Kick out the jams- Its the Long Board Sub, a sealed tempest sono for music only

Discussion in 'Archived Threads 2001-2004' started by Brian Fellmeth, Aug 15, 2001.

  1. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    http://members.aol.com/brianf1429/sub/Sub1.jpg http://members.aol.com/brianf1429/sub/sub2.jpg
    Been working for 2 months on this thing. Except for refining the french polish finish, its finally done. I'll decribe aspects of the project that differ from most of the others.
    1) Shellaced endcaps with top inspired by the Hawaiian wooden long surfboards of the 60's. Should have used Koa, but thats stained Cherry. Nobody seems to use shellac, but after being frustrated trying to brush or spray without skill, I can tell you that wiped on shellac (French polish) is the best.
    2) A cove was routered into top edge of endcap and painted black to avoid the ugly 90 degree corner. The top layer of the top endcap is void-free birch plywood which I was originally going to shellac unstained to make a light wood ring in the cove, but the color of the various grains of the birch looked bad so I had to spray paint it black.
    3) Berber carpet fragment for covering. Elminates wrinkles, doesn't look too bad. Here is how it looked before the endcaps were placed :
    http://members.aol.com/brianf1429/sub/sub3.jpg
    4) Double thickness sono. I found 24 inch and 23 1/2 inch diameter tube. The small space between the tubes was injected with expanding insulating foam which locked them tight :
    http://members.aol.com/brianf1429/sub/sub4.jpg
    5) There is a chamber routered into the inner layer of the endcap to help it fit into the not perfectly round sonotube. The endcaps are sealed with weatherstripping and pressure from threaded rods- this idea stolen from the "flexisub" guy Earl- no glue or caulk. Also stole Patrick Sun's excellent idea of laminating plywood on the inside surface of both endcaps to help with mounting of hardware :
    http://members.aol.com/brianf1429/sub/sub5.jpg
    6) No dowdy wood dowell church lady legs here. These are from Ikea, and they have screw adjustable feet :
    http://members.aol.com/brianf1429/sub/sub6.jpg
    Bottem endcap complete :
    http://members.aol.com/brianf1429/sub/sub7.jpg
    The 5.4 cubic feet is generously stuffed with poly batting (did I do this right ? is this too much ?)
    http://members.aol.com/brianf1429/sub/sub8.jpg
    Here is a view of the bottem with driver mounted :
    http://members.aol.com/brianf1429/sub/sub9.jpg
    7) DIY active line level crossover with tunable low boost (very helpful for sealed design) is mounted in a box shared with the passive crossovers for the two way mains. By keeping my main crossovers outboard, they can be modified or I can go to active biamping without breaking into the main cabinets. Inside and outside views. The style of the crossover box matches my mains with the sloped black front :
    http://members.aol.com/brianf1429/sub/sub10.jpg http://members.aol.com/brianf1429/sub/sub11.jpg
    8) DIY circle jig with peg board laminated on top- very handy for picking the spot to drill the pivot holes. The jaspar jig is great, and I use the small one, but its precision is overkill for cutting the endcap discs, so I saved 40 bucks with this :
    http://members.aol.com/brianf1429/sub/sub12.jpg
    OK, its done and ready to move into music room.
    DOH! http://members.aol.com/brianf1429/sub/sub13.jpg
    I finally got it through that door. How does it sound ? After tweaking the pots on pomann's crossover, I was very happy to get this FR : (First point is 20 Hz)
    http://members.aol.com/brianf1429/sub/FR.gif
    Current setup : nOrh CD-1, Bryston 11b preamp Anthem MCA 3 series II amp (one channel for sub, the other 2 for mains) ACI 65HZ high pass filters on mains. John pomann's active crossover for sub nOrh Prism 6.9 mains. Sounds real nice.
    Thanks to many for their help, esp Patric Sun, Dan Wiggins, Derwood, John Pomann, TV, and Tyson for getting me started in this madness.
     
  2. ThomasW

    ThomasW Cinematographer

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    Very nice woodworking job [​IMG]
    Might consider repositioning the adjacent passive XO inductors so as to decrease potential coupling.
    [​IMG]
    [Edited last by ThomasW on August 15, 2001 at 07:37 PM]
     
  3. Patrick Sun

    Patrick Sun Moderator
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    Brian, nice job!
    Re: poly batting for the stuffing, the rule of thumb is for every cubic foot of internal volume, 1 pound/ft^3 is considered 100% stuffed. So depending on what percentage of stuffing you were going for, just divide the number of pounds of stuffing by the internal volume, and that will give you the percentage stuffing for the sub.
    ------------------
    PatCave; HT Pix; Gear; DIY Mains; DIY CC; Sunosub I + II + III; DVDs; LDs
     
  4. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    Thomas : Good idea, wish I had it before glueing the coils down pretty hard. I'll try to ger some of them up to turn.
    Patrick : I have no idea how much all that stuff weighs, but its certainly way under 5 lbs so I guess I'm ok.
     

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