someone suggested infinite baffle - need details

Discussion in 'Home Theater Projects' started by Sam A, Oct 6, 2004.

  1. Sam A

    Sam A Stunt Coordinator

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    ok in another thread, Chris Brock suggested I make my sub an IB since my GF doesnt want big speaker boxes. it would be great to hide the sub but to me, it still looks as though my sub will sound like a lowrider. also, im buying a house this week and Im really not keen on the idea of tearing up walls as soon as I get the house, but Id like the HT setup as soon as possible.

    ive done my reading online and seen the IB cult pages. impressive looking subs. I guess I came to the diy section to see what help I could get keeping this as clean of a project as possible. there is a coat closet in the main room that I could use, and I could replace the door if necessary...
    hmm a light bulb just went off.
    ok if took the door off, and stored the door [its an older wood frame raised panel door]
    then built a solid door of MDF and mounted the speakers in it, how would I make sure the door didnt rattle in the frame, I would assume I would still want to use the closet as a closet, liek those walk in freeser door handles where it really pulls the door shut. i would need a few of those.
    also, how many speakers would I need? ThomasW on the IB cult site has 12 x 12"s!!!

    OMG!

    any thoughts ideas or corrections are very welcome
     
  2. Chris Brock

    Chris Brock Second Unit

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  3. Andrew Pratt

    Andrew Pratt Producer

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    The number of drivers you can use will be partly determined by how much space you have in the closet. You typically want to shoot for a space that's 10 times larger then the VAS value of the driver. If you take the Tempest as an example then it would be 10 * 317 L per driver. So if you have 10 foot ceilings and the closet is 5 feet deep by 5 feet wide you'd be pushing it to get two tempests in that area...which for most people is a good number of drivers for a variety of reasons.

    Out of curiosity what's above and below this room? Would it be possible to cut a hole in the top or bottom of the closet and cover it with a grill to increase the area available?
     
  4. Rich Kraus

    Rich Kraus Stunt Coordinator

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    andrew hit it on the head, you want to take a look at the space available to vent into (closet, attic etc....) and then calculate how many drivers that space will support (in terms of 4-10X vas)

    dont be afraid to cut a hole and vent in to the attic/basement. youll like the sound. its only going to boom like a low rider if you calibrate the system to be bass heavy, then play some bass heavy music.

    how large if a space are you trying to add bass to, and how loud/low are you wanting your system to play?

    if you want 130dB at 15Hz in an 20X30 room that opens to another room, well youd better be ready to spend some money [​IMG]

    in my upcoming room (12x15, sealed) a pair of 15's and a few hundred watts should be enough.

    if you are limiting yourself to the closet, you may find you are unable to add enough drivers to meet your bass level needs /vs room volume.
     
  5. ThomasW

    ThomasW Cinematographer

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    Closet IB's, yeap we got closet IB's. Just don't forget to cut a hole in the top of the closet, to vent the IB into the attic. Otherwise you've just got a big box sub.

    [​IMG]

    There are more details of this install on page 4 of the IB gallery.

    Mike Knapps line array is also a closet install with the drivers mounted on an outside wall of the closet. It too is vented to the attic

    [​IMG]
     
  6. Sam A

    Sam A Stunt Coordinator

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    yeesh, well I was hoping to make the door the baffle and I guess I could cut a hole in the ceiling of the closet. Ill have to mesh the hole or something so insulation and dust doesnt fall on the clothes in the closet. what about using the hole in the ceiling of the closet as the speaker hole? would I have to keep the closet door open?
     
  7. ThomasW

    ThomasW Cinematographer

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    You can certainly flush mount the woofers in the door. People have done that, I just don't have any pictures of those installs.

    There are going to be phase issues if you put the drivers in the top of the closet. As a result I don't recommend doing that.

    I'm not sure how the others have addressed the hole in the top of the closet issue. Making a grill cloth is one option to keep the insulation and other stuff in place. Note that insulation can not cover the hole. There must be an unobstructed flow from the closet into that attic.
     
  8. Allen Ross

    Allen Ross Supporting Actor

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    Thats some serious weight to be putting on those hinges, i would be little worried about it, also getting a nice air tight seal on the door might be tricky
     
  9. Sam A

    Sam A Stunt Coordinator

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    Thats some serious weight to be putting on those hinges -
    have you ever tried to carry a solid wood 6 panel door? ha.


    also getting a nice air tight seal on the door might be tricky - thought of that - liek those walk in freeser door handles where it really pulls the door shut. i would need a few of those.. wouldnt have to be air tight, just firmly held within the frame. if I understand IB correctly, there is no comression of the air other than the sounds because there is no enclosure it must conform to, or something like that.
     
  10. ThomasW

    ThomasW Cinematographer

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    Depending on the woofers being used, one might want to consider using ball bearing hinges.

    Lining any gaps with closed cell neoprene foam tape should take care of rattles
     
  11. Andrew Pratt

    Andrew Pratt Producer

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    Are you still planning on "using" the cloest as a storage area?
     
  12. Sam A

    Sam A Stunt Coordinator

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    Are you still planning on "using" the cloest as a storage area? - you mean do I want to use my closet as a closet? ...uh yeah. the way I see it, it shouldnt hurt anything at all. I definately wont be putting on a coat during movies or anything like that so I wont really be moving the door much when its in use. but I dont see how the sub could be damaged in anyway even if I constantly swung the door open and closed while it was playing. if that is what you are getting at. its not that big of a house, so I have to maximize space. if you have concerns, please explain them to me. I havent been to the house but once this week, but I do all the papershit tonite. wish me luck and ill definately look closer at the closet this weekend.

    remember, im not comitting to this yet, but I do appreciate the info and the questions from you all. im sure im overlooking alot of stuff.
     
  13. ThomasW

    ThomasW Cinematographer

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    Sorry but no, you won't be able to use the closet for a ton of storage. If you want to use it as an IB it has to be basically empty.

    Is there a specific reason why you can use an attic mounted IB?
     
  14. Sam A

    Sam A Stunt Coordinator

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    Thomas, im not the best carpenter. im not a good one, im not even a crappy one. I really dont want to bust open holes in my home. the closet was a good idea to hide the hole to the attic, thats why I like it, can you explain why the closet should be more or less empty?
     
  15. ThomasW

    ThomasW Cinematographer

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    The closet should be empty because the goal of an 'infinite' baffle is to have an infinitely large space behind the drivers that has no obstructions.

    Trust me when I say that cutting a hole in the ceiling drywall, and slapping together a box for an attic IB, is mindless compared to skill required for custom building a door mount IB and hanging that door. Also patching the ceiling is no big deal if the IB needs to come down. Actually one can just save the cutout piece and put it back up as the patch

    Having a door mount IB makes the closet very impractical to access. One must be extremely cautious to not damage the drivers or bash one's head when accessing anything in the closet.

    The door mount is really only to be used when there are no other viable options. Mike Knapp has cathedral ceilings, so an attic mounted IB was physically impossible.
     
  16. Sam A

    Sam A Stunt Coordinator

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    "have an infinitely large space behind the drivers that has no obstructions"

    but if the baffle is infinite, then what is in the closet really shouldnt matter. PS my new 'door' would have been 1 sheet of 1" and one sheet of 3/4" mdf painted to match the walls and the grill covering the woofer would be the same as the walls to hide it. glueing 2 sheets together isnt hard at all. Ill get my neighbor to route out the holes
     
  17. ThomasW

    ThomasW Cinematographer

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    Nope that's not the point. There should be no obstructions in the area immediately behind the drivers. The rear wave needs to cleanly exit up into the attic.
     
  18. Chris Keen

    Chris Keen Stunt Coordinator

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    Sam, how many drivers are you looking at using, and what size?

    Is it possible that the hole for the manifold you cut can be disguised as a Central A/C register or vent? I'm looking into this currently myself. Even if I make a speaker grill to cover the opening for the manifold, I want to pre-plan and size it where I can go back and put a register over it later on. That's a much easier thing than going back and patching a large hole in the ceiling. At least IMHO, it is for me.
     
  19. Jason Dalton

    Jason Dalton Stunt Coordinator

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    OK, this is an issue I've had with many people with regards to IB subs. Why are people worried about cutting a hole in drywall? I know not everybody is good with carpentry, but patching drywall is about as easy a project as there is and even if you didn't feel like doing it I'm sure it would be extremely inexpensive to have someone do it for you.

    I mean if we are talking about cutting a hole in hardwood flooring, thats one thing, but drywall is an easy fix.
     
  20. Chris Keen

    Chris Keen Stunt Coordinator

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    Yes and no. If you have texturing on the drywall, it can be a bit tricky to blend that in and not show the problems.
     

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