sub box help

[hurleypunk3269]

I made a sub box for two 10s. i made it to fit in my friends extendend cab truck. It is shaped to fit in the back but between the front seats. the box fits perfect but the box is just a little over 2sq ft. The Pioneer subs he has (which suck) only need a 1ft each sub. But the guy that he is having put all this stuff in said that the box is way too small even if we put a divider in. I asked him if we can port it and he said no because there still wont be enough available airspace. He said that he will make a box for my friend if he pays him. what diff does it make if the box is 3 inch longer like he said it needs to be? the box is already big enough for the subs and you can always port it or divide it so the subs dont pull against each other right? please help me.

 

[Turbo Guru]

You shouldn't need to divide it if both subs are in phase with each other and running off a single channel (e.g.- Mono bridged not stereo.)

If you need a slightly larger box volume than the one you have; you can fill the one you have with polyfill (pillow stuffing material found at Walmart.) Put in 1 pound of polyfill per cubic foot of volume, this will trick the subs into thinking they have a (slightly) larger box. (In this case 2 cubic feet = two pounds of polyfill.)

Ported boxes (in most cases) requires a larger box volume than sealed, so that will not work in this case. Porting is not about increasing the size of the enclosure, it is meant to make a 3db increase in the frequency that the port tube is tuned to. This is just the basics, more if you need it, just ask.

Hope this helps,
Joe

 

[hurleypunk3269]

so i can make this box work? they just need to be off a single channel? can i bridge them and run them in series? i spent alot of time on this box and i want it to work.thanks alot

 

[Turbo Guru]

What is the resistance of each sub (e.g- how many ohms?) Most amplifiers can handle a minimum of 4 ohms mono bridged (1 channel.) or 2 ohms stereo (2 channels.)

If they are 8 ohms each, run them in parrallel, this will make the total resistance 4 ohms into 1 channel (for mono bridged operation.)

If they are 2 ohms each, run them in series or in stereo, this will make the total resistance 4 ohms into 1 channel (mono bridged) or 2 ohms into 2 channels (stereo) respectively.

If each are 4 ohms to start it with is better to run them in stereo (4 ohms into two channels.) If you are running stereo, you don't have to divide the box but it would make an (small) improvement if you did. Again, make sure each sub is in phase with the other (moving in the same direction at the same time.)

Joe

 

[pilsner]

alright guru, you got some splainin t'do! i have a question about the polyfill. are you saying that for every 1 pound of polyfill, it 'makes' 1 foot of space? i've never known just how much extra space that stuff makes, only that it does. please help me!

 

[Turbo Guru]

No, I did not say it "makes" 1 foot of space. I said that you need to fill the enclosure with 1 pound of polyfill per cubic foot of enclosure volume. I did also say that it lies to the subs about how much box volume they actually have, but I did not give a specific number in regards to the extra space. I will, however, look in my "Installer notes" (a 12 year collection of things I have learned "on the job.") and find an answer for you, if I can.

Joe

 

[pilsner]

yeah, that's cool, i've just never worked with the fill, so i thought there might be some sort of numbers worked out or something. plus, that first post kinda led me to believe so, as you were saying 1lb per foot. why is it 1lb per foot? (not trying to be rude, just curious) if you find some more info, though, it would be greatly appreciated.