Just finished AV12 for a friend

Discussion in 'Home Theater Projects' started by Stephen Hopkins, Oct 24, 2003.

  1. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    Just finished an 3 ft^3 AV12/Rythmik sub for a friend. Built from 1" MDF w/ 3 x 3" x 11.5" flared PE ports (multiple tunings). The finish is PE Black Oak Vinyl. It looks a little funny in the pictures, but that's just finger prints and smudges on spray on furniture polish. If sounds great. I like it for music w/ 2 ports open, F3 around 25hz, and a nearly a 4 db boost @ 35hz. For HT I like it w/ 1 port open, F3 around 21hz, and flat response. My friend likes it w/ 3 ports open, F3 around 30hz, and a almost 7db booste at 40hz, for both HT and Music... to each his own I guess. The 3rd port (not shown) is bottom firring. It'll actually be on one side until we get the big spike feet from PE.

    Only problem so far is some port noise, even w/ all 3 ports open, at loud volumes. It's not audible from the listening position, but is within 4 or 5 feet of the sub. I figured w/ 3 3" flarred ports this wouldn't be a problem... any idea why (other than just moving alot of air)?

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  2. Brian Bunge

    Brian Bunge Producer

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    Stephen,

    Looks great! I think I see what the problem is though. I only count 2 ports![​IMG]
     
  3. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    LOL. The third is on the bottom (side until we get feet) and it's not visible in any of the pictures.

    Everybody's a comedian [​IMG]
     
  4. Brian Bunge

    Brian Bunge Producer

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    I guess I shouldn't quit my day job, huh?[​IMG]
     
  5. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    Well you don't have to worry about me stealing any of your clients so your day job is safe... and with that said, maybe you should stick with it LOL [​IMG] j/k. I don't think it's quite up to your standards Brian, but the fact that you were the first to comment did give me an insurgence of pride in my work. I'm sure you can see the many imperfections in the edges of the vinyl. We cut an oversized piece for each side then trimmed with a utility knife. I'm wondering if perhaps we should have wrapped four sides then used the cut/trim method on the remaining 2 sides? My original plan was to paint it w/ satin black latex paint and use some kind of stained hard wood trim pieces like my own EBS AV12, but my friend wanted the finish to match his Klipsch RF3s, RB3s, and RC3. This would have hidden the MDF joints and butt ends and it's hard to mess up. But he's happy with it, so I am too.

    Any one have any ideas on the source of the port noise? I don't hear any on my EBS AV12 using 2 of the same ports in a 5.359 ft^3 box. Would my EBS AV12 being down-firing make the port noise less audible, or does the difference in enclosures make a difference? Is it possible since 2 ports are facing one way and the 3rd is facing perpendicular to that cause the air to be turbulent before it even exits the ports?

    Thanks [​IMG]
     
  6. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    I liked how the vinyl worked out, but if I ever use it again i'll do some kind of extra adhesive because it tends to peel away at the edges fairly easy with any interaction. My friend wanted the black oak to match his speakers, so i figured why waiste the time, effort, and money on veneer when it was just going to get painted black anyway. Because of the vinyl being fairly easy to cause to pull away we've decided to probably add black corner covers similar to those used on PA type equipment. Shouldn't detract too much from the asthetics and should add quite a bit of durability to the finish because the corners seem to take the most abuse (one has already been knocked into a door, luckily it was on the back/bottom).
     
  7. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    Anyone have any ideas on the source of the port noise?

    Thanks [​IMG]
     
  8. MichaelDDD

    MichaelDDD Supporting Actor

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    Just wanted to say NICE JOB! [​IMG]

    I've built quite a few subs myself...and they work great. But are ugly as sin to look at. [​IMG] I think you did a good job with the vinyl.

    It looks store bought. [​IMG] The recessed plate amp looks killer.
     
  9. Rory Buszka

    Rory Buszka Supporting Actor

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    Your port noise could be caused by multiple tuning points. When you have a downfiring port, the distance from the port to the nearest outside edge of the box also contributes to the port length, I think, though I don't know how to mathematically relate this because the extent to which it happens varies with the ground clearance of the bottom of the cabinet.
     
  10. John E Janowitz

    John E Janowitz Second Unit

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    As Rory said, the ground can make the port act like it is longer if it is too close. Basically you add flow resistance to the port. That makes the port act like it is longer. You would then have more air going through the other 2 ports than through that one.

    John
     
  11. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    right now we have the port that is planned to be on the bottom facing to the side, so that's not an issue right now.
     
  12. Aaron Howell

    Aaron Howell Stunt Coordinator

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    Just as a tip, if using laminent spray paint the edges of the box a similar color so that if it does peel, or the edge is perfect it isn't nearly as visible. It does look nice though. I've been really impressed with the laminents I've seen on here. Nice job. [​IMG]

    As far as port noise, the only thing that stands out to me is how close those ports are to the side of the enclosure.
     

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