Woofer on Top of bottom

Discussion in 'Home Theater Projects' started by BenSC, Sep 25, 2003.

  1. BenSC

    BenSC Stunt Coordinator

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    So I decided for my living room sub to use to PE Quatro 8" sub (295-545) and their 120W plate amp. I'm building an eclosure that can stand in the corner, so its gotta be tall and skinny to take up a small amount of floor space in the corner. Another requirement is that the woofer and port(s) be on the same side (the back) for visual, so that limits port depth.

    The design I have is exterior 9.5" wide, 6.5" deep, 26.5" tall. On the back, the sub will be mounted either on the top/bottom half, then the ports will be on the other (6 .5" ports at 2.65" long [mach of .12]).

    My question is, should the woofer be on the top half, or the bottom half? I'm not sure if it makes any sonic/tactile difference or not. Also, I'm going for clarity here, not room shaking bass.

    Thanks.
     
  2. Brian Bunge

    Brian Bunge Producer

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    Ben,

    I thought you wanted to build a subwoofer? This design will completely negate practically anything be low 40Hz and will be tuned to 43Hz.

    I'd suggest going slightly larger, say 22L, and tune to 33Hz. You can accomplish this by making the cabinet 1" deeper. Also, add feet to the bottom of the sub and go with dual 2" ports at the appropriate length. Unibox is showing me that with 6 .5" ports at this tuning frequency you'll pass 25ms port air speed at 85Hz and it just skyrockets past there.
     
  3. BenSC

    BenSC Stunt Coordinator

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    Hmm... one of us must have our stats on this speaker wrong then..

    I modeled it with WinISD. Interior volume of .797 ft^3, tuned to 36htz, with those vents gives a vent mach of .12 I hadnt' thoguht of putting the port(s) at the bottom (so I could make them longer), that's a good idea since I already plan on having spikes on it.

    As this will mostly be for TV/Music (theater room does the movies), anything below 36htz probably isn't needed much for me.

    I also modeled a 1.25 ft^3 box at 30htz, but it didn't give as smooth of a curve as the 36htz enclosure did. Although.. at first I looked at the curve and thought it was much quieter in the under 100htz region, but looking at it now it's only down by like 1db. So maybe I'll go that route.

    I'll look into doing it that way too, though it's gona take up more space. However, still looking for an answer on placement on the back, high or low?

    *edit*
    Interior size I have for a 1.25ft^3 is 10x7x31. Not too bad.
     
  4. Brian Bunge

    Brian Bunge Producer

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    Ben,

    What material thickness are you using? I assumed 3/4" which, with your external dimensions, gives me .5787ft^3.

    Using your .797ft^3, tuned to 36Hz gives a good response curve but port air speed is still too high.

    Concerning driver placement, I'd just leave it near the bottom to keep it from getting too top heavy.
     
  5. BenSC

    BenSC Stunt Coordinator

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    Doh! I just went back up there and looked, those numbers are 1" shy, it's 10.5x7.5x27.5

    Hmm, how come WinISD says the port speed is fine? Should I be using a different program? Yea, I was planning on bottom for just that reason if it wouldn't make a difference sonically.

    Also, my GF just pointed out the obvious, too. "Why not make it a triangle if it's going in the corner?" The woofer would have to face forward, but I could get more volume out of the same floor space.
     
  6. ThomasW

    ThomasW Cinematographer

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