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View Full Version : how to reduce box CU



johnmatt
12-06-2008, 04:24 PM
So im thinking about buying a custom fiberglass box from bassforms... there internal dimensions are about 1.3 but i kinda want it to be closer to 1... can i just screw like a small block of wood or something into the back of the enclosure or something?

Thanks for your input

john denver
12-06-2008, 04:25 PM
Yes but if its ported it will change the tuning

PhatTonyDeMarco
12-06-2008, 04:28 PM
I would use foam, the expanding **** in a can for filling gaps. A block of wood will not be the best for your boxs internal aerodynamics. You can spray some foam in there and then once it dries shape it to what you need.

Rashaddd
12-06-2008, 05:21 PM
I would use foam, the expanding **** in a can for filling gaps. A block of wood will not be the best for your boxs internal aerodynamics. You can spray some foam in there and then once it dries shape it to what you need.

How will foam be good for aerodynamics? not to mention it has different dampening properties than a solid, non-compressing object (like MDF)

Fiercetimbo17
12-06-2008, 05:22 PM
How will foam be good for aerodynamics? not to mention it has different dampening properties than a solid, non-compressing object (like MDF)

very true, also wiht wood you can calculate the amount of airspace you are taking up, with foam good luck

Rashaddd
12-06-2008, 05:32 PM
very true, also wiht wood you can calculate the amount of airspace you are taking up, with foam good luck

Exactly, I mean he said trim it down to your desired specs, which is acceptable, but then even if it was rigid enough, that would mean it's going to be just as bad for airflow as wood once you trim it down into a rectangular volume...

sqhertz
12-06-2008, 05:44 PM
just throw some random **** in there.
maybe some shoes. an old tire. a box of cereal.







most FG enclosures are have very irregular shapes so i wouldnt be too worried about something like a piece of 2x4" effecting the boxes 'aerodynamics'.

johnmatt
12-06-2008, 06:27 PM
honestly I was just thinking about figuring out what size piece of MDF would take up .3CU and just screw it (well) to the back of the enclosure... (does anyone thing .3 will even make a difference from 1.3) or should i just leave it alone and run it like it is...
THIS IS THE BOX (http://www.bassforms.com/ProductDetails.asp?ProductCode=BF212COBALT)
THESE ARE THE SUBS (https://ssl.perfora.net/www.ficaraudio.com/sess/utn15493b09e879756/shopdata/0050_Speakers/0040_SSD/product_overview.shopscript)(12" with copper coil)
-and just for fun here is the AMP- (http://www.soundstream.com/amplifiers-tarantula.htm) (its the 1500D)

Rashaddd
12-06-2008, 07:03 PM
Those will probably be fine in that enclosure anyway...the way you find out how big a piece of wood for .3 cubes would be is multiply by 1728, then divide by each dimension, in inches

So say you are using a piece of 3/4" MDF you want this size...1728 x .3 = 518, 518/.75 (3/4"mdf) = 691.2, now say you can have it be 30" long, divide by 30 = 23" = the width. So a 30 by 23 by .75" piece of wood would be .3 cubes

hopefully that process made sense...

johnmatt
12-06-2008, 07:31 PM
yea no that makes sense... i guess the more i think about it ill probably just put them in the enclosure and call it done... seems like i could end up causeing more harm (damaging the enclosure, causing poor internal acoustics, etc) than the slightly smaller airspace is worth....