2x15" IB - anyone built one ?

Discussion in 'Archived Threads 2001-2004' started by Mats Kellberg, Dec 4, 2001.

  1. Mats Kellberg

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    Hi!
    I'm planning to build an IB for my HT, in the house that I'm moving to (my fiancée is coming along aswell, but is not allowed to voice her opinion on the matter [​IMG]).
    What I don't know is whether or not 2x15" subwoofers in an IB-setup will be enough. The IB will be placed upstairs, with its' outlet in the livingroom (downstairs) - I'll simply put a large closet to good use [​IMG]
    The livingroom dimensions are approx 8,5m x 3,2m, height 2,4m (equals approx 27,8ft x 10,5ft, height 7,8ft).
    Is there any likelyness that the IB will displace enough air for this room, or would I be tremendously better off if I choose to use, say 4 or 8 15":ers.
    I already have 2 of the woofers, but I will probably be able to buy some more if I wish to do so.
    I'm thankful for any input or ideas anyone might have
    /Mats Kellberg
    PS. I don't if it's of any importance, but the data for the woofers are as follows: Vas = 550 l, Qts = 0,54, Fs = 21 Hz.
     
  2. MarkDesMarais

    MarkDesMarais Stunt Coordinator

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    Hi Mats!

    My room is 15x15x8-16 (sloped cathedral ceiling) and opens onto a stairway and a 12x12x8 dining room. My living room alone is 2700 cubic ft, compared to your 2276. I have a single Shiva (12" sub) cut into my floor in IB configuration. I find it is PLENTY loud. Reference levels no problem, stomping dinos right there. Ok, I don't have pictures falling off the wall, or cracks in my drywall as some IB users do, so I guess it could be louder- but then again, I am not turned up all the way on my amp either.

    Cautions- I have a couple of annoying nulls- if I had had some way of testing before hand to determine where they were, I might have put the sub elsewhere- or maybe not- my choices were fairly limited ;-). It sounds like your room is nice and rectangular- you might want to model it to see where you should place your subs.

    Markd
     
  3. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    When you're asking "will they play loud enough?" then you're really interested in how much air they move. Xmax and Sd are the numbers you'd want to evaluate.

    Seems like there's a guy here running a pair of Tempests (15 inch Adire drivers) in an IB with 250 watts and has managed to crack his drywall. 2 decent 15 inchers should be plenty for all but the most extreme bassheads.
     
  4. Dustin B

    Dustin B Producer

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    The Qts, along with the FS is extremely important as well. Since you don't have a box to affect tuning and Qtc, the drivers specs do this.

    So you want a nice low FS (21hz will do, but I think
     
  5. Mats Kellberg

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    Thanks for the response, there always seems to be at least a couple of the members here who have already tried whatever I come up with [​IMG]
    Mark: I'm thinking of removing a couple of walls, so as to get an open staircase - as it is now it really annoys me.
    With that done I think the room volume will probably be something similar to yours.
    It is a drag there is no easy way to test IB-placement, I seriously believe my fiancée would not like me making holes all around the ceiling (ins't she strange ? [​IMG] )
    Hearing that you get along fine with 1x12" does however comfort me, I'm not really looking for really loud - rather really deep (when my internal organs start digging the music I just might have gone too far [​IMG] )
    Ryan: Me being a cheapo, The drivers are not all that great in respect to Xmax (I would imagine something like 15-20mm).
    I think you might be referring to Mr Kraus, his page (and the 12 dancing Shivas) were the sites that got me thinking about an IB. Personally I will be using an old pro-amp, capable of 2x550W in 4Ohms load - I reckon that if I decide I want some EQ it is desirable to have some headroom.
    Dustin: Believe me, if I find out that this works I will probably go and get myself a pair of much better 15":ers, and I will be looking for low Fs (=expensive [​IMG] ).
    This is sort of an experiment, if I don't like it however, I'll probably try and EQ the bottom end to try and get deeper bass (problem is, the drivers will probably fry - but hey, that ought to cut heating costs [​IMG].)
    Oh, and I love your comment about people. I didn't realize this myself until I was like 24.
     
  6. MarkDesMarais

    MarkDesMarais Stunt Coordinator

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    Hi Mats-

    I didn't do any numbers analysis- I was getting set to grind through all that for a sonosub, when I saw the references to using the Shiva in an IB alignment in the Shiva white paper. Better performance, less work, no loss of living space- what's not to like?? I don't know what impact different specs might have.

    As far as testing, if you have access to a sub of some kind, I think you could get an idea about placement by sticking its business end as close as you can to where you propose cutting the hole- the frequency effects of the room should be about the same.

    As far as really deep, I get some response at 10Hz- I don't remember the exact value. I'll try to look at my notes tonight. On the internal organs note, I am only allowed to run low freq test tones (esp warbles) when my wife is out of the house, as they make her feel sick, even when she isn't in the immediate vicinity (open floor plan though).

    Markd
     
  7. Rich Kraus

    Rich Kraus Stunt Coordinator

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    yup, one cracked drywall seam. not the board itself, just a joint that got mudded, but not taped. (and a broken light bulb in the next room, and a few other small resonance related fall-downs)

    the two 15's is plenty for me, but YMMV. the tempest/shiva is a fairly strong driver for an IB though. already asked, but whats the Xmax on the drivers you have?

    i came from a single 10" driver in a 55l inclosure pushed with 80w. this is not just a night and day diffrence, its night and next month.

    oh, performance numbers? it tests flat at the sweet spot +/- 2dB from crossover to crossover (~20-80hz) after some EQ'ing.
     
  8. Mats Kellberg

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    Rich:

    I think the Xmax is something like 15 mm (total), and

    Sd = 0,076 m2, that ought to give a displacement volume

    of approx. 1,15 dm3 (times two, of course).

    That sure doesn't sound much to me, is this ridiculously small ?

    Mark:

    That's a good tip, I'll just use my current sub in order to find out which of the possible placements is most satisfying.

    Regards

    /Mats
     
  9. Dustin B

    Dustin B Producer

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    A single Shiva can displace 1.5L. Twin Tempests can displace 5L.
     
  10. Rich Kraus

    Rich Kraus Stunt Coordinator

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    the tempast Xmax is 16.4mm ONE WAY (32.8mm total)

    if your 15mm figure is total and not one way, then youll need four of them to get close to two tempests.

    if its a one way figure than they are otherwise pretty close.
     

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