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DIY Cab: Help me with the configuration!

Discussion in 'Amps and Cabs [BG]' started by teej, Mar 16, 2006.

  1. teej


    Aug 19, 2004
    Sheffield, AL 35660
    I'm working on several cab designs, but I can't decide which I should do. I do know that the cab MUST have at least one 12 in it, with at least another 12, a 10, or an 8. Basically, I'm trying to make a compact cab that can handle a lot of power and provides both low end and punch. I've already got a spare grill that will fit a cab measuring 24" x 15", so I'd like to use it, if I can.

    So far, I'm torn between two main designs:

    The first is what I've dubbed the "1208." It's a 12 paired with an 8 and tweeter. I figured this way, I'd have the low end of the 12 with the punch and speed of the 8. I'm just affraid that the single 12 wont give me enough low, though. I can make it as small as 24" x 15" x 12", so it will fit the grill I have. (See image.)

    The second is your typical 212. The problem with the 212 is that it's a bit boxy and bigger than I would like. I'd like to do this one because it's a tried and true design, but the smallest I can get it is 24" x 24" x 12" which means it won't fit the grill I have already.

    I suppose I COULD do the 212 like Schroeder (straight 12 / angled 12), but I'm not a fan of the angled driver design. On the upside, it WOULD fit the grill.

    I've thought about doing an isobaric design, but I'm not at all familiar with the physics involved there, so I've ruled that out as an option.

    At the very least, I could take the 112 studio monitors I've got and replace the existing drivers with new, high power 12s. These monitors have been in the family for AT LEAST 15 years, though, and according to my dad, they still sound as good as the day he got them, so I'd rather not modify them.
  2. ESP-LTD


    Sep 9, 2001
    Last time I bought expanded metal it was only $10-15 for a grill. I wouldn't base my design on that feature.

    For a 12/8/tweeter look at Bill Fitzmaurices Omni 12 for parts.
  3. yeah, check out www.billfitzmaurice.com I am seriously considering building a couple Omni 10s, and an omni 12. I have heard nothing but good things about his designs.
  4. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    The non-12 will be in its own sub-enclosure...right? If not, the air displaced by the 12 will push the 8 all over the place...

    Tweeters typically aren't on the bottom edge of the cabinet...
  5. ESP-LTD


    Sep 9, 2001
    True, unless you use a sealed-back midrange like the Eminence Alpha 8 AMR.

    True as well ...
  6. seamonkey


    Aug 6, 2004
    A coupld of questions.
    Why do want at least a 12? Volume?

    You're looking for a cab that can handle a lot of power - but do you want it to produce a lot of volume? If you look at AI cabinets that have a 10", they're compact and light, and can handle a lot of power - but they're quiet.

    On the other hand, if you look at Bill's cabinets, they're meant to be high efficiency, so you don't need a lot of power to get a lot of volume, but they're not going to be compact as an AI.
  7. This is a typical design where the layout is done for asthetics or to accomodate parts on hand.

    I'm not pissing on your parade here, just pointing out what every other commercial cab manufacturer already does. Expect yours to sound similar. IMO, you will do all this work and be disappointed.

    The layout shown is not engineered for performance and sound quality. If it was, the drivers would be on a vertical center, with a 6" driver in a subchamber, and tweeter above it. Vertical alignment will give you the most even response (lack of combing) in the horizontal plane. A slot port will give you the largest port area without putting a big hole in the baffle.

    Recess the 6" so the vertical alignment of the voice coil matches the woofer voice coil. This will give you proper time alignment at the crossover area. Ideally, do the same with the tweeter voice coil.

    Select components accordingly, so each component has a minumum of 1 octave flat response above and below the intended crossover point. This will eliminate any ragged response in the crossover region. Be sure to select components that have a similar sensitivity, as it makes the crossover design easier to build. Bi-amping with an active crossover is easier.

    Easy, huh?


    Again, I'm not pissing on your parade, just pointing out that it ain't as easy as pounding together a few panels and slapping in the drivers. After all that work, it really sucks to have somebody show up with an Omni 12 and kick your butt with it.

    My advice is do not re-invent the wheel. If you want a DIY project, buy the plans for the Omni 12. You will have something that is known to work and easy to build. Then you can go out kick other guys' butts instead.
  8. teej


    Aug 19, 2004
    Sheffield, AL 35660
    Thanks for the link!!

    I didn't plan on puting the 8 in a sub-enclosure, but I'm guess that I should? And will having the tweeter on the bottom cause a problem?

    I just like the lows and punch that you usually get with 12's. Best of both worlds, I guess.

    You're absolutely right about the asthetics. I'm a design major, so I know a lot about making things look good, but next to nothing about engineering and what all of the parameter #'s mean. As a result, I'll take whatever advice, comments, and suggestions I can get! :D

  9. You are welcome.

    What kind of design? Graphic? Web? Architectural?
  10. teej


    Aug 19, 2004
    Sheffield, AL 35660
  11. teej


    Aug 19, 2004
    Sheffield, AL 35660
    Approximately how much would it cost to build an Omni 12 (not including the drivers)??
  12. ESP-LTD


    Sep 9, 2001
    Hmmm ...

    I have always figured any cab at all needs about $35-$50 of wood and hardware.

    I am not using the passive crossover (biamp), recycling a lot of parts, not using a tweeter, and building a pair at once. I haven't priced the finish yet and a few other things so an answer would be premature.
  13. teej


    Aug 19, 2004
    Sheffield, AL 35660
    How do the Tubas compare with the Omnis?
    Also, what is it about the Omnis that give them the added response? Not trying to infringe on any patents or copyrights or whatnot - just trying to get a better grasp on cab design. :smug:

    By the way, a friend of mine just bought an Avatar Neo 212 and wants to swap the Emis with some higher power drivers she's got. Said she'd give me the Emis if I wanted them. All the more reason to use 12s somewhere.
  14. ESP-LTD


    Sep 9, 2001
    The 12 is firing into a horn of sorts, and the vent for the 12 is also firing into a horn, while the 8 is at the back of a horn. The cab isn't big enough for the horn to really support the 12, but it helps some. The speakers are firing thru small openings (4x9 and 2.5" square) so they are less likely to be directional.

    To me, the big features were:

    1. I had a pair of Delta 12LF's
    2. I wanted more mids/highs than pushing them solo
    3. I wanted better dispersion so bandmates could hear me
    4. I didn't want to carry much more than 50#
  15. HA!:D
    It's the little things that kill you. Wood glue, screws, tolex, corners, jackplate, handles, port tube, grill screen, new circular saw blade, new jigsaw blade, circle cutting jig...and the fact that most places wont sell you a half sheet of plywood.
    Recycling items off of other cabs helps, but even $50 is a dream, at least in my experience. It cost me right about $100 to build this, NOT counting the speaker:

  16. From my understanding the tubas are a more complex build, but something that might appeal more to a design student like yourself. Check out some pictures of other's projects at: www.audioroundtable.com/BillFitzmaurice/

    The Tubas, from my understanding, are subs and meant to be used with a second cab, not as a stand-alone—like the omni 12.

    C7: I dig the color and visual design configuration on that cab, very nice.
  17. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Right. If all you're going to do is build a simple ported box my best advise is don't, you won't save a dime over an inexpensive commercial cab like an Avatar, and it won't sound any better either. DIY is not a way to build an average cab for less money than you can buy one for. DIY is a way to get performance equal to or better than the most expensive commercial products available, and do so for less than half what it would cost you to buy one.
  18. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    The Tubas are subwoofers, the Omnis are full-range cabs. Look at the PLANS area on Bill's site.
  19. teej


    Aug 19, 2004
    Sheffield, AL 35660
    Saving a buck was my initial purpose for a DIY cab. I tallied the cost of the 1208 I was planning, and not including the plywood, bracing, etc. it would have cost me $140 (shipping included) for the parts, and that's if I use some low-end drivers. After seeing Bill's site, though, I may be able to save a buck and have killer performance? :p
  20. ESP-LTD


    Sep 9, 2001
    You forgot to include buying a car to get to the lumberyard. :)

    I was adding the cost of components, like you listed: Wood glue, screws, tolex, corners, jackplate, handles, port tube, grill screen

    -but not the tools and overhead: new circular saw blade, new jigsaw blade, circle cutting jig

    After building a few, you already have a pretty good stash on hand of paint, insulation, and such, and yet any individual cab only uses a small amount of those so I don't include the full cost, just what it takes for a specific box.

    But, Bill's comment is 100% correct. Add up the parts and then look at an Avatar; you'll be lucky to get within $50 building it yourself.

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