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Aperiodic stuffing data

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  • Aperiodic stuffing data

    Fellow tinkerers, I just completed an aperiodic sub using the B-52 1804's and actually think they have some great potential once I get a chance to measure and adjust the resistance. In my search for fibers to load the "vent" with I came across an interesting point regarding fiberglass; it DOES cause breathing disorders...and the wife already has issues. So I've spent at least 6-8 hours looking through the interwebs for no kidding empirical data for different materials...to no avail. I have fiberglass, natural wool and dacron batting all on hand but was just wondering if I could save some pain. Any EXPERIENCE or data would be much appreciated. Thanks much, Brad

  • #2
    I would definitely not use fiberglass insulation. While it might work "ok" in a sealed box, I would just avoid it, if for no other reason than it's not fun to work with. If you stuff your ported box with it, you'll eventually end up with some of that fiber flying out, and no one wants that. I'd go for the Dacron batting if I had to, but you might try other types and amounts to see what works best for you.
    "If we weren't all crazy, we'd just go insane..." -Jimmy Buffett

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    • #3
      Fiberglass insulation is in a lot of residential walls. All kinds of air, and water vapor, passes over fiberglass insulation through wall leaks unless you have a tightly sealed house. Regardless of what you use for your speakers you should probably filter small particulate matter in your house.

      https://www.youtube.com/watch?v=kH5APw_SLUU

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      • #4
        Maybe a little grill cloth or other fabric in front of it? After all it'll just be part of the resistive material.
        A mains
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        • #5
          Am I wrong for thinking that any cloth/material that has a static flow resistance would work fine as long as the measurements confirmed the correct flow (/air spring) was obtained? Seems like grill cloth for aesthetics and any kind of felt, batting, dacron or wool would work fine. Measure your "tuning" with DATS and a mic and you should be good to go.

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          • #6
            Fiberglass batting was used historically, like in the old Dynaco A25s. These days I'd try waste cotton insulation like Ultra-Touch.
            Francis

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            • #7
              Well here is an update. I ended up using dacron batting. I used fiberglass initially and was able to get the impedance fairly flat (7-9 ohms, DATS v2) from 20 Hz to about 90Hz where there was a dip down to 5ohms. The sub is crossed at 95Hz so I'm OK. I tried wool and was able to get the same results as fiberglass with roughly the same, exceptionally thin membrane; less than 1/4 thick. The I went to dacron...HOLY COW! It took 10 layers, 3-4 inches tall, to equal the fiberglass and wool. I ended up getting the exact same impedance curve and FR plots...just a LOT harder to compress all that into 3/4 thickness but the wife's lungs are safe. ;) All in all quite happy with the sound and the fact that I have an 18" driver in a 1.3 ft3 enclosure. Thanks for the inputs guys.

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              • #8
                Fiberglass is hard to beat for low frequency damping.
                Francis

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                • #9
                  I thought everybody knew now a days that fiberglass is severely detrimental to one's lungs, lol.

                  Although now I'm wondering: would fiberglass' effectiveness be drastically reduced if one sprayed a "sealer" of some sort on the exposed surface, so as to trap the fibers and prevent them from coming loose and into the air? Something like a spray glue to lightly coat the surfaces. Or perhaps even covering exposed surfaces with plastic mesh aka mosquito screens that come in rolls that you see at the hardware stores?

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                  • #10
                    Originally posted by fpitas View Post
                    Fiberglass is hard to beat for low frequency damping.
                    True, when it's Owens-Corning Type 700 rigid batts or the equivalent. High acoustical resistivity, and low potential for particles getting into the air. But it's not compressible, so you wouldn't use it for stuffing. Regular home insulation is compressible, but it doesn't work as well as Type 700, is nasty to handle and can make its way out of ports, so it shouldn't be used for speaker damping.

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

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                    • #11
                      guitar maestro...yea...everyone but me apparently ;) Just kiddin. I expected a lot of flow through these vents so I didn't want to take any chances.

                      bill...agreed. I've used that itchy house stuff in sealed and vented boxes before and I always hated it. I've seen those 700 series panels and NEVER realized they were for acoustic treatment. Thanks for the day's knowledge nugget.

                      This whole aperiodic thing came from an "N" Type Ripole sub(L&R) that didn't really flip my lid. I heard them in Richard Clark's Grand Nat WAY long ago and remembered how nice they sounded/integrated.

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