There are three adjustments that are critical to make the bass easy to play and sound good.  The first is the truss rod adjustment.  This adjusts the curve of the neck.  If the neck doesn’t have enough curve, the strings will buzz on the frets.  If it has too much curve, it will be hard to play in the upper part of the neck.  The truss rod is different on different basses.  Irv can show you how to adjust the truss rod on your bass.

The second is individual string height adjustment.  This allows for fine tuning of string height for each string individually, whereas the truss rod adjusts them all together.  Again, if a string is too far away from the fretboard, the bass will be hard to play and painful for the fingers.  If it is too close, it will buzz.  Irv can also help you with this.

The third is individual string length adjustment.  It is important that this adjustment be correct or the bass will be out of tune with itself.  There is a procedure for adjusting/tuning strings that Irv can show you.  If you change string gauges or types, or adjust the truss rod, the string lengths will need to be re-done.