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Old 15th July 2009, 01:19 PM   #1
DAMIC is offline DAMIC  Seychelles
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Default The easiest way to reduce box volume

Hi,

I have very nice finished sealed woofer box, the only problem is that the volume is about 20l bigger than it should be. Adding some wooden blocks inside the box or plastic bottle/bag filled with sand come to my mind. Anyone have some other idea which could be later eventually easy reversible?

Thanks in advance
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Old 15th July 2009, 01:29 PM   #2
AndrewT is offline AndrewT  Scotland
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Question reflex design

experiment with changing the tuning of the port.

I mistakenly cut 6inches out of a tower speaker because it did not measure according to the data supplied by the kit assembler/speaker designer. I tuned it to the impedance curve presented in the build instructions.

Only later did I discover that using a bigger box than optimum and tuning lower than optimum creates a rolloff that can be made similar to Bessel. And that Bessel rolloff minimises bass emphasis that destroys good bass reality if there is any bass reinforcement coming from the installation.

Sorry this is off topic but gives background for others.

Can Bessel rolloff do any good for a sealed box? Qbox~0.5
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Old 15th July 2009, 02:57 PM   #3
tf1216 is offline tf1216  United States
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I once reduced the volume of a subwoofer cabinet by purchasing hard foam panels from Home Depot and gluing them into the cabinet. It seemed to work great and I bet they could be dug out if you wanted.

Another time I used blow foam to fill unwanted volume. I was able to dig out the foam but it was a pain.
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Old 15th July 2009, 03:43 PM   #4
GM is offline GM  United States
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Squirt it into a plastic grocery/whatever bag.

GM
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Old 15th July 2009, 07:32 PM   #5
DAMIC is offline DAMIC  Seychelles
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Thanks a lot for replies,

Andrew, the sealed box is in question as I noticed with two Kef B139 SP 1044 in isobarik clamshell configuration, so total of 4 pc B139 in 2 boxes. Actually, now I have 43 liter volume/box what gives me according to WinISD Qtc = 0,6 .

Bass sounds very good and although doubled the drivers on some CD tracks, the woofers show insufficient power. I checked on WinISD and it shows much better power response upto 45Hz with smaller volume of about 25 liter and Qtc = 0.7

Btw, woofers are active x-overed at 100Hz 24dB L/R, system is tri-amped.

GM, your idea seems the simplest; I just have a lot of old wardrobe ready to dump, so putting it tightly in plastic bag could be the best choice.

Regards
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Old 16th July 2009, 12:44 PM   #6
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Default carpe librum

I have been of the "two birds with one book" school in the past and experienced less clutter in my study and a neutral mass of know quantity by using unwanted books to stuff boxes. As I think about it there is a third benefit. You create a time capsule for future generations to enjoy. I recently took a large B139/B110/T52 KEF project built in 1984 out of mothballs and found some old New Yorker magazines. The automobile advertisements are particularly amusing.

Being of little brain, I have wondered if using a large motorcycle inner tube modified with an inlet and outlet tubes would be a dynamic way to change volume and tune a cabinet. One could fill and empty the tube with some precision and known volume. A permanent book collection, a volume of known volume could then be secreted into the box. I don''t have the background in physics or practical experience with water in a rubber tube to predict if this would be a neutral space filler. I have wondered if air alone would be sufficient to change the volume, but air would be tougher to measure consistently than water volume.

I am in the process of reducing the volume of a reflex box for drivers I am playing with and using a foam swimming pool noodle. I have cut this $1 5foot long open cell tube into 3" lengths and am gluing them to the back and sides of the box to both fill space and to break up the "cavern" and potential for standing waves. This seems to have worked out nicely though "waves" have been more of a bogeyman in my experience, it is none the less satisfying to put these barriers in place.

A walk through the house and garage finds all sorts of potential space fillers.
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Old 16th July 2009, 06:10 PM   #7
Pano is offline Pano  United States
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There was a similar water balloon idea posted here a few years back. The idea was to tune the cabinet by adding or removing water, IIRC.

I like the books and magazines idea.
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Old 17th July 2009, 05:51 AM   #8
DAMIC is offline DAMIC  Seychelles
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brucegseidner, the idea with books is really great

Regards
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