Front Wide speakers are supposed to fill in the "hole" between Side Surrounds and Front speakers. They get the most use when DTS Neo:X sound enhancement is used.
Front Height speakers are supposed to provide overhead sounds. Again, DTS Neo:X seems to make the best use of them, but they're also used by Dolby ProLogic IIz and Audyssey DSX. They'll also be usable by Dolby Atmos, which works best with four overhead speakers.
Edited to add: several Blu-ray titles were intentionally mixed for home systems which have the additional Height and Width speakers supported by DTS Neo:X: Dredd, The Expendables 2 and Step Up 4: Revolution
Marantz SR7009 avr + MM9000 amp --> Atmos 7.1.4
Fronts=NHT 2.9+AC2, FH+TM=DefTech PM1000, LCR+TM amped
Last edited by Selden Ball; 09-01-2014 at 06:59 AM.