Improving Cornwall I crossovers

[Clipped and Shorn]

I have a pair of 1978 Cornwalls (serial # 17S717) for a dedicated two channel system. I am thinking of eventually running them with a diy SET 2A3 amp. Currently I do not play the Corns much because of midrange harshness with any good volume (even with my Eico HF-81). I understand that the crossovers can be improved and the design that ALK has available online claims to have helped with the annoying spikes in question. There is even a proposed upgrade to his original design. Anyone have any experience with these ALK crossovers for the Corn I either made by Al or diy, and/or any other stories of improving Cornwall characteristics by upgrading the crossovers. A few years ago I did go inside and damped the woofer frame and the the mid horn as per instructions on these boards.

-Clipped and Couponed

[Guest " "]

I've heard many cornwalls that sounded just fine.

The harshness you are hearing could be due to a lot of factors.

If we make the assumption that you have already re-capped the crossovers. The next thing I would investigate is what type of mid driver you have.....if k-55...which one...the push-pin or the solder type? If, for example, you have the push-pin k-55, there is a crossover modification called a p-trap that may improve your existing crossovers. A lot of folks report that particular k-55 as sounding harsh.

[Clipped and Shorn]

That's good to know. Maybe I could start with a simple cap replacement. As far as I know everything is original. Not sure which type K-55 is in there.

I am still curious to know if anyone had tried the ALK modified design and what their experience may have been.

[Deang]

I used to build them for Al under license -- everyone I built them for really liked them over their Type B's.

[Tom Mobley]

Clipped,

if you're going to be using the Corns with a SET amp you might want think carefully about the ALK crossovers as they will smooth out the impedance dips of the Corns considerably. Most of the heritage line have some pretty nasty impedance peaks and dips. Al's B crossover was more complex than the others due to trying to iron this out. You could build a set or get Dean or somebody to put together a set. Might be very worthwhile running a SET.

[Clipped and Shorn]

My Cornwalls are serial # 17S718 C-BR which makes them vintage 1978. Is it possible that the page of instructions that came with these speakers originally was titled "Instructions For Cornwall II" I thought that "Corwall II" didn't start until 1985 or so, and that the units I have here would be definitelly Cornwall I, being 1978.

The reason I ask is that there was an envelope with literature that came with these used Corns and it seems unlikely that the seller would have had anything but the literature that came with the speakers originally, (but I could be wrong). There are two sheets, one called instructions (Corn II) and one for wood care.

-C7alt

[JJkizak]

After installing the new Dean crossover in my 1965 Cornwall it brought it back to life.

JJK

[IB Slammin]

Clip,

The CW l and CWll thing drive me nuts. If the back comes off, they are CWl. ?

You do some Altec, so I thought that you might like this. Anyway, love the ESN for the CW, or "Alcorn" as I call them. The steep slope cures many ills for PWK's reflix. (IMHO)

tc

Edit: Can't speak to the SET end of it as the ESN's tend to open up slowly. I run tube CD and pre, but drive some nasty old SS power amps. Might make a difference with a low watt system. ????

[BEC]

There are older and newer Cornwall IIs.

If the back does not come off it is a Cornwall II (newer version)

If the back comes off it may be either a Cornwall I or II (older version)

If horns are vertically oriented it is a Cornwall II (older version)

I won't even ask if that clears things up because I think it was probably meant to be confusing.

Bob Crites

[Clipped and Shorn]

I am getting excited now about finally getting these Corns happenin'. I have way too much into them to ever sell. Think I will probably diy a set of Alks, and yes, the back comes off with screws so I have Corn I, that literature is confusing tho. Wonder if I should use Al's 2nd version instructions?

Those Altec mods are cool. I really like that JBL tweet myself and have them in three different systems, those are the 'baby bottoms" right?

Actually I have an embarrassing number of Altec based systems around here. I like to have something to listen to in all the spaces where I work, but I admit it is excessive and also an excuse to justify buying stuff along the learning curve. Three of my Altec systems use Rane electronic crossovers which makes cabinet designs almost a no-brainer and no expensive passive crossover components. Then, last year, in order to use up a bunch of Altec components bought along the way I made a Valencia system from scatch out of laiminated pine planks that were discounted to almost giveaway at a going-out-of-business sale at the local Yardbirds. This stuff is perfect for my stoneage carpentry skills. Yabba-Dabba-Doo! You just cut and screw together, the material is so thick that there is no issue of what to do with the edges and no need to build a support framework behind the panels. Its like falling off a log. They came out nice. I added the JBL tweeter (2404H) in a separate box which sits on top and also houses all the crossovers (since I needed every bit of net volume in the main cabinet given the amount of that pine material I had). I am going to post this, then go up and take some photos, hopefully to post in an edit later.

-Crossed and Shorted

[Deang]

Could be the Cornwall 1.5 -- quite a few of those things running around.

What mid-drivers and networks do they have?

Build the original Cornwall ALK design, not the new one.

[Clipped and Shorn]

Thanks Dean, I will go with the original ALK type Bs. He gives some sources for the parts including the Litz wire chokes.

IB, those crossovers are beautiful. Did you make them? Where did you get the design for using with the Altec and the JBLs? Is that atop a Corn or a Khorn? I will assume those are Cornwalls, then I am wondering what the second crossover if for, the JBLs I presume, so where did the specs and design for that crossover to the JBLs come from? Where did you crossover to the JBL ? 7000hz?

WHAT DRIVERS are behind those 511 (?) horns?

Also, glad to hear of the positives for the Dean Xvrs. Is that the original ALK design or the revised ALK. See below:

From Al's site:

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 original design 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", may 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!



The schematic of the changed area is mods.gif.



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.

[IB Slammin]

There are older and newer Cornwall IIs.

If the back does not come off it is a Cornwall II (newer version)

If the back comes off it may be either a Cornwall I or II (older version)

If horns are vertically oriented it is a Cornwall II (older version)

I won't even ask if that clears things up because I think it was probably meant to be confusing.

Bob Crites

...............If horns are vertically oriented it is a Cornwall II (older version)...............

Bob,

No, no, and not!

This is what makes me so crazy!

I ordered my first pair of Cornwalls from a Klipsch catalog in 1973. They were verts and the catalog named them CORNWALL. Not Cornwall ll. However, the catalog (stapled to the back of each unit at the time) displayed the horz configuration only.

So from the manufacturer, my vert CW's are Cornwall. No red letter stamp L or R, just Cornwall.

tc

[Clipped and Shorn]

Hi Dean,

Thanks for the info. I now need to mess up my living room and take the back off of a Corn. Will do. Meahwhile, here is a photo of the sweet little diy 2A3 I was planning to use with the Cornwalls. It was my first from scratch so to speak (many other prior upgrades of Eicos and Heathkits). Worked fine right out of the shute. The 2A3 sounds better through the diy Valencias than the 45s, either can work without changing anything in this design, a tad more power with the 2A3. I got a kick out of using an extra vintage 80 I acquired when restoring an old Atwater Kent radio that fini found at the county dump.

c7s

[Clipped and Shorn]

OK, no big surprise, here is what inside my Cornwalls:

K33-E

K55-V Push Pin type (mounted horizontally)

K77

Type B crossover.

Everything looks so nice in there, but I am going to assume that a new ALK design crossover will make some important differences.

-Klept and Maniaked

[Clipped and Shorn]

"Anyway, love the ESN for the CW, or "Alcorn" as I call them. The steep slope cures many ills for PWK's reflix. (IMHO) "

Sorry to be so dense, but what is ESN ? Is that another term for the ALK crossovers I have been considering? Extreme Slope Networks???? just guessing.....

-Sneezed and Coughed

[Clipped and Shorn]

After installing the new Dean crossover in my 1965 Cornwall it brought it back to life.

JJK

Were you using the SS amplification when you heard that improvement? That seems like it would be a good endorsement as well since the Corns are supposed to sound so much better with tubes.

-[popisjjsanmgk and akjas;dljto

[IB Slammin]

The networks are on loan, and were built by Dr. Pipes as the ALK 600 ESN.

That ugly stuff sits atop a heavily braced CW bin with BEC cast frame 15" woofers. 511b/902-16a mids and the JBL 2404's on top

. My preference is to cross the mids a bit lower, but the ESN 600 has opened my eyes to slopes. As to the design limits of PWK's reflex, I think that I have pushed (with much help) the single woofer Cornwall design to it's max. Make no mistake, they are kicking my a**!

JW Cullison is the only forum member to hear the Alcorns. (a bad review WILL affect our friendship)

Just kidding, I know that you had some LF room issues. I will work on that.

tc

[BEC]

There are older and newer Cornwall IIs.

If the back does not come off it is a Cornwall II (newer version)

If the back comes off it may be either a Cornwall I or II (older version)

If horns are vertically oriented it is a Cornwall II (older version)

I won't even ask if that clears things up because I think it was probably meant to be confusing.

Bob Crites

...............If horns are vertically oriented it is a Cornwall II (older version)...............

Bob,

No, no, and not!

This is what makes me so crazy!

I ordered my first pair of Cornwalls from a Klipsch catalog in 1973. They were verts and the catalog named them CORNWALL. Not Cornwall ll. However, the catalog (stapled to the back of each unit at the time) displayed the horz configuration only.

So from the manufacturer, my vert CW's are Cornwall. No red letter stamp L or R, just Cornwall.

tc

Terry,

This picture of the well worn tag on the back of my 1967 Cornwall II vertical is posted for your edification.

Bob

[IB Slammin]

Bob,

I done been edificaded. ?

I don't think that this an argument between you and me. This is about Klipsch at the time. I can show you labels from vert CW's that say Cornwall, not Cornwall ll. My argument is that not all CW verts are CWll's.

tc