putting speaker vertical or horizontal?

True audiophiles should not use horizontal center channels, even MTM arrays, for music systems. For the reasons why, see Tom Nousaine's article in the Dec/Jan issue of The Sensible Sound (not available online) or on the Audio Critic webzine (subscription required):

http://theaudiocritic.com/blog/index.php?op=ViewArticle&articleId=12&blogId=1

So, sometimes it pays to look at NHT's web-site. The M5 is a center channel speaker and should be placed horizontally.

Regards, Rich

Pabelson...Why don't you just tell us why MTM speakers don't work well horizontal, instead of citing links we can't use?

Horizontally-arrayed drivers which are farther from each other than 1/2 wavelength, based on frequencies which both play (for example, at crossover), will result in a pattern of cancellations and reinforcements in the horizontal plane. This results in varying frequency response as one moves even slightly off dead-center. Besides, both ears cannot be dead center at the same time, anyway.

Kal

Kr4...I understand what you say, but it doesn't always seem to work that way. Suppose you had two drivers spaced 6 feet apart...wouldn't they (ideally) image as one driver between them? Now, put the tweeter at that spot. As a point of interest, just about every speaker designed for center use is of the MTM configuration.