Well...
Used to be, finding a 5-string with a non-floppy low b was incredibly hard to do for me (including those I just heard, as well as ones I actually tried). So naturally, any of those would sound "weird" to me as well.
However, in the last few years, build quality on 5+ string basses has gone up enormously in my opinion. So B's don't usually sound weird to me unless the gauge is funky or else whoever the person is is playing really badly.
A few months ago I was considering trying an 8-string Galveston (I've never played more than 6 and was curious). The soundclips I heard all had a low-end I can only describe as mushy...so I stayed away after hearing that and reading about others' hit-or-miss experience with the brand. The reason this is relevant I think is that "mushyness" might be what you're noticing on a bass if someone has cut corners on quality of string, nut, bridge, and/or electronics...