Let's Build a Driver Test Box

[BEC]

Lorenzo.

The bass box measures 24 X 24 X 24 inches outside. That gives an internal of 22.5 X 22.5 X 22.5 inches. This is slightly larger than a Cornwall volume. Figured I can play around with decreasing the volume a bit with blocks of wood if I want to try to tune it in better.

Shelf extends 9.5 inches back from motor board.

Ports are 9 X 2.75 inches. (two this size)

Bob Crites

[lorcoll]

Bob,

I haven't understood why I can't use the same caps of type A (13 and 2 uf) for a 400Hz cut.

It would be necessary to change (on the type A) only the taps in the TA2.

Why have you changed the 13uf cap with a 7uf one?

I am building the Cornscala with the Cobraflex because I haven't the K-400 horn.

Thanks.

Lorenzo.

[BEC]

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On 4/17/2005 5:11:21 AM lorcoll wrote:

Bob,

I haven't understood why I can't use the same caps of type A (13 and 2 uf) for a 400Hz cut.

It would be necessary to change (on the type A) only the taps in the TA2.

Why have you changed the 13uf cap with a 7uf one?

I am building the Cornscala with the Cobraflex because I haven't the K-400 horn.

Thanks.

Lorenzo.

----------------

The crossover I used for the Cornscala is sort of a combination of the Type B and the Type A. Perhaps the easiest way to do this crossover is to build it as a Type B and just change the called for 4 uF cap to a 7 uF. I think 6.8 uF is a bit closed, but 7 uF is what I had handy when building mine and that works good. The Type B schematic calls out the taps to use on the autotransformer that will match the driver sensitivities. The change of the 4 uF to 7 uF crosses the mids lower to make more use of the abilities of the K-400 horn compared to that of the K-600 horn the Type B was designed for.

I am not sure what, if any, difference might be seen with your use of the Cobraflex. In any case, the crossover described above should be a good starting place and you might have to tweak it in from there. I am sure that the crossover I am using could also be tweaked in some. I considered the one I am using to be a "trial" crossover also. Just happens that it works well enough that I haven't seen any urgent reason yet to make changes in it.

Bob

bobcrites@centurytel.net

[colterphoto1]

Bob, for someone wanting to 'duplicate' your CornScala speaker, wouldn't it be better for the dimensions of the bass bin to be three dimensions that are not identical or mathmateically not in cahoots (ie doubles or halves) for the purpose of reducing the number of box 'nodes'?

Noting, of course that the 24" cube is very efficient use of plywood (as in the LaScalas bass bin), but it of course is not an enclosure of those dimensions, since it's a horn.

Michael

[BEC]

Michael,

Could be. I don't know.

I meant to do all sorts of tweaking on these things just considering the first build as a starting point. But, honestly, I like the way they sound so much that I just haven't wanted to do anything to them.

Bob

[BEC]

bump

[Daddy Dee]

I've been thinking that one could cadillac the bass bin and put one of those nice B&C HF drivers on top for a two way. That's assuming that the woofer could perform up to the needed crossover point.

There has been alot of discussion about this and other HF drivers in the Jubilee threads. I think maybe they are crossing between 600hz and 800hz.

Food for thought anyway. I can't afford to satisfy the curiosity of my very good taste in audio.

[Marvel]

Having the woofer be a direct radiator would allow it to go much higher than any of the folded horns.

[colterphoto1]

lets keep this up top, shall we?

[D-MAN]

There ARE better woofers available for reflex-ported boxes than the K33E which is "optimally" a horn driver.

Something interesting to think about.

DM

[jwc]

D-man,

Are you referring to using a different driver in Bob's particular cabinet or you just saying there are better direct drivers.

If so, I would like to hear of some other drivers to place in a Cornwall/test box and how well they would integrate with the other klipsch drivers?

jc

[D-MAN]

Just better reflex-ported drivers, that is, drivers that are specifically designed for reflex porting.

Bob's box is a virtual Cornwall, and the K33E in one would expectedly perform the same as an actual CW.

Personally, I think that the K33E is a compromise in such a box, and performs BEST in a horn which it was designed for. That is not to say that its performance in the CS will not be satisfactory, only that other drivers other than the K33E may perform even better given the same enclosure.

DM

[BEC]

D-MAN

That is something I would like to get around to trying. I can change the woofer in my box in a minute or so. I think it may be hard to find one that will perform significantly better for the price, but I haven't checked into any of the options.

Bob

[D-MAN]

Excellent point, I am blue-skying only.

DM

[IndyKlipschFan]

At what point do these become a non Klipsch speaker... or "close" to a non Klipsch Speaker, where drivers networks etc etc and we tweek to death inventing something entirely different?

Course in the name of, "were just making it sound better?" Any tweek I guess is allowed?

Just a thought. Not knocking any of you at all. Like I said, "The idea of a split La Scala, with a front firing woofer that goes as low as a cornwall woofer," does interest me to hear your thoughts and I want to hear one, one day too.

BTW, I think Trey said at one time Paul Wilbur Klipsch tweeked his own k horns over the years in production over 60 times too. So he was a tinkerer as well.

[Frzninvt]

How about a JBL 2235H or make the hole smaller and use a Dynaudio 30W100.

There are probably many other choices, but I think the K-33E is a decent choice, and as stated it keeps it more Klipsch sounding.

[D-MAN]

Yes, it depends on the "sound" one wants out of it.

Certainly, the Klipsch "sound" is a proven winner.

But other drivers and crossover combinations will also have a different "sound", which, like wine, depends on personal taste.

DM

[colterphoto1]

When I first bought my Cornwalls I had to have the woofers reconed. I temporarily put two pa woofers I had spare, think they were EV EVM-15L. They sounded great in the unmodified Corn enclosure. Plus they have very high power handling capability and cast frames.

Michael

[mike stehr]

I'm using a pair '81 vintage Fostex Lab Series Alnico 15's in my Cornwalls.

The Eminence K-33 is helluva woofer for what it is. But I had listened to the Fostex 15's off and on for a couple of years and always liked the tone of them.

The guy that had them, used the woofers in smaller cabinets and it just wasn't optimum.

He didn't feel like building larger cabinets, and had moved on to other woofers. So when he brought up he was ditching the Fostex woofers, I snarfed 'em.

The optimum enclosure volume for the Fostex 15's is a little over 6 feet, Cornwall size.

They roll-off real close to the K-33, maybe a hertz or two higher. I think they are a little bit more sensitive.

Sounds good to me, they measured rather well with this POS EQ/RTA with pink noise, a lot better than my homebrew 2-way's.

I'm currently using a old vintage '70's JVC integrated that I cleaned up and re-capped with the two-way setup.

Lafayette/Criterion 10" woofers running FR in vented cabinets tuned to 35 Hz or so, with Usher tweeters on top crossed in at around 3500, 4000 Hz using vintage 600 volt oil caps bypassed with 600 volt russian teflons.

It does seem better with the bass boost, but the speakers are voiced more for tube amps....sumthin'like that.

The little 10" woofers have a real good lively midbass and upper midbass, but a little lacking in the LF's.

The bass boost helps that, or dial in the subwoofers at 40 Hz.

Five dollar integrated with a Toshiba 3950, running the homemade two-ways, the cabinets were ten bucks, the 10" woofers ten bucks. The Usher tweeters were 100 bucks, the caps were garage sale items that came with a boatload of tubes.

Sounds rather nice to me for a budget $200 system.

The homebrew cabinets of mine can have the baffles swapped out. I can swap between 10" and 12" woofers, and use cardboard tubes for port tuning.

I have a nice pair of Realistic/Utah "Americana" 12" coaxial speakers. The cone tweeters kinda suck, but I can remove them, and use a helper tweeter on top of the cabinet.

A little 3/4" neo-magnet tweeter that had a threaded hole on the back would be nice to try.

blah...

[jwc]

Yes, we are all anxious for Bob to try out different woofers in his box but his goal was probably just to test repairs of K33's.

Maybe someone can help me understand something here. I don't know exactly how to read the specs on woofer drivers to know wheter they are an option or not in a cabinet. I understand impedance, wiring, dB, freq res...etc. However, stuff like Fc,Qms,Qes,Qts,Xmax Throws me off completely.

Now I know this isn't the thread really to do this but since we got going on woofers in a "CW" like enclosure...maybe someone such as Dman and others can chime in.

For instance...tell me why this wouldn't work as an option (exclude expense) and the fact its 8 ohm. they make it in 4 ohm.

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=294-470

thanks

jc