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Round cab & Aperiodic Vent (DIY)

Discussion in 'Amps and Cabs [BG]' started by warx, Oct 13, 2017.

  1. warx


    Sep 13, 2010
    Marin, CA
    I'm converting my 1x10 mini slant cab to use round cab using a Keller drum shell. I'm not sure on how deep to cut the shell to at the moment - it will be 6-12" tall (and 12" diameter). The slant cab was "OK". It was my first build since I did 2x18 subs 35 years ago. I should not have just used left-over 3/4 Cherry ply for one thing (normally I fabricate with metal/fiberglass).

    At 6" tall the volume is 580cu.in. It will be ported with a 4" hole on the underside and then the gap between the floor will be a tapered port. With 1" tall feet the underside taper port starts at roughly the same area as the 4" hole = 12sq.in and increases to the outside of the 12" diameter = 37sq.in.
    Will be fun to play with - I can make the feet height variable to tune the port. Might even try aperiodic with a restriction in the 4" hole. I've given up trying to model the tapered port using Helmholtz - so trial and error from here on out.

    My one fear is that the round wall is equidistant from the driver (given they're concentric). I have room to offset it a bit (10" driver in a 11.5" round baffle) but that might look like a mistake or poor workmanship... Maybe it's not a concern.

    I'll post back as I proceed.

    Attached Files:

  2. This will either be a spectacular success or a catastrophic failure. I'm hoping for the former, but either way...sub'd! :D
  3. buldog5151bass

    buldog5151bass Kibble, milkbones, and P Basses. And redheads.

    Oct 22, 2003
    Is there any reason for this other than curiosity (seriously - not trying to be snarky)? Seems it would be tougher to load, and less stable on stage.
  4. TB member Joey Dahlia (JOEYDAHLIA) experimented with drum shells as speaker cabinets.

    I don't know if he is a genius or a nut. ;)

    I have no idea if it worked, but I did find this: joey

    He called them Klops Drums.

    It's good to see people try things that are out of the ordinary.
    Last edited: Oct 14, 2017
  5. warx


    Sep 13, 2010
    Marin, CA
    A lot is curiosity. I had chatted with a friend way before I built the first one and he had some pretty radical ideas about drumshells, fiberglass spheres and other "organic" shaped cabs (since I'm more comfortable with composite layups than woodwork). Ultimately I did what I did and built the slanting cab (along with 3D printed corners etc.) but way too heavy and missed the HF element.
    So I decided to build a regular looking 1x12 (3012LF4 & BGH25-8) cab (hopefully with great sound) and this leaves me free to experiment with the 10" driver. I saw the new Upshot and it inspired me to try the drumshell.

    Now I'm trying to consider the height since my maple Keller shell is 12" tall I could cut into two 6" pieces. Visually 6x12 is very appealing. I could make it 8" but eyeballing it looks too tall/disproportionate - more like a vessel or container. 8" would give me 0.43cu.ft instead of 0.34 so that would be nice but perhaps there's more lost visually than gained sound-wise.

    Thanks for finding that!! I'll check out his posts.
    buldog5151bass likes this.
  6. He has not been active on TB since 2014.

    I sent him a PM linking your post, but he may not be logging on here anymore.
  7. warx


    Sep 13, 2010
    Marin, CA
  8. warx


    Sep 13, 2010
    Marin, CA
    I'm trying a height of 7.5". Looks a little tall proportionally but good for volume.

    Figure I can just do a simple brace from the bottom to the underside of the magnet. I'll add some small bits of ply where I want the handle to attach and the speakon connector. I can probably cut these from the drum shell cutoff so they are pre-curved.

    Attached Files:

    dukeorock and buldog5151bass like this.
  9. seamonkey


    Aug 6, 2004
    Sonus does something like this
    Opportunity to mix in passive radiator on the bottom if the top driver has good mids
  10. Love my upshot! Good luck on the build.
  11. warx


    Sep 13, 2010
    Marin, CA
    My cab has come together. Got the driver mounted. Figuring a way to mount the waffle grill w/out using the four clamps (no room around the edge).

    The passive radiator thing got me thinking... I could still try it - there's a reasonable 10" one from Parts Express ($25 and 1.5lb or so) but I'll probably stick to ported and make sure I use a good HPF with the amp to really cut off around 65Hz or so (I ordered an fdeck one "I think")

    Talking of ports I was looking at the tapered exit here as I want to keep my feet to 0.625" tall. If I put a 4" Precision Sound flare it works out that it's outer diameter gives me an area similar to the 4" hole itself - then expands to bigger as it goes out. Basically a taper from 12 to 23 sq.in.

    If I tune the cab to 68Hz I need 13" length @ 12sq.in so maybe since it's tapering to twice that it should work OK since there's 2.5" in the flare then maybe 3.5" under the cab.
    Using a 3" port/flare I need 7.25" length but the taper is much greater from 7 to 23 sq.in.

    I guess the only way is to try both. Of course fitting the smaller port flare back in is going to be tough once the hole is cut bigger.
  12. warx


    Sep 13, 2010
    Marin, CA
    OK, so my plan for my port is to fit a 4" Precision Sound outside flare and then going to print two of these to fit inside it. I'll print them in ABS so I can glue them in trapping some Polyfill inbetween. well, at least one and perhaps use small screws for the second so I can re-open to adjust the amount of Polyfill. Basically, a custom fit aperiodic vent.

    I determined that a 3" port was too small here. A 4" is too big but with two of these dampening plugs and polyfill I think it will be about right.

    Attached Files:

  13. warx


    Sep 13, 2010
    Marin, CA
    I decided not to use the Precision Sound 4" flared port after all. It gets too close to the back of the driver. I printed up a new flanged restrictor that I can easily just bolt up to a hole in the bottom. Now I just need to guess how much polyfill to stuff in there... Anyone have any ideas? I'm trying to make the two sides attach temporarally to try out different stuffings but that is pretty difficult. I guess if I stuff a lot in there I can pull some out (and back in too).

    More pics attached.

    Attached Files:

  14. warx


    Sep 13, 2010
    Marin, CA
    It's finished. Sounds pretty nice! Need to try it in places other than my boomy house. Weighs in at 11lb 2oz.

    Anyways, some final pics. The drum shell was finish grade maple while the top and bottom are baltic birch and has an amber water based dye on it then a few coats of polyu. The birch does not take the dye nearly as well as the maple.

    Attached Files:

    scuzzy and BigBobbyBass like this.
  15. jlepre


    Nov 12, 2007
    Parsippany, NJ
    WOW! Can we see how it looks in a standing position, and how you mount a head?
  16. scuzzy


    Feb 15, 2006
    Troy, MO
    How does it sound?
  17. BadExample


    Jan 21, 2016

    It could take a while, but be sure and train the drummer to not beat the cone with a stick. They respond best to negative reinforcement.
    dukeorock and warx like this.
  18. That looks amazing
  19. zorf


    Dec 27, 2007
    i put together a couple speaker in drum shell projects.
    sounded pretty good.
    I would like to experiment more, but, you know.
    Time and money.
    And space. These things start to pile up.
    dukeorock likes this.
  20. zorf


    Dec 27, 2007
    Also, sure didn’t take long for people to start copying the acoustic image speaker. ☺️

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