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Thread: JBL 130A Break In?

  1. #1
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    JBL 130A Break In?

    Hi everyone,

    I just got a pair of 130A 15" woofers for a DIY Hartsfield project. The cones are the correct 130A cones with the paper dust cap and are marked as such in white pencil on the cones.
    I noticed that one speaker has a much softer suspension than the other and the cone move much more easily when very lightly pushed with my hand. Also when I tap on the cones, the fundamental of the loser cone is much lower than that with the stiffer cone.
    loosen

    My question is should the firmer cone loosen up with use like the other?
    Im thinking that the loser one was used more than the stiffer one. Does this make sense or does "break in" not make the cone much looser?

    I obviously want the drivers the be well matched for both speakers.
    The cones look to me like older re-cones that were not used much since the look nearly brand new and the speaker dope on the surround also look like a re-cone job and not stock JBL.

    Thanks,
    Matt

  2. #2
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    Quote Originally Posted by mbeards View Post
    Hi everyone,

    I just got a pair of 130A 15" woofers for a DIY Hartsfield project. The cones are the correct 130A cones with the paper dust cap and are marked as such in white pencil on the cones.
    I noticed that one speaker has a much softer suspension than the other and the cone move much more easily when very lightly pushed with my hand. Also when I tap on the cones, the fundamental of the loser cone is much lower than that with the stiffer cone.
    loosen

    My question is should the firmer cone loosen up with use like the other?
    Im thinking that the loser one was used more than the stiffer one. Does this make sense or does "break in" not make the cone much looser?

    I obviously want the drivers the be well matched for both speakers.
    The cones look to me like older re-cones that were not used much since the look nearly brand new and the speaker dope on the surround also look like a re-cone job and not stock JBL.

    Thanks,
    Matt

    How I dealt with two different vintage (and sounding) 130As that I owned (purchased at two different times, the typical MONO to STEREO transition system) One would go objectively (measured with test tones and an SPL meter) as well as subjectively "deeper" than the other, but exhibited no other issues or mechanical problems. Both were unmolested factory originals in every way, just different ages :
    The paper compliance rolls need to be treated with something..........I went with a PVA intended for this, judiciously applied to the compliance rolls/pleats ONLY. In other words, right up to the spot where the surround transitions into "cone" and no further. This to prohibit the inevitable splitting that will come with daily use of an all paper cone that's at least 40 years dry. Make certain that the roll where the cone ends, and compliance begins, is well treated. I measured the best I could (with a cheap digital scale) and feel as if this added negligible mass to the overall cone once dry. I applied (3) evn coats, the first being the "heaviest" as this will be the one to do the most good (absorption) by the extremely dry paper.
    Take care to measure out and apply THE SAME AMOUNT of material to both drivers.
    It took some time but they smoothed out sound wise (one was a bit "tight" sounding when I got it). Basic frequency sweeps and my ears could find/hear no issues.
    Short of sending them to a true professional, someone like "edgewound" that can truly and scientifically test and measure their output, I think this is about as good as you can do.
    I applied the material with the help of a modified "lazy susan" bearig, a piece of MDF for support and a good quality soft brush. The results looked "factory":
    http://www.acehardware.com/product/i...ductId=1296568
    Mine sounded just fine and balanced after a few weeks of playing them daily. They did appear to need to be "woken up" after years of dormancy in storage. I started out by playing them gently and gradually increased what I was feeding them. In the end, they performed flawlessly.
    Good luck; those are very nice sounding old woofers!
    Thomas

  3. #3
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    Quote Originally Posted by mbeards View Post
    Hi everyone,

    I just got a pair of 130A 15" woofers for a DIY Hartsfield project. The cones are the correct 130A cones with the paper dust cap and are marked as such in white pencil on the cones.
    I noticed that one speaker has a much softer suspension than the other and the cone move much more easily when very lightly pushed with my hand. Also when I tap on the cones, the fundamental of the loser cone is much lower than that with the stiffer cone.
    loosen

    My question is should the firmer cone loosen up with use like the other?
    Im thinking that the loser one was used more than the stiffer one. Does this make sense or does "break in" not make the cone much looser?

    I obviously want the drivers the be well matched for both speakers.
    The cones look to me like older re-cones that were not used much since the look nearly brand new and the speaker dope on the surround also look like a re-cone job and not stock JBL.

    Thanks,
    Matt

    My comments obviously apply depending on what sort of "dope" you have on your edges already. If it is the semi-soft pasty or stcky "goop" and the coverage is good, then just break them in by playing them reasonably at first and see what happens.
    You can't hurt anything if the edge treatment is still good and compliant and is still maintaining a good bond and penetration with the paper fibers of the surround.
    If it's the dry, shiny looking stuff I have seen on some vintage drivers (no longer "tacky" or flexible at all) and appears more like a hardened lacquer like substance, I would still dress them with PVA. Some of the material I have seen used from the '50 and '60s just seems to eventually dry out completely and becomes little more than clear "paint", offering little "moisturizing" effect to keep things supple.
    Thomas

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