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You will have to work backwards.

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In Reply to: X-OVER will drive me crazy!! posted by blackrock john on November 30, 2006 at 09:18:48:

Given the known quantity and values of caps and coils and the driver complement, you may be able to work out the crossover if it's very simple and textbook. That being said, you can probably get better xover parts today and build you own, especially if you know the specs of your drivers. You may have to experiment but some people actually enjoy that kind of thing if you can beleive it. Check out the link below and see if you can come up with anything. Also check out the high eff asylum for lots of info and guidance. Cheers.

http://www.mhsoft.nl/spk_calc.asp (Open in New Window)

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Re: You will have to work backwards. - blackrock john 13:14:11 12/01/06 (2)
Here are the pics @ the url below and a list of parts, anyone up to the task?
O K Below is the url for our visual tour of the parts. You might enjoy the purist music LOL. We are in real estate and the Virtual Tour is the only way to get you all pics. Also the dicriptions of the markings on the parts I also have the new cabinets and the large jbl drivers not pictured but would be glad to include them for you.
Thanks so much for considering the chalange on how to build this x-over.
John
http://www.visualtour.com/show.asp?T=822905
2-JBL 15" woofers
2-6" mids brand unknown #115H-1
2- Morrell Liquid Cooled Tweeters #MDT-30
2-smaller spools of red wire w/ .4MH or 4MH printed on them
Lg yellow resisters w/ REL-CAP 4.0MFD +/-10% 200v ppmf405k2a rsl8904
2-sm yellow resisters with trw8519 4.0+/-10% 8279058 printed on them
2-sm black ones w/ 1068-7610- 4-65cxr 3-50ac-b 3uf-50vac
4 Versa tronics 100v np85-c 9242
- Your bill of material doesn't jive with the photo... - Presto 12:22:31 12/04/06 (1)
  "2-smaller spools of red wire w/ .4MH or 4MH printed on them"
  -> These are 4mH inductors
  "Lg yellow resisters w/ REL-CAP 4.0MFD +/-10% 200v ppmf405k2a rsl8904"
  -> These are actually capacitors, 4.0 microfarad...But how many?
  "2-sm yellow resisters with trw8519 4.0+/-10% 8279058 printed on them"
  -> There are likely 4 ohm resistors - need to confirm
  "2-sm black ones w/ 1068-7610- 4-65cxr 3-50ac-b 3uf-50vac"
  -> These are again capacitors, 3.0 microfarad
  "4 Versa tronics 100v np85-c 9242"
  -> These appear to be the tall skinny blue inductors (since there are four of them) We need to get a value for these, either by the "numbers" or you can simply have them measured.
  But here is what I count from the picture:
  4 blue inductors
  2 red inductors
  2 large yellow capacitors
  2 black capacitors
  2 black capacitors (by each crossover)
  1 "Cluster" with 2 small black caps and 1 small yellow resistor
  1 "Cluster" with 1 med. black cap and 1 small yellow resistor
  The two "clusters" could be a component substitution, where both "clusters" have the same "net" impedance. This can be measured. It may also be helpful if the individual cluster components can be isolated and measured - you need to be sure that the "small yellow resistor" in this cluster is indeed a resistor - and not a cap (just like the LARGE "resistor" was a cap... right?
  Hey - nobody said this was going to be easy!! But this is a really simple circuit for a three-way to be honest...
  My initial guess? This is a first order three way parallel crossover with an RC countour network. There would be no L-pad on the tweeter circuit meaning no series resistor in the tweeter path. The woofer circuit would likely be the two blue inductors in series. The mid circuit would be the red coil in series with one of the caps *and* the contour network (most likely the countour is on the mid circuit, but this needs to be confirmed). The tweeter circuit is the "other" large black cap in series with the tweeter. But, of course, this is just a preliminary guess - so don't run with this just yet.
  Get back on the discrepancies I have outlined.
  Don't connect anything yet...
  Cheers,
  Presto
  - Correction. - Presto 09:06:57 12/05/06 (0)
    "2-smaller spools of red wire w/ .4MH or 4MH printed on them"
    -> These are 4mH inductors
    This should have read:
    -> These are .4mH inductors
    If that inductor is about 2" across with a 1" diameter "hole" and is about 3/8" thick then it's definately a .4mH.
    It would need to be about 3" in diameter and 3/4" thick to be a "4".
    Cheers,
    Presto

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