EV Georgian crossover question

Discussion in 'Speakers' started by gtojon, Oct 3, 2017.

  1. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    Put a meter on those controls and see what kind of resistance you get.
     
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  2. gtojon

    gtojon New Member

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    Yes the horns are definitely working, though muted and quieter than my other speaker. Thanks for the ideas.
     
  3. gtojon

    gtojon New Member

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    This makes sense, I will check out the threads for more info..
     
  4. gtojon

    gtojon New Member

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    Curious what everyone thinks. If I can get the speaker cranking like it should, would it make sense to change the X336 to the dual X325/X36 crossover combo? Would it make any difference?
     
  5. sheltie dave

    sheltie dave Addicted Member

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    Last edited: Oct 11, 2017
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  6. gdmoore28

    gdmoore28 Super Member

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    Thanks to Dave for the great references.

    So, the only difference between the two crossover options is that the X336 offers a second-order (12dB/octave) slope on the high pass portion; the "combo" gives a first-order (6dB/octave) slope. All other points (crossover frequencies, impedances, etc.) are the same. Dave can correct me, but I doubt you would be able to hear a difference, but the tweeter would certainly like the 336 slope better simply because it attenuates the mid frequencies faster and prevents them from entering the tweeter.

    But, it still has not been ascertained that either of the crossovers are bad. There are still all the connections to check for corrosion and the B&P pots to check and clean. Like Tox, I'm betting that the problem is going to be found in one or both of those areas. If not, and the process of elimination eventually points to the crossover, I would remove that "thermoplastic asphalt" potting material from the crossover and simply replace the capacitors.

    All of this is very simple stuff - even for an uneducated dolt like me - but it takes a little time and persistence to iron out the problems that accumulate over fifty years. For me it's quite fun and educational - because I don't have to do it every day for a living. ;)

    GeeDeeEmm
     
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  7. gtojon

    gtojon New Member

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    I have some work cut out for me. I really appreciate all the info, and suggestions. These speakers, and system mean a lot to me and I want to keep it sounding as I remember it,
     
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  8. gdmoore28

    gdmoore28 Super Member

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    Which GTOs do you like/own, Jon?

    My favorite was the 1969 model. Had three of them, the last one was a frame-off, ground up restoration except for the paint.

    GeeDeeEmm
     
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  9. gtojon

    gtojon New Member

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    I've had a few including a '69. My first car was a '68. I currently have a '64 convert, and a '70 Judge. But no one here cares, let's talk vintage speakers! Lol.
     

     

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  10. gtojon

    gtojon New Member

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    Ok all-
    I have cleaned all the "brilliance and presence" controls on both Georgians. They were not working properly on the speaker that doesn't sound quite right. The controls work now, full sweep from each control. But this one still doesn't sound like the other one. If someone can give me any hints on what to check next, caps? And how to do it, great. I'm a newbie so anything helps!
     
  11. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    I don't know what caps were in these originally but we'll get to that. First you have to get to the caps! If they are potted, you will have to warm and soften/melt that stuff enough to get to the circuitry. Keep in mind this process can mess up the paint on the outside. Google up 'remove potting material transformer' for example (you have no transformers here but many old electronics had potted transformers and the old radio crowd has methods for unpotting them). A warm outdoor gas grill is one option.

    Once you get to the caps, if they are oil caps (especially in a metal can) it might pay to test the capacitance and ESR and consider keeping them. Many multimeters nowadays have a cap testing function that will measure capacitance only. You'd need a separate meter for equivalent series resistance, which is a measure of how much signal will actually get through. It is often high on old caps even if the capacitance is still OK. This is a lot of trouble and expense for the equipment, so if the speaker doesn't sound right you can just replace them. Given their age they are most likely bad anyway. If you want some recommendations for replacement we can help you with that. A lot of us use the 5% tolerance Dayton metallized polypropylene caps from Parts Express.

    https://www.parts-express.com/cat/crossover-capacitors/292

    You don't have to be too fussy about exactly matching the values. 17.7 can be replaced with 18 uf, 13.3 with 13, etc. The old ones are probably so far off that they will sound much better regardless, and caps have tolerances anyway. The old ones were probably +/- 10 or even 20%. But if you like you can parallel a 0.3 or 0.25 with 13 to get closer to 13.3, etc.

    If there are values over 15 or 20 uf, they get large/expensive in the film types so you can use nonpolarized electrolytics which are much smaller and less expensive. These are usually in the woofer circuit. Best to use the film type when it's in series with the tweeter especially, and the midrange if you can. These are usually the smaller values. All depends on your ears and your wallet.
     
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  12. gtojon

    gtojon New Member

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    Thanks for the next step. Really appreciate the time you are taking for this. So, I have a couple of crossovers I can try removing the potting material as a test. If I'm successful, then I would try it on the one on the real (X336) one. Are these caps soldered in place? Is it a matter of just removing and replacing? How many caps are there in the X336 crossover?
    Thanks in advance!
     
  13. gtojon

    gtojon New Member

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    So, I have a spare X36 crossover and thought I should open it up and see what I'm going to be up against as far as the potted items in my X336. This is what I see. So the tar substance down there, are there more things in there? What am I looking at?!
     

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  14. 22frank

    22frank Member

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    Last edited: Dec 16, 2017
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  15. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    Sorry for the slow reply...Those look like modern film caps, so they appear to have already been replaced in that crossover. Probably why there is no potting tar in there too. Looks like the spec sheet on the 336 says they are potted in 'thermoplastic asphalt' which means warming it will make it soft again.

    In any case you can see what a simple soldering job it is once you identify the cap values and get replacements.
     
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  16. gtojon

    gtojon New Member

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    Thanks guys for responding. I will take the x336 apart next to see how much tar is in there. This extra X36 has just a bit of tar at the bottom (top when upright) the tar is definitely holding that coil in position, and 2 strands of the coil are buried in the tar. Does the coil generally stay, and the caps get replaced?
     
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  17. jwrauch

    jwrauch AK Subscriber Subscriber

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    EV used film caps in a lot of their crossovers. JOHN
     

     

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  18. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    Maybe that's original then. It sure looks more modern than the 1958 data sheet for the crossover. :biggrin: Just saying. But Amrad's history page says that in 1966, they formed the "Precision Capacitor Division which specializes in close tolerance, highly sophisticated, film dielectric capacitors." I did not really know when film caps were first made but they go back quite a ways.

    http://www.americanradionic.com/about-us/history/

    As for the coils (inductors) you can just leave them alone. They're just a coil of copper wire and as long as they aren't melted through they'll work just fine. Nothing to wear out.
     
  19. 22frank

    22frank Member

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    The X325 has connections for the 4 ohm-15WK woofer , the 16ohm- 15W woofer and the 848HF horn, the X36 adds the T35 tweeter.
    The X336 has connections for 4-ohm 15WK, 848HF, and T35 tweeter.
    What components do you have? The insertion loss is different between the 2 set ups, perhaps the L-pad controls could compensate for this. IMHO if your speakers have identical drivers I would use the X336 for both.

    These would be a nice addition to the family http://www.critesspeakers.com/electro-voice-crossovers.html
     
    Last edited: Dec 19, 2017
  20. gtojon

    gtojon New Member

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    All great info here, thanks everyone! The T35 and 848HF's are the same in both. I don't know for a fact if both woofers are exactly the same. I do know one got reconed in the mid 1980's.
    The older speaker has a X336, and the "newer" one (mid 1960's) has a X36, and X325.
    The speaker in question is the X336 one.
     

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