope these little rambling thoughts have been of some help.


Link to comment
Share on other sites

  • 8 months later...

Saw your post on the University Classic, and then followed the thread back. These are great!

I built a pair of these, and loaded them with Eminence 15" drivers. The upper end is EV DH1012 on EV HR9040A horns. This is a magnificent combination. Absolutely stunning! I biamped this setup with great results.

I then picked up a pair of Speakerlab K's for a song. Changed the drivers to EV15's, no joy. Changed to K33E's, and found bass, but the response was really peaked in the midbass area. Installed a Type A crossover, and viola! I had that Klipschorn sound that I was after. I still like the mid and top end of the Classic's I've built, and I'm about to fit EV HR90's (little brothers to the HR9040's, which are simply enormous) to the top of the K's. This ought to settle it, really. The HR9040 is gigantic for home use, but, ohhh, the sound...

The classic is a great design that performs very very well. I would guess that loading these with K33E's would be even better; I would expect NO issues in the 300-400 Hz range, based on what I heard on my K's.

Anyway, nice to see this.

Link to comment
Share on other sites

one Karlson builder tried to improve S9 - think he pretty much decided it was good from the getgo.

whcih Eminence spec do you have in Classic?

I've got HF6040 but not been able to try them - wonder if they'd ly decent with Altec 806 wiht adaptor?

re:T30 I need to find some for Karlson tubes

Link to comment
Share on other sites

And here's an HF-206. There are better tweeters nowadays, but during its time, it was probably one of the better ones. Again, it's a good-looking tweeter, but I will only get a pair, if the price is right...cheap.

I have 2 hf-206's brand new in a box. One Box I opened, the other came opened. What are these worth?

Link to comment
Share on other sites

The part I'm using is an Eminence 151311:

Qts=0.31, Qes=0.32, Fs=38Hz, 8 ohms, Vas=299Liters, die cast frame.

This set of T/S pars is ordinarily characteristic of a driver that is suited to horn loading.

However, I wonder how the K33E will do in this design (that is, I'd like to hear this); I know the T/S pars on this woofer, they've been published many times. But, I suspect that the K33E has a rising (or at least shaped) frequency response, when measured on a baffle, in order to offset the attenuation experienced in the folded corner horn. This is why I suspect that the K33E will almost always be a better bet in almost any folded bass horn design; the folded designs always suffer in the 'mass roll-off' range of the driver, and will struggle to get to 300 Hz or higher in an acceptable manner. I'd love to see a K33E response plot, if anyone's got one. I'll bet its response is tuned up this way.

The University Classic does a better job than most folded designs in the upper end of the bass because the folding is less re-entrant.

This Eminence driver works pretty well in the Classic. On top, I have the HR9040/DH1012 being driven at around 350Hz on the biamp setup, using 24db slope crossover, and in home audio environments, the driver tolerates this just fine.

There are alot of the HR9040's running around, for a song. You just need to find 'em locally, because they'll cost you twice what you paid, by the time you get 'em shipped, because they are so unbelievably large. The DH1012's are likewise available for not a lot of money, and they are a pretty credible driver. One thing: the HR series horns are 1.4" throats, so your driver choice is going to be limited a bit, although one can use adapters and run 1" drivers (finding 1" drivers that will go to 3-400 Hz is another challenge, though, unless you are looking at the K55/Atlas types).

When Keele first published on this new design in the 1970's (AES, 'What's so special about exponential horns?'), he noted the similarity of this design to the midrange horn PWK patented in the 1950's- you know the one: the pretty big radial type design that you see on the 1950's vintage KHorns. Anyway, EV's early HR series are the ones that started the whole industry stampede toward so-called Constant Directivity designs, with the industry trying to reduce the overall envelope of the horn to accomplish the same ends. But, physics will, in the end, have its way. The early HR series sound awfully good; if they're big, well, that's the compromise that must be wrought.

PWK is on record about the trials and tribulations of the midrange on the KHorn, and the struggle to get it right, and at an acceptable production cost. I would guess that the reason the K400 horn was introduced had more to do with production cost than it did with sound properties: the older, radial type design had to be significantly more expensive to produce. Mods like the Trachorn are appeals to deal with the directivity issues that have always plagued classic exponential, and especially cellular (lobe issues) designs. This is why I am going to use the EV HR90 on the KHorn; I'd LOVE to use the HR9040, but, this thing is too monstrous to integrate into the overall envelope (e.g., for reasons of domestic peace, I'm going to the HR90...).


Link to comment
Share on other sites

You are very knowledgeable about EV products, if could ask a question?

I have a couple of EV 1828R mid drivers mated to 8 HD horns (look somewhat similar to K600). They came out of a set of old PA monitors, I had them mounted in a CW type cabinet with EVM15L and T35 tweets at one time.

Would these be better mated with the Cobraflex horns? Or are they pretty utilitarian?


Link to comment
Share on other sites

I don't know too much about the 1828R, but I have attached the EV datasheet on this driver, which clearly indicates that this driver was specifically intended for re-entrant PA style horns like the Cobraflex. I would guess it is a good match.

It's curious how this driver ended up on an 8HD, which is, if I recall, an 800 Hz type horn. The 1828 goes much lower, which is why it is suited to things like the Cobraflex.

The Cobraflex was used on the University Classic BECAUSE of the difficulties in folded bass horn/drivers making it to 300-400 Hz in an acceptable manner.

I have never heard one of these (knowingly, critically), but I would expect, due to the re-entrant design, one would see some interesting response characteristics as the frequency moves up (e.g., phase cancellations in the turn, when the frequencies/wavelengths are on the order of the size of the turn dimensions). Probably best to cross it out lower than normal and let the tweeter take up the slack.

On the other hand, it may be pretty good over a fairly wide range, response-wise; the issue will be the choice made by the designer with respect to where the bend occurs. Radiation pattern will be another issue. Anyone got polar plots on the Cobraflex?

1828R EDS.pdf

Link to comment
Share on other sites

151311 was madisound's $80 edgewound 15 and EM's spec said xmax ~2mm vs Mad's larger spec - I don't have a loose K33e as seemed lackluster jump-factor wise in Karlson boxes vs things like Altec 421. IIRC K33E has a fairly straight-sided cone. 151311 probably has curvlinear SP15 style cone with a peak around 2Khz (?). I think K33E is kinda missing in action on the top in k-horn but never put one in FH1 to find out. there should be plenty of graphs for K33e on these forums (???)

If i ever feel up to it I'll pull k33E and plot in a 3.6 cubic foot reflex vs a woofer kinda like 151311.

EM's specs for 151311

02-PART # 151311

03-MODEL # 1525F8037

05-RE OHMS 5.62 13-FS HZ 40.35

06-LE MH .68 14-MMS GMS 52.98

07-QM 4.80 15-CMS mm/N .2937

08-QE .350 16-RMS NS/M 2.7959

09-QT .330 17-VAS LTRS 302.47

10-XMAX MM 1.80 18-SD SCM 856.34

11-BL TM 14.59 19-EBP 113.7

12-EFF % 5.40 20-SPL dB 99.3

re:K400 - its that old expo flare logic with length truncated back from mouth. I think time issues at xover points might be audible too along with basshorn resonances.

inroom bassbins - Sentry/1298 vs K-horn K33E

heres the modest EBP pym1298 in Sentry IV vs K-horn with low EBP CTS K33E. an EV12L might have more top yet than the pyle/eminence

Posted Image

here's a cobraflex graph outdoors - I think on and 30 degrees off axis with 1829 driver, 16R in parallel and 50uF. IIRC they get weird used up real high with honks and HF seeming to hug one wall

Posted Image

Link to comment
Share on other sites

Hello Freddy:

Thanks for the plots- they clearly show how the KHorn is about the only game in town to get that last octave deep with a horn in a reasonably sized package. They also show the superior ability of a design with much less re-entrance, like the Classic, with respect to the upper end bass response.

The data you have on the 151311 is nice to see; I have an older EM datasheet that Madisound published with the 151311 (which is where I bought it), and the parameters I gave earlier came from this sheet. I would expect your data to be more representative of current production. These were bought about 4-5 years ago, and sat until I had time to build these bad boys, about a year ago or so.

Good point on the EV12L having potentially more on top; I have a couple EV15Ls that I might just put in the cabinets to give a look-see.

Hope your health is better than you expect. That's not fun at all.

Link to comment
Share on other sites


Missed that altogether! Hmmm. Maybe I need another cup of coffee.

Your remarks on the sound in the upper register are not entirely unexpected, are they. The off-axis response tells this pretty well.

I am a little surprised that they don't show stronger performance at the low end. But, I have not seen a plot on the Cobraflex before. Yours is the first I've seen.


Link to comment
Share on other sites

Cobraflex has slow flare but not much mouth - wonder how it would do/sound with a curved or "V" baffle to offset teh diffraction step?

FWIW heres (probably defective) EV driver on thriee horns in-room with cap highpass. Impedance interactionss with xover must play a roll - SM120 looks like its in trouble.

Posted Image

Link to comment
Share on other sites

Thanks for the spec sheet- wow that driver of mine goes down to 200HZ!

What does 'reentrant' horn design mean? Apparently the 1828 was intended for full range vocal reproduction in outdoor PA settings. But you're right, the 8HD is the wrong horn for this type of application.


Link to comment
Share on other sites

Re-entrant means that the horn pathway passes next to its previous section in opposite directions on its way from the throat to the mouth. The Khorn, as an example, is therefore re-entrant but the La Scala is not. Almost all modern brass instruments would be re-entrant, also, like trumpets, trombones, and even saxiphones, etc.

In other words the pathway contains at least one 180 degree turn (or a number of lesser angles that add up to 180)...


Link to comment
Share on other sites

No, it is related but not quite a true "W"-pattern horn. It is more of a "U" pattern, IMO.

As far as including the distance between the actual cone and the baffle throat opening, that is not considered part of the horn channel per se. At best it is a non-expanding column of very short length, and at worst, a front compression chamber which varies its volume with excursion and frequency.


Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...