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Old 20th May 2002, 09:03 PM   #1
WBG is offline WBG
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Question Buried Subwoofer

Goodday,
I am trying to find an alternative placement for my sub. Two (usual) problems, wife and space. The room is big enough; however, the floor space is limited. I have been considering building an enclosure under the floor and venting into the room. Vents could be placed in front corners of the room or could even be in the floor directly in front of my entertainment center. I ran across a couple of in-floor subs at partsexpress, but would rather use my own powered sub. I would appreciate any suggestions or ideas.
Thanks,
Bill
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Old 20th May 2002, 09:57 PM   #2
Bill F. is offline Bill F.  United States
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Bill,

I feel like a bit of an evangelist about this (I've mentioned it in a few posts recently), but I alway like to bring up the topic of infinite baffle (IB) subs.

An IB sub takes up virtually no space (can be flush or manifold mounted to floor,wall, or ceiling). It is a boxless design, or rather for its box it uses an entire room/attic/crawlspace behind/above/below your listening room. Since the enclosed volume is so large as to be extremely compliant and virtually unreactive, response is deep and rolls off gently. The only resonance is the drivers' Fs. Since IB-aligned drivers can be driven to full excursion with only a few watts, they are quite efficient in sub-bass regions. Furthermore, since total Q equals the drivers' Qts, you can choose any Q you like (above Qts) by adding in-line resistance.

Your other idea of in-floor sub enclosures has merit too, I think. I've dreamed of reinforcing a bay between two floor joists, adding a lower panel, and sealing up the whole thing to create a large in-floor enclosure.

A key in both of these designs is to use opposed driver force cancellation and basked decoupling to minimize the noisy structural vibration the driver(s) will load into your room.

Bill
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Old 21st May 2002, 12:19 AM   #3
WBG is offline WBG
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Bill,
Thanks for your quick response. Some of what you said makes good sense. Some (I meekly admit) was way over my head. Concerning the IB Sub: is that something that can be purchased as a unit or must it be constructed from scratch? As far as the enclosure under the floor, I had intended to build a box from 1 1/4" plywood subfloor material. Would probably be suspended by angle iron and lined with acoustical material. It should be heavy enough to eliminate any rattles, etc. It would be vented into the room by either a heater size vent or perhaps a air return vent (depending on location in the room).
Thanks again,
Bill
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Old 21st May 2002, 03:48 AM   #4
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An IB is like just cutting a 12" diameter hole in your floor, putting a driver in it, and then your done! The enclosure would be your entire basement (or the room below). Its the easiest type to make...

This is an extreme, but still the same idea... (Click the 12 dancing Shivas Link, on the left hand side of the page)

Good luck to ya!
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Old 21st May 2002, 04:11 AM   #5
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Quote:
I've dreamed of
reinforcing a bay between two floor joists, adding a lower panel, and sealing up the whole
thing to create a large in-floor enclosure.
I have dreamed of the same thing, well put.
-andy
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Old 21st May 2002, 03:47 PM   #6
Bill F. is offline Bill F.  United States
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Bill,

There is no IB sub package/kit available that I know of. However, it really is a simple thing to build, in its basic form. The harder part is keeping it from vibrating the surface it's mounted to (unless shaking and/or buzzing is a design goal ). Visit the "Cult of the infinitely baffled" to learn all about IBs. http://f20.parsimony.net/forum36475/

Regarding an in-floor box, you may be unhappily surprized how much vibration a bass driver will set up, even in a heavy, firmly mounted box. That's why I suggest a force-cancelling push-pull or push-push setup. This was covered pretty well in this thread when designing a 2 woofer enclosure...

If you have any more specific questions, I (and I'm sure others) would be glad to help.

Bill
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Old 21st May 2002, 07:17 PM   #7
WBG is offline WBG
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Thanks, everyone, for all the info. I'll sort through it all and come to some kind of conclusion. I'll let you know what I decided and (most importantly!) how it works.
It's a pleasure to find a forum that provides good information freely.
Regards,
Bill
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