Subwoofer strange noise

I have a less than year old B&W ASW300 Sub. I just moved it to another part of my audio room closer to where I sit and the sound has improved dramatically. However, I am hearing a "clicking" or "knocking" coming from the internal woofer at each beat when the unit is being driven, not excessively but at a decent volume level. It almost sounds like it has a tear in the cone material but it doesn't. I've looked very closely and there are no defects that I can see. Is this normal? This is my very first SW and don't know if this is a normal sound or not. Can anyone guide me on this? Does this sound like a defect in manufacturing? Thanks.