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Type AL Crossover


BEC

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Al,

Thanks for the schematic. I have a customer who is blowing tweeters using Lascalas with the AL network. From the schematic, looks like good tweeter protection. If that network is working right, I can't see how he blew the tweets.

Bob

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Dean,

Either diode being open would disable that part of the protection. But, bad on both crossovers? That is getting a bit tough to believe. Also tough to troubleshoot this one by email. Perhaps I can get him to shoot me some pictures to see if someone has "worked" on it.

Bob

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Bob, the AL doesn't have zener diodes.

I have run into this same exact problem with the AL network and it is the ground connection for the tweeter inductor (which is on the 2µF cap for the elliptical filter).

With this connection open the network goes to 6dB and breaks tweeter leadout wires in no time.

Before I found the problem I added the zener diodes and a lightbulb to no avail.

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Well, I compared the schematic that ALK posted to the one that I have which claims to be an AL-2 and they seem to be the same. I am thinking now that I still haven't seen a schematic of the AL and, if that is correct, would still like to see one.

Bob

post-9312-1381925801187_thumb.jpg

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Dean,

The guy is using lots of power and using them as PAs. What Dennis said is really likely. I know from testing that a K-77 can stand very little power below 3 khz. I blew one with less than one watt at 2.5 khz, just took the voice coil apart and made a slinky out of it. If that is the case (lows getting through) even the zeners could not protect against that.

We need to investigate the question of whether "clipped" power is somehow different from "clean" power as far as driver damage is concerned. My gut feeling is that "power is power" but you have to calculate it a bit differently because average power increases somewhat as clipping becomes extreme.

Bob Crites

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That thing Al posted is bizarre. It has the AL-2 tweeter section, yet shows the diodes in place as the AA. Then we have a 6uF cap feeding into a T3A autotransformer, and a LCR circuit in parallel with the midrange. I have no idea what to make out of the action with the 2.7mH inductor at ground of the Autotransformer. This thing looks like a mod of some sort, I don't think it's a "Klipsch" network at all.

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Dean,

Looks like some of us have some schematics that are suspect. If the AL is like the AL-2 you posted, I think Dennis has hit it right on the head. Still will be difficult to talk a rather non-techincal guy though a fix by email.

Bob

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