Four 15s wall help

[jf1984]

Hello everyone. It's been a while since I've last been in here, Finally got motivated to build my wall For my 15s.  And it seems I may have done it wrong. I was told by many different people to build as large as I can and I did. So I guess I'll break it down the best I can with what I know. After port and subwoofer displacements,  My Box is at 19 ft³. Port area is 7"x32"x22"long.  225 in². Sub woofers are four ZVX v2 15s. Amp is rp3500@ .5 ohm.  I have the amp  Wired this way just for testing purposes. The Box seems to peak at 40 to 45 hz.  Anything in the thirties seems muddy and hardly any output.   My theory is the box is too large and port may be too small. If any other information is needed please feel free to ask. As for my question,  What did I do wrong,  And how can I correct this issue?  I'm not looking to be spoon fed any information as I am learning in would like to learn by putting in the work. Thank you in advance.