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Thread: DIY 2235h, 2206h, 2446J Be or TAD 4001 and 2405H Build Thread

  1. #46
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    Quote Originally Posted by Champster View Post
    Thanks for your comments here everyone. There are certainly no shortage of opinions on this topic. Just for kicks, I'm going to remove the drivers from my B&W HTM1 tonight to see what they use. I'll post pictures.

    Does anyone other than Lee and me use Dynamat or something more like Black Hole?
    I think it's more than one topic. There are lots of ways to deaden a speaker cabinet, but that's not really what the fiberglass is used for. You get more apparent enclosure volume with a fiberglass lined enclosure, so some of the volume you lose to drivers and braces and such can be reclaimed. It's not really "stuffing" like a sealed cab, and it's not really "deadening" like Dynamat. There used to be threads or links or something that was more easily located around here that spelled all this out, but I'm not finding it.

  2. #47
    Senior Member Champster's Avatar
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    Attached are pictures of my B&W Nautilus center channel. To continue the general topic of cabinet treatments, they use foam blocks and pads that are glued to the wood and don't use any cabinet deadening material like Dynamat. They do use lots of internal bracing and have many curves to the cabinet design to add strength and reduce resonances. The interior of this cabinet look very similar to Lee's cabinet with the exception that Lee's is stuffed full of foam. B&W's allows for air movement. I don't know whether Lee's cabinet is sealed or vented but the B&W is sealed with each woofer and the midrange having their own enclosures.

    So this is interesting. JBL's top of the line uses fiberglass, whereas B&W uses foam. Both only line the walls rather than stuff the cabinet. Also interesting to note is the varying thickness of the wood at the opening of the hole for the speaker.

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  3. #48
    Senior Member Lee in Montreal's Avatar
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    Parts Express sells "egg crate" foam. Not cheap

    http://www.parts-express.com/acousti...ul-94--260-517



    Walmart can supply "egg crate mattress liner" for much less. It is white and very cheap. Panels are about 6'x5' ;-)




  4. #49
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    yes, I've seen that paper too. Acoustically FG was superior to almost everything else, except maybe lambs wool?? but, I don't recall if any of the newer special acoustic foams were included.. FG is also fire-resistant, which is important if you expect crossovers and voice coils to over-heat and possibly ignite (ie abused/pro-sound). (Yes, wood, burns, but most foam plastics give off toxic fumes when they burn - this was the potential liability issue once explained to me by a commercial designer for the choice of FG over foam inside a pro-sound cabinet.)

    (edit: I think the discussion on FG vs polyfill is in the Vance Dickason Loudspeaker Design Cookbook.)

    edit 2: in a sub, do you need any acoustic damping? if crossed over below 100 HZ there's not much HF reflections to damp out??


    Quote Originally Posted by JeffW View Post
    There was a paper here once, I can't find it any more, that went into the thermodynamic properties of different materials for lining speaker enclosures. Fiberglass was much better at converting sound energy to heat than the usual suspects like polyfill. Polyester fibers just didn't have what it takes. Yet polyester fiber fill is cheaper than fiberglass. If cheap was the driving force, seems like polyfill would be in JBL cabinets.

    I don't recall if any foam products were tested in the paper, but the type of foam is pertinent in sound absorption. The wrong type of foam, even if it looks good, can act as a reflector.

    I didn't find the product sheet on the 66000/67000 series, but pretty sure they have fiberglass lining, too. Did JBL really go all out on these systems only to save a few bucks on the lining of the enclosures, or is fiberglass the correct material after all?

  5. #50
    Senior Member 1audiohack's Avatar
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    [QUOTE=Lee in Montreal;366136]Parts Express sells "egg crate" foam. Not cheap

    http://www.parts-express.com/acousti...ul-94--260-517

    Walmart can supply "egg crate mattress liner" for much less. It is white and very cheap. Panels are about 6'x5' ;-)

    Hi Lee and all;

    I do note that you closed with a wink so this shouldn't be seen as argumentative. There is enough "angertainment" going on elsewhere here.

    Proper acoustical foam is reticulated urethane (fully open cell) while the mattress foam is usually latex foam (nearly fully closed cell bubble foam. The little balloons offer the physical support for the job of keeping you off the hard and or cold floor.

    The acoustical properties are nowhere near the same. I bought the majority of a decommissioned mixing/mastering studio's acoustical treatment and spent a weekend measuring it along with some other stuff I have. For fun I included some of the mattress foam and other egg crate type things, like egg crates, and found them to be, on axis simply a reflector and off axis a very very narrow band diffusion devise. Practically useless even if free.

    I wish I had more time to test things like this and had the time to document more of it besides the saved file notes. It's fun and the asurety going forward is nice to have.

    In the end? Make mine fiberglass.

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

  6. #51
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    Quote Originally Posted by tomee View Post
    yes, I've seen that paper too. Acoustically FG was superior to almost everything else, except maybe lambs wool?? but, I don't recall if any of the newer special acoustic foams were included.. FG is also fire-resistant, which is important if you expect crossovers and voice coils to over-heat and possibly ignite (ie abused/pro-sound). (Yes, wood, burns, but most foam plastics give off toxic fumes when they burn - this was the potential liability issue once explained to me by a commercial designer for the choice of FG over foam inside a pro-sound cabinet.)

    (edit: I think the discussion on FG vs polyfill is in the Vance Dickason Loudspeaker Design Cookbook.)

    edit 2: in a sub, do you need any acoustic damping? if crossed over below 100 HZ there's not much HF reflections to damp out??
    Thanks tomee. If that's correct, then that would explain why I remembered reading it but couldn't find it here. As for subs, I found the 2245 sub paper on the computer at home and it mentioned lining the sub enclosure with FG except for the back of the baffle.

  7. #52
    Senior Member Champster's Avatar
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    Quote Originally Posted by JeffW View Post
    Thanks tomee. If that's correct, then that would explain why I remembered reading it but couldn't find it here. As for subs, I found the 2245 sub paper on the computer at home and it mentioned lining the sub enclosure with FG except for the back of the baffle.
    Very well then. That was a very interesting discussion. Thanks to everyone for their contributions.

    My main cabinets are well underway at this point and I'll be posting pictures in a week or so.

    thanks
    Paul

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