I got the Logitech z506 surround sound speakers yesterday as a gift and I got everything connected and such but when I try to play some music the rear speakers just give out a little vibrant echo. Is that what it's suppose to do? Every time I do a test for the speakers, everything gets played out from each speaker vividly. Is this normal or is there something wrong? Id like it to have all the speakers playing vividly and noticeable.