That's a tough one. First thought that came to my mind had been your room acoustics. When you mention turning down the treble I got the impression that the sound you're getting is bright and harsh. This is something you should research as acoustics play a huge role in the sound of any speaker.
I used the Titan's you have as a rear channel and had tried them on their own to see how they sounded. I don't remember anything about being harsh. Your receiver can also be part of the problem. Most importantly is the Room Acoustics.
I used the Titan's you have as a rear channel and had tried them on their own to see how they sounded. I don't remember anything about being harsh. Your receiver can also be part of the problem. Most importantly is the Room Acoustics.