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Thread: Fiberglass wool- revisited

  1. #16
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    JBL B460 Insulation question

    Hello all!

    I am building three JBL B460 Subwoofers. Now I've come to insulating them. I use fiberglass wool (the yellow glass wool) It is 30 mm. thick, about one and 1/4 Inch thick. From the pictures I've found online I have not been able to determine if the insulation shall be everywhere inside of them. In the JBL Professional Enclosure guide I read that five or six of the interior sides should be insulated. But I have seen pictures online with insulation in the bottom.

    Should the insulation be in the ceiling, bottom and on all sides?

    Also, should I attach the insulation with staples even though the staples may make a "dent" or make the insulation more compressed at the place where it is attached with a staple?

    I am on the lookout for long staples and such a staple gun but considers some glue perhaps but it does not feel right if the owner wants to change the insulation in the future.

    (The bottom in one of them is 20 mm. or about 3/4 of an Inch higher and one of them is turned as per customer request)

    Thank you all for the forum and all knowledge you contribute!
    Kind Regards Johan in Sweden
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  2. #17
    Administrator Robh3606's Avatar
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    Hello!

    Nice project! Keep the pictures coming! Sides, back, top and bottom as per the DIY article on the site.

    http://www.lansingheritage.org/html/.../1983-subs.htm

    Rob
    "I could be arguing in my spare time"

  3. #18
    Senior Member RMC's Avatar
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    Hi Johan,

    Depending on wood type used (hard or "soft" wood), an easy trick to hold insulation in place and make it removable is to use finishing nails 1" - 1 1/2" long depending on fiberglass and wood thickness. You hammer the nails in the wood say 1/2" or bit less deep and then with pliers you simply bend the nails so that their head touches the fiberglass a little without compressing it. Done it many times and it works fine. Removing the insulation is easy, simply pull the nails out with pliers. Note that i use 3/4" plywood for my boxes, never particle board in which nails are more difficult to put as in hard woods.

    Another possibility i haven't tried yet is to use proper length screws with somewhat larger heads or with a larger washer, screw them in up to screw head/washer touching the fiberglass without compressing it too much. Then simply unscrew to remove insulation. Regards,

    Richard

  4. #19
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    Quote Originally Posted by RMC View Post
    Putting a piece of stockings, or any other fabric covering the vent inside or outside, is generally not a good idea acoustically. This makes a somewhat resistive vent to air flow in/out the port. And resistive vents tend to make the box act as partly vented and partly sealed (a mix of the two). Therefore reducing some of the vent's "magic" action on LF driver which lowers driver excursion and distortion.

    The only place i would put some "see through" lightly stretched fabric, assuming there's no other such protection, is on a driver's back vent, only to prevent fiberglass fibers from migrating into the woofer gap for example. With very little spray paint or hairspray on the fiberglass then a driver back vent cover would probably not be required.

    Free vent air flow is important for proper box operation and should remain King.
    And yet we use speaker grill cloth a few mm from the port openings ....the ladies tights idea works and doesn't restrict air flow.

  5. #20
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    Enclosure damping

    If using fibreglass as a damping material I believe its advisable to use a well stretched fabric over any port exit as a precaution to prevent the fibres escaping. Stockings are ideal and have negligible effect on airflow. There are also many lightweight polyester materials that are very stretchable and equally suitable. As far as enclosure stuffing goes you might also try low density memory foam (40kg/ metre cubed). It has very good acoustic properties and non of the drawbacks of fibreglass.

  6. #21
    Administrator Robh3606's Avatar
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    I think you guys are making a problem that just doesn't exist. When you handle and cut it I can see taking precautions but once it's installed in cabinet I just don't see an issue. Give it a quick coat of hairspray if you are concerned.

    Rob
    "I could be arguing in my spare time"

  7. #22
    Senior Member RMC's Avatar
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    + 1 for very light hairspray or spray paint.

  8. #23
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    I would not use fibreglass. Use Mundorf angel hair, I used this in my Everest and it’s awesome.

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