What kind of subs did you have before?
I've used Klipsch KSW-10, SUB-12, SW-112, SW-115, Def Tech SC Reference. Still own SC Ref. Of all these subs, SC Ref has the worst price performance ratio. Um still pulling my hair as to why I wasted money on SC Ref. It gives nothing but resonance. Those two PRs coupled with the size of the box and no bracing makes the box unstable and weak.
Before taking on Dayton HO 15 for DIY, I made another ported box with Alpine SWR-1223D (In my signature)......this build proved to be fantastic. Raw listening shows it is surely going down to 15-16hz. Though I haven't calibrated and run any REW sweeps on it. This sub has depth, as well as, tremendous mid-bass. So compared with Alpine, Dayton is lacking in this area.
Your graphs look pretty flat so maybe you don't like a flat response?
You are right. I always dial in 6-7dB house curve in the passband. But even without the HC, it is giving me tremendously strong depth.