Quiet driver - volume issues

So we have some logic w bins loaded with Colossus 15s and of the two we're testing one is working perfectly, the other is very quiet (at the same gain). Both drivers are brand new.

We have swapped the amp channels, speakons, the entire speakon place and all the wires leading a banana plug where the wires continue on to the driver.

They're wired +2. -2 and we have checked for consistency in the wiring and everything should be working, yet the driver is still very quiet in one bin.

Does anyone know of any reasons or causes of this problem?

Thanks in advance!

Have you swapped the drivers in the w bins? Also what do you mean by very quiet, if it's just barely any sound, it could be a connection problem. What happens when you attach the driver directly to the amplifier (amplifier, cable, driver), does it sound all right then?

Cheers for the reply Cubo15! So we haven't swapped the drivers around yet, we are going to and check for the connections between the banana plug and driver terminals. Between all of the guys working hours we haven't got around to it yet! Likewise we will test the drivers in free air. I'll post an update as soon as we know more!