Does it have to be connected to the battery or can the power lead be grounded to the floor?

 

the +12v goes to the battery, the earth can go to the chasis

 

Well, the floor is technically connected to the battery anyway so its an odd question.

I've always grounded them to a decent point on the shell/floor whatever.
I'm sure some audio-nutter will say thats totally wrong though.

 

as above power lead to battery with fuse as close to the battery.earth lead as short as possible.run rca leads the opposite side as your power cable aswell otherwise you may get interference

 

Cool...thanks bud.

 

Sometimes you can pick up interference, so may need to move your earth location, it will sound like a constant hum sound if interference, but a ground loop isolator will soon cure it, try not to put it with any other earth as well.
The modern leads are so well insulated that I have run all together and had no problems at all.
tabetha

 

you MUST have a 12v line to the battery and you MUST have a good earth to the cars Chassis

the question you asked made no sense :-
can the power lead be grounded to the floor? - that makes it sound like you want to run a 12V line through the cars floor therby giving you or anyone touching the car an electric shock?!

DO NOT run the 12v line and the Audio lines down the same side of the car - run them down opposite sides, this gets rid of the bussing alternator whine interfeerence that you'll get.