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  • 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

  • #2
    Stuffing is usually done to absorb mid to higher frequencies or to damp (lower the Q) of a sealed system. It's also used to slow the spreed of sound waves in transmission lines. I have heard of stuffing reflex boxes, be sure not to block the port. I think it would change the tuning and damp the reflex action. In full range reflex cabinets the walls are lined with an inch of damping material.

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    • #3
      And if I use pritex on the back of the enclosure will this help and will this affect the internal volume of the box and affect the tuning because it works a little as a spring

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      • #4
        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.
        www.billfitzmaurice.com
        www.billfitzmaurice.info/forum

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        • #5
          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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          • #6

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            • #7
              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.
              Electronics engineer, woofer enthusiast, and musician.
              Wogg Music

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              • #8
                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.

                www.billfitzmaurice.com
                www.billfitzmaurice.info/forum

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                • #9
                  If you can get a copy of Vance Dickersonís 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.

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                  • #10
                    Looks like you could mate two pieces together with a little spray adhesive to get a sheet of flat foam.

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                    • #11
                      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

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                      • #12
                        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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                        • #13
                          Originally posted by Scarface1 View Post
                          Wow that's a lot off money,...
                          pm sent
                          "Not a Speaker Designer - Not even on the Internet"
                          "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                          • #14
                            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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                            • #15
                              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.
                              www.billfitzmaurice.com
                              www.billfitzmaurice.info/forum

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