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Thread: JBL d130/375 crossover? help

  1. #46
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    hi Richard - thanks for covering all the bases - I was specifically wondering about preventing black glue getting on the aluminum.

    I had figured that it would have to be taped, but didnít want to use the wrong kind of tape -
    glad to know that the 3m blue painters tape is not too sticky as to damage the cone. And will pull slowly.

    Also, great advice on practicing with the glue/flow on joining a short amount. I was thinking something similar but my way may have wasted a bit more glue.

    This again is so helpful - thank you!



    Quote Originally Posted by RMC View Post
    RE how to keep the aluminum clean?

    Not sure i understand your question correctly. Keeping Alu cap clean because its dirty or preventing black glue on the edge of dustcap?

    If its for dirty cap then i assume an Alu cleaner would be what you need, but have none to suggest to you right now.

    If its for avoiding black glue on cap then cover its perimeter with masking tape, such as 3M Blue painter's tape, made for easy removal (slowly), contrary to 3M's cheap Tartan brand which is very sticky.

    RE but worry it might still put out too much glue. but worry it might still put out too much glue.

    I have a number of various size syringes and wouldn't use that here, too much trouble. The applicator from a Simply Speakers black glue plastic bottle should do the job. If you're not comfortable with too much or not enough glue, i suggest you do a short trial run with the glue bottle. Put two small pieces of scrap wood at a right angle and try to fill the joint between them on a short distance to avoid wasting too much (similar to siliconing joints inside a speaker box). This little test should give you an idea about how the glue flows and its actual application for covering the open space on your dustcap.

    With a plastic bottle, if need be you can cut off a little of the nozzle with a knife to make a wider glue line.

    Richard

  2. #47
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    dear Mr Widget and to anyone else who may know,
    Finally received the 2405.
    It showed the DCR reading for both at 6.8/6.7 and was wondering if this shows that they are in fact original and working at least from the DCR reading as they should.

    Also upon taking the slot cover off, I found the housing to be an older casing and one of the slot covers had a screw visible?

    the serial numbers are 15515 and 16027 if that helps.

    thank you again in advance.




    Quote Originally Posted by Mr. Widget View Post
    You can try adding glue, but my guess is that you probably have a voicecoil that has warped and is slightly out of round. These older drivers have a very narrow gap and it is not at all uncommon to develop a slight rub.

    You can test this by very gently pressing on the cone. If you press straight in and hear a slight scratchy noise you need to repair the driver.


    Widget
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  3. #48
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    Just to be clear, you do want black glue on the aluminum dome. The dome and the slope of the cone form a V groove where they meet. You want to fill that groove with glue evenly all the way around with equal amounts of the glue bead on the dome and on the cone to ensure a reliable glue bond that will survive years of vibration. Your original photo was of an incorrectly done glue job. It's not a good reference. If you do have glue in places that you don't want it have a small bottle of MEK solvent and some Q tips on hand for clean up.


    Quote Originally Posted by alfmonster View Post
    hi Richard - thanks for covering all the bases - I was specifically wondering about preventing black glue getting on the aluminum.

    I had figured that it would have to be taped, but didn’t want to use the wrong kind of tape -
    glad to know that the 3m blue painters tape is not too sticky as to damage the cone. And will pull slowly.

    Also, great advice on practicing with the glue/flow on joining a short amount. I was thinking something similar but my way may have wasted a bit more glue.

    This again is so helpful - thank you!

  4. #49
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    hi Riley,
    yes of course - was hoping to avoid any glue getting on the aluminum cone. Just in its edges like you mentioned.
    But amazing suggestion about the MEK solvent hadnít thought of that ó will pick some up later today. I purchased some lint free foam qtips so will have that on hand as well.



    Quote Originally Posted by Riley Casey View Post
    Just to be clear, you do want black glue on the aluminum dome. The dome and the slope of the cone form a V groove where they meet. You want to fill that groove with glue evenly all the way around with equal amounts of the glue bead on the dome and on the cone to ensure a reliable glue bond that will survive years of vibration. Your original photo was of an incorrectly done glue job. It's not a good reference. If you do have glue in places that you don't want it have a small bottle of MEK solvent and some Q tips on hand for clean up.

  5. #50
    Senior Member RMC's Avatar
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    2405 JBL's factory DCR spec is Min. 5.7 and Max. 6.7 ohm so your drivers are borderline. However, maybe you haven't calibrated your multimeter's residual resistance, which has an effect on readings.

    Set meter in ohm mode and hold both test leads together until the number shown is stable, what reading do you get? (one of mine gives me 0.6 or 0.7 ohm). That number is the residual meter resistance and it must be subtracted from your driver DCR readings. This meter adjustment or correction might bring your 2405 measured numbers more in line with specs. Try it.

    Btw to avoid any confusion Riley is right about the black glue application, but if you're affraid of going too wide on the dustcap (e.g. make a glue mess) you can still use the Blue tape to mark where the glue line width will stop on the cap, this would save you a potential cap cleanup job...

    Richard

  6. #51
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    Honestly I had no idea about this calibration - I just got home and calibrated my meter and it stabilized at a reading of .3
    So the final DCR numbers with the subtracted .3 I think would bring the 2405 more inline with the specs.
    I remeasured the 2405 also and got 6.6 and 6.7

    These 2405¬ís seem a bit older - have these gone through different versions? Like I noticed once the slot covers come off the inside casing is black. However in another version it shows more of a brushed steel color. The mounting bracket also seems a bit different from the ¬ďnewer¬Ē version. Are there sonic quality differences between these versions of the 2405?

    Also agree that I will probably have the MEK on hand just in case and the blue tape initially to make sure the glue will go on neat.

    Quote Originally Posted by RMC View Post
    2405 JBL's factory DCR spec is Min. 5.7 and Max. 6.7 ohm so your drivers are borderline. However, maybe you haven't calibrated your multimeter's residual resistance, which has an effect on readings.

    Set meter in ohm mode and hold both test leads together until the number shown is stable, what reading do you get? (one of mine gives me 0.6 or 0.7 ohm). That number is the residual meter resistance and it must be subtracted from your driver DCR readings. This meter adjustment or correction might bring your 2405 measured numbers more in line with specs. Try it.

    Btw to avoid any confusion Riley is right about the black glue application, but if you're affraid of going too wide on the dustcap (e.g. make a glue mess) you can still use the Blue tape to mark where the glue line width will stop on the cap, this would save you a potential cap cleanup job...

    Richard

  7. #52
    Senior Member RMC's Avatar
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    The good news is that now your 2405 are clearly in the factory DCR range, even more so with the meter correction. That's a good start.

    Richard

  8. #53
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    I would avoid putting painters tape on the dome. The adhesive is not paint, it's very robust stuff and you're likely to end up with a permanent fringe of blue paper tape under the adhesive if you do end up getting glue on the tape. If you want to get a nice 'factory finish' glue bead just practice a few times in a piece of cardboard before going at the speaker. Some sort of turntable will make it much easier to get a good looking job.

  9. #54
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    A couple of comments.

    I would definitely not attempt to put tape or anything on the aluminum domes. They are extremely thin and the risk of dents is greater than a sloppy glue line.

    Regarding the DCR measurements of any driver. A DCR measurement provides evidence of life, but is hardly a measurement of quality. Yes, being close to spec is good, but a DCR measurement only tells you that you may have functioning drivers.


    Widget

  10. #55
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    Thatís a great word of caution - thank you Riley and Widget for the heads up on this.
    I havenít received the glue yet so havenít touched the drivers yet.
    I do however have a turntable thatís ready to use for when I re-glue the cone.

    widget - as far as the 2405 Iím going to give that test hopefully today.
    I have one newer 2405 on hand so Iíll try all of the to calibrate my hearing to these tweeters.

    A question I had was (if the 2405 is working properly) do the earlier 2405ís have different characteristics either negative or positive from the later 2405?

    im guessing not - but again my experience with these are limited.
    thanks again everyone

    Quote Originally Posted by Riley Casey View Post
    I would avoid putting painters tape on the dome. The adhesive is not paint, it's very robust stuff and you're likely to end up with a permanent fringe of blue paper tape under the adhesive if you do end up getting glue on the tape. If you want to get a nice 'factory finish' glue bead just practice a few times in a piece of cardboard before going at the speaker. Some sort of turntable will make it much easier to get a good looking job.
    Quote Originally Posted by Mr. Widget View Post
    A couple of comments.

    I would definitely not attempt to put tape or anything on the aluminum domes. They are extremely thin and the risk of dents is greater than a sloppy glue line.

    Regarding the DCR measurements of any driver. A DCR measurement provides evidence of life, but is hardly a measurement of quality. Yes, being close to spec is good, but a DCR measurement only tells you that you may have functioning drivers.


    Widget

  11. #56
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    Hi Richard,

    If the 077/2405 were to measure differently say one measures at 5.7 and the other at 6.3 but still with in the 5.7-6.7 DCR specs would that mean one is in worse condition than the other? Or would that difference translate to issues with audio quality?



    Quote Originally Posted by RMC View Post
    2405 JBL's factory DCR spec is Min. 5.7 and Max. 6.7 ohm so your drivers are borderline. However, maybe you haven't calibrated your multimeter's residual resistance, which has an effect on readings.

    Set meter in ohm mode and hold both test leads together until the number shown is stable, what reading do you get? (one of mine gives me 0.6 or 0.7 ohm). That number is the residual meter resistance and it must be subtracted from your driver DCR readings. This meter adjustment or correction might bring your 2405 measured numbers more in line with specs. Try it.

    Btw to avoid any confusion Riley is right about the black glue application, but if you're affraid of going too wide on the dustcap (e.g. make a glue mess) you can still use the Blue tape to mark where the glue line width will stop on the cap, this would save you a potential cap cleanup job...

    Richard

  12. #57
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    Quote Originally Posted by alfmonster View Post
    widget - as far as the 2405 I’m going to give that test hopefully today.
    I have one newer 2405 on hand so I’ll try all of the to calibrate my hearing to these tweeters.

    A question I had was (if the 2405 is working properly) do the earlier 2405’s have different characteristics either negative or positive from the later 2405?
    On paper at least, the 077 and 2405 have not had any changes and they should all perform the same whether an example of their earliest production in the mid '70s or the latest production in the early 2000s. Years ago I measured a number of JBL's ring radiators and found a fair amount of unit to unit variation. Because the tolerances are so tight at these frequencies I imagine unit to unit variation was always an issue. On top of that this is compounded by age and possible years of misuse.

    Quote Originally Posted by alfmonster View Post
    If the 077/2405 were to measure differently say one measures at 5.7 and the other at 6.3 but still with in the 5.7-6.7 DCR specs would that mean one is in worse condition than the other? Or would that difference translate to issues with audio quality?
    Within reason, I don't think a DCR variation will directly correlate to any audible differences. That said, if the goal was to have a perfect pair of 077s or 2405s I would want to gather a large sample group and carefully measure their responses. I would then pair them based on their measured FR and sensitivity. I wouldn't be at all concerned by their DCR measurements. I think this number is mentioned so often, because it is the only measurement most eBay sellers have available to them, not because it is of any particular importance.


    Widget

  13. #58
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    thank you for this reply Widget, again so helpful.

    I was thinking about your earlier post about the DCR readings having little to do with the actually sound quality of the tweeters when I test one of the older 2405 with a newer production 2405 . And even though both sets had a close DCR reading well within their required specs - the newer one sounded better. It was smoother and more beautiful.

    Iím not sure how else to describe the sound but it was, by a touch, more pleasant sounding.

    Itís also great know that seeing a discrepancy with the DCR numbers donít necessarily mean a degraded quality.



    Quote Originally Posted by Mr. Widget View Post
    On paper at least, the 077 and 2405 have not had any changes and they should all perform the same whether an example of their earliest production in the mid '70s or the latest production in the early 2000s. Years ago I measured a number of JBL's ring radiators and found a fair amount of unit to unit variation. Because the tolerances are so tight at these frequencies I imagine unit to unit variation was always an issue. On top of that this is compounded by age and possible years of misuse.

    Within reason, I don't think a DCR variation will directly correlate to any audible differences. That said, if the goal was to have a perfect pair of 077s or 2405s I would want to gather a large sample group and carefully measure their responses. I would then pair them based on their measured FR and sensitivity. I wouldn't be at all concerned by their DCR measurements. I think this number is mentioned so often, because it is the only measurement most eBay sellers have available to them, not because it is of any particular importance.


    Widget

  14. #59
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    Quote Originally Posted by alfmonster View Post
    I was thinking about your earlier post about the DCR readings having little to do with the actually sound quality of the tweeters when I test one of the older 2405 with a newer production 2405 . And even though both sets had a close DCR reading well within their required specs - the newer one sounded better. It was smoother and more beautiful.
    The newer one sounding better is hardly surprising.

    High mileage compression drivers tend to show their age and those with with aluminum diaphragms may also show signs of work hardening which may cause them to have higher distortion than fresher examples. That said, I am sure there are older units out there that have been in storage forever and are in fine shape and there are likely newer units that were played hard and often and are now way out of spec.

    Since even the later production 2405s are now decades old, it will be increasingly difficult to find an optimal pair of these drivers.


    Widget

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    I had read recharging the magnets would help with the sound quality. Is there a list you may have of places that are still around and able to recharge the magnets on the 2405/077 tweeters, d130 and 2441 drivers?

    I kept seeing the name Orange County Speaker come up but found they had stopped repairing speakers.

    lastly it even possible to get a 32ohm d130 reconed to something that sounds similar to what it might’ve been?

    Quote Originally Posted by Mr. Widget View Post
    The newer one sounding better is hardly surprising.

    High mileage compression drivers tend to show their age and those with with aluminum diaphragms may also show signs of work hardening which may cause them to have higher distortion than fresher examples. That said, I am sure there are older units out there that have been in storage forever and are in fine shape and there are likely newer units that were played hard and often and are now way out of spec.

    Since even the later production 2405s are now decades old, it will be increasingly difficult to find an optimal pair of these drivers.


    Widget

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