i have the logitech z906 and have had them since 10 years back. they have been put through alot of torture and it has left its mark. Due to the treatment i´ve given them they cant produce cirtain frequencies. i belive that it would be fixable except i CAN NOT operate on the sub. There are no spare parts such as only the sub plus control module availeble so i would have to buy a brand new complete set instead of only the sub.