I removed the dash speaker from my 2017 Titan SV King Cab. It is 4 ohm, 40 watt max, 20 watt nominal. It measured 2 3/4". I replaced it with a Polk Audio tweeter, 4 ohm. It came with its own bass blocker. I don't know what the factory door speaker ohm rating was. The guy at Best Buy destroyed it to use the factory plastic mount for new 6x9 Alpine. But it now has 4ohm tweeter and 4 ohm coaxial, in parallel, bringing load to 2 ohms, I guess. Anyway, it sounds very good, other than the weak Nissan head unit driving the aftermarket speakers. I do know the rear door speakers were 2 ohm, 40 watt max, 20 watt nominal. Eventually may add an amp. I did put in a Kicker Hideaway subwoofer under the rear seat. I installed the Polk Audio tweeters using universal radio strap bracket with holes. This is stiffer than the plumbing strap from the hardware store. I bent the bracket so the holes would align with the mounting holes in the dash. The tweeter has mounting option to use screw in the bottom of the speaker mount and bolt to the universal strap bracket. Then I angled the tweeter slightly toward the occupant. The picture of the Polk had to be taken from outside the windshield, so there is some reflection glare. BTW, I shined a light into the hole where the factory dash speaker was, I could see light below on my floorboard. Good to know if I ever want to do a rewire.