Fi IB3 18's In The Ceiling? - Page 2 - AVS Forum
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post #31 of 36 Old 08-30-2012, 06:05 PM - Thread Starter
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Originally Posted by N8DOGG View Post

Thats not really true, your placement will depend on your room, sub orientation not so much. In my room, I have 2 stacks of my 4 x 21's opposing each other and get get the best results in my room that way.
Well, I don't even live in this house or room yet. So I don't know how to plan it. But, no matter what, there will be a way to make 4 FI IB3 18's work, right? So I can buy them now...
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post #32 of 36 Old 08-30-2012, 08:23 PM - Thread Starter
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I would also like to clarify one more thing. I'm not entirely sure what "opposing" means here. Is that where you put two subs across from each other, and as one pushes out, the other pulls in?
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post #33 of 36 Old 08-31-2012, 12:28 AM
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Originally Posted by Jeremy1998 View Post

I would also like to clarify one more thing. I'm not entirely sure what "opposing" means here. Is that where you put two subs across from each other, and as one pushes out, the other pulls in?
What it means here is that subs directly accross from one another are in the same phase. They are both pushing out or in at the same time. The advantage gained by having them directly opposite one another is that the forces they each exert on the manifold cancel out to reduce vibration. If they were were out of phase (one pushing in, the other out) the masses of the cones would be going back and forth in sync and would be vibrating the manifold much more.
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post #34 of 36 Old 08-31-2012, 05:54 AM - Thread Starter
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Originally Posted by Bushi View Post

What it means here is that subs directly accross from one another are in the same phase. They are both pushing out or in at the same time. The advantage gained by having them directly opposite one another is that the forces they each exert on the manifold cancel out to reduce vibration. If they were were out of phase (one pushing in, the other out) the masses of the cones would be going back and forth in sync and would be vibrating the manifold much more.
Ooh. See, I understood that wrong. I thought it meant one pushing in, one pushing out. And from what I've known, that's not good... So I will see what space I'm working with, and I will design it around dual opposing subs.
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post #35 of 36 Old 08-31-2012, 10:29 AM
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Originally Posted by Jeremy1998 View Post

Hmm. In normal situations, it is bad to have your subs "opposing" each other. So, I guess the rules are different in IB?

Dual opposed means that the drivers still move outward, into the listening room in phase with one another. However, their reactionary forces that otherwise would affect the cabinet, manifold, etc., cancel. Similarly, a dual opposed box subwoofer utilized a driver on opposite sides of the box, ...thus canceling reactionary forces that would otherwise be transfered to the box.


Below is an example of a dual opposed, IB manifold,.... driver config, they are firing into the listening room;



If you merely mount the drivers without a manifold, extra stiffening of the surface (whether that's a ceiling, wall, etc) would be warranted because any reactionary motion of the surface, lessens the ideal transfer of energy to the listening room. Previous builds have illustrated that these forces are significant, and some DIYers have regretted not heeding other's warnings about their significance. It's doable, just be mindful it takes quite a bit of extra bracing. However, utilizing a dual opposed manifold, renders these concerns a non issue.

Thanks


edit, missed the above post, clarifying things redface.gif

------------------------------------
Flat, Deep, Clean, Linear, and Loud
------------------------------------
Active 16.8kw, 7.3 system
(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
(2)Seaton SubM-HP, (4)18" IB
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post #36 of 36 Old 09-01-2012, 05:18 PM - Thread Starter
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Originally Posted by FOH View Post

Dual opposed means that the drivers still move outward, into the listening room in phase with one another. However, their reactionary forces that otherwise would affect the cabinet, manifold, etc., cancel. Similarly, a dual opposed box subwoofer utilized a driver on opposite sides of the box, ...thus canceling reactionary forces that would otherwise be transfered to the box.
Below is an example of a dual opposed, IB manifold,.... driver config, they are firing into the listening room;

If you merely mount the drivers without a manifold, extra stiffening of the surface (whether that's a ceiling, wall, etc) would be warranted because any reactionary motion of the surface, lessens the ideal transfer of energy to the listening room. Previous builds have illustrated that these forces are significant, and some DIYers have regretted not heeding other's warnings about their significance. It's doable, just be mindful it takes quite a bit of extra bracing. However, utilizing a dual opposed manifold, renders these concerns a non issue.
Thanks
edit, missed the above post, clarifying things redface.gif
:/ not gonna look as awesome as my original plans, but it's all going to be covered by a speaker grill anyways, so who cares.
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