Ah. That's one of my concerns for multi-driver model. Either the wire is simply not connected (or got disconnected on transit or after some use) or wrong polarity or the driver is dead.I'm speaking of phasing between drivers in the unit, not overall polarity. I agree that is an issue as well but that is generally far more pronounced. Throw the BQ3 on REW or ARTA and look at the phase diagram and you will find what I am referencing.
Now I remember one of the reasons why I prefer chi-fi with less drivers.