In order to drive the speakers from a soundbar, you need significantly more power than any iPhone or iPod or phone can put out. This is where you will need to add in a head unit to drive the speakers- it's probably best to use an aftermarket unit with an amp to drive the speakers at clean volume levels so that you can easily hear them. But the amp is just a luxury, wiring speakers right to the head unit is typically plenty.
Usually factory head units don't put out the power required to drive speakers with enough power, so they won't get loud enough and you can actually blow the speakers.
My 5.2L Build thread
-1989 Jeep Wrangler 2.5L, soon to be 5.2L
-1996 Jeep Grand Cherokar 5.2L, donor and rainy day driver
-2004 Kawasaki KLR650 sunny day driver
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