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Thread: JBL woofer refoaming question

  1. #1
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    JBL woofer refoaming question

    I bought 5 JBL 2235H off craigslist couple days ago. The seller collected so many 2235H from 15 years ago but never really used them. All units are in great condition with the original JBL cone. Yesterday I tested them with 20Hz signal and I found one issue. All units create a 'click' sound when I increase the volume to some level. I figured out that the foam surround was not glue all the way to the edge of the frame, so when the cone has large movement, the foam surround hits the frame and make some noise.

    Is this a big problem? I think I should not hear the click if I put the unit in cabinet and play music with it - the music should cover the small click sound anyway. And I can fix it by re-foaming it. My question is: when I do the refoaming, do I need to apply downward force to the cone to make sure the foam is glue to the very edge of the frame?

  2. #2
    Senior Member grumpy's Avatar
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    Xmax of .3" at 20Hz (also it's resonant frequency) will be pretty easy to hit in free air and it won't be loud to warn you.
    Woofers can start to make odd sounds as you start to overdrive them in free air (nothing to impede the driver's natural resonance vs the resisting spring force of air in a sealed cabinet or a counteracting port resonance).

    If it's really a soft click you might be right. There's also a 'mass ring' glued inside the voicecoil under dome that will smack the pole piece rather rudely... but I wouldn't call that a 'click'.

    http://www.audioheritage.org/vbullet...trolling-Rings

  3. #3
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    I re-foamed one of the driver today. the 'click' sound was gone. All five drivers were bought from eBay. So if you buy from eBay, you need to re-foam it anyway, people just do a lousy re-foaming job.

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    Administrator Mr. Widget's Avatar
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    In the past when I bought used drivers I always assumed that I was buying cores that would need a full rebuild. Now days since most cone kits and high frequency diaphragms are no longer available from JBL, buying used drivers is a much bigger gamble.

    Great news that a simple refoam was able to correct your problem.


    Widget

  5. #5
    Senior Member edgewound's Avatar
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    Quote Originally Posted by Mr. Widget View Post
    In the past when I bought used drivers I always assumed that I was buying cores that would need a full rebuild. Now days since most cone kits and high frequency diaphragms are no longer available from JBL, buying used drivers is a much bigger gamble.

    Great news that a simple refoam was able to correct your problem.


    Widget
    Are you of the expert opinion that very good...if not exceptional...results are not possible with the proper execution of suitable aftermarket parts?

    It's an honest question that deserves an honest answer.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  6. #6
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by edgewound View Post
    Are you of the expert opinion that very good...if not exceptional...results are not possible with the proper execution of suitable aftermarket parts?

    It's an honest question that deserves an honest answer.
    Other than the TruExtent beryllium diaphragms I have no personal experience with aftermarket diaphragms or recone kits. Logically it should be possible to match the performance of the original driver, but I am not aware of anyone who is not a top flight manufacturer (JBL, TAD, Meyer Sound etc.) who has the resources to verify the performance of an installed diaphragm or cone kit.

    That said, today if someone has a vintage driver that is not in spec, and there are no factory repair parts available there are few options. Finding a gifted recone shop like yours is the best option.


    Widget

  7. #7
    Administrator Robh3606's Avatar
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    Quote Originally Posted by edgewound View Post
    Are you of the expert opinion that very good...if not exceptional...results are not possible with the proper execution of suitable aftermarket parts?

    It's an honest question that deserves an honest answer.
    Hello Edgewound

    Depends doesn't it?? I have never seen measured T/S or Frequency response plots to verify performance of these prepackaged after market kit sold on the internet or elsewhere. Maybe I missed them?? I mean 2235 kits with no mass ring as an example??


    I did my own comparisons of stock pair of JBL 2425 to available aftermarket "replacements" Yeah they worked but were terrible in comparison.

    Old thread

    http://www.audioheritage.org/vbullet...rket+diaphrams


    The normally available kits without actually testing them??? Or seeing data I would be very skeptical.

    Now if you set out to match the originals that's another story. I can see a professional having the skills to do it but that's different from mass produced kits in my mind. You have access to original kits as a baseline. The prepackaged kits are low cost replacements compared to the originals that will give you working drivers.

    How well?

    Which aftermarket kits are the best??


    A question wouldn't a custom built replacement kit that matches the original be about the same or more than the JBL kits original cost??

    You have to do the R+D on a replacement that can't be a quick process??

    Rob
    "I could be arguing in my spare time"

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    Hi Rob,

    I agree on it depends?

    Like how do you know what happened prior to an eBay purchase?

    Itís an unknown unknown.

    Only an experienced user or a skilled loudspeaker repair technician could reasonably make a determination on the diaphragm installed and the condition of the entire assembly. I agree with Mr Widget the default is it will need to be looked at.

    If the driver came with a service history thatís a different matter. If it was generally done very well why donít service technicians provide a service history?. If they valued their work so highly why donít they? An A4 diagnosis and repair sheet. Okay

    An example

    My 2245ís had the foam surrounds damaged in a relocation.
    The diaphragms were original but the foam wasnít.

    The technician pulled apart the whole driver and replaced the spider with a new spider and a new surround. He check everything else. This particular technician had rows if racks with all sorts of driver diaphragm components. I got it back in two weeks with a document of the work done and the parts installed.

  9. #9
    Senior Member 1audiohack's Avatar
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    Quote Originally Posted by Robh3606 View Post
    Hello Edgewound

    Depends doesn't it?? I have never seen measured T/S or Frequency response plots to verify performance of these prepackaged after market kit sold on the internet or elsewhere. Maybe I missed them?? I mean 2235 kits with no mass ring as an example??ÖRob
    Or what about the paper even? The C8R2235 kit uses a Hitachi hard paper cone. Can the aftermarket acquire or duplicate them? I donít know.

    My faith in aftermarket kits is very low. That is unsubstantiated for the record.

    Also I would bet Edgeís kits are very good.

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  10. #10
    Senior Member edgewound's Avatar
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    Quote Originally Posted by Robh3606 View Post
    Hello Edgewound

    Depends doesn't it?? I have never seen measured T/S or Frequency response plots to verify performance of these prepackaged after market kit sold on the internet or elsewhere. Maybe I missed them?? I mean 2235 kits with no mass ring as an example??


    I did my own comparisons of stock pair of JBL 2425 to available aftermarket "replacements" Yeah they worked but were terrible in comparison.

    Old thread

    http://www.audioheritage.org/vbullet...rket+diaphrams


    The normally available kits without actually testing them??? Or seeing data I would be very skeptical.

    Now if you set out to match the originals that's another story. I can see a professional having the skills to do it but that's different from mass produced kits in my mind. You have access to original kits as a baseline. The prepackaged kits are low cost replacements compared to the originals that will give you working drivers.

    How well?

    Which aftermarket kits are the best??


    A question wouldn't a custom built replacement kit that matches the original be about the same or more than the JBL kits original cost??

    You have to do the R+D on a replacement that can't be a quick process??

    Rob
    Hello Rob,

    Several months ago you asked for measurements of my no-rot "2236H" recone kit to replace the 2235H. Here's the post to refresh your memory.

    http://www.audioheritage.org/vbullet...l=1#post439551

    Those that have chosen to go this route are thrilled with the results. One customer even chimed in on this forum to report his satisfaction.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  11. #11
    Administrator Robh3606's Avatar
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    Quote Originally Posted by edgewound View Post
    Hello Rob,

    Several months ago you asked for measurements of my no-rot "2236H" recone kit to replace the 2235H. Here's the post to refresh your memory.

    http://www.audioheritage.org/vbullet...l=1#post439551

    Those that have chosen to go this route are thrilled with the results. One customer even chimed in on this forum to report his satisfaction.

    Great thanks your right I did forget. Wish there were more like you out there.

    Rob
    "I could be arguing in my spare time"

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    Is the Qts is a little too high? I tested my 2235Hs, the Qts is in 0.25 to 0.27 range, and Fs is in 20Hz to 24Hz. Vas is around 330, only one has the Vas of 474.

    I will test them again once I finish all the re-foaming work.


    Quote Originally Posted by edgewound View Post
    Hello Rob,

    Several months ago you asked for measurements of my no-rot "2236H" recone kit to replace the 2235H. Here's the post to refresh your memory.

    http://www.audioheritage.org/vbullet...l=1#post439551

    Those that have chosen to go this route are thrilled with the results. One customer even chimed in on this forum to report his satisfaction.

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