I have owned a pair of M3Ti's for around 3 years. They have always sounded great and never fail to impress listeners. Lately, they are sounding somewhat flat and "boomy" in the bass.I have not changed anything in my system. They are being powered by a Denon DRA685 receiver. The cd player is a JVC and the speaker cable is 12 gauge Parts Express wire. Something is not quite right. Any suggestions? Thanks.