few noob box build questions

[mrbomb 10+ year member]

ive started my first build for a sub box, unfortunately i need to decrease the air space to come down to sub specs would adding insulation in the box do this for me or should i tear it apart and try again?

another question, the space is currently aprox at 3 cu. ft. i would like to have two round ports maybe 3 in. dia. how long should these be if i want to tune to around 35hz? and how do you calculate this dimension

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[BuckyBoy 10+ year member]

For 3ft^3 @ 35Hz, two 3"x8" aero ports or two 4"x15"

What airspace is the box you built and what do you need to get it down to?

Did you account for sub and port displacement?

 

[mrbomb 10+ year member]

somehow i knew you would be able to come through on this one for me

but its around 3.4 now and for specs it should really be like below 2.5, way the hell off, but would be fine if i just get it to around 3? or should i just go ahead and make the box into two seperate chambers where i will be able to get it closer

since this is one of my first systems i dont think i will be able to tell if it doesnt sound perfect

 

[BuckyBoy 10+ year member]

How did you determine the volume? If you used external dimensions, then the number you got for your volume is a little high already. Did you use internal measurements?

And yes, it would be fine if you could get it to around 3. It will probably be fine the way it is. It is better to have more volume than less volume. Some people actually recommend more volume than manufacturer's suggest.

You could always cut some pieces of MDF for bracing or just secure them to the inside walls of your box to reduce the volume if you really want.

 

[mrbomb 10+ year member]

and the dub displacement is only .03 per sub so dont really count on that for much and i was waiting for the dimensions of the port to count that

 

[mrbomb 10+ year member]

ok that makes me feel better about it then, i was planning on adding some bracing in there anyway so i might just do that and call it good

so how do you calculate the port dimension?

 

[BuckyBoy 10+ year member]

ok that makes me feel better about it then, i was planning on adding some bracing in there anyway so i might just do that and call it good
so how do you calculate the port dimension?

a program called WinISD.

if you use two 4x15 aero ports you can take around .2 off of the volume