Changed port volume, lost DB....

[BassheadMS]

I currently have 2) Skar audio Evl 12's, inverted, in a 5.7 gross box. Dimensions are 34 wide 24 deep 15 tall... Soooo.. I was working with a 13.5x 4.2"  29" slot port before. So my box was.roughly 4.2 cu ft net. It pours! Was getting a good bit of port noise, and I felt like it was tuned too low for what the subs wanted.. so I changed it up, port": 8"x8" x 25" long.... Very disappointed. I don't have a meter but I'm certain it's lnot as loud. Maybe 2-4 DB difference... I'm running a hifonics Brutus brx 2016.1 d wired at 1 ohm.. it's worked fine with 3 different setups and still functions properly..... So not the amp.. I'm just wanting to know why the loss in sound?? I think it is more musical now (more noticeable higher notes).. but I want it to be a ground pounder... 24ish hz - 55ish is cool with me, doesn't have to go that low but I like the low lows... Could anyone maybe mimic my setup in a program and see where I went wrong?? I'm just so disgusted that I wasted this enclosure and the last 2 days for gains and wound up losing..... Any help is greatly appreciated guys thanks