Center channels: why only horizontal arrays?

aesthetics and practicality. most people just don't have the space for a vertical speaker under their tv.

i think they both screw up the imaging and run the risk of directionality myself.

i'm getting a funny image in my head, though, with the way you've got "aesthetics" spelled there, Pmcneil - i'm seeing a bunch of buddhist monks watching movies on a nice home theater system, but it has a horizontal center channel because they've renounced the luxury and materialism of a vertical center channel...

(i'm definitely not one to nitpick on spelling, it just happened to give me a chuckle there!)

Its just more practical for the average consumer,I have tried them both ways and for a center application there is often no huge difference worth worrying about in sound quality.

If you cannot get decent mid and tweeter alignment between center and mains the I'd recommend you go phantom for a small audience of one or two. More trouble than it is worth in many cases but you'll definitely need one if you have a crowd over with seats way outside the sweetspot.

There are some good stand mount speakers that are designed to do vertical or horizintal. Like the now discontinued Wilson Audio Cubs. In better times, I owned 3 Cubs: 2 on stands for left and right fronts and the third sitting horizontally on top of my old 52" rear projection TV.

when i used a rptv, i used the horizontal, but after moving to the front projection, i have exclusively used a full range tower speaker. I have used it below my screen when my room allowed and currently use it behind my screen. I believe most of the early designs are based on sitting on a traditional tv or RPTV as it was difficult to figure out how to put that big tower speaker or even small monitor around the center without taking away from the aestitics of the "theater" effect.