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Thread: My Mass Rings Arrived!

  1. #1
    Senior Member Loren42's Avatar
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    My Mass Rings Arrived!

    After I did a Fs sweep of my 2235Hs and found the Fs was the same as the 2234H, I decided to order 4 dust caps and 4 mass rings.

    After some leg work I found that JBL still sells these and bought four of them. They arrived today.

    I think they are made of zinc. I massed one and it weighs 33.39 grams.



    Now I need to cut off the old dust caps, install these, and put the new dust caps on and the drivers should operate like they were originally designed to.

    Central Florida Speaker Repar in Orlando got these for me for about $3.00 each.

    Anyone ever cut off an old dust cap? I would think that I could cut them off with an Exacto-knife, but I am concerned about the affect of the magnet pulling on the blade while I work.

    I can just imagine the knife blade getting sucked into the voice coil as I cross the JBL event horizon.

  2. #2
    JBL 4645
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    Loren42
    Wow what is a Mass Ring? What size are they I can’t tell by the picture?

  3. #3
    Senior Member SMKSoundPro's Avatar
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    Use a sharp utility knife and slice around the dustcap a little towards the center o the dome, away from the glue line.

    Be careful not to get paper bits down into the VC - gap area, so you may hold the basket on edge to keep the little particulate matter from falling in. I think you understand that gravity is not yoru friend, here.

    Then, once you have sliced out the dome, keep slicing with the knife to the glueline and clean that area up of glue.

    To install Mass ring. Lay a bead of glue onto the outside of the ring and place it atop the voice coil former. There is a little ridge on the mass ring so that it does not slide down into the vc former. (Don't file that off.)

    Be careful not to use too much glue or it will run down into the vc gap and dry, and that is a whole nother kettle of fish!

    Let the glue dry. When dried, inspect the mass ring for good adhesion, and if satisfactory, glue on new dome, again being careful not to use too much glue as, once again, its another kettle of fish.

    Voila! A 2235 in born.

    Any questions, just ask.
    Scotty.
    One step above: "Two Tin Cans and a String!"
    Longtime Alaskan Low-Fi Guy - E=MC² ±3db

  4. #4
    Senior Member jcrobso's Avatar
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    My guess is about 4".

    Quote Originally Posted by JBL 4645 View Post
    Loren42
    Wow what is a Mass Ring? What size are they I can’t tell by the picture?
    That would be the VC size of a 2335H.
    As far as magnetic attraction, get one of those ceramic knifes, thay are non magnetic.

  5. #5
    Senior Member SMKSoundPro's Avatar
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    Just use a sharp knife and be careful.
    One step above: "Two Tin Cans and a String!"
    Longtime Alaskan Low-Fi Guy - E=MC² ±3db

  6. #6
    Senior Member Loren42's Avatar
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    Quote Originally Posted by JBL 4645 View Post
    Loren42
    Wow what is a Mass Ring? What size are they I can’t tell by the picture?
    Outside diameter is 3.893" and it is .250" tall.

    On the 2235 series they installs this mass ring on the inside top edge of the voice coil former to bring the mass of the cone up from 105 grams (2234) to 155 grams. This lowers the Fs by about 3 Hz and suppresses the upper midrange SPL a few dB while extending bass response.

    I bought these two JBL 2235Hs from a Craig's List sale. They were shipped across the US in a box facing each other and held together with small tie wraps. Then they were packed with white packing peanuts inside the box (just for extra protection) When I received them the tie wraps gave their lives so that the two drivers could co-mingle and flatten each other's domes.

    Luckily, the damage was mostly constrained to the domes. However, when I did a Fs test I found that the Fs was actually 23 Hz instead of 20 Hz. The drivers appear to have been reconed a few years ago and my bet was that the owner cheaped out and had generic cones put in. Generic cones do not include a mass ring.

    So I bought 4 rings and domes since they are so cheap and figured I would DIY the domes and if my theory was right and there are no mass rings, put them in.

    Some day when genuine JBL recone kist start to get scarce I'll have them reconed, but I don't have the $500 to do that right now and this should be a good temporary fix I can live with until the day I can afford it.
    You probably didn't care to hear all of that, but I am long winded by nature.

    P.S. My avatar is a picture of one of the drivers after I opened the box - that was the first thing I saw when I opened the lid.

  7. #7
    Senior Member Loren42's Avatar
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    Quote Originally Posted by SMKSoundPro View Post
    Use a sharp utility knife and slice around the dustcap a little towards the center o the dome, away from the glue line.

    Be careful not to get paper bits down into the VC - gap area, so you may hold the basket on edge to keep the little particulate matter from falling in. I think you understand that gravity is not yoru friend, here.

    Then, once you have sliced out the dome, keep slicing with the knife to the glueline and clean that area up of glue.

    To install Mass ring. Lay a bead of glue onto the outside of the ring and place it atop the voice coil former. There is a little ridge on the mass ring so that it does not slide down into the vc former. (Don't file that off.)

    Be careful not to use too much glue or it will run down into the vc gap and dry, and that is a whole nother kettle of fish!

    Let the glue dry. When dried, inspect the mass ring for good adhesion, and if satisfactory, glue on new dome, again being careful not to use too much glue as, once again, its another kettle of fish.

    Voila! A 2235 in born.

    Any questions, just ask.
    Scotty.
    Thank you!!!

    I am going to try one of those Exacto knives with the smallest blade I can get. The handles are aluminum, so only the blade is magnetic.

    What would you recommend for a glue for the rings?

    I think Elmer's White glue is the right stuff for the domes.

  8. #8
    RE: Member when? subwoof's Avatar
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    elmer's a nono

    Ask edgewound - I believe the black "bostik" is the correct glue. you do NOT want a brittle glue here....

    sub

  9. #9
    JBL 4645
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    Loren42
    I think I follow now. Good luck with the DIY provide some pictures as you go along with it.

  10. #10
    Senior Member Loren42's Avatar
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    Quote Originally Posted by subwoof View Post
    Ask edgewound - I believe the black "bostik" is the correct glue. you do NOT want a brittle glue here....

    sub
    I take it epoxy is a little too much?

  11. #11
    Senior Member SMKSoundPro's Avatar
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    No epoxy!
    Attached Images Attached Images  
    One step above: "Two Tin Cans and a String!"
    Longtime Alaskan Low-Fi Guy - E=MC² ±3db

  12. #12
    Senior Member pos's Avatar
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    I don't see the point in adding a mass ring when using a digital crossover.
    The 2235 is just 3dB less efficient is the midrange, the LF response remains the same. For me a mass ring is just a loss of energy (aquaplass is another story, because it can help damping the cone).
    Attached Images Attached Images  

  13. #13
    Senior Member herki the cat's Avatar
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    Mass rings & knives

    [quote=Loren42;281348]After I did a Fs sweep of my 2235Hs and found the Fs was the same as the 2234H, I decided to order 4 dust caps and 4 mass rings.Now I need to cut off the old dust caps, install these, and put the new dust caps on and the drivers should operate like they were originally Anyone ever cut off an old dust cap? I would think that I could cut them off with an Exacto-knife, but I am concerned about the affect of the magnet pulling on the blade while I work. [quote/]

    Loren42 I think you are a pretty nice fellow & I hate to see you compromise those drivers with mass rings and cutting the dust cap off. I agree with Member POS on this subject. It sounds like your diaphragms already have enough mass. Any more mass will hurt the transient response & the upper frequency spectrum . Using MEK solvent to remove the dust cap can melt the foam plug in the motor pole piece vent hole, which will then drift into the voice coil gap.

    Hold up for a little while. later today I can send you the CP Moyen cement & solvents data sheet if you like.

    cheers herki the cat

  14. #14
    Senior Member timc's Avatar
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    Will not the mass ring also help with reduce resonances?
    2213 + 2435HPL w/aquaplas + H9800 (Matsj edition)

  15. #15
    Heather [Senorita member] hjames's Avatar
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    Quote Originally Posted by pos View Post
    I don't see the point in adding a mass ring when using a digital crossover.
    The 2235 is just 3dB less efficient is the midrange, the LF response remains the same. For me a mass ring is just a loss of energy (aquaplass is another story, because it can help damping the cone).
    Thanks for the charts!

    I have 2234s in my L200 3ways (see avatar image), but they originally came in my 4341 4ways. I got a pair of 2235s - tried them for a while in my L200s, but when I swapped the 2 pair so the 2235s were in the 4341s, and the 2234s were in the L200s, both sets sounded MUCH better.

    But it was a subtle difference.
    2ch: Oppo, JoLida 502CRC, JBL L212, 18ti,240ti; Heath AS101, Von Schweikert VR4
    7.1: Oppo BDP103D, B&K, UREI 809A, JBL B460

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