Uncompressed sound problems

[DeadMike]

Hello all,

I am brand new to the forums and could not find if this issue has already been discussed. I am also not very tech smart on theater systems, so I don't know all the terms. I'll start with the equipment I am using:

Panasonic DMP-BD10A Blu-ray player
Sony STR-DG920 Receiver
I am using an HDMI cable between the two
I also have some older (5 or 6 years) Kenwood speakers (5.1), with standard speaker wires, and a coax for the sub

My problem is this, when watching TV (via HDMI) my 5.1 sound is great. Watching old DVD's, 5.1 sound is great. Watching Blu-rays, sound is hit and miss. When I use any of the HD sound types sometimes it sounds "grainy". I don't know how else to describe it. The speech sounds terrible, almost like though a cell phone. Sound effects seem ok, but I might not be able to tell b/c I tend to get too frustrated to continue watching the disc. And like I said, it does not happen on all Blu-ray's.

Any clue what can be causing this? Since HD sound is 7.1 and I have a 5.1 setup would that make a difference? My instinct says no, but you never know. Could it be the age/quality of my speakers? The Sony receiver has an auto calibration that I have completed, and like I said, all other sound quality is great. So I am quite stumped. Please let me know any ideas on a solution.