first time box build dual l7 12s

I'm working on the plans for building my first box, and have some basic questions that I'm hoping to get help with. I'm thinking about going 2 chambers with 2.5 ft^3 each, ported and tuned to 33Hz. My questions are, when calculating the port size, does the height / width matter, or do I just pick them semi-arbitrarily based on the cross sectional area that I need? Like, would I get different results from a 3"x12" port as from a 4"x9" port, for example (both 36 in^2 area)? Also, I wanted to make sure that I'm using the right numbers to calculate the port length, I use Vbox - Vsub - Vport right? So do I calculate this as if the box is 2.5 ft^3 and then actually make the box slightly bigger to compensate for the extra volume added by the port? I don't have specific dimensions to work with yet because I've been a little bit confused trying to figure out these formulas, but I can try to come up with some if it would help to get my questions answered. Any advice that people have with regards to these planned specs would be appreciated as well. I'm sure most people here have more experience than me with regards to building sub boxes. Thanks

The height and width don't matter much to a point. As long as you keep about 1" in width for every 11-12" inches in height you are okay. So you would be fine with either of the two ports you listed. The internal volume is not including port or sub displacement so the formula you were using previously was correct. You have to account for extra volume of the port and sub seperately. What type of sound are you looking for from your L7s? Are you looking for sound quality (I know I shouldn't mention SQ in the same sentence as these subs), loudness, a combination? That may help us with recommendations for a design. It has been awhile since I have modeled the L7s but 33Hz seems a little low. I could be wrong though I am just wondering how you came up with that tuning. Did you use a program like WinISD or something?

The 33Hz came from browsing through forums and finding that people generally recommended low 30s (like 30-35 is what I found). So I figured I'd split the difference and go in the middle. I want this to be loud. Before this project, I had a single L7 in one of the Kicker prefab boxes, and was pretty happy with it. I want it to be loud, without completely sacrificing SQ, if that's even possible. From what I'd been reading, it seemed that higher tuning (in the 40s) was recommended for SPL setups, and lower tuning into the 30s was for maintaining a bit of SQ. This is just going to be a daily driver, I don't plan on doing competitions or anything at this point. Also, while we're on the topic, the amp that I have is a Rockford 1501BD, which puts out 1500W at 2Ohms. I think this should be fine to power these two subs, but if anybody has any insight into this, I'd be happy to hear it as well.

First of all, with a tuning that low, you are probably going to be sorely disappointed with the output. That's WAY too low, IMO, for SPL. Secondly, if SQ is even remotely in your interest, then the L7s are the wrong woofers, and then you are using a poor choice of an amplifier as well... The L7 and ANYTHING Rockford are ONLY SPL choices. That combination is as far from SQ an any combination I can think of.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Ok I appreciate the input on SQ vs SPL with this setup. Ignore what I said earlier and lets just focus on what I can do with the box to make this setup sound as good as possible. What tuning frequency do you think would work best, and does 2.5 ft^3 per chamber seem like enough room? I'm working with slightly limited trunk space ('94 Camry), but could probably fit a bit bigger box if I had to and was willing to sacrifice my whole trunk. Being loud is my main goal. Would I be better off tuning in the upper 30s? Maybe 38Hz or so? I am grateful for peoples' responses so far, and helping me to understand what is / isn't possible to achieve with what I've got. Like I said, this is my first try at building my own box, so I'm sure that there's quite a bit of learning ahead of me, but just trying to iron out as many of the kinks before I actually get to the construction.

I got a chance to model that sub up a little bit. From what I saw I think that a higher tuning frequency would be better if loudness is the main goal. Something around 38Hz or so would be good for a daily driver that gets loud and still sounds good. Also, going up to about 3 cubic foot would be good as well. If you don't have the space then that is fine as 2.5 cubes will be good as well. You could tune higher or make the enclosure slightly larger then that as well. Kicker's recommendations for a SPL/Deep Bass enclosure are 3.25 cubes at around 42Hz. This is going to be slightly too high for me. You will get a little more output but the response is a little too "peaky" for me so that is why I recommended a slightly lower tuned enclosure.

Thanks for the helpful advice, whiterob. After getting some good tips from here and a few other forums, I think I'll try going around 38Hz. I'll see how much extra space I can squeeze out of my trunk to figure out if 3ft^3 is doable.