Compression is a funny thing, i never really understood fully or worked out what it did, tried a few compressors and patches on my Zoom. But then i got a seymore duncan studio bass compressor and its set at around 10 o clock, attack and blend about same, volume/level to suit, and it works great, just rounds off and emphasizes the individual notes a little better.
Funny thing is i was playing the other day and some thing was not quite right, though i was i little out of tune or there was some drop in sound thought maybe a connector jack was loose, then i realized the compressor was not on, turned it on every thing fine. Think its one of those things once you get it set up right for what you want you do not notice it until its not on.