In my opinion, a very worthwhile purchase.
Can't really say it has any noticeable adverse audible effects, but it does have a positive effect on speaker excursion in those inaudible frequencies.
You know, the ones you can't really hear, because the driver can't really reproduce them, but which do make a speaker motor work hard ...and therefore hot.
It sits there, doing what it does, no need for further comment really.
Edit: I play 4 string. I dunno about low b...