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Thread: Please help with 128H's in L150A's. :)

  1. #31
    Member DerekTheGreat's Avatar
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    So that's a bad picture but if you blow it up you can make out the "original" cones. Original to me, but not the L150A's that is. Those LX44's are for sale if anyone wants them. Best offer.

  2. #32
    Member DerekTheGreat's Avatar
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    I picked my 128H's up this past Saturday. The cones look to be the same or similar to the ones they replaced; dark purple color & textured rear, just no AquaPlas coating of course. I bought that one eBay listing for a true replacement but that's just one cone. So I'll stash that until I find another and need to recone these speakers or another set. In the meantime, if someone needs that recone kit, PM me.

    I decided to paint them white using that 1-2-3 paint and the materials I listed earlier. Only it didn't end up working out for us the way it did for the person I got the idea from. A 1:1 dilution with water was too much, and so I ended up coating with 3:2 instead. (150mL paint : 50mL filtered water) Only used about 50mL of paint total, took four coats before the purple was completely hidden. We didn't end up using that 1" Purdy brush at all. Instead we used 1" foam brushes and some fine tip paint brushes to paint around the dust caps & speaker leads and the surrounds to avoid painting parts which we didn't want to be white. My wife did all the detail work around the dust caps & surrounds as my hands are just too jittery for that sort of stuff. We had trouble building up paint on the ridges of the cone and so after painting coats 2-3 with the foam brushes 360 degrees, I dipped the tip of foam brush in the paint and dabbed along the ridges to achieve hiding. A heat gun was used between coats as well as a cake turntable. Hopefully this information will help someone else who finds themselves in this sort of bind.

    The results are 100 times better than my wife and I expected. Here are some before and after pics, please let us know what you think, especially about the color. Initially I thought the paint was too "white" (especially compared to the old cones) but after referencing some JBL sales literature I think the color & gloss is spot on.

    First pic are the speakers as I received them. Second is after paint and third is same as second but with the old cone for color reference. Which is closest the color JBL actually used?
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  3. #33
    Member DerekTheGreat's Avatar
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    This is just a bonus post. I thought I'd post pics which show the damage to the voice coils, which were indeed rubbing and the source of that "pop" I was hearing. I haven't actually listened to the speakers yet but I moved the cones by hand as I did before I did not feel any rubbing so I'm confident my problem was the previous job. I'll post pics of the 150A's later too.

    First pics is of an old cone which shows "129H". Second pic is of one of the new cones installed on the 128H basket, "128H". Remaining pics are of the old voice coils, one having more damage than the other. Explains why both were popping, just one before the other, hopefully anyway. Fingers crossed that after all of this I can finally enjoy my speakers! I still need a VU meter for my Marantz 510M though! If anyone can help with that, please let me know!

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  4. #34
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    Thanks for the pics Derek! ( plus the update on the cone painting mixture ).

    I you still have them ( I humbly suggest that you ) hold on to those cone assemblies ( that were lifted out as a single piece ).

    They ( or parts of them ) may be re-usable in the future to a master tech. ( especially the aquaplased cone ).


  5. #35
    Member DerekTheGreat's Avatar
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    Thanks for the response, Earl!

    I do still have the cones, but suspect they were painted and not original. We also cannibalized them to practice our painting techniques as one was already damaged on the outer edge. I was hoping someone on here might be able to tell us if they were originals or original replacements, as well as verify if the color was right. One pic I posted has the "original" cone in the center of the ones we painted. The white we used is much more vibrant than that cone but perhaps the old cone has just faded due to age and such.

    On a different note, I got the JBL C8R128H kit in yesterday. I'll pull that out of the box and snap pictures of it as well. But, it isn't an original cone either so who knows how close it is the factory stuff? Being that it's from JBL I'm going to assume it's as close as you can get but what would I know? I need your guys' help and advice here!

    I still would like to know how to test how well my cabinets are sealing up too. How is this done?

  6. #36
    Senior Member RMC's Avatar
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    Hi Derek,

    RE: "I still would like to know how to test how well my cabinets are sealing up too. How is this done?"
    In order to know this you have to measure the driver's motional impedance at the voice coil. I can't show what I have on this as its copyrighted and the author clearly indicates prior permission required to reproduce his stuff even in part... So you'll need to search the Net on this driver motional impedance issue.

    I haven't followed your project consistently and in detail but the latest posts made me react. I sure don't intend to rain on your project since I do appreciate the amount and quality of work you and your wife put on this. However, I think its important you realize the implications associated with painting driver cones. By wanting to "improve" driver aesthetics you may, at the same time, have shot yourself in the foot on the technical side of things.

    When painting the cones with four coats of paint you added mass to these and that has some consequences, as explained by Bullock (P. 9-10): Woofer resonance frequency Fs, cone mass Mms and suspension compliance Cms are related. For example, playing with Mms or Cms can lead to a notable change in driver Fs. Driver Q parameters will also vary: Qms considers Fs and others, while Qes considers Fs and Mms among other too. Hence driver Qts will also be impacted since it is calculated with Qms and Qes. Domino effect...

    Fs, Qts and Vas are the three basic parameters to calculate box data. Qts affects proper box size, as well as Vas ["volume of air whose compliance is the same as a driver's acoustical compliance Cms" as defined on LH Forum; in a way Vas is another representation of compliance (Cms)].

    The above is probably what made Bullock say re one of his own projects : "Investigation revealed air leaking through the driver's dust cap. I sealed the cap with glue, remeasured the driver's parameters which were altered by the additional mass (the glue) and realigned ..." P.8

    Some glue on a dust cap seems like a relatively small change compared to 4 coats of paint on the larger cone area. If one was to add Aquaplas on the back side of a painted cone, mass would increase again, with further T/S deviations (but that is taken into account by the driver's design engineer at the factory).

    Moreover, cone mass and suspension compliance (Mms and Cms) have an impact on driver transient response, thus on how a driver will effectively sound.

    I don't see white cones giving more value to the drivers since the work was not done by the manufacturer (i.e. not original). At the time of say a resale, its not sure a potential buyer would be pleased or interested in homemade painted cones that may well have shifted T/S. As long as they please you that's what counts.

    The above doesn't mean you have worthless drivers after modification. They will still produce sound in the enclosures, the question is how well of a fit and reproducer are they now. My suggestion is you should get yourself something like the Dayton Audio DATS V2 in order to measure the new actual T/S parameters of your modified drivers to assess if they're still properly suitable for the cabinets' Vb/Fb. Then go from there.

    Sorry for being the bad news messenger. Regards,

    Richard

  7. #37
    Member DerekTheGreat's Avatar
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    Quote Originally Posted by RMC View Post
    Hi Derek,

    RE: "I still would like to know how to test how well my cabinets are sealing up too. How is this done?"
    In order to know this you have to measure the driver's motional impedance at the voice coil. I can't show what I have on this as its copyrighted and the author clearly indicates prior permission required to reproduce his stuff even in part... So you'll need to search the Net on this driver motional impedance issue.

    I haven't followed your project consistently and in detail but the latest posts made me react. I sure don't intend to rain on your project since I do appreciate the amount and quality of work you and your wife put on this. However, I think its important you realize the implications associated with painting driver cones. By wanting to "improve" driver aesthetics you may, at the same time, have shot yourself in the foot on the technical side of things.

    When painting the cones with four coats of paint you added mass to these and that has some consequences, as explained by Bullock (P. 9-10): Woofer resonance frequency Fs, cone mass Mms and suspension compliance Cms are related. For example, playing with Mms or Cms can lead to a notable change in driver Fs. Driver Q parameters will also vary: Qms considers Fs and others, while Qes considers Fs and Mms among other too. Hence driver Qts will also be impacted since it is calculated with Qms and Qes. Domino effect...

    Fs, Qts and Vas are the three basic parameters to calculate box data. Qts affects proper box size, as well as Vas ["volume of air whose compliance is the same as a driver's acoustical compliance Cms" as defined on LH Forum; in a way Vas is another representation of compliance (Cms)].

    The above is probably what made Bullock say re one of his own projects : "Investigation revealed air leaking through the driver's dust cap. I sealed the cap with glue, remeasured the driver's parameters which were altered by the additional mass (the glue) and realigned ..." P.8

    Some glue on a dust cap seems like a relatively small change compared to 4 coats of paint on the larger cone area. If one was to add Aquaplas on the back side of a painted cone, mass would increase again, with further T/S deviations (but that is taken into account by the driver's design engineer at the factory).

    Moreover, cone mass and suspension compliance (Mms and Cms) have an impact on driver transient response, thus on how a driver will effectively sound.

    I don't see white cones giving more value to the drivers since the work was not done by the manufacturer (i.e. not original). At the time of say a resale, its not sure a potential buyer would be pleased or interested in homemade painted cones that may well have shifted T/S. As long as they please you that's what counts.

    The above doesn't mean you have worthless drivers after modification. They will still produce sound in the enclosures, the question is how well of a fit and reproducer are they now. My suggestion is you should get yourself something like the Dayton Audio DATS V2 in order to measure the new actual T/S parameters of your modified drivers to assess if they're still properly suitable for the cabinets' Vb/Fb. Then go from there.

    Sorry for being the bad news messenger. Regards,

    Richard
    I'm a fan of constructive criticism, would have appreciated the comments sooner though. Seems most lurk and watch from the shadows and then bash after it's too late for the OP to go back.. Anyway, I also researched in great length about the caveats of painting the woofers, how I determined the stuff I was going to use. I really wanted to nail the color, looks like I got as close as possible to the real thing. Also, the cones I had to begin with weren't original. OE replacements at best, and after reviewing the JBL 128H replacement woofer I got, which was complete with AquaPlas, it is consistent with my old woofer. Old woofer's color was faded and yellow, new paint on new woofer is slightly more vibrant and whiter than the JBL NOS woofer. I'm still very pleased with the aesthetic so far. Well, to me the color matters, especially as a buyer. I would not have bought the speakers if the woofers weren't white.. I do consider myself to be an audiophile, but I don't get out the slide rules and fancy equations, I just listen to the music. I'm not there yet and don't personally know people that are. I've read through a lot but without any context, the equipment to experiment for myself or someone to answer questions, most of it is lost on me. So I just use my ears and basic deductive reasoning, it's gotten me this far. I'd like to have that equipment, but without any real means to discern the literature & contrast against my findings, I don't think I'd be able to make much sense of it. Like, how do you realign a driver once it's already in place? Every question I'd answer would most likely leave me with two more.

    But yes, paint adds mass. The cones I just replaced have what appear to be the same woofers (according to the rear & front texture, please see the pics) as the new ones that I painted, only they just don't have the AquaPlas coating, which also adds weight. I began to peel some away and it's considerably thicker and denser than the paint I used. I used between 30 & 40mL of paint total, so roughly only 15-20mL per cone. It was also reduced, 3:2, so 40% of that volume of used paint was straight water which evaporated. I don't have actual weight measurements, but from the threads on other forums I've read, they added less than 6 or 7 grams of paint per woofer, which is probably similar to what that AquaPlas coating weighs if not less. So as I use my ears to discern the difference, what I'd be comparing the sound to wasn't original to begin with, I have no true frame of reference. So far, my Marantz gear isn't back, should be today. I'm using the awful Yamaha R-V1105(?) natural sound receiver which came with buying the speakers. That amp is absolutely terrible. Sound stage is much narrower and it handles transients poorly. Bass stinks too. But is that the woofer?? Dunno, I'll find out when I get my beloved Marantz stuff back. If it is, this is exactly why I bought the replacement woofer another member was kind enough to link in their message. I just need one more. I'm still searching for it. Another member said that as a JBL reconer, he can get them. Unfortunately, he won't order one and send it to me though. So I will wait until another opportunity arises. Until then and if these woofers don't sound right, I will wait until I get that kit and then have them reconed again. But, hopefully none of that will be necessary. What a nightmare this has been. I still don't know if my original issue has been solved.. From the hour session I had yesterday, it appears it has, but I need my original gear back. I also heard you're supposed to break in the new cones. Guess I'll just let them play awhile.

  8. #38
    Administrator Robh3606's Avatar
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    Hello Derek

    From the other side of the fence it takes a significant change in mass to have a appreciable difference in FS. A coat of non loaded pigment only paint won't do it. There is a 30 gram difference between a 2234 and a 2235. Fs of 20 hz 2235 to 23Hz 2234 so a net change of 3 Hz using the identical suspension system. Coat of paint who cares! I sure as hell wouldn't loose any sleep over it.


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  9. #39
    Member DerekTheGreat's Avatar
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    Thanks Rob!

    I sure thought about it for awhile and that is ultimately the conclusion I settled upon. The wife and I rather like how they look now.

    Is there a layman's way of testing how air tight my cabinets are? If I tap on either woofer the other moves the same amount in the opposite direction. If I hold either woofer in, the other will quickly settle back to it's resting position after moving out. I can't imagine foam surrounds/suspensions are 100% air tight..

  10. #40
    Senior Member Ian Mackenzie's Avatar
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    Hi Derek,

    If you can arrange a 30 hertz sine wave into the loudspeaker then run your hand around the enclosure to feel for leaks. That will identify any issues normally.

    You can download an App for that.

    The theory of operation is quite interesting but donít get bogged down in it.

    Those cones look great btw.

    Please post more pics.

  11. #41
    Senior Member DavidF's Avatar
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    Quote Originally Posted by DerekTheGreat View Post
    "... I just need one more. I'm still searching for it. Another member said that as a JBL reconer, he can get them. Unfortunately, he won't order one and send it to me though. .."
    Just for context's sake, Derek, it would a breach of his JBL service contract to sell the replacement kit without also installing the kit. So, not so much he won't, but can't.
    David F
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  12. #42
    Senior Member Doctor_Electron's Avatar
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    Quote Originally Posted by DavidF View Post
    Just for context's sake, Derek, it would a breach of his JBL service contract to sell the replacement kit without also installing the kit. So, not so much he won't, but can't.
    That has been a hard and fast rule in JBL authorized service since "day one".
    To be authorized is not a trivial matter. I worked for an authorized shop 20 years go. The owner had his contract suspended because he did not obtain a set of gap gauges to work on newer drivers with smaller voice coil gaps.

    If I were a JBL Pro authorized shop I wouldn't sell any parts I as not authorized to. You make an agreement and that is your word. Even in this day and age that means something to me.
    Last edited by Doctor_Electron; 08-01-2019 at 12:16 AM. Reason: Loose Nut behind Keyboard.
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  13. #43
    Member DerekTheGreat's Avatar
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    Quote Originally Posted by Ian Mackenzie View Post
    Hi Derek,

    If you can arrange a 30 hertz sine wave into the loudspeaker then run your hand around the enclosure to feel for leaks. That will identify any issues normally.

    You can download an App for that.

    The theory of operation is quite interesting but donít get bogged down in it.

    Those cones look great btw.

    Please post more pics.
    Thanks Ian! I'll snap a pic of the replacement cone soon, hopefully we'll get to touching up the cabinets and such. I'm a bit embarrassed to show the L150A's until we've cleaned the crayon off & polished them up. At least now the faces of the speakers look great haha.

    Which app do you like? I bought a test CD off eBay and while it has a lot of useful stuff on it, the lowest test tone I have is 50hz.. I saw some stuff from other forums in which you could download some software to make your own tones but if I could get an app on my phone that would be easier and then I could just hook that up to my computer and record it later if I wanted to, rather than risk a virus or something.

    Quote Originally Posted by DavidF View Post
    Just for context's sake, Derek, it would a breach of his JBL service contract to sell the replacement kit without also installing the kit. So, not so much he won't, but can't.
    Quote Originally Posted by Doctor_Electron View Post
    That has been a hard and fast rule in JBL authorized service since "day one".
    To be authorized is not a trivial matter. I worked for an authorized shop 20 years go. The owner had his contract suspended because he did not obtain a set of gap gauges to work on newer drivers with smaller voice coil gaps.

    If I were a JBL Pro authorized shop I wouldn't sell any parts I as not authorized to. You make an agreement and that is your word. Even in this day and age that means something to me.
    Thank you fellas, that puts it into perspective. If he was closer, I'd of had him do the work, honest! I don't know how I got the woofer kit I have now but I'm glad someone was selling one. Just need one more... Looks like it could be awhile before one turns up and hopefully I won't need it anyway.

    Istill fear I'm going to hear that "POP!" though.. I've read about speaker break ins, not sure if that is a thing or not but I let the speakers play all morning and into the afternoon yesterday with that junky Yamaha, at a volume that was just higher than "casual" so the cones moved a decent amount. Is this necessary or good to do before trying to jam out?

  14. #44
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    Quote Originally Posted by Derek

    I picked my 128H's up this past Saturday. The cones look to be the same or similar to the ones they replaced; dark purple color & textured rear, just no AquaPlas coating of course. I bought that one eBay listing for a true replacement but that's just one cone. So I'll stash that until I find another and need to recone these speakers or another set. In the meantime, if someone needs that recone kit, PM me.

    Derek,

    Color me confused here.

    I thought you were getting ( from your preferred reconer ) bona-fide JBL recone kits.

    Is that not the case? ( Price wise, were they inline with a costing from "
    sguttag" ? > ignoring shipping charges )

    I was under the impression that a bona-fide 128H type JBL recone kit would have Aquaplas on it ( somewhere, be it either front or back ).

    Is that eBay recone kit painted with aquaplas ?

    What about the 2 kits that were removed ? ( did they have any aquaplas on them anywhere ? )



  15. #45
    Administrator Robh3606's Avatar
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    I was under the impression that a bona-fide 128H type JBL recone kit would have Aquaplas on it ( somewhere, be it either front or back ).
    Both of the 128h-1 I have don't have aquaplas on them. They have a very ruff coating on the back of the cone almost like papermachte

    Rob
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