DIY 15" Quatro complete

Discussion in 'Home Theater Projects' started by DevinJC, Jun 27, 2005.

  1. DevinJC

    DevinJC Stunt Coordinator

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    DIY 15" Quatro complete

    --------------------------------------------------------------------------------

    Wow. Damn. Cool.

    Built pretty much to specs ~ 5.5 cu ft box, 4" port that right now is about 11" long (short story involving beer and a flimsy hacksaw) and PE 240w amp. Oh, and lined everything but the front baffle with eggcrate foam.

    Significant step up from the Dayton 10".

    Corner loaded it's flat to 16hz, or well capable of being flat. I've got some pretty exciting peaks and valleys from 50-80hz. My head exploded from listening to test tones before I could get the BFD fully dialed in.

    Now I just need to figure where the tuning truly wound up, and diagnose the hum I discovered this morning. It's not a ground loop. Either the power strip or some interaction between the BFD and the Sub.

    For a ~$300 sub... damn.

    Of course, it is stupid big. And currently unfinished, so the WAF is off the charts. Fortunately she's very tolerant of this sort of thing.
     
  2. MikeGee

    MikeGee Second Unit

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    do you have any pics of the construction? I'd like to see what the inside looks line after it was lined with the eggcrate foam.
    How did you go about building the box and getting the specs so you know it'd match up well?
     
  3. DevinJC

    DevinJC Stunt Coordinator

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    Sadly, I took no pics of the construction. I modeled a little bit with WinISD, poked around in Unibox, and found a spreadsheet that would model the actual box by volume for you.

    With those and the suggested box size for the quatro, I just started putting things together. For fun, and from reading around, I decided that with a 6.5 cu ft internal volume box before bracing/driver/amp I'd probably be close to 5.5 installed.

    Then I built the box leaving the front and back baffle off. Got good and drunk with a friend of mine, did some cute triangle bracing (probably making my box about 6 cu. ft), liquid nailed/stapled the eggcrate on... heh yeah liquid nails.

    Basically, I read about as much as I possibly could about the DIY process for this driver; spent a week playing with spreadsheets and mental images; tentatively started the process, paused, and then I just built it. Close enough dimensions and a mostly square box was the goal. Worst case I spend $25 on another sheet of MDF and start over.

    I'm happy with it for now, dialed in, I'm flat from 80-16 (well a little house curvey) and no problems with 100db peaks.

    Hey, check me out, I wrote a book. mmmm beer
     
  4. Geoff L

    Geoff L Screenwriter

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    5.5ft^³-->4"x 11"= 21Hz tune

    6.0ft^³-->4"x 11"= 20Hz-11.12" actualy

    Your 4" port is either longer than you think, the box volume bigger than you think, applied major eq-boosting down low, or your getting (some un-godly low Hz room gain to be flat to 16Hz)...!!!
    If thats it, room gain down that low and that strong, man I want some...

    The driver should begin unloading below tuning and down at 16Hz pretty/very quickly spl wise, & bottom out.

    I belive you can be flat in room down to 16Hz with room gain and applied eq,, but not with anywhere near the spl the sub will easily do at say 22-25Hz on up. It will and should bottom the driver at 16-17Hz pretty quickly "spl wise",,, (going by your spec'ed cab size and port length)...!

    Also, don't that 240 plate amp have a (rumble/ss-filter built in at 20Hz or so) also..???

    Have you run any test tones to find the actual tunning..?????

    When the driver stops or (moves the least), will be very close to tune. Don't need to be loud to check for this, 80-85db is plenty spl.

    Glad your happy with your new BASS toy, "thats what is most important".!
    DIY is fun & amazing what $300.00 and some beer-->[​IMG] will buy/build..[​IMG]

    Cheers
    Geoff ¥
     
  5. DevinJC

    DevinJC Stunt Coordinator

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    Almost positive the port is only 11". Given the box's outer dimensions, it can't possibly be larger than 6.0 cu ft, unless the eggcrate I used was extra fluffy and it just thinks it's bigger.

    Soooo I'm left with 3 things, either I suck with an SPL meter, the test tones I'm using are not what they say they are, or I'm getting some sick room gain. All of which are plausible.

    That amp does have the rumble filter. And I still had to BFD down a peak around 20hz. I think I only have one boost eq'd, which is +5db around 71hz.


    I may have misspoke with the 100db peaks, at least at on the bottom end. The highest verified was a 16hz test tone around 92ish, which was a AVR volume calibration mistake (imagine the thought process of: 80db at 80hz and 92db at 16hz? Wait. What? Something is not right! 80hz was @ 91db [​IMG]). I haven't actually ran a test tone to 100db, cause, well, plotting the thing at 80db makes my bones ache after an hour.

    I'll try to get the freq response graph up later today or tomorrow, and will see if I can isolate the tune point tonight. Dropping 2 pair of new Paradigm Studio 20s into the room at the same time has led to lots of tweaking.
     
  6. Geoff L

    Geoff L Screenwriter

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    Just curious:

    How big is the room that you are filling with bass.??

    Are you taking your Spl/FR measurments from the listening position and if so "how far away is the sub from you".??

    Cheers ¥
     
  7. DevinJC

    DevinJC Stunt Coordinator

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    oh hell, I just erased all of this.

    anyway.

    Room is 9.5'Wx15.5'Lx8'H. with a 3.5'x7' opening into the kitchen which has an opening into the laundry room and one into the living room.

    Port is absolutely no longer than 11.5" and is flared. Sub appears to be tuned between 18hz and 20hz, felt closer to 18hz. Apparently the old eggcrate foam I used added what, roughly a cubic foot to the apparent volume?

    16hz tone gets nasty at uncorrected 94db. Corrected is 105.5db.
    Nasty like about to launch a driver, distortion blech.
    18hz tone is fine to uncorrected 95db. Corrected is 103db.
    Holy god. Too late to run anymore tests that loud, thank god for a plaster walled house though.

    thanks for the responses so far Geoff, buying the studio 20s caused me to skip really analyzing this sub, and your questions have gotten me to go back and pay attention to it. Nice getting the knowledge for the next cabinet I build. [​IMG]
     

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