Dolby TrueHD & DTS MA Subwoofer.

[Audiophile_At_Birth]

Basically He is saying that the New audio codecs for HD sound have a tone freq range from 5hz to inf khz (within reason). and most subs for the average joe range from about 20hz to 120hz which would match up well with the old Audio codecs like DD and DTS which range from 20hz to inf khz (again within reason). So when your subs limit is reached when playing an HD audio codec all you hear is a muffled sound that isn't very clear or loud for that matter.