Good question!
For proper film, center is for dialogue only-so that leads one to believe you could use a different speaker successfully. Music/effects are NOT sent to the center. However, there are some newer mixes that defy this and who knows what future mixers might do? So this sort of says "the only safe bet for the future" is all speakers the same. In my own case, I cannot do the same so I use (the same brand center) that is voiced the same as my L/R/SR/SL. Less low end in it (fine for dialogue) but sounds very much like the mains. I spent more than I thought I would for the center but all other lesser options sounded too different. I am glad I did, sounds really nice now.
For music, different story completely. Music mixers DO use the center for music, they can sort of do anything they want, so this means all speakers must be the same, rear channels, center, fronts.
Brad
For proper film, center is for dialogue only-so that leads one to believe you could use a different speaker successfully. Music/effects are NOT sent to the center. However, there are some newer mixes that defy this and who knows what future mixers might do? So this sort of says "the only safe bet for the future" is all speakers the same. In my own case, I cannot do the same so I use (the same brand center) that is voiced the same as my L/R/SR/SL. Less low end in it (fine for dialogue) but sounds very much like the mains. I spent more than I thought I would for the center but all other lesser options sounded too different. I am glad I did, sounds really nice now.
For music, different story completely. Music mixers DO use the center for music, they can sort of do anything they want, so this means all speakers must be the same, rear channels, center, fronts.
Brad