Thomas Chen has at some point suggested a B+ format combining 1st order ambisonic B-format with two additional channels L/R dry channel recording. He is elaborating on the idea here.
One of the really interesting aspects of this idea is the separation of dry signal and ambience so that the mix of dry and ambient signal can be dynamically mixed depending on the space used for playback as well as the preferences of the listener.
From the perspective of how I use to work on sound for (gallery) spaces one of the disadvantages of the format is that it assumes a frontal listening situation. B+ might work well for recreating a concert setting movie etc. but it’s not able to project the dry signal into three-dimentional space. Also the format is lacking the front center channel for dry signal that is often used in 5:1 for better localiasation of speech.
Maybe a better (but more expensive) approach would be to extend the format with two additional channels and make it a pair of two b-formated signals one for dry signal and another one for the ambient signal.
Chen has implemented modules for working with B+ in Creamware Sonar but I’m not sure if they have (yet) been released commercially.
