Stereo hook up

[Zcook11]

I just got a kenwood marine stereo and 2 Infiniti 6.5" marine speakers that I am going to put on my 2007 precedent. My cart has 4/12 volt batteries. I read somewhere that if you had 6/8 volt batteries you had to use a voltage reducer. Is this the case with the setup I have? My batteries test out at 50 volt total and each one separate are around 12.6 to 12.9. Any info on installing this would be helpful, any input at all. Thanks.