i have a quick question if someone would be willing to help me out. when i first wanted to build a sub i built a full marty from GSG and my wife hated it so i compromised and went with 2 of the 4 Cu Ft flat packs from DIYSG. well since then i have gotten upgradeitis and purchased another amp to add 2 more ultimax 18's to the mix for a total of 4, the amps i have to run these are a behringer NX6000D and a crown XLI 3500. so the question i have is would it be best to build 2 more of the 4 cu ft flat packs for a total of 4 sealed. or since i still have the full marty box and now that these will be behind the couch so i think the wife would let me get away with putting that full marty in the back corner kinda out of site would it be best to only build 1 more sealed box for a total of 3 ultimax 18's in sealed boxes and 1 in a full marty. thanks for any help
Four sealed boxes would be the easiest to integrate together. Ported subwoofers have a phase shift /rotation as they approach their tuning so they don't often blend easily with sealed subwoofers across the whole frequency range, they can be made to work but it usually takes a little extra effort.