Dont know if this is right or wrong to be posting this, but o well,
If you went to this gig then they are offering a full refund to people because of the sound quality. If you havent thought of complaining then there is incentive to as theyre refunding the face value of the ticket (which for this gig could have been a lot!)
If you went and where you were the sound was ok, then you might as well drop them an email "complaining". As i said, slightly wrong perhaps but could mean some money back. Its your prerogative.