Leaderboard

The best thing to do would probably be to model the subs in box simulation software. A larger rear chamber will get you more output below your front chamber tuning. It also increases cone excursion though, so it’s going to depend on how much power you are running.

2.5 sealed total.

You'd be hard pressed to bottom these out in a 4th order lol. It'd take around 3000 watts per sub and some low lows to reach xmax on these. Tune to around 44hz on your ported side and go with 2.5 sealed 5 ported for a nice 30hz total bandwidth. Like triticum said, you should model your enclosure with some design software. 4th orders are pretty straight forward. The bigger the ratio the peakier it'll be. The smaller the ratio the flatter the response. 2:1 usually yields a pretty desirable output. Feed the beasts! Good clean power. These subs sound great in 4th and 6th orders.

1.0ft³-1.25ft³ sealed per driver. After that however big you want your ratio is on you. I'd do 2.25ft³ sealed and 4.5ft³ ported personally. 6.75ft ported max for a 2:1.0- 3:1.0 ratio.