The front door speakers are likely to be full range so just 2 wires to connect. If there was an issue with the wiring you wound get no sound at all.
You say Renault did this?, I'd go back and explain/complain if needed. You can get a duff speaker if the cone is damaged or obstructed, wires touching the rear of the cone can dampen sound. It's not an upgrade if it sounds worse. I have test CDs that go through the whole range of 16hz to 20k hz, but as the Kadjar has no CD input that's not much use to you. You can probably get these now on a stick, might be useful if you end up arguing.