L40 tweeter problems

[Studiomaster]

I just got my 127H woofers back from refoaming (at long last). I popped them back in the cabinets and they sound great. Now for the problem: One of my dome tweeters appears to have died, coincidentally.

I took the woofer of the offending speaker out and checked all the wires inside, thinking that perhaps I had disturbed the wiring either when I removed the woofer or when I reinstalled it. Not the case...everything appears very secure.

Before I removed the woofer, I tried rotating the high frequency control on the crossover full clockwise and counter clockwise, thinking that maybe it was an intermittent thing or that the control was dirty. No luck there.

How do I troubleshoot this? Did my tweeter suddenly die or could the problem be in the crossover? (Yes, I swapped both systems from left to right, just to determine that it's not some sort of high frequency loss in the amp).

Another thing I can't figure out is the so-called acoustic resistance shell that's in place behind the woofer. All these years I was under the impression that it was a solid foam basket. I was amazed to find that it's nothing more than a pair of strips made from the same stuff used to insulate the inside of the cabinet, stapled to a cardboard ring. The manual says you can "lift the acoustic resistance shell out of the cabinet", yet mine appears to be glued in place.

Any ideas on what ails my tweeter? It worked OK before I removed the woofer. Thanks.

[John]

First Check the coil on the tweeter in question to see if it is open.

Do you have a voltage meter?

[Studiomaster]

First Check the coil on the tweeter in question to see if it is open.

Do you have a voltage meter?

Ah...of course! You can tell I've been away from electronics for a long time.

It checks A-OK. So...does that mean it's the dividing/crossover network?

Thanks for the quick reply.

[Robh3606]

What does the DCR measure in Ohms?? Could be a dirty potentiometer. Did you try rotating it through its full range a couple of times?? Did you swap with the working tweeter to see if it's the crossover or connection in the one speaker??? Be careful pulling the terminals off the tweeters. If I remember right they are not supported so when you pull the leads just make sure you support the tan colored material that the clips are attached to.

Rob

[oznob]

You could swap tweeters and see if it works in the other cabinet. If it does, you may have a wiring problem. Check the connectors on the wires that attach to the tweeters, assuming they aren't soldered directly to the tweeter, and make sure the exposed wire is not corroded and is attached securely. If not, you may have to cut a small portion from the end, strip the insulation, and re-crimp the wire on the connector. I would also check where the wire is attached to the crossover and make sure that is secure also.

[Studiomaster]

Yahoo!

It worked...although I'm not sure exactly what worked. I tried all the things you guys suggested...the tweeter and network checked OK with the meter. Then I swapped the "dead" tweeter into the other cabinet, and it worked fine.

So I finally checked all the connections inside the cabinet, polished the terminals on the tweeter and reinstalled everything. I rotated the network control through its full travel maybe a dozen times, and voila! (Can you hear the Springsteen album in the background??? Gotta break in those newly foamed woofers).

Thanks a ton, everybody. This board rocks (not to mention my JBLs)!

Later...

[oznob]

Glad to hear they are back up and running!

[Robh3606]

Great!!!

Rob