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Old 6th September 2002, 03:49 AM   #1
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Default cube shaped sub box

I was wondering what the problems would be if I used a 20x20x20 box for a 12" dayton mk II with a 4"x17" vent?
I would line the inside with that mattress foam material.

all comments welcome
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Old 6th September 2002, 04:17 AM   #2
griff is offline griff  Australia
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Brace it well and you will have no problems at all.
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Old 6th September 2002, 04:47 AM   #3
navin is offline navin  India
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brace it at irregular intervals and line the walls with egg crate foam I have done something similar and it worked out well.
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Old 8th September 2002, 07:53 PM   #4
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Hi Hunter,

You will run the risk of standing waves in the box. The fundamental standing wave shouldn't be to much of a problem at about 700Hz (~18" inside dimension). The typical foam wall lining should damp this rather well, plus it is of a high enough frequency to be out of the operating range of the subwoofer.

The problem will come from the 1/2 order standing wave of about 350Hz which is much closer to the sub's operating range. This frequency may be a little more difficult to damp. It wouldn't be as much a problem in a closed box, but the port in a bass reflex enclosure will allow the sound out of the box. What's worse is the port length is very close to the inside box dimension and will support the same standing wave (not to mention that you will have to bend the port away from the opposite wall).

I would suggest a diagonal partition in the box. It wouldn't have to separate the box completely. Only just enough to disrupt the standing waves in the box. This can be in the form of cross braces with 6" or 8" wide boards. A steep low-pass filter for the sub will also help. Also, your port is a bit on the long side. You might want to double check the length calculation. Where did you get this the 4" X 17" dimension from?

Hope this helps.
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Old 9th September 2002, 04:52 AM   #5
navin is offline navin  India
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brace as much as you can.

I use MDF sheets with hole cut outs to make simple braces.

yo can make braces out os 1x1" wood just make sure it is at irregular intervals. dont brace the box isn half.

20x20x20

brace at 5 and 6.5" in each direction. the box will then be 3 parts 5", 6.5", 8.5"

regards
navin
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Old 11th September 2002, 02:53 PM   #6
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i was using the program winisd and added the amount of cross bracing to the box volume should i have done this? I used all the specs that parts express gave me for the titan II 12" I plan on crossing over at about 60Hz with 200W on the sub, as my mains go down to 44Hz. I was wanting to use it as a end table if you wonder why I went with this shape of box.
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Old 12th September 2002, 05:11 AM   #7
navin is offline navin  India
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i use my slide rule. Yes I stil reallyl use a slide rule! It needs no batteries and is just as fast for simple (BODMAS) calculations. I might also be on a few who kows how to use an Abacus or Log tables.

it dont take sophisticated software to do this but if you got it and find it accurate and are comfortable with it use it. I am too old to learn new tricks other than sit, beg and roll over.
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