JBL L5 Xover rebuild/cap

[BernieH]

Hello All:

Longtime lurker first post:

Picked up a pair of JBL L5's for next to nothing -- they need some cosmetic work but with some grill repair and enclosure refinishing they will "look" great. Having a hard time finding any information on the xover rebuild/re-cap. I will confess, just got them, they sound fairly good, and I have not yet opened them up. I have re-capped Dynaco A25's (easy) as well as KLH Model 5's but in looking at the L5 xover diagram there is a bit more to this one.

I've seen a few postings about re-doing the L5's but they all were sending the xover out to be re-capped. Can anyone direct me to or provide with additional detail for this xover -- I do see there are some caps which will be hard to find so I suspect I'll have to combine some to reach the right numbers.

Appreciate any guidance you could provide.

Thanks,

 

[RossW]

I'd do electrolytic for the low frequency stuff (the 128, 80, and 47). You might have to use a 12 instead of a 13 (or combine a 6.2 and a 6.8), but the 3 and the 10 should be pretty easy to find in film caps.

 

[powerman]

Hi BernieH here is a link to the crossover schematic if you do not have one.
https://manuals.harman.com/JBL/HOM/Technical Sheet/L5 ts.pdf
You will also have to set a budget on how much you are willing to spend as good caps are not cheap.
For the first 3 big caps I would use Solens the other 3 with either Jantzen, Audyn or Clarity. My bypass I use Audiocaps
You can find caps on Parts Express, Madisound, Parts Connexion and others. These are the products I use most of the time. There are other brands of caps also but seem to be very pricey.

 

[BernieH]

Thank you for the responses. Looking forward to this project and I will post progress as I go. As for the cost it does seem like it can get up there for a speaker which will be nice but not have significant resale value. To add to this I have determined 1 of the 8” drivers is shot 708G-1 - needs reconed. I see one on ebay but $100 is about 5x what I paid for these. There is an aftermarket RE-cone kit available for this for around $30 https://reconingspeakers.com/product/jbl-708g-8-aftermarket-recone-kit/ wondering if others have experience with this they won’t say the resulting specs only that they get it as close as possible to original...how close is it? And if do this do I need to do both (in that case the $100 starts to look better).

Project is getting more expensive than I would like especially since my objective was to get these in shape so that I can use them while I re-wire / recap my Maggies (MG-1 Improved) then sell the JBLs.
More to follow but appreciate any insight on the RE-cone or other.

b

 

[StimpyWan]

It's interesting that JBL used bypass capacitors on all values. That's rare. If present, a bypass cap is usually only on the tweeter, to save money. If desired, you could probably leave the 0.01uF bypass caps, as they're most likely film, and should still be good. Of the rest, C7 and C11 are high pass capacitors for the tweeter and midrange. I'd use good poly caps for those. The 80uF C3 cap is also a high pass cap on the lower mid. You'll pay around $20 a cap for those in a poly. An 82uF poly cap is easy to find, and is within acceptable tolerances. All the other main caps are shunt capacitors to ground. I'd use electrolytic, since they already have a film bypass cap across them.

Good luck.

 

[BernieH]

Thank you...on the “shunt capacitors to ground” does this mean I could or even should use a polarized electrolytic? have a local store here with an hundreds and hundreds of Capacitors but 99% of them are polarized.

although I spend hours in this store and always come away paying somebody’s mortgage, I’ve never been able to buy caps there — this would give me yet another way to spend money local

b

 

[StimpyWan]

Thank you...on the “shunt capacitors to ground” does this mean I could or even should use a polarized electrolytic? have a local store here with an hundreds and hundreds of Capacitors but 99% of them are polarized.

although I spend hours in this store and always come away paying somebody’s mortgage, I’ve never been able to buy caps there — this would give me yet another way to spend money local

b

No, do not use polarized capacitors. All caps need to be bipolar. While a polarized cap could work, they'd likely explode, the first time you cranked the speakers. While that might be fun, I wouldn't recommend it, if you value the speakers.