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Stuffing and damping

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  • Scarface1
    started a topic Stuffing and damping

    Stuffing and damping

    Hi I'm building a portable boombox and are almost finished. Now I'm asking if I can do some damping or filling in the subwoofer chamber because it's a bassreflex box. Does anyone have some tips.

    Thanks

  • billfitzmaurice
    replied
    That's where it came from, real egg crates. They were actually used in radio stations and studios, not for damping reflections, but for high frequency diffusion. When acoustical foam came along someone had the idea to make them a similar shape, as it was already associated with studio use. But where diffusion is concerned they have no effect, because they don't have the ability to scatter reflected high frequency waves.

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  • djg
    replied
    Egg crate?

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  • billfitzmaurice
    replied
    Originally posted by Millstonemike View Post
    Looks like you could mate two pieces together with a little spray adhesive to get a sheet of flat foam.
    I'd sooner just buy flat foam, which would be far more cost effective.
    the reason I want to stuf it is because on loud volume the box sound if the speaker is uncontrollable and the bass totally disappear,
    If the design is flawed stuffing won't fix it.

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  • Millstonemike
    replied
    Originally posted by Scarface1 View Post

    Do you mean glue 2 pieces of pritex together with points directing to each other
    Yes.

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  • Sydney
    replied
    Originally posted by Scarface1 View Post
    Wow that's a lot off money,...
    pm sent

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  • Scarface1
    replied
    Originally posted by malboro2 View Post
    If you can get a copy of Vance Dickerson’s 6th or 7th edition of THE LOUDSPEAKER DESIGN COOKBOOK, there is a very long article on damping and damping materials with impedance measurements and Q measurements. But if you are making a boombox, how big can your woofer be, unless you are using the expression "boombox" to specify a ported design? With the advent of the T/S parameters and computer aids to that, the use of the term for a ported design has pretty much disappeared.
    Wow that's a lot off money, 50 dollars. I gonna search for a loudspeaker design book but In Dutch so I understand it better. Maybe I also can find a bit cheaper one. By the way the reason I want to stuf it is because on loud volume the box sound if the speaker is uncontrollable and the bass totally disappear, the only thing I hear is the speaker itself what make a uncontrollable movement noise like if it isn't the right speaker for this project. I'm pretty sure it's not reaching it's limits. If I play outside it sounds a lot better so as in a other topic maybe it's the room issue.

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  • Scarface1
    replied
    Originally posted by Millstonemike View Post
    Looks like you could mate two pieces together with a little spray adhesive to get a sheet of flat foam.
    Do you mean glue 2 pieces of pritex together with points directing to each other

    Leave a comment:


  • Millstonemike
    replied
    Looks like you could mate two pieces together with a little spray adhesive to get a sheet of flat foam.

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  • malboro2
    replied

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  • billfitzmaurice
    replied
    Originally posted by wogg View Post
    Looks like garden variety egg crate foam..
    +1, and where damping is concerned it does't work as well as flat open cell foam. It looks like it should, but while foam damps, air doesn't, and those spaces between the pyramids are air.

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  • wogg
    replied
    Looks like garden variety egg crate foam. I have an endless supply of scraps of that stuff where I work, but some folks get a cheap mattress topper and use that.

    Lining a ported box walls is usually a good idea, has little to no effect on the bass performance but will help keep mid-range reflections more under control. Stuffing like you would a sealed box is different, that will get in the way of the port efficiency depending on how much you shove in there and where it's at.

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  • Scarface1
    replied

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  • Scarface1
    replied
    I don't have a pc, that's mostly the problem so if I want to calculate something I have to go to a friend. Pritex is a triangle shaped surface constructure of foam

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  • billfitzmaurice
    replied
    What's pritex? In any event you can model the effect of damping on low frequency response in WinISD 0.7 by changing Qa, it's in the instructions. You can't model the effect on the midrange, but where that's concerned a bare cab interior is never a good idea.

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