Crossover gurus... I need a schematic

Discussion in 'Archived Threads 2001-2004' started by Jeff Hoak, Aug 20, 2002.

  1. Jeff Hoak

    Jeff Hoak Stunt Coordinator

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    I'm pretty much married to my JBL S38's for a while. At least until I can find a "proven" design for something along the lines of a M&K S150.

    Anyway I thought I might try to improve the sound a bit by building a better crossover. I figure that JBL installs about the cheapest crossovers they can get their hands on.

    What I need is a 3 way, 2nd order (12db/octave) with crossover points at 800 Hz and 3200 Hz (these are factory spec). While I'm at it I'd like to change the connector plate (and hookup to the crossover) to allow for bi-wiring or bi-amping if possible.

    I've located a number of vendors that sell "high quality" components and I handy with a soldering iron so all I'm lacking is the design.

    Yes I have done a lot of research on crossover design. Franky I'm a bit confused and hoping that someone here already has a good working design on paper.

    I realize that this is a lot of trouble for what amount to a pair of fairly low-end speakers but they fit nicely in my entertainment center and the decorator has "0" tolerance for any speakers outside the cabinet.

    THANX!
     
  2. Patrick Sun

    Patrick Sun Moderator
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    Why not just upgrade the components (the values should be on them). Replace the (I'm guessing) electrolytic capacitors with polypropylene caps (you can get them from Madisound's Bennic caps or Parts Express's Dayton caps, as a start), and replace the inductors with a thicker gauge wire, and replace the resistors with non-inductive Mills resistors (Parts Express).
     
  3. Jeff Hoak

    Jeff Hoak Stunt Coordinator

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    I thought of that. I looked at the existing Xover and can easily discern the capacitor values. The resistors are of course obvious, but the inductors don't appear to have any markings. I figured that they "may" be marked on the mounted side but that would require de-soldering and removal.

    Assuming that the inductors aren't marked, do you suppose that using the values determined by the various crossover "calculators" would be usable?

    Of course all of this still doesn't address the possibility of bi-wiring or bi-amping.

    Actually it's all probably an excerise in futility...
     
  4. Ron D Core

    Ron D Core Stunt Coordinator

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    I would try to figure out the schematic of the x-overs before replacing parts. Some parts will not be worth it. Such as just about anything wired in parallel with the drivers. Who knows what they might have used, those companies have a way of coming up with really weird designs for the sole purpose of increasing profit margins. I have dissected many speakers in my never-ending quest for crossover knowledge [​IMG] I honestly wouldn't do more than buy a handful of bypass caps and just bypass what is there. Unless you have a nice DMM to test the values, I wouldn't mess with the inductors.
     
  5. Mark_E_Smith

    Mark_E_Smith Second Unit

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    I would try just replacing the things you can see. I think the caps are most likely the most important, esp in the tweeter circuit.

    Edit; Im not a guru though
     
  6. The BIGGEST THING....get rid of any and all electrolytic capacitors. Do not upgrade with anything better than solen. Do not increase the awg too much. Just step up 3 awg's max. Doing more may do more harm than good do to changing the XO point (which may be a blur to begin with)
     

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