wiring harness for aftermarket speakers

I cut the plastic connectors right off that were going to the factory speakers, then attached the proper connectors to the wires that will fit on the Alpine's.

 

I put a new head unit in with the factory speakers and even they sounded way better. The weakest part of the system is the factory head unit, it's just awful. An aftermarket head unit paired with new speakers sounds amazing, but I've since upgraded again, I've got a JVC head unit and the speakers are being powered by the tiny Alpine KTP-445U amplifier. Sounds excellent!

 

I just switched all my speakers for my new 2020 Prime. This reply may be applicable to other previous Prius models.

3.5" dash speakers, Rockford...Punch:
You do not need to take the dash cover off. Just take a small screwdriver and pop off the speaker cover from the rear side. The front side is held by the clips and you just need to slide the cover out. The front dash speaker has White, 4 wire connector. take it off. You will be reusing this White connector. Closely verify the +/- conductor based on where the small capacitor is connected on the connection. Capacitor is always connected to the + wire. With a marker, mark the + connectors. Before you install the new 3.5" speaker, you will need to solder a new 600 htz. capacitor to protect the speaker from the low freq. as well as to retain the mid range. The connector has 4 wires because the channels front door speaker through this additional 2 wires. Without the dash speakers connected, the door speakers will not work. Tape the white connector to the new speaker magnet and install.

6.5" Front door Component speakers, Rockford.. Punch 6.5" mid with 1" twitter:
After installing the 6.5 Coaxial speakers, I found the dash mid, voice speakers were all mid range wo. the highs. The coaxials were located too low in the door for effective highs. So, I switched them out to a separate component to improve the bass and treble. The door speakers are riveted. So, you may have to rip it off. Buy (4) 2 conductor, Toyota speaker connector from Amazon and solder new 18 GA. wires. Before you install the speakers, Buy and install some self adhesive foam insulation inside the door. As for the 1" twitter, there is no suitable, flat place to install a separate twitter in Prius Prime. So, I decided to surface mount the twitter. between the dash and the door opener. make sure you purchase a system that will allow you to angle mount the twitter toward the seat headrest. Rockford Fosgate Punch system had a surface angle mount option.
Clip the connectors and install the new speakers. Make sure all installation is tight and tape all loose wires to eliminate rattling.

6.5" Rear door Component speakers, Same as front speakers:
Same. I had to switch out a coaxial speakers. Too much mid range and highs and not enough sound from the rear. The separate twitter did the job to balance out the sound from front to rear. Having said that, The Prius is a front emphasized system. Meaning the front speakers are the main source of sound even if you adjust the front to rear fader. I don't think there is effective solution to this problem unless you replace the head unit. Which is harder on a 11.6 in. display unit. The twitters were installed in front of the door handle. Which was a flat surface compared to the front.

Overall, the sound is about 3 to 5 times better. Better sound with a little more mid bass and high. Better balance from front to rear. More mid range. Maybe too much so, you may have to tone down the mids and the highs to your liking. My factory head unit is better than the standard. But, Not a JBL system. I had a JBL system in my 2005 and I didn't find them to be that much better. Although these new speakers are 4Ohm speakers, they require and can handle much more power. The new speakers can use an external amp. Currently, even with a factory head unit, they sound much better at 50 volume level than 20. Much more dynamic. As for the low end, the car can use a subwoofer. Currently, the 6.5" mid range speakers do not produce too much bass. I will be installing a 8" Rockville powered under seat subwoofer soon. I will repost later.