In my experience, most new Velodyne subs that cost up to $600 and 50 lbs or less will come without any type of suspension or damping foams. Their internal are VERY simple design. Thus, by adding/glue-ing some type of foams to inside walls, the Velodynes (or any others) would sound so much smoother and have a better bass control. Diff will be night and day. I personally use 1" thick pink packaging foams (egg shell).
Note:
-Its port must maintain free of clearance.
-Too much foams added, the sub might/will sound muddy or stuffy.
-Since you changed the sub's characteristic, relocate or re toe-ing it may be needed.
Adding SMALL bag of sand would help stablize the sub, minimizing vibration. But its internal volume would be degrease dramatically so just try one step at the time to see what fits you most...
Note:
-Its port must maintain free of clearance.
-Too much foams added, the sub might/will sound muddy or stuffy.
-Since you changed the sub's characteristic, relocate or re toe-ing it may be needed.
Adding SMALL bag of sand would help stablize the sub, minimizing vibration. But its internal volume would be degrease dramatically so just try one step at the time to see what fits you most...