What disadvantages are inherent in Surround EX setups?
Limitations common to the Dolby Pro-Logic decoding scheme still exist in Surround EX. In particular, since DPL is based on detect of signal dominance in the soundtrack, subtle elements that may be intended for the surround back channel may be steered towards a much more dominant right or left surround. So you have a center wandering effect. In soundtracks that are not EX encoded (you dont have the Surround EX specified 45 degree phase shift in the l/r channels) rear effects can tend to collapse and blob up in the surround back channel. The above limitations can be dependent upon the quality of the decoder being used. Other decoder manufacturers such as Smart Devices Circle Surround EX decoders have stated that their matrix decoding methods avoid some of the pitfalls of Dolby Pro-Logic by keeping the l/r surround signals intact and filling in the center surround when necessary.
