Artnovion corner bass traps - anybody know if any good?

Oh, I figured out that the larger Artnovion "sub traps" are very expensive at about $2,200 each.  That would be $4.2k for a pair.  They are 2.5 x 3 feet (which is larger than GIK), but a heck of a lot more expensive.  They do have a reflective diffuser type front grill, so it would absorb the higher frequencies as much.

Why would i tune a bass trap to target a tight wave range?  
Does installation of a good bass trap improve base sounds?

i saw the sub bass traps and these are curious, not sure what they improve, Very Expensive!

do a search on this forum for "bass nulls" and "acoustic treatment".  You can also google for this.  The information and explanation is out there.