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Thread: Pieceing together a JBL 4350 build in Australia

  1. #46
    Senior Member grumpy's Avatar
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    If they were mine, I'd spend the extra few minutes to not have 15lbs hanging on a lever arm, torquing the front panel.
    Even a bolt/nut + pipe hanger strap + wood screw would relieve most of the stress (ugly and not particularly recommended but you get the idea).
    The yoke/brace is pretty straightforward and de rigueur.

  2. #47
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    I received my 2202a drivers today.

    They both have original JBL cone kit but one is labelled 2202a and the other is 2202h. Do you think there would be a difference in the two drivers? They are both 2202a frames.

  3. #48
    Senior Member grumpy's Avatar
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    C8R2202 was listed by JBL as the recone kit for both 2202A and 2202H... as recently as 2004.

    I'd expect they'd be fine, but someone else here may know better. Materials and adhesives were updated over time.

  4. #49
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by kelossus View Post
    I received my 2202a drivers today.

    They both have original JBL cone kit but one is labelled 2202a and the other is 2202h. Do you think there would be a difference in the two drivers? They are both 2202a frames.
    If you check the T/L parameters the 2202A and the 2205H are virtually identical. The 2202H was the ferrite conversion from Alnico back when there was a shortage of cobalt. There were some improvements in high temperature adhesives and some variations in the suspension to deal with dc offset but the drivers are otherwise identical. Jbl did a lot of testing on the ferrite drivers to ensure they met the spec of the alnico counterparts.

    I would not be concerned about it.

  5. #50
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    Lanselites

    I just noticed a tiny hole in the surround of my 2202 driver. Can you patch this in a way that will not degrade performance a possibility? Or am I looking at a recone or replacement driver?

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  6. #51
    Senior Member 1audiohack's Avatar
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    I would use a drop of the Moyen adhesive from a recone kit. Iíve fixed cutís and tears in surrounds both cloth and foam with it. Kept thin it is plenty flexible and durable.

    Finding some there in AU might be a trick but some reconer has to have some.

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

  7. #52
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    Quote Originally Posted by 1audiohack View Post
    I would use a drop of the Moyen adhesive from a recone kit. Iíve fixed cutís and tears in surrounds both cloth and foam with it. Kept thin it is plenty flexible and durable.

    Finding some there in AU might be a trick but some reconer has to have some.

    Barry.
    I have some of the Moyen cement. I have a few recone kits stashed away and they weren't purchased that long ago. The glue should be good.

    Should I apply a cloth backer to the rear of the surround before patching the hole? Or the glue will strong enough to bridge the hole by itself.

  8. #53
    Senior Member 1audiohack's Avatar
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    I am quite sure it will hold a hole that small.

    Add a tiny bit of fiber if your worried.

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

  9. #54
    Administrator Robh3606's Avatar
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    Don't use too much you don't want a hard spot or a lot of mass added to the surround.

    Rob
    "I could be arguing in my spare time"

  10. #55
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    I took the 2202s to friend who has a DATS software to measure the drivers. Are these two drivers close enough for use? Please note the T/S specs are on the right

    As mentioned both are 2202A frames but one has the original 2202a kit and the other has been reconed with a genuine 2202H kit.

    2202A with 2202A Kit
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    2202A with 2202H Kit
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    Over layed
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  11. #56
    Senior Member RMC's Avatar
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    Checked quickly the first one only, the TS don't seem too far off, looks acceptable to my eyes.

    For Vas, added mass method was selected but i don't see the result. This is sometimes the parameter where people have problems getting a number that makes sense, never mind accurate. Not a big problem, input the driver TS you measured in WIN ISD software, click auto calculate missing parameters, and the program will calculate Vas based on the other known parameters. Its often the best way to go in relation to Vas with DATS.

    I don't see Mms either, then use JBL spec since yours are original recones that should measure close to factory data. Sorry gotta go.

    Richard

  12. #57
    Senior Member RMC's Avatar
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    Just checked quickly the TS for the H, similar to the A, except for Qms on the H is far off, less than half what it should be. That's the wild one. However, if you input the numbers in Win ISD as mentioned in previous post the auto calculate feature may change some of the figures as often happens, hopefully might improve somewhat the bad Qms on the H??

    Richard

  13. #58
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    Quote Originally Posted by RMC View Post
    Just checked quickly the TS for the H, similar to the A, except for Qms on the H is far off, less than half what it should be. That's the wild one. However, if you input the numbers in Win ISD as mentioned in previous post the auto calculate feature may change some of the figures as often happens, hopefully might improve somewhat the bad Qms on the H??

    Richard

    I did notice the QMS on the H was wildly different, yet the QTS on both drivers is very close. Isn't the QTS a function of the QMS and QES??? Doesn't make sense but I don't have a really good understanding of this.


    I only stopped in quickly and he performed the measurements, do you think it's worth going back to verify all this?

  14. #59
    Senior Member RMC's Avatar
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    RE Isn't the QTS a function of the QMS and QES???

    Yes, its a product over sum equation for Qts = Qes X Qms divided by Qes + Qms

    RE do you think it's worth going back to verify all this?

    Might not be worth the trip in my view because all your numbers seem to make sense (not too far from specs), except for one Qms only. If the Dats was defective or improper measures done my impression is that you'd have other weird numbers but you don't, just one. In a sense its a relatively good sign.

    Shortly, Qes is electrical damping (amount of control) and Qms is mechanical damping (amount of control) of the driver. Not sure though one should lose sleep over the single rogue Qms number:

    "The Qms is the control coming from the suspension system's damping abilities. (...) The Qes is a gauge of the control on a driver coming from the counter-EMF generated in the voice coil. Qes is usually a smaller value than Qms, meaning that the electrical damping is the primary controller of the driver's behavior near resonance." (Ray Alden, Advanced Speaker Systems, p.15)

    Since both of your drivers have Qes lower than Qms, even on the H one, then my understanding is that the electrical damping remains the primary controller of driver's behavior. So it might not be so bad after all. It could be that H driver suspension system-surround or spider- has a some issue? However its possible you may not even hear a difference between the A and H on program material? You'd need to test them in sealed box to know.

    Btw, i also checked JBL DCR specs for your two drivers and both of them are within factory ranges. Another positive item.

    Hope the above helps you.

    Richard

  15. #60
    Senior Member Ian Mackenzie's Avatar
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    The impedance peaks are different.

    One of the magnets being Alnico could be slighted magnetised.

    Once you have the drivers in a tuned bass reflex enclosure run impedance curves and do a comparison. If there are any differences there that is what matters.

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