Ideas for a small sub?

Discussion in 'Home Theater Projects' started by MikeBi, Jun 8, 2005.

  1. MikeBi

    MikeBi Auditioning

    Joined:
    Apr 28, 2004
    Messages:
    12
    Likes Received:
    0
    Hello,

    I'm thinking of building myself a small (approximately 12" cube) sub to hook up to my bedroom stereo system. I was looking around on the forums and have gotten a few ideas, but I'm so new to this that I'm really clueless as to what I'm doing.

    First, I looked at the Dayton Quattro 12" because it had plans that build a box in my size range. I then stuck that speaker in WinISD and plotted out the curve with the box size from PE. Now I realize that a small, sealed box is not going to have the low bass extension of a bigger, ported box, but this graph drops like a rock after about 50Hz. Is that normal (read: did I use WinISD correctly?)

    Next, I saw other people posting about the Ascendant Atlas 12 being on sale for $100. Assuming there are any left, would this be a better choice than the Quattro? I'd guess yes since it's only $25 difference in price and much more xmax.

    Next problem: the Ascendant site has specs for several different sized sealed boxes. How do you choose? Again, rookie talking [​IMG]

    Last question. If I decide that 2 cu^ft (arbitrary number) is the right volume for me, how do you choose box dimensions? I'd much rather have a cube shape than a tall, slender box - is that advisable?

    Thanks,
    Mike
     
  2. Jack Keck

    Jack Keck Second Unit

    Joined:
    Nov 23, 2001
    Messages:
    269
    Likes Received:
    0
    This is a great tool for determining box sizes. One Caveat: It assumes you are building two boxes like for a stereo pair of speakers. If you switch it to one, then it still calculates braces for two. As long as you're aware of that, it's cool.

    http://www.audiodiycentral.com/tools.shtml

    I did up a sealed box with a Quatro 12 in WinISD and got about what you did. That might be good enough for a bedroom system, though. You might want to look into a ported 10" or even 8". I don't think a 12" driver will fit into a cubic foot box.

    Then again, a lot of people like this one http://www.partsexpress.com/pe/pshow...number=300-632

    It's small and goes reasonably deep. And you don't have to build it yourself
     
  3. Dan Wesnor

    Dan Wesnor Second Unit

    Joined:
    Apr 28, 1999
    Messages:
    389
    Likes Received:
    0
    I have 2 subs. One is an old Shiva Mk. I in a 14" cube with a Linkwitz transform. In room, it is flat to 20Hz. The designed roll-off is Q=0.707 @ 30Hz. It is not Earth-shattering, but this is a big room. I mourn the loss of this driver.

    The other is a 12" Dayton Titanic Mk III (I think) in a 16.25 inch cube with the standard PE plate amp that has some boost. It is Earth shattering. I have not measured it in-room, but it moves chairs, and that's good enough for me. The design roll off is Q=0.707 @ 35Hz or so.

    Don't assume that if it's not flat to 20Hz in the software that it won't do the job.
     
  4. MikeBi

    MikeBi Auditioning

    Joined:
    Apr 28, 2004
    Messages:
    12
    Likes Received:
    0
    Well, 2 hours after I post this, my friend tells me he's giving me 2 JL Audio 10W04's. These look like they're going to be much nicer in a small box than what I was looking at.

    So I cranked up WinISD and it told me 32.7 liters (1.2 cubic feet) is the way to go. I did some math and it appears that once I drop a plate amp into it, I can build it 15" cubed and a 1.5" front baffle and get right about the correct volume.

    Question: When I put my numbers in Boxy Cad (thanks for that link btw), what does the "full length brace" mean? Is that a brace midway to the back of the box with a circle cut out?

    I'm pretty pumped about the JL's. I can put the PE 125W amp in and build the box for only $100 and a tiny bit of mdf!

    Thanks,
    Mike
     
  5. BlakeN

    BlakeN Stunt Coordinator

    Joined:
    Sep 15, 2002
    Messages:
    185
    Likes Received:
    0
    When trying to build a small box dont forget to sutract the speaker displacement from the internal box volume for actual volume.



    It looks like that driver has a displacement of .05^3 so its not that big of a deal I thought the magnet would be larger. Here is a link to the stats for that driver http://www.jlaudio.com/subwoofers/pdfs/10W4_BDS.pdf.

    I can't look at winisd right now I am at work but you might think about a passive radiator as well. That would give you more output but you would also have a higher delay (just like a port).
     
  6. MikeBi

    MikeBi Auditioning

    Joined:
    Apr 28, 2004
    Messages:
    12
    Likes Received:
    0
    Blake - thanks for the idea on the PR. I am new to this so I was originally trying to stick with super simple designs but, after reading a bit, the PR doesn't seem too complicated at all.

    As of now, I have two options: a sealed box and a PR box. The sealed comes in at 14.625x14.625x14.75 with a total volume of 32.7 liters and hits -3dB at 40Hz and -6dB at 30Hz. The PR is a slightly bigger 18x18x18.25 box with 67.5 liters but goes flat to 30Hz and hits -3dB just under 25Hz.

    These dimensions account for the inner bracing I'm putting in and also displacement of the driver and the plate amp I'm planning to mount to the back.

    Do these sound about right? I can't think of anything I'm missing but again, I'm new to this [​IMG]

    By the way, the parts express PR I'm looking lists it's mass at 200g but my math says I only need 196g of mass to do this. I figure that's pretty darn close - is that within the real world tolerances?

    Again, thanks for all the help. I'm looking forward to ruining my lungs with MDF dust soon [​IMG]
     
  7. Jack Keck

    Jack Keck Second Unit

    Joined:
    Nov 23, 2001
    Messages:
    269
    Likes Received:
    0
    "Question: When I put my numbers in Boxy Cad (thanks for that link btw), what does the "full length brace" mean? Is that a brace midway to the back of the box with a circle cut out?"

    Yep. It can be one big circle or a bunch of small ones. Mine has two openings, the one on top was done to accomodate my port.
     
  8. BlakeN

    BlakeN Stunt Coordinator

    Joined:
    Sep 15, 2002
    Messages:
    185
    Likes Received:
    0
    Could somone look over the numbers for this driver. Xmax is 10mm I tried using winISD alpha to run some calculations and it seems it bottoms out very easily. At 200w with the PR you have chosen and box it looks to me like your going to be bottoming out at 50Hz. I am far from an expert so I would like somone else to check this out.
     
  9. MikeBi

    MikeBi Auditioning

    Joined:
    Apr 28, 2004
    Messages:
    12
    Likes Received:
    0
    Actually, xmax is only 8.6mm. I think you might be getting past that because it's only rated at 125W. It definately has a bump in the excursion though - I'm toying with box sizes trying to avoid that...
     
  10. BlakeN

    BlakeN Stunt Coordinator

    Joined:
    Sep 15, 2002
    Messages:
    185
    Likes Received:
    0
    That would make sence then [​IMG] I must be looking at the wrong specs.
     
  11. MikeBi

    MikeBi Auditioning

    Joined:
    Apr 28, 2004
    Messages:
    12
    Likes Received:
    0
    Well, I can't get my cabinet to look any better than what it is now. So I'm building this sucka and see what happens. If it goes south, I can always scrap the $5 of MDF and start over [​IMG]

    Here's what I came up with:
    * 34.80 liter enclosure
    * 15.125" cube (taking into account the internal bracing and whatnot)
    * Tuned to 27.14Hz
    * Add 200g to the PE 12" passive radiator

    At 125W, WinISD tells me I can get down to about 23Hz before bottoming out and -3dB is right at 32Hz. Assuming that everything works exactly as it's modeled, that should be fine for listening to music and the occasional movie. If I want to feel tooth shattering bass, I'll stick with my monster SVS [​IMG]

    Assuming I've not made any mistakes, I think I'm good to go. Wish me luck! Oh, and tell me if adding 200 grams to a 12" passive radiator is insane - I think it says you can go up to a toal of 500g so I'm ok...
     

Share This Page