Mine's barely 3" from the wall. Never had any port noise or chuffing. I did have those problems with at VTF-2 sub however. Returned it in favor of the VTF-3. My room is about 325 sq. feet. (just under 2500 cubic feet.)

later,
simp
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Marantz av7005 Proc.
Oppo BDP-83
Rotel RB-991 (mains)
Outlaw Audio Model 2200 (center)
Rotel RMB-1075 (ss, rs)
f, B&W DM604S3
c, B&W LCR600S3
ss, B&W DM302
rs,Polk M3II
HSU VTF-3 MK3
APC H-15 Power Conditioner
Display: Panny PT-AE4000 Proj. + 92" DIY Screen
Little Dot MKIII Headphone Amp
Denon AH-D1100 Headphones (needed a quick, cheap set. looking for an upgrade worthy of the h/p amp.)