So my buddy put an alpine type R 15 in a sealed box, and its hitting way lower than my 10^ft box tuned to 35 hz with two 18s in it, similar to the dc lvl 4's. Granted, im giving them 1k a piece but they rms at 2500, but what's the deal here ? I mean, I THOUGHT 35hz was fairly low. But that sealed box he has his subs in is giving incredible bass response. Now, I didn't build the box the 18s are in, but it looks like it has enough port area ? I'll post pictures when I get to a computer, but any idea what it would be ??