parameters

Okay so i was curious, whenever i look at subs i look at the specs and i have noticed something with every reputable brand. For example the most recent sub i looked at was the AA Mayhem. I don't understand why the parameters for the same size same model sub, change based on whether it is 1 2 or...

I'm in the process of designing a box for 2 SA 12's, 4ohm. i was wondering if anyone had the specs for them, after they were broken in? i couldnt find them anywhere. Thanks for any help!

i was wondering what the following parameters are for the BRZ15D4. i have two of them wired in parallel (if that makes a difference). i need the folowing parameters for the subwoofer. Qts vas Fs Re Le Xmax Z Qms Qes SPL Pe BL Dia SD thanks a lot