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CW B2


Schu

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Wow those look awesome... This hobby is so fun but costly. :D

you know, the way I look at it these type investments are not consumables, so I take the plunge one time and I'm good to go for the life of the product. if the hobby required constant investment in order to maintain a level of performance, I would probably find another hobby.

the only downside to this purchase, if I can find a downside at all, is that now I can no longer own a pair of Klipsch speakers without knowing that I have to make this additional modification.

Edited by Schu
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Great pictures, they show all of my screw ups. :)

You have the same part I used, you're good to go. Just connect one end of the coil to tap 3 and the other end to squawker positive. There is no reversal in polarity. .17 is correct, so it adds a little less than 1/4 ohm of resistance in series with the horn. The inductance value is what you get when you calculate for a 6kHz crossover point using 15 ohms, the impedance of the driver at the crossover point. This number may actually be closer to 13 ohms, but with a first order filter, the difference is insignificant. The electrical first order combines with the acoustical 3rd order natural/mass rolloff to increase the steepness of the slope -- which is actually a form of attenuation, since the driver is receiving less energy. So, the coil dials things down a bit, and you don't have to worry about changing caps values. Speaking of cap values, the primary cap is a 3.3uF, which measured 3.22, both caps were matched to within 2%. The B2 uses a 3uF. If I can stay within less than 10% on a first order crossover, well, I'm not going to get to wound up over that. Early networks like the K1000/5000 and K500/5000 used a coil in series with the horn, which PK later removed -- apparently no longer feeling the need for them with the new horn and driver. However, I've been doing this mod for a long time, and everyone likes it quite a bit. It takes some of the bite out of the midrange without requiring the move to something like a Universal. This also leaves more money left over for some capacitors that really smooth and open things up.

Ok, I went ahead and did this. My Cornwall network was pretty much stock B2, except I was using a 3uf Sonicap for the input cap, and a Jantzen standard 1uF in parallel with a 1uF Jantzen Silver Z-cap for the tweeter. I'm using a 22uF Jantzen standard for the woofer that I'ved used all along.

I listen near-field, and the Sonicap used with the midrange has always been a little objectionable.( spitty/harsh) The networks have been this way for a couple years. Even with tube amplifiers, the midrange has the same slight attribute.

These are '83 Cornwalls, with the K51V, and Crites CT125 tweeters. I've been broke lately, so I can't buy any nice 3uF capacitors. So I found the original Aerovox 3uF oil capacitors, and measured them with a cheap but decent enough LCR meter. 2.92uF for one, 2.93uF for the other, close enough...Don't know the ESR #s, however...

I scrounged up a couple Cornell-Dublier 600 volt 2uF oil caps that measure 1.8-1.9uF. Used these for the tweeters.

I'll have to listen to things for awhile, but with the first take I was using a CD player and a Scott LK48B integrated amp. For near-field, the midrange is a lot more relaxed than it was before, I can live with that.

The tweeters may be a little too laid back using those Cornell-Dublier 2uF capacitors, there seems to be some "sparkle" lost...I'll have to listen for a little longer to really determine that.

I may go ahead and put back the Silver Z-cap, and Jantzen 1uF cap back in the networks for the tweeters.

Maybe I should have tried the mod without the cap changes...oh well...

I've pondered using the Russian Military capacitors for the 3uF input cap, but 3uF seems to be a odd value with respect to those caps.

I do like how the midrange sounds now, however.

Mike

Edited by mike stehr
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