Battery disconnect for stereo install?

just need a quick confirmation before I tackle the project. I will be replacing the HU with a Kenwood very soon. I ordered the Kenwood from Crutchfield. The tech guy there had told me that I actually do not need to disconnect the battery for this replacement as I am simply reconnecting the stereo harness. Is he correct or am I risking possible electrical damage to the stereo or the rest of the car's electronics?

If I do need to disconnect, it is the ground wire/cable to the car's chassis I disconnect, or the negative post of the 12v battery?

 

Just finished the HU install. Kenwood sounds phenomenal. The equalizer helps tremendously on the bass.

Got stuck a few times. Dropped the stereo chassis screw into the abyss behind the panel. Spent almost an hour retrieving two of them. For any future installers I would strongly recommend stuffing some double-sided tape in the inside of the socket wrench where it contacts the screw so it won't fall as you're removing/tightening it. Another key thing that people ought to do is to tape a temporary protective cover(paper or cardboard) over the HVAC display. It got scratched up pretty bad while I was removing all the trim. The shifter should also be protected. I just threw a latex glove over it and that worked just fine.

I ended up disconnecting the battery, at the point where it is secured to the chassis. The manual had strongly discouraged that as the loose cable end may accidentally contact the positive terminal and cause a possible short. I just threw a leather glove over that to isolate it.

I picked up a 6x9 speaker at BB just to see how the fit was. The cutout was fine, but it was too deep. The magnet protruded too much in the back. It probably would hit the window glass as it rolled down. I saw a Sony 5x7 and picked that up. Will see if that may fit and compare the sound to a 6.5"

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