Two port questions

Discussion in 'Archived Threads 2001-2004' started by tom_furman, Jul 31, 2002.

  1. tom_furman

    tom_furman Stunt Coordinator

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    Does it matter at all if I put the port at the top of my sub, as oppsoed to the bottom encap? I don't think it should, but I'm just making sure.

    Also, is there anyway to use a speaker grill to cover the port opening on top? Hopefully someone has a picture of how this was done.

    I dont think I'll be able to fit a 24" tube in my room, so i'll have to go to an 18" probably and port the top.
     
  2. Dustin B

    Dustin B Producer

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    Checkout my website. Tempest ported out the top, and pair of Dayton DVC12" subs ported out the top with grille covers (plus SVS does it). If I was to do the DVC12" subs again I'd get the 10" grilles and flush mount them. You just have to route a half inch or so wide grove that would fit the grilles bracket to flush mount them. There was a nice example of this a couple weeks ago, but I can't remember who did it.
     
  3. warrick

    warrick Stunt Coordinator

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  4. tom_furman

    tom_furman Stunt Coordinator

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    Hum...i like the flush look. I think the 20" would fit nicely in my room...24" just looked plain ridiculous!

    Do you think it would be possible to flush mount the amp, like Warrick did, on a 20" tube? I see he used 24". Or would that cause the amp to stick too far back into the tube and make it sound crappy.
     
  5. Dustin B

    Dustin B Producer

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    That's the one I was trying to remember, thanks Warrick.

    You should be able to mount the amp even in 18" tube. It doesn't matter how far it sticks in, as long as you compensate for the volume the mount takes up inside the tube and it doesn't end up hitting the driver or port (which if you mount a foot or so above the bottom of the tube should be impossible). In fact, it could help the sound as it would breakup and standing waves that could form on the length of the tube.
     
  6. tom_furman

    tom_furman Stunt Coordinator

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    Ok,,i spoke with Adire and the gave me the following specs:

    For home theater applications, we recommend 8 cubic
    feet tuned to 18 Hz. For 20" diameter sonotube (assuming 1.5" thick
    endcaps, and the nominal ID of the tube is 19.5"), you would want the tube
    to be 52" long. Use dual 4" diameter vents, each 17" long.

    What is the advantage/disadvantage of two ports? I heard that a buffeting sound can be created by having a small port, so would I be better off going with one 6" port?
     
  7. Robin Smith

    Robin Smith Stunt Coordinator

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    Hey, thanks for the props on my flush-mounted port cover!
    It was easy to do... I routed the bigger hole at ~0.25" depth first, then routed the smaller hole all the way through for the port to mount.
    To answer you original question, it does not matter if the port is on the opposite endcap than the driver. That is my config in fact (as you can see in the other pics on my site) as well as many others.
    The link to the grill I used is on my site also. It install's real nice as you screw the mounting ring down first and then slip the grill over top to finish it. I went with the 10" grill to cover the single 4" flared port I used. I selected this size mainly because it balanced nicely with the ~21" endcap. You could get away with an 8" (but not any smaller due to the flare of the port).
    Instead of flush mounting the amp I just built a simple external box for my amp a la Patrick Sun. I was scared of cutting holes in the side of the sonotube. It sure look nice when done well though (see Warrick's site for the best example I have seen). I was also afraid of the extra weight it would add as this thing is heavy enough!
    The tube diameter is also more a matter of looks. The wider the tube the shorter your sub can be. Mine is a little taller than I would have prefered, but to get the 214L volume I wanted, it ended up this height (~50" tall) with legs and base plate.
    Good luck!
    Robin Smith
     
  8. jeff lam

    jeff lam Screenwriter

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    I used an 8" grill from PE to cover my 4" flared port, it fit perfect since the flare was about 7" or so. I also flush mounted it. I'll try to get pics up soon of my whole thing that I finished months ago but just never got around to scanning the pics. I don't have a digital camera.
     
  9. jeff lam

    jeff lam Screenwriter

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  10. Dustin B

    Dustin B Producer

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    I really should have taken the time to do that on the Twins.

    Is it possible to get the grille off after you put it on without pushing from the other side?
     
  11. Brian Bunge

    Brian Bunge Producer

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    Dustin,

    Can you say "coat hanger"? Some sort of wire like a coat hanger could be stuck through one of the holes of the grill and used to gently lift it up.

    Brian
     
  12. warrick

    warrick Stunt Coordinator

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    Dustin,

    You could stick a piece of contact (self adhesive platic sheet) over the grille and crank up the sub
    Should pop straight off

    Warrick
     
  13. Dustin B

    Dustin B Producer

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    I don't think a coat hanger would fit in the holes, but I guess you could feed a thinner wire around the grille in a couple places and pull it up. It takes sufficient force to get those grilles off their mounting brackets that even not flush mounted I find it difficult to get the grills off the twins.
    And Warrick [​IMG]
     
  14. jeff lam

    jeff lam Screenwriter

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    Use a small nail or screw. Poke it through one of the holes close to the edge of the grill, lift up. It should come up. Use 2 nails if you have to and work it up slowly from each angle if it's tight.

    The only problem is, you no longer have a pilot hole to cut your reccess with. How are you going to make a perfect circle? That is, if that's what you had in mind.
     
  15. Dustin B

    Dustin B Producer

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    Are you talking to me Jeff? I'm not going to counter sink them. Too late to do that, I won't attempt it without a center hole. Just lamenting the fact I didn't do it.
     
  16. Neil Joseph

    Neil Joseph Lead Actor

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  17. warrick

    warrick Stunt Coordinator

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    Jeff,

    When I blew up the 12" driver and had to replace it with a 15" tempest, I cut out a hole perfectly in the centre where there was no centre hole.
    All I did was draw a square on a piece of scrap using the diameter of the plug/end cap as the side measurement for the square, draw a line across from corner to corner to find the centre point.
    Drill a hole for the circle cutter in the centre of the square where the lines cross. Screw down the end cap so it fits perfectly in the square. You may have to lengthen the pin a bit but this system works well.

    Regards

    Warrick
     
  18. tom_furman

    tom_furman Stunt Coordinator

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    Hey..two more questions i have stumbled upon while buidling my sub (about 70% done!)

    Before I cut my port to length, do I count the 1 3/4" of MDF as part of my overall port length? I have 3/4" endcap and a 3/4" plug.

    Also...what type of epoxy is best to adhere the port to the MDF? there are a zillion types out there and i'm not sure which is best for this application.
     
  19. Dustin B

    Dustin B Producer

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    You account for whatever portion of the plug and endcap that will add to the ports length (excluding any of it that is rounded over).

    I just used polyurethane (bulldog grip). And some silicone to make sure it was air tight.
     
  20. tom_furman

    tom_furman Stunt Coordinator

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    ah-ha...thanks! i calculated my port to be 24" so if my two layers of MDF are 1 3/4" I need to cut my tube to 22 1/4" (i'm not rounding off the corner)
     

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