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Changes to ALK Cornwall network


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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", 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!

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..

14.gif

post-2934-13819253507834_thumb.gif

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Hi Tom,

I was curious about how the AKL Cornwall x-overs sounded vs. the original x-overs.

It seems you are expert in this area.

Also, changing the diaphram...do they just get old?

What is the best bang-for-your buck...replacing parts in the x-over or changing out diaphrams?

THanks in advance,

-bob sacco

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Al,

What modifications are necessary (if any) when using K-55V's (with the nested phase plug) released in March of 1980?

When Klipsch began using the "new" K-55V's they soon after updated the "B" crossover to the B-2, per Dope from Hope.

Thanks in advance!!

Mike

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Mike,

I don't think any changes are needed. The tap settings on the transformers were the same in the B, B-2 and B-3 network. This makes sense to me as most of the Klipsch squawker driver have the same sensitifity. At least all that I have tested do. I am quite sure there is no difference between the old and new K55V. Even the K55M was the same.

It was the change in tweeter with the Cornwall II (K79 versus K77) that was different. The K79 is less sensitive. That is why my Cornwall design can't be used on the newer Cornwall II.

AL K.

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