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Should I build University Classic or La Scalas?


Quisitive

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Chris,

I got your email. The picture of the HF-206 is perfect. I can insert that in AutoCAD and trace over it, as long as I have one good dimension. TNX a lot.

Did you get my email, though?

I forgot the dimensions of the room, so I'm guesstimating from the pictures you sent. But like what I was saying in my email, I think you don't have a problem. If you use the Classics as lowboys, butted against each other, with the mouths at the far ends, I think you will have enough stereo separation, and plenty of space left to open the door and use the printer. Place the stereo rack which is not that deep, to the left, or place your components on top of the Classics. There is a picture coming up with that setup, but I'll post some drawings first.

The Classics don't look that big when they have no grilles. That's the factory base shown, a taller one or legs might work out better for your setup.

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This last one, I told Dana that I will post under Updates and Mods, I'll just keep it here.

I call this one the "Electrogon", because I use mostly EV drivers.

With the butted arrangement of the Classics, cut the tops and the bottoms (when used as lowboys) as shown. Make a notch for a curved reflector. The reflector can be made from thin plywood, the kind used on kitchen cabinets, with back stiffeners. (This will be hardest part of the construction). (And I have the plans from another speaker to do it..).

Add some fancy legs..................................................

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Armando -

Got your earlier email and glad the picture of the HF-206 works for you.

These are some truly amazing designs! You are incredibly creative. I hadn't really considered going the low-boy route before now -- if it will fit.

As far as the dimensions of my room, I have exactly 10.5 feet along the wall I need to use. If the Classics protrude 24", I'm limited to 7.5' of wall space due to the bi-fold door on the left and my monster printer on the right. So if the Classic is 40" wide each, that makes 80", leaving only 10". Hmmm.

So I could consider the idea of using the tops (sides, whatever) of the speaker to hold components, but all of my current and future gear is tube. So I'm a bit concerned about vibration. Also for CD-transports and the occasional vinyl playing.

So this may not work. If I only had 12' to use, I think it would.

Oy yes, your last picture made me think of the University TMS-2 tri-mensional, which had horns on either side a single CW15 as a bass driver in the center. This was back in the days when consoles were all the rage.

Maybe I should consider you University Belle design. That's really been capturing my imagination since you posted your drawing. Show's great promise, even though I still want to build a pair of Classics.

Could be I need to go with something like the University Belle today, and a few years down the road when the kid is off to college, building something a little larger when I have more room. Just thinking out loud.

Armando, keep those thoughts and drawings coming. You're a great talent and resource.

Chris

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Maybe you guys should listen to what Q-man said. Otherwise, you're leaving a pretty big hole between 250 (290?) Hz and 600-700Hz.

Stick with the Cobreflex.

my 2¢

Chris

Chris,

Q-man doesn't have a Classic. He has a Dean.

I dissected the folding of the Dean twice, and translated the dimensions to a graph. The expansion starts very slowly at the throat, a little faster after the first bend, chokes off on the second, then expands like crazy at the last turn towards the mouth. It is not a smooth curve like a horn's expansion should be but a stepped arrangement of lines. What's the flare rate, I can't tell. The horn's folding looks good on paper. But it needs adjustments to improve the high end.

I disagree with Dana, with all-due respect, on the no-reflector requirement statement he made earlier about the Dean. It needs reflectors, real bad. Like I said earlier, if reflectors are mirrors correctly positioned, and you're looking into the horn at the mouth, you should see the driver's cone. It will never happen on the Dean, because there are no reflectors, other than the one at the throat. It also has the wrong angle. Thus, it is only good to 350hz.

Dana has a light mirror demo in an earlier post.

Earlier in this thread, Dana also said:

"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."

In the first Classic thread, we agreed on a center divider at the throat of the Classic, not the Dean, to prevent phase cancellations, a 47 degree reflector at the first bend, a change at the angle of the throat reflector and a slight change at the large reflector, all of which are aimed at improving the response.

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"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."

Can you tell me why the Cobreflex sounds so good with radius

reflectors? I would think that with a semi-spherical wavefront, 2 x 180

degree radius-type bends would sound good from 200Hz up to the range

covered by a tweeter. I might guess that shorter wavelengths would have

a tendency to "bounce back" into any type of 180 begree bend, but I'm

guessing.

I also really like your ideas.

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The difference is the Cobraflex uses full radius TURNS or CURVES in the pathway, not reflectors.

In a planar-surfaced horn channel (like a bass horn made out of plywood) for a radius fold, a partial channel-covering hard surface reflector across the channel is used. It actually defeats the purpose as the non-reflecting portion is a 180 degree reflector, and is more appropriate for air conditioning duct work than a folded bass horn!

If you could build a bass horn that uses full radius curves for its bends then that would work fine, but that is generally not the way to build things economically speaking plus it takes alot of room inside the cabinet to accomplish...

However, like I said earlier, consensus is that below 200Hz it doesn't matter much, so for subwoofers, no reflectors are required at all.

For wider bandpass bass horns, it becomes essential or you limit the upper frequency corner to a lower crossover point.

The University C15W has a mass rolloff so it needed to be used below 350Hz (B. Edgar). The Univ. bass horns themselves are capable of a higher bandpass, possibly as high as 500Hz which would be the ticket, wouldn't it?!

Armando, I'm thinking that YOU are probably more knowlegable about horns than me! I've been preaching to the choir all this time!

DM

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I thought the classic also suggested a low crossover point of 350.

Chris,

I really don't know the high end cut-off of the Classic since I have not done any measurements.

I know the low end cut-off of the cobreflex is 350hz.

Was the N-3 crossover designed for the Classic or Dean's high-end cut-off, or the cobreflex lowest usable frequency of 350hz?

In his book, Cohen talked about comparative package systems (woofer drivers, midhorns, tweeter horns and crossovers) available from EV, Jensen and University.

"In the University system the crossover points are 350 and 5000, in the Electro-voice system they are at 800 and 3500 Hz, and in the Jensen system they are at 600 and 4000 Hz."

(The University package includes the C-15W woofer, cobreflex or H600 midhorns, T-35 middriver, HF-206 tweeter and the N-3 crossover. The EV includes a 15W-1 woofer, 8HD midhorn, T-25 middriver, T-35 tweeter and X8 and X36 crossovers. The Jensen includes the P-15LL, RP201 midhorn, and RP302 tweeter horn and A-61 and A-42 crossovers).

"In all these systems, crossover points were chosen to be compatible with the CUT-OFF CHARACTERISTICS OF THE HORNS." (mid and tweeter horns, that is.)

"In choosing components such as these, which have been engineered by the manufacturers to be the equivalent of a package, the home constructor is faced only with the choice of the enclosure"........" (blah, blah). "He may use a bass reflex...." (blah, blah) "or he may use a horn..."(blah, blah) .

Actually, the N-3 has 350 and 700. 350 hz setting for a package system with a cobreflex and 700 for the H600. A tapped inductor and strapped cap take care of the change)

.

So, is it possible, when University built the Classic, that they took an off-the-shelf crossover, the N-3, optimized for the cobreflex and the HF-206 tweeter, and said, "This will work just fine".

And now, we're thinking the other way around, that the N-3 was designed specifically for the bass horn? and that the Classic (or Dean) is only good up to 350 hertz?

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The difference is the Cobraflex uses full radius TURNS or CURVES in the pathway, not reflectors.

In a planar-surfaced horn channel (like a bass horn made out of plywood) for a radius fold, a partial channel-covering hard surface reflector across the channel is used. It actually defeats the purpose as the non-reflecting portion is a 180 degree reflector, and is more appropriate for air conditioning duct work than a folded bass horn!

If you could build a bass horn that uses full radius curves for its bends then that would work fine, but that is generally not the way to build things economically speaking plus it takes alot of room inside the cabinet to accomplish...

DM

Does this explain why additional reflectors are not required on the Dean? the bends approximate a curve?

Armando, I'm thinking that YOU are probably more knowlegable about horns than me! I've been preaching to the choir all this time!

DM

No way, man! No way.

English is my second language. When I can't comprehend what people are saying, I'd say,

"You have a good command of the English language!"

"Why do you say that?" is their usual answer.

"Because I don't understand what you're saying!"

You know a lot about horns!

I have to read over and over, your horn explanations, because you're telling me things that I don't understand!!!

(LOL!)

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Maybe I should consider you University Belle design. That's really been capturing my imagination since you posted your drawing. Show's great promise, even though I still want to build a pair of Classics.

Could be I need to go with something like the University Belle today, and a few years down the road when the kid is off to college, building something a little larger when I have more room. Just thinking out loud.

Armando, keep those thoughts and drawings coming. You're a great talent and resource.

Chris

Thanks for the kind words.

I'll draft the plans, regardless, then we'll revisit this again sometime. I'll give Dana a copy for his chop, and we'll go from there. Keep in touch via emails. The good thing is, with your schedule, and my schedule, there really is no deadline for this. But I'll work on it. I understand you have deadlines for/at your work. So do I, and I hate deadlines.

I'm still thinking what I can trade you with for those HF-206's.

Will you take my mother-in-law?

Armando

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