I ordered my Hydraulic head to get rid of the over and undertones on my 16" floor tom, which I have tuned very low for a nice deep rumble. It's important the drum head doesn't go too limp on you when tuning low, otherwise you'll end up with a wet, flappy sound. These Evans heads don't seem to do that.
I'm thinking about getting them for my whole kit, altough it is a shame they don't come in white as well, since I love the classic look of a drumset with only white ambassador drum heads.