Built some new x-overs for my old Cornwalls yesterday.

[Allan Songer]

I have been flip-flopping between the original networks and the "prototype" ALK networks for the last few years. The ALKs offer a much tighter bottom end but lack a certain smoothness in the upper registers--at least to my ear when compared with the originals. So I decided to build a NEW set of ALKs using Al's updated and "improved" Cornwall design--but with Jensen PIO caps (my GOD these things are expensive!) for the two horns (I used the "standard" Solens elswhere).

I finished soldering about 8:57 last night (just in time to catch this week's "The Sopranos") and finished hooking them up around 11:00. I played only a couple of cuts but my initial impressions are VERY positive.

I will report back later in the week with more details.

[IB Slammin]

Please do!

Regards,

Terry

[Charles Turner]

I was apparently one of the few who bought a set from Al for my Cornwalls in 2002 right before he stopped making them. I think I recall the version I purchased was the "improved" design but I'm curious, what design improvement are you refering to?

thanks

[Dflip]

Alan:

I assume you are aware that Al K. made some changes to the Cornwall B network. They are posted below with a gif of the modifications. If not, here is the text. I have it saved in a Word file at home with some pictures but I can't upload here. I can send you a copy later if you want.

Don

Al Klappenberger

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Cornwallers:

Progress marches on! Even though I am no longer building the Cornwall crossover network, I haven't lost interest in the project. Now that I have the equipment to actually measure the complex impedance of a loudspeaker woofer, I am able to do some fancier designs. The type "B" network design that is still downloadable from my web site works fine, but I have worked up a new woofer crossover section that I think will be an improvement. The old design assumes the Cornwall woofer presents a 4 Ohms resistive load to the network. I no longer have a Cornwall to test, but extrapolating from measurements made on my "Big Heresy", my Belle woofer and on a Khorn by a friend, I have come to the conclusion that it is more like 6 Ohms in series with a 1 mHy inductor. This lets me modify the values in the Cornwall network to compensate, at least in the computer. This will also allow the impedance presented to the amp by the speaker to be changed from an uncertain 4 Ohms to a good stable 6 Ohms. This also will move the crossover from about 750Hz down to 600 Hz. At 600 Hz it is no longer compatible with the Heresy though. It's for the Cornwall (original) only!

My apologies to anyone who just got done building it the old way!

The schematic of the changed area is attached.

Here is the changes:

Old Part --> New part

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

1.3 mHy of #12 AWG --> 2.4 mHy of #14 AWG (It's about the same size).

1.3 mHy of #18 AWG --> 2.0 mHy of #18 AWG.

39 uFd to ground --> 62 uFd to ground (across the woofer driver)

39 uF in parallel with 1 uF bypass --> 30 uFd in parallel with 1 uFd.

5.6 Ohms 20W in parallel with transformer (taps 0-5) -->

10 Ohms 10W in parallel with transformer (taps 0-5)

Al K.

NOTE: I forgot to change the 39 uF cap to 62 uF on the schematic I uploaded. I can't seem to upload the new one over it. I am going to upload the corrected one in the next post..

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Here's the corrected schematic of the Cornwall network update. Ignore the attachment above if it's still there!

Sorry,

[Allan Songer]

I built them with these modifications.

Listened three more LPs tonight. I like what I'm hearing so far--but too early to write anything.

[leok]

Allan,

Did you condition the caps? If not, you might give it a try. The result can be significant.

I would expect you'll like the PIOs. By the way, conditioning them will get you through a rather long breakin. The good news is they do seem to eventially break in, unlike the plastics which may stay lossy until conditioned.

Leo

[Allan Songer]

Didn't condition them. I'd been meaning to build these things for months and finally got around to it.

How do I condition an already assembled network?

[leok]

Allan,

Based on the fact that all of the caps in the mid and tweeter circuits are PIO, the only thing conditioning will do is spare you the significant burn-in time. I think the circuit will be fine without conditioning.

Leo

[Deang]

Please keep us updated Allan.

[Allan Songer]

I listen for about 1.5-2 hours every evening and since Kelly told me once that Jensens can take up to "several hundred hours" to break in, I guess I'll be reporting back in about a year!

Just kidding--I'll post something about the way these sound as of the end of this coming weekend--and I'll take some pics too--but NO FAIR making fun of my shoddy workmanship!

[Allan Songer]

The crossovers have about 30-35 hours on them now and are starting to come into their own--at first there was some slight shrillness in the upper mids that was annoying but that seems to be clearing up. Listened to a lot of piano trio last night (Sonny Clark Trio--Time Records, Bud Powell Time Waits--Blue Note, Hampton Hawes--Everybody Digs Hampton Hawes--Contemporary, Horace Parlan--Moovin' and Groovin'-Blue Note, Phineas Newborn--A World of Piano--Contemporary, Randy Weston--Trio and Solo (w/Art Blakey)--Riverside)--a solid three plus hours of intent bourbon enhanced LP piano jazz listening and I have to tell you these "new" ALKs with Jensens are really something! They really do seem to combine the best of the original B networks with the the best of the ALK design.

More later with pics.