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Thread: Sub 1500 questions

  1. #1
    Member jcdahl's Avatar
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    Sub 1500 questions

    Well, I have built my Sub-1500 boxes and are almost ready to try them out.

    The inside dimensions are 23" H x 17" W x 15" D
    total internal volume (allowing for the cone and bracing) is 3.04 cubic ft.
    Two questions:

    1) How much fill should be used inside each sealed enclosure (I have the Dacron wool from PE called Acoustastuff)?

    2) I read about breaking them in. What is the best procedure to properly break them in?

    I am driving them with a Mackie M2600 at 800W per channel. crossing over at 90HZ with a 24db per octave filter in the Amplifier.

    Thanks
    JCD
    John

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    RIP 2010 scott fitlin's Avatar
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    Acousta-stuff

    According to manufacturers recomendations, about 1/2lb per cubic foot of the enclosure. So 1- 1/2lbs of acousta-stuff for your cabinet.

    But, you can play with the amount till the cabinet gives you the sound you like best!

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    Adiabatic conversion occurs when the dimensions of the wavelength are on the order of the dimensions of the
    fill material. Given that your enclosure is 23" in the max dimension and assuming you stuff it with a jellyroll of fiberglass insulation, the effect of the insulation will significant at
    frequencies around 400Hz and above. I suspect that your sub
    will be attenuated a couple of octaves below this so stuffing it will be of no value.

    Regarding "break-in", just listen to it and enjoy it. The break-in part is a consquence of entropy, we all get old, break-down and eventually fail.
    Last edited by John Warren; 05-31-2004 at 04:37 AM.

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    Registered User MJC's Avatar
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    Re: Acousta-stuff

    Originally posted by scott fitlin
    According to manufacturers recomendations, about 1/2lb per cubic foot of the enclosure. So 1- 1/2lbs of acousta-stuff for your cabinet.

    But, you can play with the amount till the cabinet gives you the sound you like best!
    It seems that I've read elsewhere, that increasing fill either acousta-stuff or fiberglass will increase the virtual volume of the cabinet. Which would be a good thing for a small box(around 2.5 cuft).
    My original L212s had both the sub-enclosures for the LE5-9 and 112A stuffed to the max.
    I've got my 2.51cuft boxes for the 1500 filled with 3.5" fiberglass all around, but I'm thinking of added an extra layer. So I'd have 7". Not sure how much the virtual volume would increase though.

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    MJC - I've never really measured the Acoustastuff so I can't say much about it. I've asked G.T. in the last couple of years if he has ever found anything to use besides fiberglass and the answer was "no" (and he seemed pretty emphatic). The fiberglass will add virtual volume. You can use it to fine tune if you want. A "typical" amount will usually offset the displacement of any drivers, ports/ducts, bracing, small subenclosures and network "boxes". For instance, the last pair of large enclosures I built were 9 cubic feet gross and ~ 8 cubic feet net (driver, bracing, ports/ducts). I used 2" thick Owens Corning fiberglass to gain back the entire cubic foot lost to displacement.

    I would not stuff the enclosure tight like the B212 was because you can actually reach a point where the fiberglass will start to take up volume. We discovered that way back in the day when we were building sealed 124/2203 and 136/2231 subwoofers.

    "Not sure how much the virtual volume would increase though."

    Measure the change in Fc.

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