ignorance is bliss.......not so much:[

[porkchop 304]

okay simple enough for the knowledgable ones, IA's 187 12" subs, port up, subs back, going with 4.5 cubes and tunning at 34hz. using 4" aero ports (4"X17") =how many, how long?

the one who answers this will receive good fortune for the rest of his days!

thanks chop

Edited July 19, 2009 by porkchop

[KU40 173]

You could probably get away with three of them, keep them 17" long. That'll make it easy for you.

[shizzzon 461]

3 4" aero ports lengthened to 16.1" long will yield optimal port velocity of 10% the speed of sound.

If u keep all 3 ports at 17" long, tuning will only decrease to 33.25hz so u might wanna just keep the length.

Please keep in mind u will need to remember port displacement.

A 4" cylinder made with 0.125" thick material subtracting 0.75" from MDF due to external displacement will have an internal length of 16.25" displacement with a cylindrical volume of 0.400 cu ft calculated for all 3 ports total.

This does not include flared displacement on the inside but is so small that it will not effect calculations audibly.

Therefore, you will need to take your 4.5cuft NET goal, add 0.4 cubes = 4.9cuft then add 0.1 for every 12 you install.

IE - if using 2 12s, you will need 5.1cuft internal GROSS.

IE - if using 3 12s, you will need 5.2cuft internal GROSS.

[porkchop 304]

Mr. Shizzzon, you are awesome! thanks so much dude. i will get the third one ordered and me and mdizzle will get to building this box asap. also on the list is his big three upgrade and add an additional battery( as cheap as possible till money gets right,{any suggestion welcomed}) and then off to the sound offs in lafeyette on the 25th, wish we could smash into chicago the 26th also, for massonics, we'll see.

truly though, thanks a million, you have helped so much.

Thanks Chop

[porkchop 304]

You could probably get away with three of them, keep them 17" long. That'll make it easy for you.

thank you also sir, the help is appreciated.

[shizzzon 461]

the only cheap battery i know is a deka intimidator 9a31.

[porkchop 304]

the only cheap battery i know is a deka intimidator 9a31.

well then i guess cheap is relitive to budget. thanks for the suggestion, we dont have $230 bucks between us. would a couple of walmart marine batteries help till something else was affordable?

[shizzzon 461]

to be honest, i strictly stay with AGM only.

They are durable to vibrations and won't vent gas when charging\discharging.