Some sonosub questions

Discussion in 'Home Theater Projects' started by Mark Wilson, May 11, 2003.

  1. Mark Wilson

    Mark Wilson Agent

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    Hello all, I'm about midway through my sonosub design.

    I'm going for the Adire Alignment Design (Only took me 2 months to decide on a design! [​IMG])

    So, I've cut my tube so I'll have approximatly 214L (How much leeway would I have on the total internal volume, can I safely be 10L out of spec either way?)

    Sadly, I don't have the precision flared ports, so I'll use the PVC method so many are fond of [​IMG] (And flaring them at the end with a round over bit)

    What size/length of PVC should I use to reach the same porting as with the FP3 twin ports?

    (So no one has the pull up the designs, it's 214 liters, tuned to 15.4 Hz, stuffed with 64 ounces of polyfill, using a pair of FP3 ports with 11" center tubes)

    Also, I notice with sonosubs that everyone mounts the driver down firing, and the ports on the top. Any reason for that? I would much rather design it with the sub on the top, and the port(s) on the bottom. It will have a baseplate, so either way, it won't be blowing right at carpet. Any reason why I should stick the driver on the top, and ports on bottom?

    One last Question, I don't really want to use any rods, I know I definatly should, but I'm hoping I'll be able to fight my way around them. I'm planning on cutting some 3/4" mdf so it fits in the end perfectly, then I'll just glue it in like crazy. I could also screw it to the sonotube, just around the back so the screws wouldn't be visible. (Not sure if the screws would be necessary)

    But, with the endcaps glued in (with lots of glue!) would it 'work?' The entire weight of the structure should keep the bottom cap in fine (It will be wresting on legs, then the baseplate) Also, I can definatly put some weight on the top of it. (I figure with the driver on the top, there's 20 pounds, then I can stick an aditional 20 lbs of something up there, perhaps some marbel would look nice. I figure the glue, and the weight would keep it firmly in?

    Thanks for any responces!

    (PS, I'm in Canada, and looking for a BFD 1124DSP, and a QSC RMX 1450 power amp, to drive them both, anyone know of any Canada retailers that would carry these, or would order them up? I'm afraid of customs tacking a large duty fee on them)
     
  2. Pete Mazz

    Pete Mazz Supporting Actor

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    Putting the driver on top makes it top heavy, which may be a problem. You may want to use a grill to protect the driver if it's exposed. You didn't state the diameter of the tube you're using, but figure 1 1/2" endcaps and don't worry about the rods. You also didn't state the diameter of the PVC you're using for ports. +/- 10% on the volume shouldn't be a problem. Just use what you've got and figure the tuning based on your final net volume.

    Pete
     
  3. Mark Wilson

    Mark Wilson Agent

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    Any other reasons then it being top heavy? I'm not worried about these suckers tipping over. Also, the top will have a disk a couple inches above it, so the woofer won't be exposed. (I have a cat of death, he'd tear it up within seconds! [​IMG])

    The tube is 20" diamater. I'm not sure what diameter port I'm going to use, as I was hoping you guys could suggest what to get. (couple ports, one huge port, lots of tiny ones?)

    The end caps will sadly only be 1" (It's just my prototype) If they don't prove to be enough, I'll definatly move it up an inch or two [​IMG]
     
  4. Pete Mazz

    Pete Mazz Supporting Actor

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    For 214 liters these would be the appropriate vent lengths for straight pipe. I would use the 6" if you can.

    1 6" vent - 38 5/8".
    2 4" vents - 34".
    2 3" vents - 18 1/2".

     
  5. TimForman

    TimForman Supporting Actor

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    Correct me if I'm missed something here but I don't see where you stated the driver that you're using. With that said, how can anyone specify port diameters and lengths?
     
  6. Mark Wilson

    Mark Wilson Agent

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    Sorry Tim, your quite correct, I feel like a noob [​IMG]

    It's the Tempest. Expect to hopefully be giving it a healthy 700 watts or so. (Not that I'll ever need 700 watts, but when power is on the cheap, why not! [​IMG])

    Thanks again everyone.
     
  7. TimForman

    TimForman Supporting Actor

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    No prob, I was confused how Pete got his numbers. Maybe he's psychic [​IMG] but his numbers are correct for the non-flared vents. I like my subs downfiring because my floor is carpet covered concrete. I feared an upfiring tube would rattle my ceiling (which is the floor upstairs) quite badly. If that's not a concern and you can make it stable I can't think of a reason not to have it fire up. If you haven't bought the tube already maybe you could make it a larger diamter (24")?
     
  8. Mark Wilson

    Mark Wilson Agent

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    Thanks for the replies guys.

    Sadly, I have already bought the tube, and cut it to length. And the 20" diameter is hard enough to work with!

    If I were to port one end of the tube, would the length increase or decrease? And if so, by how much?

    I'm not to sure if that long of a port is going to fit in the tube, with the sub (I was planning to put them both in the center, the magnet might be interfereing with the long tube)
     
  9. Pete Mazz

    Pete Mazz Supporting Actor

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    I've seen the Tempest alignments enough to spot it. [​IMG]

    Besides, tuning is only based on enclosure volume, port size and length.

    Pete
     

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