Forgive. I will try so...
I have AS HELON 12 SPL.
I build BR (bass reflex) box for SPL competition (Iasca IDBL).
BR box 100-110l tuned to 48-49Hz.
Photo: http://photofile.ru/users/legych/3796635/all/?mode=xlarge
(Resonanse car VAZ-2107 52Hz)
There are others, the best, variants box?
P.S. I already build BR box for music...54l tuned to 38hz.
Photo: http://photofile.ru/users/legych/3777240/?mode=xlarge