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Thread: E155-4 testing (long)

  1. #1
    Senior Member grumpy's Avatar
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    E155-4 testing (long)

    Sometimes you win, sometimes not so much:

    Recent E155-4 acquisition

    LF tone from precision sinewave oscillator into D45 amp produces some undesirable noises, even at fairly low excursions.

    JBL spec says sweep test is 7v 20Hz-1.2kHz so I mostly kept to that or lower.
    Did notice some pretty buzzy distortion right around 100Hz (something loose/resonant)... would have guessed tinsel leads, will have to double-check that.
    Higher freqs (albeit lower excursion) sound fine. I could see where someone would briefly test this with music and call it 'good'.
    Checked tinsel leads. Did not notice interference or cone slapping (but didn't sweep through 100Hz until later ) .
    Checked rear vent filter. OK (probably replaced when reconed... -looks- fairly recent, hard to tell but still quite pliable/not disintegrating) .
    Cone is marked MWE155 224 04 (dome glue line looks pretty good).
    Tested with rear vent unblocked, holding on-edge (vertical), shooting for free-air environment.
    Not noticing any rubs/scraping when carefully moving cone manually (evenly, just outside the periphery of the dome/downward, or from underneath/forward) being careful to not induce any side motion that would tilt the voice coil.
    VC resistance appeared normal, and did not jerk around when cone was moved (i.e., steady when not moving... coil vs magnet motion will make the measured value change while moving).
    Magnet did not appear shifted. Frame did not look damaged.
    Rotating driver to terminals up seemed to change the noise characteristic -slightly-... that was the only clue I could find.

    Compared with another E155-4 to make sure test was 'fair'... it was fine with even lower freq and higher excursion levels.
    Have not tried it in a box yet. Have not put it on a WT2 woofer tester (I only have their initial low level device). Haven't tried green eggs and ham with a fox yet either... bucket list?

    At any rate, I don't think I'm just being picky. LF drivers in free-air do tend to make some unexpected noises.
    I'll keep poking at it, but I'm quickly running out of ideas.
    Funny that I found one mounting screw had been left in and was held captive by the front-side gasket (alas, it was not the culprit).

    Suggestions, re anything I forgot before attempting a return?
    I'd prefer to have a working unit, but if truly faulty and not reasonably repairable it would be an expensive core to start over with.



    Maybe someone else can use this as a check list, if nothing else. Thanks for listening.

  2. #2
    Senior Member grumpy's Avatar
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    Silver lining: Seller was quite reasonable and understanding (refund).

    ... and I at least have a big impressive frame and a magnet to show for my efforts.

    If I get this sorted out further (findings/repair/recone/or just use until it explodes),
    or take up any useful suggestions, or even if there are just questions, I'll try to respond in this thread.

    Thanks all and best regards,

    -dave

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    Quote Originally Posted by grumpy View Post
    Silver lining: Seller was quite reasonable and understanding (refund).

    ... and I at least have a big impressive frame and a magnet to show for my efforts.

    If I get this sorted out further (findings/repair/recone/or just use until it explodes),
    or take up any useful suggestions, or even if there are just questions, I'll try to respond in this thread.

    Thanks all and best regards,

    -dave
    Have you checked the spider glue line where it attaches to the cone? It can appear intact until you push on the cone enough to see a separation. That join can be brittle. I have a 2245 that cracked right there about 1/3 way round.

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    Senior Member grumpy's Avatar
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    Thanks!

    Will check. I did push around on the spider a bit, checking on voice coil alignment changes and didn't notice loose bits, but you're right, I should give it a specific look-see.
    You'd think that would be up there in my brain, what with the SUB1500 issues folks had from the PE sale. Spider to frame and spider to voice coil...


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    Senior Member macaroonie's Avatar
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    Gasfan beat me to it. That glue line is out of sight so out of mind.
    Can you gen a spot frequency that will excite the noise in a stable way that you can use a McGuyver stethoscope to sniff out the fault ?

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    Administrator Robh3606's Avatar
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    Hello Grumpy

    Do they have cloth surrounds?? I once had a 2118 they had a small tear in part of the surround on the outside edge against the gasket. It would buzz with sweeps. Almost impossible to see found it using a pen light behind the cone. Good luck!!

    Rob
    "I could be arguing in my spare time"

  7. #7
    Senior Member grumpy's Avatar
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    Gasfan and Mac nailed it. Wasn’t nearly as apparent before testing.

    Glue Epoxy recommendations?

    (... and yes, treated cloth surround. Noticed the tan line on the spider/cone interface while checking with a light... so all has been helpful! )

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    Quote Originally Posted by grumpy View Post

    Glue Epoxy recommendations?
    Not sure what the composition is but I would use JBL's own. Probably the black one used for the dust cap. But you need a long thin nozzle available at hobby shops for RC planes etc. so you can reach in there and lay a neat bead ideally just the way it sits in the pic, then press it back into place so it's glued to the former and not just to old glue.

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    Here's an example. Amazing I have not repaired a driver in a few years now and all my tubed glues are still not dried up
    Attached Images Attached Images  

  10. #10
    Senior Member edgewound's Avatar
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    Quote Originally Posted by grumpy View Post
    Gasfan and Mac nailed it. Wasn’t nearly as apparent before testing.

    Glue Epoxy recommendations?

    (... and yes, treated cloth surround. Noticed the tan line on the spider/cone interface while checking with a light... so all has been helpful! )

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    Maxi-Cure CA with accelerator by Bob Smith Industries.

    FYI...that is an aftermarket recone. This is not a bad thing, with suitable parts, as long as glue joints such as this don't come apart. The seller should have tested it before shipping it. Glad you got a refund.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  11. #11
    Senior Member grumpy's Avatar
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    [edit] Oops... left this response open for too long. Thanks Ken!!

    Pretty sure it was a recone from the get go... had that look,
    ... seller was very apologetic and not keen re a lot of what he got from one source.
    It would be great if everyone on ebay did a sweep test and published impedance curves
    I just try to assume the worst and bid accordingly.

    [/edit]

    Thanks. Got me looking.

    JBL brand Moyen RS-3087 Cement? ... Perhaps there's another formulation for VC/spider/cone attachment.
    I thought epoxy was the norm for this particular use, perhaps CA being used more recently? But there are many variations of both.

    RS-3087 -> "Use for: attaching dust caps, attaching cones/surrounds to speaker frames, replacing/attaching foam surrounds, attaching gaskets."

    I also have a 2220H missing it's dust cap, so the Moyen will also go in the check-out cart
    Do I properly recall that there's a also a thinner (generic?) to help with the leveling/smoothness of the glue line?
    (beyond a turntable, a steady hand, and experience)

    -dave

  12. #12
    Senior Member macaroonie's Avatar
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    Big squish of Dow will do it.

    😀😀😀😀😀😀😀💗

  13. #13
    Senior Member macaroonie's Avatar
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    I see the cone ID is MW xxxxx

    That's MWA in Arizona I think , Ken will
    confirm or not , were they Waldom ?

  14. #14
    Senior Member grumpy's Avatar
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    2220H ... another work in progress

    Needs a bit more trimming on the glue line before replacing dust cap. (driver arrived sans dustcap).
    Foilcal came off cleanly with a hair drier and some gentle persuasion.
    Fired up the ancient Electrolux to vacuum out the old foam filter bits and around the inside of the voice coil.
    A similar heating and pressure re-adhered the foilcal (pic is just after it was loosened).
    Think 21057 is the correct cone (perhaps for several drivers).
    Glue line looks pretty good (what's left).
    That crap in the vent sure looked "stock"
    Sweep test sounded fine... even though the former doesn't -appear- to be perfectly centered in the picture.

    Cheers.

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    Senior Member grumpy's Avatar
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