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Old 20th July 2014, 05:12 AM   #1
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Default Underfloor sub

I'm interested to know peoples thoughts on a sub under a timber floor, primarily for movie use. I'm just not too sure how effective it will be outside of the room (in fact it's technically outdoors, however safe from the elements).

My mains will play well down to about 40Hz, so the sub will be expected to perform from around 40Hz down.

It has an exceptionally high WAF obviously, can be large and doesn't need to look pretty. I would be attaching it to a bearer that sits in a suitable location.
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Old 20th July 2014, 05:28 AM   #2
sine143 is offline sine143  United States
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i wouldnt take the mains lower than 50 certainly, perhaps even higher than that.

throw a gjallerhorn or 2 down there.
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Old 20th July 2014, 06:07 AM   #3
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What speakers can you get? (au or overseas)
Is the driver diaphragm facing the room?
What size or volume (to build the speaker enclosure) you have available (sealed/reflex/other), 300/500L?
For a 340/350L reflex you have,
18" Beyma 18LX60V2 pdf
15" TD15S - AE Speakers site
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Old 20th July 2014, 07:11 AM   #4
epa is offline epa  Netherlands
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why not infinit baffle?
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Old 20th July 2014, 01:47 PM   #5
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This is entirely outside of the room - I'm not going to cut through a nice hardwood floor.

I have an old JBL car sub (GT3-12) that models well in a large ported box, or I can do EQ, however I wouldn't rule out buying something new. Availability in Aus other than car subs and brands like Vifa is limited however, and shipping from the US or Europe is very expensive, however sometimes items can be found from parts of Asia for acceptable shipping.
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Old 20th July 2014, 02:52 PM   #6
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Default JBL GT3-12

Quote:
Originally Posted by phreeky82 View Post
I have an old JBL car sub (GT3-12) that models well in a large ported box
That's more than enough. If it doesn't work, buy more...
You can build a 200L reflex or go to the "stupid complex" 6th order bandpass, with no woofer on sight, only two (or more) vents.
6th order: Va = 172 L, Fa = 12 Hz, Vb = 64 L, Fb = 36 Hz
Va, Vb is the volume for the 2 vented compartments (net).
(color pic from another member, hope he doesn't mind)
Attached Images
File Type: jpg 6th order bandpass.jpg (19.5 KB, 150 views)
File Type: gif 6th-order bandpass - 3d-sketchup.gif (65.5 KB, 151 views)
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Old 20th July 2014, 02:59 PM   #7
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Quote:
Originally Posted by phreeky82 View Post
My mains will play well down to about 40Hz, so the sub will be expected to perform from around 40Hz down.
Yes,
that's the range for the 6th order bandpass,
-3 dB - 20 to 55 Hz
-6 dB - 17 to 65 Hz
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Old 20th July 2014, 04:08 PM   #8
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Do i understand you correctly you are looking to transfer the sound through exciting the flooring ie there will be no port or speaker firing directly into the room .
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Old 20th July 2014, 05:01 PM   #9
GM is offline GM  United States
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That's what I'm taking it to mean. There were a few DIY pioneers that used basements to build huge horns to create [incorrectly called] subsonic floor couplers, but I don't see how any typical 'sub' could generate enough acoustical power to excite a well anchored hardwood floor. Maybe a dozen or two, but not a single and even then it would have to be a large area floor to get its resonance down enough to make it worthwhile.

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Old 21st July 2014, 07:10 AM   #10
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Quote:
Originally Posted by phreeky82 View Post
This is entirely outside of the room - I'm not going to cut through a nice hardwood floor.
Then it's not going to work.

SOMEHOW the air must be able to move from the subwoofer cone into the room. If there is no hole somewhere somehow, you may hear something, but it sure won't be a "subwoofer" it will be some random distant low frequency sounds.

Maybe some pictures of your room would spur some other ideas. Like, can you put a sub in the ceiling? Or is there an upstairs floor?
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