Others will chime in here I'm sure that have more expertise than I but I think those are "Heresy Industrial Slant Monitors". And look to be in pretty nice condition to boot.
Mine came palletized and delivered by R L Carriers with a lift gate truck. Stiil had them delivered to work where we fork lifted onto a small trailer that could be maneuvered close to my basement doors. Used manpower and a hand truck from there.
Oops maybe it was Old Dominion.
Yes the low pass filter setting on an active (amp and controls all contained in the sub) will handle a full freq range signal and reject the higher freqs that the sub can't handle. If you're talking about a passive sub with a separate amp you will need a separate filter also. I hope that makes sense.
Like dis:
https://www.climbingwallservices.com/shop/climbing-holds/m10-round-back-t-nut/
Oops that's across the pond how's 'bout:
https://www.lowes.com/pd/Hillman-3-8-in-Zinc-Plated-Standard-SAE-Brad-Hole-Tee-Nut/3012553