Does anyone here own these speakers? I bought one and I'm wondering whether or not I got a defective unit. When I put my mac's volume to full and turn the z2300's speaker dial all the way down, it still outputs sound! The sound is very faint, but all the previous speakers I've ever owned have all muted the sound when the dial was turned all the way down. I'm curious if anyone who has this unit also has this "problem?"