Brahma or Shiva Iso?

Discussion in 'Archived Threads 2001-2004' started by Brian J Dupuis, Dec 3, 2001.

  1. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Hello,
    First-time DIYer here looking to build a small but powerful sub. I posted earlier this year and was primarily steered toward an isobaric Shiva application. Now with talk of this new Brahma driver, I'm wondering if that advice holds true.
    Essentially I need a very small enclosure (I'm sure my wife would love if I decided to get a Sunfire, if that gives you any indication). But, as usual, I want excellent performance. Good extension, tight, room-shaking [​IMG]. My original thought was a shielded clamshell isobaric Shiva in about 27 liters (half the 54 liters of a Q = 0.707 enclosure). With everyone raving about the upcoming Brahma, I decided to see if someone thought a Brahma-based solution would be a better performer while maintaining that volume (or less if I can get away with it).
    Those that would recommend the Brahma over the Shiva, what would you recommend for powering it? I have a room with quite a bit of cubic feet to fill (cathedral ceilings) and I've heard people talking about feeding it 1000 watts, but I have yet to find a plate amp with that rating.
    Thanks.
     
  2. if you are look at a small sub with all the boom for HT, then there are very few ways to go.

    I would look into either the brahma or the BPD1203. Youwill be running these sealed and will REQUIRE either a linkwitz transform, or a shelving filter...and you most likely need a parametric EQ like the BFD. as long as the unperturbed qts is < say 0.707 (which you can easily do in a small enclosure) then you can actually use the BFD alone.

    As for amps....I would look into getting a power amp. If you must have a plate amp, then adire has two that would probably work:

    a750--just an amp...no XO or anything, so you would need either a seperate LP XO or use the reciever XO.

    HS500--all in one plate amp
     
  3. Jack Gilvey

    Jack Gilvey Producer

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    Hi Brian,
    As Anthony points out, and as was discussed in this thread , the BPD 1203 and Brahma do require quite a bit of power and eq. Plate amps need not apply, for the most part.
    For more reasonable power requirements and no real need for eq (except for room problems, of course), the Shiva idea is a good one. You could also try two of these , which would require an even smaller box for the same Qtc.
    Still, having only 1 12" driver to fill a large space is a tall order.
     
  4. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Thanks guys.
     
  5. AjayM

    AjayM Screenwriter

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    Dan Wiggins once sent me a file for LSPCad with the details on an Iso Shiva vented setup. Box volume was 57.6l (roughly 2cu/ft), had a single 4" port...but here's the kicker...the port needs to be 5ft long for a tuning of 16Hz (this will semi-closely emulate a Low-Q sealed box response). For a little better in the port area, tune to 20Hz and the vent length shrinks to 3ft.

    Both of these are good for some decent SPL (LSPCad says around 105, give or take) with the Adire 250W plate amp (and you're bumping into excursion limits with the Shiva in that alignment).

    Figure out what to do with the port and it would be a winner!

    Andrew
     
  6. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Interesting, though the port length (and indeed internal volume for that matter) make it somewhat infeasible for my application. That's over double the internal volume of the isobaric Q = 0.707 sealed enclosure (27L). What would the benefit of the ported enclosure be over the sealed enclosure?

    Thanks for the input.
     
  7. Brian J Dupuis

    Brian J Dupuis Second Unit

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  8. Jack Gilvey

    Jack Gilvey Producer

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  9. Brian J Dupuis

    Brian J Dupuis Second Unit

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  10. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Just so I don't misunderstand, are you suggesting an isobaric clamshell Dayton application? I think that's what you're saying, but want to make sure we're on the same sheet of paper. So an iso pair of Daytons in 30L should make me smile, eh? Anyone have a project page of one I could go by?
     
  11. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Wow, thanks Jack. Actually with a bit more finger walking, I've found quite a bit of info on some projects with the Dayton, including your Mini Sub [​IMG]. Looks nice!
    Sorry for all the questions, I'm just having a hard time making a decision on what would ultimately be best. I want something that I'll be happy with for at least a little while, you know? Do you feel that the 30L Dayton provides a decent sub for the size? Would you still recommend this over the iso Shiva for performance?
     
  12. Jack Gilvey

    Jack Gilvey Producer

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  13. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Sounds like a winner. And it should save me a bit of cash going with a single driver.
    So, looks like I'm going to be placing an order for a Dayton DVC 12" and the Adire ADA250 amplifier, for something very much like what you came up with for your little Mini Sub. You wouldn't have happened to keep any design drawings for that thing, would you have? [​IMG]
    Thanks for all your input!
     
  14. Vince Bray

    Vince Bray Stunt Coordinator

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    Jack (expectedly) gave you some good advice and I thought I would throw in another viewpoint, likely not as appropriate, but just my experience. I have gotten very good WAF numbers from end-table subs. If you can rest a lamp and a drink on it you're more likely to have more leeway. Also, 24" or so is a great height for an end table. Doesn't have to be that wide. Maybe this is not the best placement for your room, or maybe there's a chair on your front wall that could use some companionship from a good-looking table. Veneer it. Make it pretty.

    Now you've got 2-4 cubic feet of volume to play with, and what do we do with that? A 15" woofer of course! Better effiency, more spl, and if you really want to shake a room, you need a 15".

    Just my .01 (recession)

    Vince
     
  15. ThomasW

    ThomasW Cinematographer

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  16. Greg_R

    Greg_R Screenwriter

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    Wouldn't a passive radiator based design give you good extension with a smaller enclosure?
     
  17. Jack Gilvey

    Jack Gilvey Producer

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