I've seen posts about that on unmodified players on AVS-forum as well:

http://www.avsforum.com/avs-vb/showthread.php?p=16494805&highlight=popping#post16494805

HD621, G98DH, G68ADV, Bc Acoustiqe ACT A3, 5200C DSP33, NuForce Reference 9 monoblocks, 2x SB3's, Velodyne DD-15 & DD-12 Subwoofers and a Meridian sub.