Subwoofer fill

Discussion in 'Home Theater Projects' started by Jim-Luc, Mar 24, 2006.

  1. Jim-Luc

    Jim-Luc Extra

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    How much subwoofer fill is enough? can there be to much?
    is it better without? The box is 24.5” tall ,19.5” deep, 19” wide. It has one port in the corner that is 15" long and 4" wide . The area inside is about 5.11 cubic feet or 144.87 liters. I bought a Dayton 15" Titanic MK III. Currently I have the box filled with enough room for the speaker to fit in. Iused the stuffing from a pillow as it looks like the same poly fill stuff I saw on line What do you guys think?
     
  2. Brent_S

    Brent_S Second Unit

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    How does it sound to you?

    As a general rule, you don't fill a bass reflex enclosure, which is what you've described. You only line the walls with something like egg crate foam or fiberglass insulation batts. At a minimum, you want an unobstructed pathway between the driver and the port, otherwise you're creating something resembling an aperiodic sealed enclosure.

    How much power do you plan to give this thing? Dropped your sub into WinISD. I used 5 ft^3 tuned to 19.4 hz, although it's probably a bit smaller than that with the driver installed. You didn't mention any bracing...bracing, driver displacement, and the port displacement all subtract from the volume your driver is using. Above 300 watts, port noise will start to become an issue below 30hz with that single 4" port. The smaller net volume you actually have raises your cabinet tuning point and also increases port air velocity for a given power input.


    wbs
     
  3. Jim-Luc

    Jim-Luc Extra

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    Wow now I just feel stupid

    Tell me what you think I should do
    First off ill remove the poly fill
    I will leave the foam on the inside walls of the incloser
     
  4. derekBannatyne

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    I'm in the middle of building my 8 ft^3 ported sub, and I'm going to line the walls with 3.5" fiberglass, it cost about $10 at Home Depot, it's R-13.
     
  5. Brent_S

    Brent_S Second Unit

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    Jim-Luc,
    no reason to beat yourself up. DIY is a learning process and this forum is a place for us to share knowledge and experience (good or bad).

    I was sincere when I asked how it sounded to you. You're the only critic that matters for your project. Some people prefer the sound of sealed subs. By completely stuffing the cabinet, you created something resembling a very lossy sealed enclosure. If you find the frequency response and SPL output acceptable then you're done. A sealed Titanic 15 in 5 ft^3 models a pretty nice response curve and is capable of 103.5db @ 20hz with just shy of 350 watts. Depending on your room size, you could easily pick up 5-10db more from room gain.

    If you want to explore the ported design, which offers the potential for significantly more output, you're doing the right things by removing the fill and leaving the lining. To help you fine tune it, we need to know your true cabinet net volume along with how big of an amp you're using. Room size and placement are also helpful. In other words, the more info the better. :)

    If you haven't already ripped the polyfill out, here's what I would do. Pick out some bass heavy DVDs and watch the big scenes in them with SPL meter in hand. Records your readings along with your volume and level settings. If you want the full sealed sub experience, use a Nerf football or something else appropriately sized to plug the port. Once you've got a good feel for how it sounds sealed, or semi-sealed. Rip out the fill and repeat your measurements with it in the full ported mode. Now you've got objective and subjective data to help you decide which design you like best.

    wbs
     

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