Reworked JBL 250Ti Crossovers

[Zonker92]

OK, after months of bugging you guys, I finally did my 250Ti crossovers. (Please don't tell me what I should have done differently; this project is OVER and I don't want regrets. I just wanted to document the process.)

Thanks for all the help! (I also posted this over on A-K)

My goal here was to upgrade the L250Ti caps, signal-path resistors, the the woofer coils. I tried not to spend a fortune but achieve good results while keeping the specs original. Note the even those these crossovers came out of sequentially numbered speakers, one of the boards is tan and the other is blue.

Here is the schematic:



(R3 is missing, but it's 5.1 ohms on the 108H shunt.)

Here is how the board looked originally:



I put mine on a piece of plywood with a metal strap to support them, so I wouldn't keep flexing the wires:



Most of the components are marked clearly, but not the off-board resistors. I went through and determined that from top to bottom (that is, with the writing on the board oriented properly), they are:



Removing the caps from the board required some leverage, as they were glued down. I heated a metal putty knife blade with a propane torch to scrape off the hot glue residue.

I replaced the signal-path resistors (and, by accident, one of the attenuator resistors) with Mills 12-watt resistors. I replaced the shunt caps mainly with Jantzen Standards, and a few Solens and Jantzen cross-caps, of the same value. I replaced the signal-path tweeter cap (2.7 uF) with a Jantzen Silver, the 104H midrange cap (10 uF) with a Jantzen Superior, and the 108H mid-bass driver (40 uF) with Clarity Cap SAs (38 + 1). I bypassed every cap (or set of parallel caps) with one Theta .01 uF. I replaced the 6.0 mH woofer coil with an ERSE Super-Q of the same value. I bought everything from Parts Express except the resistors (Parts Connexion) and ClarityCaps (Madisound) and some of the Thetas (Opentip). It was NOT cheap. The resistors and bypass caps are over $4 each. The higher-end Jantzens and the big ClarityCaps are around $50. Apiece.

I mounted the new coil on some plywood, stacked up and screwed to the crossover board. I glued everything down with Goop and replaced the original tie-wraps.







It's been a month since I started this project, so I can't say I really remember precisely how they sounded before, and I now have a "new" Adcom (250WPC) driving them, but I do like how they sound now. (The cabinets are L250s but the drivers and XOs are Tis.)

[grumpy]

...but I do like how they sound now.

Congrats.

[Zonker92]

Thanks, Grumpy!

[rdgrimes]

Will probably never be a more handsome speaker ever made. I like the jig you made for working on them.

[Zonker92]

Will probably never be a more handsome speaker ever made.

Now, if only you could convince my wife of that! I like how the L250 cabinets don't have the grille holes of the Tis.

I like the jig you made for working on them.

Thanks! Yeah, about ten minutes to make the jig, and it must have avoided at least fifty bending cycles on the wires.

[DavidF]

"...I finally did my 250Ti crossovers. (Please don't tell me what I should have done differently; this project is OVER and I don't want regrets..."

It's over?? Hmmm, we'll see.

Those are some fat caps, indeed.

I like the setup in the room. Looks like a good fit. Well out from the corners and room to expand a good wave front. I liked my Adcom 555 with the LE-14-1. Others have mentioned this, too. Seawolf97 I think, for one. I used it for the bottom end in a passive bi amp until it quit on me. Have not heard your model but perhaps it has some of the same appeal.

Have fun.

[Zonker92]

Thanks, David! So far, so good ... now on to the next project.