Trunk 4th order ported through ski hole

[Bassin865]

So I was going through the closet and found some old audio equipment. I used to sale used car audio on eBay. So I was thinking I’d like to do a budget build and maybe start going to some shows and get involved as a hobby... I have a 1997 Nissan Maxima that doesn’t get drive much any more and thought there we go. So I know a thing or two (used to be caco member) but not much real world use. So I have old school power bd1000a1 in the closet and I’m thinking that should be plenty for my plans. I am wanting to build a fourth order ported through the ski hole in the back seat. I’ve been reading a lot and most are saying 3:1 ratio or 2:1 ratio. Tuning in the mid 40s range. The subs I’m considering is An American bass 15” elite. Rated at 1200rms and the power 1000a1 is underrated and should peak just about right for this build imo. So the areas that I’m needing some guidance are determining the proper sqft ratio and how to figure my port size.

are there any guides on the forum or elsewhere? Recommend designers on the sight that could give me a cut out sheet?

[Triticum Agricolam]

So, the way I design 4th order bandpass boxes is to start with the rear chamber.  The larger the rear chamber the more output you will have below tuning, but the higher your cone excursion will be.  The AB Elite 15 doesn't have a huge amount of Xmax, so we are going to have to keep the rear chamber a reasonable size for sub safety.  On 1200 watts I would go no bigger than 1.25 cu ft net.  

With that out of the way we are on to front chamber sizing and tuning.  How big you make the front chamber determines how much boost in get in output around the tuning frequency.  Make it big and you will get a higher peak SPL number, but at the expense of being more peaky in output and having a narrower bandwidth.  In your case I would probably shoot for 3 cu ft of net airspace.  

For tuning frequency 45 Hz is a good starting point.  There really is no way to know for sure what will be the best because it going to depend on what kind of music you listen to, how you like it to sound, and how much cabin gain you get in your vehicle.  I would strongly suggest you make the port removable so you can change the tuning at a later time if you need to.  For port area, assuming 1200 watts and a 3 cu ft chamber tuned to 45 hz I would go with no less than 60 sq in of port.