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Thread: Urei 813b Crossovers

  1. #1
    Junior Member samo's Avatar
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    Jan 2017
    Los Angeles

    Unhappy Urei 813b Crossovers

    Hello all. I've adopted a project and was hoping for some advice, as I've reached a spot that I'm not quite sure how to proceed through-

    A few months ago, I bought a pair of what were advertised as 'Urei 813 monitors' for $80. Picked them up without the ability to test or hear them at all, simply because the price. Cabinets are a bit rough, the helper woofers need new foam, but everything else seemed ok.

    I began to disassemble the speakers for restoration, and noticed something odd. The crossovers appear to be from 813A's, where as the drivers are all what you'd expect to see in an 813B... The cabinets themselves are stamped 813A. The crossovers are a model 839. The drivers in both cabinets are: Urei 801B (PAS CXL 1580 15" with JBL 2425) and Eminence 800W helper woofers.

    A System Component chart can be found here.

    From my research, the Time Aligned Crossovers for the different versions of these monitors were very different from one another. I also seem to understand that getting the Time-Align thing right, is the whole point of what makes these great. So I'd guess the mis-match of components that I have could never really work together as they're supposed to. In comparing my 839 crossover's schematic that of the 840 that should accompany my drivers, they do indeed seem very different.

    813A, 839 schematic here
    813B, 840 schematic here

    My questions are:
    • Does anyone have any leads on where I could find a pair of 840 crossovers?
    • Does anyone have any other thoughts on how to get the Time Align system operating as it should?

    I've already talked to several people in the Los Angeles area to see if they have any spare Urei stuff around, but no luck yet.

    Any help or insight would be greatly appreciated!

  2. #2
    Junior Member samo's Avatar
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    Jan 2017
    Los Angeles

  3. #3
    Senior Member
    Join Date
    Feb 2009
    annapolis, md usa
    Greetings, and welcome to the forum.

    You're correct that the time alignment is what makes these speakers special. They are very coherent, and image beautifully.

    I would imagine the only place you're likely to find a set of original crossovers will be on eBay, if someone parts out a pair. The crossover "cards" were sold separately as a replacement item for studios and may occasionally show up on eBay as well. There is someone advertising 801B drivers right now, but mentions the crossovers aren't available. Didn't say which model they came from either.

    I suppose the only other options would be building a new passive crossover, or going active with a digital crossover. I'm pretty sure no one here has built new passive crossovers and posted about it, or gone digital and tri-amped either, for these speakers. You'll need access to measuring equipment either way, of course. Sorry I couldn't be more helpful.

  4. #4
    Junior Member samo's Avatar
    Join Date
    Jan 2017
    Los Angeles
    Thank you Rusty. I'm gonna stay hopeful, and keep my eyes peeled. Hopefully by the time I finish restoring the cabinets and drivers, I'll have something sorted...

    I do fortunately have some friends with the equipment needed to measure time alignment accuracy... but it'd be so much easier to find a solid stock solution!

  5. #5
    Senior Member eso's Avatar
    Join Date
    Aug 2009
    Long Beach, CA
    I haven't posted here in ages. I built a new pair of 840 crossovers at the beginning of the year. The parts count is very high, and as a result the cost is too. But they were worth the effort. Prior to building these I too was using the wrong model, 839 I think the the time alignment was off and they had other issues as well.

    Curious, do you have any pictures of your 813Bs? I sold a pair I had assembled a few years back. The OEM helper woofers are unobtanium and Eminence has no records that far back to duplicated them. I have a pair in the clones in my studio, but I'd like to make some more.


    840 clones built as mirror image pair
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    My reverse engineered Hardwood horns
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    Working towards a domestic pair.
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    30Hz Bass Horns/K151, Custom mid bass & midrange horns/Cogent DS 1428 & 1448 field coil drivers, Fostex T925a tweeters.

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