ok i have a custom built box its one big square box. the volume of the box is 1.9 cubic feet and i have 2 12's in it and the polarities are reversed so they hit at different times and it is pretty frickin loud. but i wondered if it would be better to put a port in it and if so wat could i use for a port tube.
you hook one of the subs up so that the positive wire goest to the positive terminals on both the sub and amp and on the other the negitives go on the positives and the positives go on the negitives. my box is not divided i think when you do what i do it makes it louder
Reversing polarity between subs doesn't contribute to SPL, it hurts it. If you reverse polarity, you are causing a 180 degree phase shift, in which the subs are producing the same wave, but completely out of phase and they cancel each other out. The phase reversal causes a bit of time delay, sometimes up to 3ms depending on the driver. If you reversed polarity and they hit harder now, then they were probably out of phase to begin with.
Subs will fire both ways anyway, they move in both directions. Reversing simply makes the speaker move in the other direction first. People usually reverse phase with tweeters and midranges (NOT midbasses) for their front stage, sometimes it helps imaging depending on driver location. In 3 way sets sometimes you can reverse a single speaker (especially a midrange on a 3-way set) and get good results and improved imaging. As far as subwoofer phase, it doesn't make as big of a difference as long as the subs themselves are in phase.
"but wen i have the polarities the same it doesnt make any noise anyway should i port it or not" That's cancellation. Maybe a wire is marked wrong or something. Stick to whatever is loudest. As far as inverting subs, it makes no difference in SPL output or SQ, people do it because it looks cool (sometimes). It does add a little net volume to an enclosure, but not so much that it will make a big noticeable difference. As far as ported boxes, if you like them, you'll see more SPL. It's not a good idea to just add a port to a sealed box, and you won't get good results. Best option is a custom built ported box. For SPL you have to think big and you simply can't crap out or go an easy route with a ported box if you want good results. Most 12" subs work best with 2 cu ft NET each, remember net means that's before the port volume and subwoofer displacement, so the box will actually be larger. Figure 2.5 per sub, for 2 12" subs it'd be a 5 cu ft box, much larger than your existing one.
One question, when I asked about inverting my sub on this forum, you guys told me to make sure to reverse the polarity, (I even think you might have told me that), and I did it and it sounds fine, I just wondered why you have to reverse polarity. I think I have an idea but I wanted an explanation. When I reverse the polarity back to normal, with the sub still inverted, I can't really hear any difference.
most people don't hear reversed polarity,but we're talkin' about two subs being in the same box,so there is no way it could play louder,if polarities are switched(one normal,second reversed).Adding a port requiers some experience,and definitely different box.there is even chance your sub is not made for ported enclosure(check Thielle-Small parameters)
Spl: Sound pressure level (how loud the sub will sound)
Sq: Sound quality (how nice and accurate the sub will sound)
Rms: recommended contiunous power handeling (Amps and subs will have Max and Rms power ratings, Max being the peak watts it can take/give, but for only very short periods of time. Rms being continuous power)