I upgraded the speakers in my MT347hc going up one size, and they still sounded like ****.
After digging into the wiring, I found some genius spliced the front and back amp outputs together in the harness going to the speaker. The OEM Jensen isn’t capable of bonding them and they end up fighting each other, so they sound like **** no matter the speaker.
It actually sounds halfway decent if you cut the link.
Not sure if the factory or dealer did it.