Originally Posted by SuperRich
OK so I just found it is possible! but I read that it can change the volume of the bass? I dont really understand much about electronics. any help?
Pickups in parallel move the frequency the resonance peak very high, generally so high that your (bass) strings don't put overtones where the peak is so the peak is effectively eliminated.
Also, if you want to do this with 2 pots or 1 blend pot you need to connect the pots "backwards" with the pickup going to the middle lug. If you don't then you cannot turn one pickup off entirely. But if you do that you also kill the resonance peak if any volume pot is not full open or full close.
This isn't specific to your situation, it's always that way with passive 2-pickup guitars or basses. The guitarists solve the second problem by using a switch most of the time which makes it acceptable to connect the volume pots in a LP "forward" (output on middle lug) which makes mixing possible while retaining some resonance peak.