Okay, to replace soundbar speakers, you're gonna need a few parts to adapt to both the soundbar and the wiring harness.
First off, look at the soundbar speaker grill, which is a 3-bolt torx pattern. This is a screw which goes thru the speaker grill and thru a steel screw clip which is slipped into a slot in the molded plastic of the soundbar.
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The diameter of the molded plastic recess for the speaker is 7.5". Just about any replacement speaker you buy will not have these 3 screw tabs extended from the speaker frame. I purchased the Rockford Fosgate 1650 (6.5") speakers, and the mounting screws are integrated into the speaker frame:
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This speaker is made with a 4-screw attachment pattern and it does not come with the Chrysler wiring harness connector, so you'll need this:
https://www.amazon.com/gp/product/B0007WTEVM/?tag=jkforum-20
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Now, I believe you can screw these speakers right into the molded plastic of the soundbar, but the inch or so left open around the speaker grill is going to look a little unfinished and the soundbar molded ABS or plastic doesn't seem all that sturdy and feels like it would vibrate a lot in a Jeep environment. So I opted to purchase this adapter:
https://www.amazon.com/gp/product/B000NWEJWA/?tag=jkforum-20
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Everything was purchased on Amazon: speakers were $109, speaker adapters were $12 and the wiring harness connector was $6.90.
I was going to fabricate my own adapters from a piece of 1/4" HPVC, but I'm very picky about seeing an unfinished look or something that looks too homemade. Besides, my time, labor and material is worth a whole lot more than $12.
This is way less than $150, so I'll be replacing the front lower dash speakers next, possibly the dash top tweeters at the same time if I can find a deal for the set.
Oh, by the way, I'm pretty confident the Rockford Fosgate 6.75" speakers will fit into the opening as well, but you'll still need the ring adapter if you want the finished look.