I bought a 4 string set a few months ago as a test set to see if I'd like them. I have a Fender Telecaster modern player (dual mudbucker) bass that I thought they'd make a real difference on. Installed them and within 30min took them off, they just overdrove the mid range and made the mudbuckers intolerable.
So I figured maybe better on a really agressive active preamp bass like my new Spector Euro 4LX which had stock strings that I wasnt fond of. Wrong, they ended up destroying the lowend, increasing the midrange and drastically increasing the left hand finger and fret noise of the bass.
The Cobalt windings were so agressive the "D" string would constantly get hung up in the nut when tuning and create a loud "twang" as each individual wind ran across the brass nut (wierd, never had that happen with any string before). I was so convinced these strings were great (based on all the TB hype) I figured my only option to improve the sound of my new Spector was to buy the $350 upgraded preamp.
Out of curiosity I slapped a new set of Elixir nanos on the Spector in place of the Cobalts and all I can say is - WOW! They completely changed the feel and sound of the bass. It's now my favorite bass to play and is exceptionally responsive in both the high and low ranges with no loss of mids. Finger and fret noise is completely gone as is the D string "twang" when tuning and note slides and left have speed are significantly improved over the Cobalts as well.
At this point I am now the proud owner of a fantastic Spector Euro 4LX that needs no after market mods and a slightly used set of Cobalt strings that are pure garbage.
So if you want a more expensive string, that slows your left hand technique down, increases fret noise and finger noise, decreases bottom end and probably wears your frets and nut out faster (and possibly from other reports I've heard dies relatively quick) go with the Cobalts.
But that's just one persons first hand experience with just one set of Cobalts on two different basses so YMMV.
PS - By the way, did I say I LOVE the Elixir nanos.
