Replacing the door speakers on the 2013 Altima can be a little difficult, first off they have used 2 Ohm speakers, and using 4 Ohm will result in low volume and less then stellar sound if you're not adding amps or a new deck. To address this I found JBL and Infinity offer 2 Ohm speakers that make a good direct replacement. Second the clearance in the doors to avoid the window hitting the speakers when completely lowered requires keeping the speaker spaced out as the OEM speakers are and using a shallow speaker type as well. I found the JBL P662S is just about perfect, if you destroy the stock speakers and use them as a trim ring for the new speakers. It also provides you with a plug socket for the factory wire to connect to. I attached the cross over to the lower edge of the magnet below where the window travels. I used a high temp super strong glue stick and clipped off the top ring above where the old speaker was as well as cliping off the basket and magnet of the factory speaker. They can now be installed using only the factory parts, and without removing the door pannels, just unsnap the bottom and you can reach the screws.