Troels Gravesen's crossover for the JBL L100 centu

I owned a pair for years that I got for $100. I thought they sounded lifeless as compared to some other vintage speakers in their price range- sorry, no offense intended. I would seriously think about spending that much on a pair of L 100. Depending upon their condition, their max value in great shape isn't much more than $1000 US. You'd never get your money back out of them. I'd sell them, add the $600 and get another speaker. You can buy a lot of vintage speaker for $1k-1.5k.
OTOH, if you are looking to experiment by building your own, and you think that you may reuse the parts, that might be different. Might is the operative word here...

Excellent advice all around. Which is why I post here ...

I'm fully aware that madness can sound like reason; especially when pursuing the 'perfect' sound.

RJJ

you can get the jantzen kit for 279 at parts express,,just built and installed it in my century 100s ,outstanding results,,vocals to die for,nice timber on instruments ,just good music.period,,and not some hyper detailed 15000 speaker which sounds like canned music,,and i have owned some good high end stuff but with my 100s and new xover along with a cayin a100t am enjoying nmusic more thean ever before