hi i have some lanzar dc 12's old school.(2 of them) They are in a 1.85 cf sealed box each and according to the sheet that came with them from lanzar that should produce a tune frequency of high 60s hz but when i run it in the car with my spl meter and did test tone sweeps i dicovered it hit loudest at 37 hz. Why is this? The box is facing the tail of the car in the trunk in a 95 chevy monte carlo z 34. with the seats up but i can fold them down but it really doesnt make a difference either way. Im running these on an mtx 81000d at 2 ohms so they are getting plenty of power. My goal is to set these up for spl id like to hit 147 db or more (147 db which someone here locally did with an opti 200 400 rms at 12.6)
as far as i know a sealed box has never been tuned before. if you want to burp your subs ... put them in a ported box and tune it really high like 60 or so then find the exact freq that would make your subs loudest.
a sealed box does have a tune frequency but i do have a sealed ported swapable feature on my box they are 55hz to 70hz pvc tubing tuned to that box that i need to test yet with my spl meter...so far all i tested was the sealed box results
A sealed box will have a reference level and then will roll off below that frequency. Some people refer to this as "tuning" of a sealed box. The smaller the box, the higher the reference level. The reason it has more SPL at 37 hz is because of cabin gain, the car actually helps the sub gain level at lower frequencies, this is why subs are designed to roll off. Without gain, the sub would lose a lot of SPL in lower frequencies. The reason you hit best at 37 is because of both the subwoofer itself and the gain of the cabin.
Not necessarily. A larger box will allow more excursion with the same amount of power and increased bandwidth (drops lower) but that won't necessarily net more SPL. The pressure in side a small sealed box can actually help excursion to an extent, assuming you have enough power. I doubt you'll notice any difference by going to a larger box unless you aren't giving the sub enough power. If you want more SPL, you need to consider a ported box, and since you hit best at 37 hz, tune it between 35-37. You could also tune at the resonant frequency of the cabin, but this is generally 50-60 hz and sound like absolute crap, this is only for competitors and you need the sub to do it with as well. I'd do a ported box tuned to 35 or so.
thanks for the reply jon i have them running on an mtx 81000d at 2 ohms and i have that swappable sealed ported combo and will test the ports next from 55 hz and up but .64 cf sealed is a 88 hz tune and a 2.25 sealed is a 54 hz tune and 4.7 cf ported to their specs is 31 hz and .80 ported to their specs is 55 hz in case that gives you any other ideas i can try based on my previous results