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Post by bassaddict on Nov 28, 2008 10:11:22 GMT -7
I am currently running a PB12/2 Ultra. I have really been tossing around building an IB setup to replace it. My question is; with all the money most of us invest to soundproof our room's, how much does an IB affect this? Here is my layout. The door is at the right front of the theater room. This leads to the lobby.  Here is a picture from the lobby that enters the theater room. The door is just to the left of where the component rack used to be.  Here is a pic of the proposed ticket window/marquee that will go where the rack used to be.  What I am thinking is; build an IB setup in the right front corner of the theater room, which would protrude into the lobby area. This would be hidden behind the ticket window which I'm hoping won't cause any interference issues. I'm just wondering how much sound issues this will cause. Currently, I can crank any movie I want without a fear of waking anyone else in the house. I'd hate to compromise this. Obviously low frequencies are tough to contain, and currently the only thing separating them from the rest of the house is a wall of DD and GG. |
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Post by ThomasW on Nov 28, 2008 11:18:38 GMT -7
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Post by bassaddict on Nov 28, 2008 13:24:01 GMT -7
I just noticed that. A false wall will not work in this situation. I will have a false wall up, but it won't be solid, which would defeat the purpose of an IB back there. Unless I'm misunderstanding what you are meaning?
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Post by chrisbee on Nov 30, 2008 12:36:46 GMT -7
To paraphrase Thomas, but using rather more words: ;D
Calculate a minimum volume of of 10 x total driver Vas behind your false wall for your chosen drivers using a suitable stand-off distance.
As you seem rather serious about your audio side lets assume 4 x 18" or 8 x 15" IB specific drivers chosen from Mike's driver page. (link above)
Use an opposed driver manifold to cancel driver reaction forces.
Use stiff timber cross braces (to taste) between your false wall and the back wall using joist fixing plates to satisfy any remaining wall stiffness doubts.
'Start a "My project" thread to share your eventual enthralment with IB bass.
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Post by bassaddict on Dec 1, 2008 16:55:23 GMT -7
Thank you for the clarification. I guess I'm not very famililar with IB setup's. I though that the drivers had to vent into or out of the room, not be part of the room itself. Other than aesthetics, what is the reason people mount them in crawlspaces/attic's?
The only thing that makes me nervous going the aforementioned route, is the vibrations. The screen will be mounted to the false wall so you can see my concern. If if not mounted to the false wall directly, I would think these things would move enough air to ripple the screen, even being an AT model.
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Post by ThomasW on Dec 1, 2008 17:40:37 GMT -7
Other than aesthetics, what is the reason people mount them in crawlspaces/attic's? That's where the rearwave off the drivers is vented. There are numerous IBs installed behind AT screens and no one has complained |
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Post by bassaddict on Dec 1, 2008 17:54:40 GMT -7
So no issues with the rearwave being vented in the same room? What are the disadvantages of doing it this way? Great to hear. Thanks again for answering my noob question's. I've been into HT for many years and have never looked into this area. It really looks like a lot of fun.  |
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Post by ThomasW on Dec 1, 2008 18:19:42 GMT -7
So no issues with the rearwave being vented in the same room? You misunderstand.... If the IB is in the attic or crawlspace the rearwave goes into that space and the front wave goes into the listening room. |
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Post by bassaddict on Dec 1, 2008 18:52:05 GMT -7
So no issues with the rearwave being vented in the same room? You misunderstand.... If the IB is in the attic or crawlspace the rearwave goes into that space and the front wave goes into the listening room. OK, I guess I don't understand. If I build the IB behind my screen wall, then obviously the rear wave will be vented into the back wall. So then what are the disadvantages of doing this? |
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Post by ThomasW on Dec 1, 2008 19:19:56 GMT -7
You would have to build a large airtight space behind the screen wall. The rearwave off the IB would go into that space
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Post by bassaddict on Dec 1, 2008 23:36:30 GMT -7
Ahhh, (light bulb clicks on). That's what I had originally pictured, but I guess my lack of understanding of the explanation threw it off. So when figuring out the Vas, what is it measured in? For example a FicaraudioIB 18" has a Vas of 381. Is this the recommended cubic feet or air space for it to operate in? If you want 10x the Vas, as the FAQ states, multiplied by the number of drivers; that means I would need 15,240 cubic feet of air space for the rear wave to vent into? Obviously this doesn't make sense.  |
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Post by ThomasW on Dec 2, 2008 0:10:18 GMT -7
Might want to reread the addendum to FAQ #6
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Eskimo
Full Member
Bass-head
Posts: 143
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Post by Eskimo on Dec 2, 2008 8:41:01 GMT -7
a VERY rough rule-of-thumb for the Fi IB18's is each driver seeing at least ~50cu.ft will be a good IB. (It's about 4x VAS converted to cubic feet) For 4 18's, if that false wall was an airspace of 2'x12'6"'x8' (after drywalling and everything else that reduces airspace), that's 200 cubic feet.. I have a feeling your theater room is wider than that  I can personally attest that in a smaller IB, you will want to brace the walls though.. I'm getting some flexing of 2 walls in my closet-based IB, and should probably try running some 2x4 bracing between them. |
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Post by bassaddict on Dec 2, 2008 9:19:05 GMT -7
Thank you for that. My understanding of Vas was throwing me off. I wasn't sure what the 381 number was calculated as. From the looks of it I'm just not going to be able to get enough space behind the screen wall. By the time I build around the front speakers that are also behind the screen wall, I will run quite a bit short. It looks like the only option is to vent into the lobby beside the theater. Thank you for all the help thus far.  |
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Post by ThomasW on Dec 2, 2008 11:15:56 GMT -7
You could use the ticket window area but the IB needs room to breath. So the panels in the ticket window would need to be grill cloth or a similar fabric. In addition the picture frames/lights etc., would probably rattle so they'd need to be attached with Blu-Tack or something similar
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