Infinite baffle question?

Discussion in 'Home Theater Projects' started by Joe Tilley, Jun 27, 2003.

  1. Joe Tilley

    Joe Tilley Supporting Actor

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    I have been tossing around the idea of doing an IB enclosure but I have one problem, Im renting my house currently. The good part is my landlord is pretty open to me doing things to the house as long as I don't do damage or as long as I repair any damage I may cause. Aside from this I most likely will be buying the house from him but it wont be for at least the next year or so.
    Any way my question is I was wonting to do a set up using 4 15" Dayton IB subs, the only problem is I don't wont to have to make such a large hole for the manifold. Im guessing using these four drivers the manifold would need to be around 18" square & that makes for a pretty good hole in the ceiling. So is there any way I could taper it down so to speak the opening to say around 12" or so without affecting performance to much. I'm thinking that the worst that could happen would be to get a chuffing noise like with a port but I'm not sure.
    Any ideas would be great. And don't worry I do intend to get full permission from my land lord before I do try anything. I would just like to keep patch work to a minimum if I should decide to not to buy the house. But as its looking I'm going to be here for awhile so I figured what the hell.
     
  2. RichardHOS

    RichardHOS Second Unit

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    My suggestion would be to go in a bit of a different direction than the typical "one on each side of a square" manifold design for four subs.

    Instead, make the manifold rectangular with a pair on each of the longer faces. Make the width of the rectangle suitable to mount to/between the ceiling joists so that you don't have to cut any of them (you certainly don't want to do that).

    So, if your joists are 16" on center, then a box roughly 14" x 36" x 18" (external dimensions) should fit nicely between the joists, have a 14" x 36" opening into the room, and a pair of drivers on each 36" x 18" face (two opposed pairs).

    If you're careful, you could probably cut the square of sheetrock out so that the removed piece is salvageable. Should you ever need to move out, simply remove the manifold, tack a couple of wood strips between the joists so that their bottoms are flush with the bottoms of the joists, tack the sheetrock rectangle to these strips putting it back in its original position, and then do a bit of mudding/sanding/painting to finish covering your tracks.
     
  3. Joe Tilley

    Joe Tilley Supporting Actor

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    Richard thanks for the suggestion but the 14" by 36" opening would be way too much. Thats what I'm trying to avoid if possible. I don't think I would have a problem with the ceiling joist cause I think ( don't hold me to it ) that they are 18" or 20" on center. I haven't measured them yet & it been awhile since I've been in the attic but from what I remember they don't look like they are 16" OC.
    I guess if I had to to get a smaller size over all I could go with 4 12" Daytons. I've considered the Titanic MKII subs, but I'm just trying to think ahead & keep myself from wondering ( what would those 15 inchers have sounded like?)
    I guess I just like to play too much. I'm really pretty happy with what I have now but I have had a couple offers on my current sub & I wouldn't mind freeing up some space & getting some more bass to boot so I've got the whole IB set up in mind.
    If anybody can offer some solutions Please let me know. If it helps any the room I'm in is is 18" by 16" & is open to a 20" by 14" kitchen to the side. If I could spare the extra I would just build another sono that matches my current one but I'm pretty limited for space so this is not an option.
     
  4. RichardHOS

    RichardHOS Second Unit

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    About the only way to really get a smaller manifold opening would be to compress that 14" dimension. You pretty much have to keep the 36" length of the opening physically mount two drivers to each side. You could make it a 36" x 12" opening without doing too much to the sound, I would guess. But something like a 36" x 6" is going to start acting like a large ill-designed port, with a tuning frequency somewhere other than where you would want most likely.

    How about approaching it from this angle... tell us the largest opening you could see yourself cutting in the ceiling, and we'll see what the "most" IB you could stuff in there would be. [​IMG]
     
  5. ThomasW

    ThomasW Cinematographer

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    One can stack quite a few 12"s into a 13.5" X 13.5" opening.

    [​IMG]
     
  6. TimForman

    TimForman Supporting Actor

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  7. Joe Tilley

    Joe Tilley Supporting Actor

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    Hay I may just have to think about those 3 inchers[​IMG] Really though I would like to go no larger than 14" square. I wont to make it as easy to hide as possible.
     
  8. Rick Guynn

    Rick Guynn Second Unit

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    Well, If 12 Shivas don't create a problem with a 13.5" x 13.5" opening, I doubt 4 Dayton IBs will either. I think you're fine with that size opening. You could probably get a bit smaller if you really wanted to.

    RG
     
  9. Bill Fagal

    Bill Fagal Stunt Coordinator

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    I believe the theory allows for smaller IB openings, it's just a question of how much compression (lost efficiency) you're willing to tolerate and how low you're planning to cross over. If you model it as a mistuned bandpass, you'll notice that the frequency of your main enemy, the fundamental front-chamber resonance, drops as you shrink the opening. As long as you cross over steeply well below it (and perhaps notch it out), you should be OK.

    Also, there's no hard and fast rule that says you have to have only one opening for your IB. If you don't like one big hole, make 4 smaller ones and spread them around.

    I've always thought an IB could be looked at as a real improvement on you home, especially if you sell someday to someone who appreciates quality bass. [​IMG]
     
  10. ThomasW

    ThomasW Cinematographer

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    Multiple openings can lead to phase issues. So one outlet is recommemded.
     
  11. Joe Tilley

    Joe Tilley Supporting Actor

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    Ok it looks like I will probably end up going with 4 12" instead of 4 15". So my next question would be can anyone give me any idea on how 4 12" either Dayton IB's or Titanic MKII's would perform in relation to my current sub? Right now I'm using a single Dayton 15" DVC in a 220 liter sono tuned around 17hz, & powering with a PE 250 watt plate amp.
    If I do go for the IB set up I was thinking about using the HS500 from Adire Audio to power it all, unless someone could suggest something more apporite for this set up.

    BTW, Thomas your set up is just insane. I have showed so many of my buddies your pics & they are just amazed by it. I wish I was close to your area to see what that that mountain sounds like. If I had the cash to try something like that I would probably do it. But for WAF & my budget I have to stay as close to a grand as I can.
     
  12. TimForman

    TimForman Supporting Actor

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    That's ok Joe, we all know Thomas is loaded. $$$$$
    You can tell by the cases of expensive wine in that photo.
    Oh wait, that's Boones Farm.
    Never mind.
     
  13. Rick Guynn

    Rick Guynn Second Unit

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    Joe, instead of running all 4 drivers off of 1 500-watt amp, you might think about using your current PE250 for one pair of drivers, and getting another PE250 for the other pair.

    That way, you can wire each pair in parallel and be pushing a 4-ohm load with each amp. With a single amp, you'll be looking at 8-ohms (unless you want to try for 2-ohms, but that would be stressing the amp quite a bit).

    Oh, and my guess is that 4 12's will probably be about double what your one 15 is now -- with better response characteristics.

    RG
     
  14. Joe Tilley

    Joe Tilley Supporting Actor

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    Rick you mentioned something I did over look, impedance. I guess I could use two of the PE amps, but I had planned on selling my current one with my sub if I go through with all this. I did do some looking over at Acoustic Visions & breezed through the different QSC amps they now carry. I'm not to sure what I'll do yet but I going to do some more digging.
     
  15. Robert_Gaither

    Robert_Gaither Screenwriter

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    Maybe an easier solution might simply be is to use a closet and remove the door and replace it with a temporary baffle. Most likely you can fit two 15s (just get another Dayton) to try this experiment out and use your existing plate amp.
     
  16. Brian Bunge

    Brian Bunge Producer

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    I do know of someone that has used the PE plate amp into a nominal 2 ohm load with absolutely no problems. It was in a multi-driver setup so that efficiency was greater than just using single or dual drivers. So the amp wasn't having to work hard to reach decent SPL's.

    Having said this, try it at your own risk![​IMG]
     
  17. MichaelAngelo

    MichaelAngelo Stunt Coordinator

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    Joe,

    FWIW, I too have been using two of the PE250's on a 2ohm load for over a year. However, they are fan cooled and the techs at PE are sure this helps their longevity. [​IMG]
     

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