Depends if your using a pick, fingers, or slap.
I use about 2.5:1 for fingers, 3-4:1 for a pick, and 6-8:1 for slap. Also the higher the ratio, the lower you should set the attack.
If your using your fingers, your sound can be vastly improved with better technique. Most guitar players who pick up the bass, or bass players who took lessons from guitar players have awful technique. Make sure you don't bend your knuckles like you would plucking a guitar. You want to keep the last 2 knuckles straight, and drag your fingers. And always use 2nd finger for notes on the beat, and 1st finger for offbeats. Being longer, 2nd finger has a natural accent which you don't want between the beats.
Good Luck
Jeff