What enhancement has Dolby made in their Pro Logic IIz (9.1) system?

The enhancement made by Dolby in their Pro Logic IIz system involves the placement of additional speakers above the main ones. This innovation allows for a more immersive audio experience by adding a vertical dimension to surround sound. It enhances the sound field by utilizing overhead audio cues, which enriches the listener's experience, making it more realistic, especially for soundtracks in films and games where ambient noise and effects can come from above. By supporting the addition of height channels, Pro Logic IIz broadens the soundstage, creating a more enveloping auditory environment.

While other options may pertain to advancements in audio technology, they do not specifically address the unique feature of Pro Logic IIz that enhances spatial audio by integrating overhead sound sources.