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midlife
12-25-2012, 05:43 PM
One of my bookshelf L15's dropped the low frequencies. Took the lf driver out and resoldered the vc wires to the tabs, hooked it backup and it sounded perfect for about 30 seconds...wth, and I don't know a transister from a capacitor; what to do?

pathfindermwd
12-25-2012, 06:04 PM
One of my bookshelf L15's dropped the low frequencies. Took the lf driver out and resoldered the vc wires to the tabs, hooked it backup and it sounded perfect for about 30 seconds...wth, and I don't know a transister from a capacitor; what to do?

Hi midlife,

First, look for a loose connection. How is the spade connector, is it tight to the wire? How is the wire to the woofer out of the X-over? Leave the speaker hooked up, but out of the cab, wiggle the wires. It sounds like a loose connection. How old is it? Do you live in a humid area? If the wire is twisted strand and old, it could have corrosion.

It could be any of a number of things, but suspect and investigate a loose or bad connection first.

4343
12-26-2012, 11:11 AM
One of my bookshelf L15's dropped the low frequencies. Took the lf driver out and re soldered the vc wires to the tabs, hooked it backup and it sounded perfect for about 30 seconds...wth, and I don't know a transistor from a capacitor; what to do?

Do you mean the tinsel leads? Soldering them back can cause the solder to flow up the leads, rendering them very inflexible.
(I always use a heat-sink clamped on the lead to prevent this. My heat-sink clamps are from the early days of DIY transistor kits, BTW!)

Perhaps one broke again due to that. Or if you have aluminum voice coils, the aluminum wire is almost impossible to solder to, and can corrode away under the black glue on the face of the cone. So,while the tinsel lead is soldered to the bead properly, the voice coil wire may have crept away from the bead. You can try chasing it under the glue, but unless it is copper, that's the point where I give up and start looking for a re-cone or replacement...

HTH

midlife
12-27-2012, 09:40 AM
The leads coming from the plug in tabs did not appear to be soldered very well, so those I resoldered. It did not render them stiff as to restrict cone movement. Put it all back together and the speaker functioned properly for about 30 seconds then the low frequency dropped out again. Not really having any background in electronics this leads me to believe disconnecting the woofer from the xover and then reconnecting it and having it work properly makes me think something is going bad in the xover; something that stores voltage and then fails? Or a bad connection I moved while attempting the repair. I could swap woofers in the cabinets and see if the problem follows the driver or stays with the cabinet (ie xover). I really like these lil L15's and hope to figure out them problem.

pathfindermwd
12-27-2012, 11:26 AM
this leads me to believe disconnecting the woofer from the xover and then reconnecting it and having it work properly makes me think something is going bad in the xover

It sounds to me like a wire was bumped slightly during the operation and then it made contact again, until the woofer began vibrating again.

I had a turntable recently that was having a problem like this. One channel was intermittent. I thought I identified the problem in a very fine wire barely hanging on a solder, I re-soldered it but continued to have the same problem. I would make sure the channel was working, turn the unit right side up, and it would stop working. Turned out to be the RCA cable (which was original circa 1970) had an internal break in it, though on the outside it looked fine. Well, it had been folded and tied during shipping and that did it, but the problem came days after getting it. Took me days to figure out since I was chasing the wrong problem. I just couldn't see the RCA cable as being the culprit, as I said, it looked fine, pristine for it's age. I finally went down the RCA bending it back and forth until I got to the break and the signal would come and go predictably. When I saw the cables all folded up, it didn't sit right with me. Though professional looking, I thought it was a bad idea to fold them so tightly. It was a clue, but because I lacked experience with broken cables, I couldn't lend it credence.

Intermittent problems are difficult to diagnose. A meter will tell you when it's working or not, but it wont tell you where a break is.

So retrace your steps, did you recently add a new RCA, Speaker Cable, Amp/Pre-amp, Source, or move or do anything to the speaker itself a few days or weeks before this problem? Did you see something that didn't sit right with you when you saw it, but it seems fine now or unrelated? Retrace the signal all the way to the source, work/wiggle all the cables and connections.

Speaking of Capacitors, I'm not sure if there are any in there, but if there are and it's bad, it would be leaking on it's top or around the base.

I did have a bad x-over once. The whole speaker just shut down with a small pop. My friend took it to work and took it all apart, tested it on high-dollar equipment, and couldn't find a problem. He put it all back together and it suddenly worked, we still don't know where the exact issue was. It had recently been moved, and that's all we know for sure.

4343
12-27-2012, 02:36 PM
The leads coming from the plug in tabs did not appear to be soldered very well, so those I resoldered. It did not render them stiff as to restrict cone movement. Put it all back together and the speaker functioned properly for about 30 seconds then the low frequency dropped out again. Not really having any background in electronics this leads me to believe disconnecting the woofer from the xover and then reconnecting it and having it work properly makes me think something is going bad in the xover; something that stores voltage and then fails? Or a bad connection I moved while attempting the repair. I could swap woofers in the cabinets and see if the problem follows the driver or stays with the cabinet (ie xover). I really like these lil L15's and hope to figure out them problem.

Swap the woofers, that will tell you where to look next. If the problem stays with the box you should take the crossover out and look it over carefully for loose wires or bad solder joints...

midlife
12-27-2012, 02:46 PM
mission accomplished, voice coil leed broke away from tab, couldn't be seen until I pulled on it with tweezers. Listening to Bonnie Raitt, all good. thanks