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codewritinfool

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Posts posted by codewritinfool

    Odd resonance

    in Technical/Restorations

    Posted

    I am running Super AA now, but the odd resonance is still there.  That's not why I changed to Super AA, but it helps rule out the crossover.  The resonance doesn't bother me as much as it did, though it is still present.  I know that sounds crazy, but I've been pretty busy these days and haven't had time to run it down further.

     

    WTB: A pair of 3619 autoformers

    in Garage Sale

    Posted

    12 hours ago, albertli said:

    Thanks Bruce, 

    I am only an old newbie and knowing not too much about electronics but good on wood.  

    I have visited Bob's site and know the 3619 unavailable but he has the 3636 instead.  Don't know if the 3636 is the direct drop in substitute. 

    Albert

    If I were you I'd call Bob directly or drop him an email.  I've communicated with him on multiple occasions and he is a good dude.

     

     

    Odd resonance

    in Technical/Restorations

    Posted

    35 minutes ago, MookieStl said:

    pretty sure he didn't totally swap the wires, just left wire to right speaker @ speaker connection and vice versa.

    Yessir, this is correct.  And when I changed the speaker connections l/r at the amplifier, it stayed with the right channel.  I have some more honeydo stuff to get done today before I can retire out to my workshop and swap the actual crossovers.

     

     

    Odd resonance

    in Technical/Restorations

    Posted

    I swapped amplifier output channels (yay speakons) and it stayed with the right khorn.  Later tonight I plan to swap crossovers between khorns and see if the problem moves to the left khorn.

     

    I've ruled out the signal chain right up to the crossovers.  I've also *pretty much* ruled out the driver itself, since the Atlas K55 driver and the Crites A55-G driver makes the same noise, even separated from the horn.  I suppose they COULD be both making the noise as a defect, but it isn't likely since one is 50 years old and the other one is a week old.  I've ruled out cabinet resonance because it happens in my hand.  I don't push my Khorns at all.

     

    Interesting thoughts about transformer delamination.  The caps are brand new so if it is indeed the crossover it almost certainly would be an oxidized connection or magnetics.  I've been soldering for about 40 years and feel confident it isn't MY connections, though anything is possible.

     

    Thanks for the thoughts.  Physical crossover swap happens next.

     

     

     

     

    Odd resonance

    in Technical/Restorations

    Posted

    Thanks for your reply.  This is definitely coming directly from the raw driver detached from the horn and held in my hand so the cabinet is not in the picture.  Exactly the same frequency points on the old K55 driver as it is on the new A55-G driver.  Since I swapped the amplifier outputs and it remained on that channel, the only thing left is the crossover and the speaker wire.

     

    I'm at work now but I can take an oscilloscope home later and see if I can see the distortion pre and post crossover.

     

     

    • Like 1

    Odd resonance

    in Technical/Restorations

    Posted

    Ok, so here's one I'm trying to solve.  While listening to music, I came across a Norah Jones track and at the beginning of it her voice slightly buzzed in a weird way from the right speaker.  I started the track over and heard it again.  It was distorted.  I fired up REW and hunted around with the generator until I discovered that between about 270Hz and 305Hz I can get this mode to pop in - complete overtone buzzing distortion coming from only the right speaker.  Sounds like the squawker.  

     

    I swapped output channels on the amp and fired it up again and it is still there in the right speaker.  This is at completely normal listening levels, but I did notice that if I pump the level up a couple of dB I can get it to pop into resonance at a few Hz lower.

     

    The only drivers on my horns that are original are the K55s, so I said screw it and ordered a set of A55G's from Bob Crites.  They came and the swap out was easy, new gaskets too.

     

    The resonance is still there.  I pressed around on everything to attempt to dampen the resonance in case it was a piece of wood or something vibrating.

     

    Last night I narrowed it down to the squawker for sure.  In fact, I removed the driver from the actual horn and it is coming from the driver.  Once again I swapped amplifier OUTPUT leads and it is still just in that right squawker driver, not the left, so it doesn't appear to be in the signal chain all the way up to and including the amp.

     

    The only thing left is the crossover, but that's a simple type A.  Anyone ever heard of such a thing coming from the crossover itself?  It has been recapped but the magnetics are original.

     

    Tonight I might swap crossovers between speakers and see what that does.  

     

    Any thoughts?

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