Heritage Tweeter Question

[Ave Bona Cornwall]

I have Khorns, Cornwall 1's, and Corwall II's (1987). I know a tweeter in one of the CII's is not working, but I still haven't opened it up to diagnose it; I suspect it is the diaphragm. If it is a diaphragm, I can either have Bob Crites replace it or order a new set of CT125s.

Questions:

1) How interchangeable are the tweeters in these?

2) Are CT125s acceptable replacements in CII's? I have never seen anything mentioned about this on the forums.

3) Does Bob's Titamium Diaphragm apply to CII's?

Thanks. I can probably ask Bob these questions as well.

[Schu]

probably should ask bob.

I have a set of CW1 tweets that I can send you, one works and one is not though I doubt it is an expensive fix.

[moray james]

ABC: check the screw connects on the crossover first. Clean them and then torque them down hard.That may be all the trouble you have to deal with. Diaphragms are easy enough to change especially on the K79 tweeter. I would recommend that you upgrade to Bob's Titanium tweeter diaphragms at $30.00 each it's the best deal you have available. You will wish you had changed over sooner.

Likewise for your Cornwall l's you can yograde to the CT125 it is a simple exchange of units and the CT125 is excellent with much better response and extension than the stock K77. Stay with the K79 on the Cornwall ll's rather than using a CT125 as the K79 has the same dispersion patters as your C ll mid horn. The CT125 is the exact same lens as that used in the K77 but you need to remembet the K77 and CT125 are diffraction horns and there polar patters are 80H x 30V degrees when the lens id mounter with the long dimension positioned vertically. So if you dropped a CT125 into a Cornwall ll you would be loosing horozontal dispersion and increasing vertical dispersion which is not what you want to do. Hope this all makes sense. Thats beside the fact that a CT125 will not fit a K79 baffle opening. Best regards Moray James.

[Ironsave]

ABC: check the screw connects on the crossover first. Clean them and then torque them down hard.That may be all the trouble you have to deal with. Diaphragms are easy enough to change especially on the K79 tweeter. I would recommend that you upgrade to Bob's Titanium tweeter diaphragms at $30.00 each it's the best deal you have available. You will wish you had changed over sooner.

Likewise for your Cornwall l's you can yograde to the CT125 it is a simple exchange of units and the CT125 is excellent with much better response and extension than the stock K77. Stay with the K79 on the Cornwall ll's rather than using a CT125 as the K79 has the same dispersion patters as your C ll mid horn. The CT125 is the exact same lens as that used in the K77 but you need to remembet the K77 and CT125 are diffraction horns and there polar patters are 80H x 30V degrees when the lens id mounter with the long dimension positioned vertically. So if you dropped a CT125 into a Cornwall ll you would be loosing horozontal dispersion and increasing vertical dispersion which is not what you want to do. Hope this all makes sense. Thats beside the fact that a CT125 will not fit a K79 baffle opening. Best regards Moray James.

There you have it.

The CT125 will not work in a CW II.

Good Luck.

[djk]

" ABC: check the screw connects on the crossover first."

Push-on terminals were used on the CW II.

"80H x 30V degrees when the lens id mounter with the long dimension
positioned vertically"

Don't know where you get your figures from, EV says the T35 is 105°H x 90°V at 8Khz, and 60°H x 60°V at 16Khz (long axis horizontal).

The reason why people prefer the long axis vertical is from the 3/4" slot in the baffle of the CW, this alters both frequency response and dispersion. EV states that the 3/4" baffle causes 7dB response deviations in the 4Khz~5.5Khz region (very important with the 6dB/6Khz crossover in the CW).

[garyrc]

Don't know where you get your figures from, EV says the T35 is 105°H x 90°V at 8Khz, and 60°H x 60°V at 16Khz (long axis horizontal).

I agree. The dispersion depends on the frequency.

To avoid the 3/4" baffle problem, should ABC (and others) buy a front mounting kit for the K77, or for the Crites? I'm happier with my K77s front mounted, but making the hole in the baffle bigger was work.

Dispersion figures, particularly when just one set is given (like 80 by 30 degrees), can be misleading. JBL used to give a "90 degree dispersion" figure for the 075 tweeter, so when I changed to Klipschorns, I expected narrower dispersion, but never heard it. When JBL got around to publishing the "dB down at specified frequencies within certain angles" data, it turned out that the K-77s, either vertical or horizontal, had somewhat better dispersion than the 075 at all tested frequencies.

[moray james]

Dennis: thanks for the additional info. Will try to find the link I found with the numbers I posted. Sounds like a surface mount K77 would be a good idea. Push mount (spring connectors?) could also be the issue. Hard solder connections would sound better and solve the problem if it is at the connector. Dennis do you have a link to the EV info you quote. Would like to make a hard copy to keep on file and to learn a little more about the diffraction lens. Still not sure that I understand how it works and how a diffraction lens differs from a standard horn. Thanks and best regards Moray James.

[Ave Bona Cornwall]

Thank you to everyone for your help. I knew I would have to get into the CW II's to trouble shoot, but at least now I know the CT125s aren't the best route to take, but the titanium diaphragm would be a good choice if it is the diapragm. I may still go the CT125 route for my Khorns at some point down the road, but I hate cutting the wires since all the connections are soldered in my Khorns.

[Digitaldad]

If necessary, replacing the tweeter diaphragms is very easy in the CW II.

[Louis Bartay]

Have you removed the back board yet? If so did you use a ohmn meter to check the tweeter?

[djk]

"did you use a ohmn meter to
check the tweeter?"

Good idea.

"Have you removed the back board yet?"

It won't come off without a chainsaw on the CW II.

[Louis Bartay]

I forgot, my 1979 models are screwed on the rear board. My Heresey II are front mounted. I have all the ohm specs

I got from Bob Crites somewhere. When you remove the tweeter PM or maybe one of the Other members will post up what the tweetrs and mid horn should measure .

EDIT K-55-V was about 10.9 ohm and the K-77-M tweeter measured 6.7 ohm on my my 1979 model Corns and sound like new with Bob Crites new Cross over boards.

[Ave Bona Cornwall]

I did find some time to take the tweeter out and test it. The diaphragm seems to be fine; a reading of 7.9 - 8.0 on the Ohm meter.

Now...how do I get inside the CW II"s to look at the crossover? I took the binding post circle off, but that is just opens a small hole in the back. I took out all the screws on the tweeter, squawker, and woofer, but I couldn't get the squaker or woofer to budge, and didn't want to force them. So, the only way in that I can find is the tweeter hole and the binding post hole!