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Thread: Any fix on this 4343?

  1. #1
    Senior Member pyonc's Avatar
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    Any fix on this 4343?

    Hi,

    My audio gear is 4343, with Mcintosh C29 preamp and Marantz power amp.
    Initially I didn't notice this, but as time went by, I suspected some sort of
    difference in loudness of the right and left speakers. And only today I concluded that
    the sound from the left speaker was a bit louder and clearer than the right one.
    I heard the same difference when I played LPs from the 60s and 70s, or CD reissues from that era, and even modern CDs where stereo recording is almost perfect.
    I reversed the speaker mode selector (left to right, right to left), and the result was the same.
    The right speaker was a bit weaker in loudness and clarity than the right one. What do you believe is the problem here?
    Do I need to bring the pair to a JBL technician for thorough check? Or is there anyting I can do some check by myself?
    Thanks a lot for your advice.

  2. #2
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    Try reversing the speaker wire connections on the amplifier. See if the condition stays or moves to the other side.

  3. #3
    Senior Member Audiobeer's Avatar
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    Theres all kinds of things you can try first to see if it's an easy fix. I know you checked the reverse stereo mode on th C-29 but did you check the cable itself and the connections? The next thing I would try is rapidly rotating the L-pads on the weak speaker back and forth to see if that is the issue. If it's still weak then you may want to set your balance at the 12 o'clock on the preamp and use the tone controls on your C-29 to see if you can Isolate which driver is having the problem, start with de-emphasizing everything but the Low frequency band, then try the mids and then the high frequency. This should help you isolate which driver is the culprit if in fact it is a driver.

  4. #4
    Senior Member pyonc's Avatar
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    Quote Originally Posted by rusty jefferson View Post
    Try reversing the speaker wire connections on the amplifier. See if the condition stays or moves to the other side.
    Thanks, Jim. I tried this, and the condition stayed the same. Maybe I'm gong to use play the audio test CD.

  5. #5
    Senior Member pyonc's Avatar
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    Quote Originally Posted by Audiobeer View Post
    Theres all kinds of things you can try first to see if it's an easy fix. I know you checked the reverse stereo mode on th C-29 but did you check the cable itself and the connections? The next thing I would try is rapidly rotating the L-pads on the weak speaker back and forth to see if that is the issue. If it's still weak then you may want to set your balance at the 12 o'clock on the preamp and use the tone controls on your C-29 to see if you can Isolate which driver is having the problem, start with de-emphasizing everything but the Low frequency band, then try the mids and then the high frequency. This should help you isolate which driver is the culprit if in fact it is a driver.
    Thanks for your advice. 'Rotating the L-pads'? That seems too technical to me, though.
    C29 doesn't have the 'tone' controls to isolate the driver, though.
    Looks like the problem comes from mids and highs, not the lows
    because that's where I feel the difference when I played an instrumental jazz CD or LP with saxophone or trumpet player.

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    Senior Member Krunchy's Avatar
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    Quote Originally Posted by pyonc View Post
    'Rotating the L-pads'? That seems too technical to me, though.
    Its not really, just just rotate them back and forth (clockwise & counter clock wise) a few times & see if that impacts the sound emanating from the drivers.
    Just Play Music.

  7. #7
    Administrator Robh3606's Avatar
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    Try turning the biamp switch on and off a couple of times. The contacts tend to oxidize just like the l-pads do. It is located on the back of the speaker where the terminals are.

    Rob
    "I could be arguing in my spare time"

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    Senior Member pyonc's Avatar
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    Quote Originally Posted by Krunchy View Post
    Its not really, just just rotate them back and forth (clockwise & counter clock wise) a few times & see if that impacts the sound emanating from the drivers.
    Thanks. I've never done this before, though I assume my previous owner did so.
    Do you have to take out the front lower baffle to do this?

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    Quote Originally Posted by pyonc View Post
    Thanks. I've never done this before, though I assume my previous owner did so.
    Do you have to take out the front lower baffle to do this?
    They're not talking about physically rotating the L-Pad in the cabinet, they are talking about adjusting the L-pad a few times through its adjustment limits. Like turning the volume knob up and down on a receiver a few times.

    Does your 4343 have three little adjustments on the front of the baffle like in this pic? That's the adjustments.


  10. #10
    Senior Member pyonc's Avatar
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    Quote Originally Posted by JeffW View Post
    They're not talking about physically rotating the L-Pad in the cabinet, they are talking about adjusting the L-pad a few times through its adjustment limits. Like turning the volume knob up and down on a receiver a few times.

    Does your 4343 have three little adjustments on the front of the baffle like in this pic? That's the adjustments.

    Thanks a lot for enlightening me on this.
    Yes, definitely my 4343 has that adjustment levels on the front.
    Currently, Ultra High, High, Mid volumes on left and right speakers are set at the same levels. What if I have the same weaker sound from the left speaker despite the matching level adjustments?

  11. #11
    Senior Member grumpy's Avatar
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    Seriously. Find a large flat-bladed screwdriver. Turn the "level adjustment" L-pads up
    and then down, several times... listening for scratchy sounds from the speaker (while
    playing music) or for jumps in level... either indicates an eventual need for replacement
    of the L-pad behind the front panel.

    Sometimes you can get away with just finding a place where the L-pad is happy (not
    oxidized, burned, or otherwise damaged in a particular area of its rotation. They wear out.
    Same with the Bi-amp switch in the back, near the speaker wire terminals. Turn it back
    and forth several times... it might scrape off some crud or oxidation that has built up
    over time (just put it back when you're done).

    Have you figured out which driver (or all of them?) is sounding less loud?

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    The contacts inside the L-pad can become a little oxidized over time, affecting the level of the driver associated with it. That's why, with the L-pads on the 2 speakers set to the same level, the actual resistance across one L-pad might be considerably different than the other. By rotating the L-pad through its range of adjustment, you can often restore the contact area by breaking loose the oxidation/dirt. That's what's behind the suggestion to rotate the L-pads through their entire range a few times.

  13. #13
    Senior Member pyonc's Avatar
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    Quote Originally Posted by grumpy View Post
    Seriously. Find a large flat-bladed screwdriver. Turn the "level adjustment" L-pads up
    and then down, several times... listening for scratchy sounds from the speaker (while
    playing music) or for jumps in level... either indicates an eventual need for replacement
    of the L-pad behind the front panel.

    Sometimes you can get away with just finding a place where the L-pad is happy (not
    oxidized, burned, or otherwise damaged in a particular area of its rotation. They wear out.
    Same with the Bi-amp switch in the back, near the speaker wire terminals. Turn it back
    and forth several times... it might scrape off some crud or oxidation that has built up
    over time (just put it back when you're done).

    Have you figured out which driver (or all of them?) is sounding less loud?
    Thanks for your kind advice. I'll do so as advised this evening. By the way,
    when I listened closer last night, mid-driver on the left speaker seemed to be the source of the less loud. Let me double check it this evening, and report back to you.

  14. #14
    Senior Member pyonc's Avatar
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    Quote Originally Posted by JeffW View Post
    The contacts inside the L-pad can become a little oxidized over time, affecting the level of the driver associated with it. That's why, with the L-pads on the 2 speakers set to the same level, the actual resistance across one L-pad might be considerably different than the other. By rotating the L-pad through its range of adjustment, you can often restore the contact area by breaking loose the oxidation/dirt. That's what's behind the suggestion to rotate the L-pads through their entire range a few times.
    Thank you! I now understand more about all this talk about L-pad. Let me carry out your suggestion when I get back home this evening, and report back to you about the outcomes.

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    Quote Originally Posted by pyonc View Post
    Thank you! I now understand more about all this talk about L-pad. Let me carry out your suggestion when I get back home this evening, and report back to you about the outcomes.
    It sounds like you're very non-technical. You can simply increase the clockwise rotation of the L-pad for the midrange to raise its loudness. You should rotate them per the other members, though, and remember to set them back to approximately where they were before you did this excercise. Check to see if they're set approximately the same place on both speakers. Wiggle the biamp switch.

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