Couple of questions

[Drummer65 10+ year member]

When calculating the cubic feet of a box, do you include the space that the subs take up inside the box? The tuning length would be different if you include the subs space or not.

Also the box i built made out of 3/4 mdf for my 4 12's flexes like a *****. Whats the easiest way to fix this problem because right now the box is flexing and rattling. The box is a common chambered box with no supports inside. Inside area is about 6.3 cubic feet.

Thanks

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[-01limited- 10+ year member]

When calculating the cubic feet of a box, do you include the space that the subs take up inside the box? The tuning length would be different if you include the subs space or not.
Also the box i built made out of 3/4 mdf for my 4 12's flexes like a *****. Whats the easiest way to fix this problem because right now the box is flexing and rattling. The box is a common chambered box with no supports inside. Inside area is about 6.3 cubic feet.

Thanks

Theres your problem with your flex. You need bracing with 4 12's and that big of a box. and yes you take in account of the sub displacement.

 

[Drummer65 10+ year member]

Whats the best way to brace the box? I have extra mdf but i don't want to just put a sheet of mdf down the middle to separate the box into two chambers because then my port lengths will be way off.

 

[-01limited- 10+ year member]

I've got a window brace in my box down the middle. That would be a good option for ya, wont split the box up.

 

[Drummer65 10+ year member]

Will a window brace with 3/4 MDF be sufficient? or do i need some stronger material?

Thanks for the help

 

[Phoenix Risen 10+ year member]

you could also use a couple pieces of 1" dowel rod, or a couple lengths of 2x2

 

[speakerdude123 10+ year member]

Another option that people have suggested to me are threaded rods, they are cheap and take up minimal space.

 

[manyhobbies 10+ year member]

When calculating the cubic feet of a box, do you include the space that the subs take up inside the box? The tuning length would be different if you include the subs space or not.
Also the box i built made out of 3/4 mdf for my 4 12's flexes like a *****. Whats the easiest way to fix this problem because right now the box is flexing and rattling. The box is a common chambered box with no supports inside. Inside area is about 6.3 cubic feet.

Thanks

Do another baffle and put at least a center window brace with a couple other braces to support the other 2 subs. I have 4-12 setup aswell but sealed and have a solid partial devider with 2 2x2 braces for the other 2 sub locations. before I did the double baffel and added the 2 2x2 braces my single baffel flexed like crazy.

 

[Drummer65 10+ year member]

The box is so tight trying to get into my trunk already that if i add another baffle the box will not slide into the trunk. I am adding the supports tomorrow and will probably try the threaded rods and dowel rods in order to keep area loss down to a minimum.

 

[05fronty 5,000+ posts]

i have found that a properly tuned midget inside the box prevents flex, while he or she pushes on the inside of the walls.

 

[RAM_Designs 5,000+ posts]

i have found that a properly tuned midget inside the box prevents flex, while he or she pushes on the inside of the walls.

Or just get one fat enough to where it's naturally pushing on all the walls.

 

[-01limited- 10+ year member]

Or just get one fat enough to where it's naturally pushing on all the walls.

best kind of support you can have hands down.

 

[Drummer65 10+ year member]

My neighbor is a midget ill ask if he's down with that

I didn't want to start a new thread for this question but I have 4 4" ports in my box right now. I only have room to make two of the ports longer to get a lower tuning so if i had 2 ports 13" long and 2 ports 21" long with that average out all ports to 17" for tuning or does it not work like that?

I didnt take into account the subs and now the supports which take up airspace so now my tuning is higher then what i wanted.

Thanks

 

[xoutofmyheadx 10+ year member]

i'm not box designer, but isn't 6.3 a bit small for 4 ported 12's to begin with? not to mention now adding bracing, ports and subs.

 

[Drummer65 10+ year member]

these eclipse subs like about 1.5 - 1.75 cubic feet of space so yes the box is a little small for all four. Anyone know about the answer to the different port lengths?