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"Spare Parts Bin" sub build

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  • "Spare Parts Bin" sub build

    finally getting around to posting this... if anyone's interested, here's some info and pics of a sub i finished a couple weeks ago. used some random leftover mdf and a JL Audio 10W6 that i had sitting in the basement, from back in my car audio days. decided to see what i could do with it in a home theater context, paired with one of Jack Hidley's foster plate amps. turns out they were a pretty good match for each other, as the venting required to get the extension needed for an ht application meant the power had to be kept relatively low. as such, it's not a db king, but it was never intended to be the primary sub in my theater anyway, so i wasn't too worried about that. modeled, it has an f3 of ~22 hz, and is capable of ~106 db.

    i modified the foster amp per jacks calculator and instructions, to have a 2nd order highpass filter, centered at 20.15 hz with a Q of .774. this gave the best combination of extension and controlled cone excusion, given the values of the resistors i had available to make the modifications with.

    i designed the box to take the place of a narrow end table sitting next to one of the couches in my theater. wound up going with 2.6 ft^3 (net) with a 4" diameter x 24" long port. optimal size (according to winISD) would have been 3.2 ft^3, but the measurements for 2.6 net were the biggest i was comfortable going with, for it's intended location. external box dimensions are 14"W x 20"H x 24"D. to give it the stealthyest appearance i went with a downfiring, bottom ported configuration, so the box height has an extra 3" added to it (for a total of 23"), in the form of four 1.5" diameter dowels used as legs. the box's horizontal edges were left square, but the vertical edges have a 3/4" roundover for aesthetic cohesiveness with the circular legs. the sides and top of the box are finished using parts express black textured vinyl laminate. bottom (baffle) and legs are spray painted flat black since they would have been a pain to apply vinyl to and they'll rarely be seen anyway.

    i haven't done much listening to it yet, as i've been too busy with other things to get it properly calibrated and eq'ed, and until i can do that, it's not really worth judging. i did test it a little bit with some music when i first got it together. i thought it sounded good. not great, but good. in its defense, the driver is about 10 years old and its had a bit of a rough life (i used to push it pretty hard when i had it in my trunk way back when). either way, certainly worth the $80 or so that i have into it.

    to view the entire album of pics, go here. comments and questions are welcome

  • #2
    Re: "Spare Parts Bin" sub build

    Nice work here. I would assume it sounds quite good.

    I personally would have went with a large slot vent to avoid vent compression at higher output levels, but I am rather picky too.


    • #3
      Re: "Spare Parts Bin" sub build

      yea, i actually messed around with several different slotted configurations when i was designing the box, but i couldn't find a way to get what i needed without eating up too much box volume. just picturing it, i expected a slot setup to be better on that front, but to my surprise, the pvc monster you see in the pic was actually less intrusive than any slot.

      according to flare-it, using the air velocities from the winisd model, the 4" diameter with .5" flares at each end shouldn't have any compression issues. winisd shows a peak air velocity of only 16.x m/s @ 21.x hz, and flare it says you don't reach the core limit until 20 m/s from 20 hz to 25 hz. it does say that i'm technically above the chuffing limit all the way up to about 27 hz, but i'm hoping that because i'm under the accepted "general noise limit" of 17 m/s and the port is down firing, i won't hear any nasties. i think the big key here is that "higher output levels" don't really exist with this sub.

      unfortunately, i still can't offer any more opinions on how it sounds. i've gotta learn to finish one project before i start five more ...