Thoughts on crossover rebuilds - go for it or leave it alone?

[dpgaloot]

Hi all,

New member here, just found this forum and thought I'd throw out a newbie question. I've rekindled an old interest in audio and been buying unobtainable items from my youth including JBL speakers. I've got a couple of systems that sound great to me, but am wondering if I am leaving something on the table by not having the crossovers rebuilt. I started back into audio by getting a few sets of vintage Polk speakers (can I admit that here) and the guys on their forum are nuts about crossover rebuilds. I had a few done on the Polks and they did seem to sound better. I've since switched to mostly vintage JBL speakers (pretty sure I can admit that here) and wonder what the prevailing thought is? I don't know if JBL just used better components than Polk originally, but after searching through this forum it seems that while some do restore crossovers it's a LOT less prevalent than in Polk land.

For reference, I currently own pairs of L-19, L-220, 120ti, and 250ti JBLs. I also lack the skills to do this myself, so I'm sure if I did anything I'd send it to a competent tech. I'm a woodworker so veneer repair and restoration is cake to me but I don't own a soldering iron.

Thanks!

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dpgaloot

[johnlcnm]

Although I am low in the "experience" department here, my two cents worth: I would replace any non polarized electrolytic caps with metal films. Most higher end JBLs used all metal film caps. Lower end consumer products used the n.p. electrolytic caps when a large value capacitance was required. However some folks here have reported a value change in old metal film caps. In my 4333B speakers I found two overheated metal films and one open in the high frequency third order sections. Both high frequency drivers had open diaphragms. Metal films should be a long lasting capacitor unless the speakers were subjected to abuse. Low power amps driven to clipping will destroy caps and drivers. That coupled with excessive libations and subdued senses can ruin speaker drivers and capacitors, although this is a better alternative then DWI!

Regards,

John

[DavidF]

If you have the patience to work with wood and veneer, you should be able to figure out soldering and circuit assemblies.:) Plenty of resources like YouTube to help.

You have to take 'improvements' from changing xover circuit components with some hesitation. It is relatively simple to swap out components. Like with tubes. Not so simple to swap out drivers or enclosures. I suspect for many this makes filter component swapping a tweaker's haven. But it becomes difficult to rely on general statements that better components means better sound. Especially, when comparing one brand to another. When someone says one cap vs. another makes a night-and-day improvement, well, unless you trust the source you just have to make your own judgments.

There is some rationale for swapping out older capacitors for newer pieces since the older parts may have deteriorated in some way and their specs have changed enough to effect the sound output. Resistors much less so. Coils not at all. Some components are of better quality than original spec'd parts and may result in a difference in sound. Perhaps better, perhaps just different. That's the gray area.

Polk's and JBL's better product lines did use good quality components to begin with. Changing out the electrolytic type capacitors is usually good insurance but not likely to improve things unless they were way out of spec or just stopped functioning altogether.

[dpgaloot]

Thanks for the input guys. Things sound good to me now, so I'm not going to mess with it on the ti's. The L-220s were pretty rough when I got them, all there but the cabinets were damaged and and the woofers and passives needed new foam. I've fixed the cosmetic and functional issues, and they are working now but don't sound as good as the 250ti's. I may dig back into them and remove or rebuild the LPads, I'll check the crossovers then.