OK, well the
ideal is to have the front Left, Center and Right speakers all at the same height with the tweeters at seated ear height. The
ideal is also to have them all be the exact same speaker model and oriented the same way (typically vertically).
But in the real world, where there's usually a display in the way, we can't always have the ideal. If you have an acoustically transparent front projection screen and the proper space behind the screen, that's about the only way to get this
ideal setup and placement. Some people position their speakers in this ideal way and simply make do with a display that is mounted way up high so that it is above the center speaker, but this is far less than ideal for the video now, so only people who care more about the audio than the video tend to do this.
What I would recommend for an in-wall setup is this:
First, work out the distance from the screen to your eyes when you are seated in the primary seat. For the sake of an example, let's say that the distance is 10 feet. 120 inches.
I recommend following the SMPTE recommendations for screen size and position. The SMPTE recommends that for HD content, your screen fill a 30 degree field of view and that the top of the screen not be higher than 15 degrees above your eye line.
So, with a 10 foot distance from eyes to screen (just as an example), you SMPTE recommended screen size would be 64.3 inches wide and 36.17 inches tall, giving you a 73.8 inch diagonal 16:9 screen. Bigger screen size than what most people use at 10 feet away, isn't it?
But that's the size at which you would have maximum detail from 10 feet away with HD content.
We'll assume a standard 36 inch height for your eye line when you are seated. It could be somewhat higher or lower depending on your height and the height of your seat, but 36 inches tends to be the norm. That is also the typical seated ear height, so it is where the tweeter of all three front speakers would be under the ideal.
At 10 feet away, a 15 degree angle to the top of the screen would put the top of the screen 32.15 inches above your eye line. This is quite high, but it's the maximum height that SMPTE recommends for a good viewing angle. That means about 4 inches of the screen is below your eye line. And then there's the thickness of the TV's frame to consider. These days, some TVs have very, very thin frames around the screen, but others have a thicker border. Let's assume a "typical" border of about 2.5 inches. So now the bottom edge of the TV is about 6.5 inches below your eye line - or about 29.5 inches off of the ground. Remember, this only applies to a 10 foot viewing distance with the SMPTE's recommended screen size for that distance. The actual distance from the ground to the bottom of your TV is going to vary from this example! But the point is to demonstrate the math: you just mulitply the tangent of 15 degrees by the distance from eyes to screen to get the height above your eye line where the top of your display should go.
Anyways, the point is to demonstrate that you are unlikely to have enough height below your TV to mount the center speaker at the
ideal seated ear height. But if you mount the TV at the maximum SMPTE recommended height, it won't be drastically lower than the other speakers.
With an M-T-M design, you'll likely want to install the center speaker horizontally so that you get the tweeter as high as possible. If you install it vertically, the tweeter is that much lower because of the mid-woofer above it. Most people also think a vertical installation looks a little bit weird
In so far as the sound quality, with a M-T-M design, you tend to get good, wide dispersion when the speaker is vertical, but limited dispersion of the sound up and down. With the speaker horizontal, you now have wide dispersion up and down, but not so much side to side. So it's a compromise if you have a wide seating area. The seats on either side of the "sweet spot" will have somewhat compromised sound quality - typically it's in the form of high frequency roll-off that somewhat deadens some of the detail.
I'm no fan of SpeakerCraft. They are cheap speakers that are WAY overpriced because they are only sold by custom installers whose goal is to maximize profit at the expense of customers who unfortunately don't really know any better. I don't blame customers for ignorance. Not everybody is going to live and breathe audio and video. People put their trust in custom installers who are supposed to be "experts". But like so many other things in life, these "experts" use the ignorance of the general public as a way to gouge them by charging WAY more than is fair. So I'm sorry to tell you that since it sounds like you're too far along to change your mind about the speakers now. But just for future reference, it's unfortunately the case that you have to do your own homework and educate yourself about everything that you purchase, 'cause you can't trust a lot of the "experts" who are just in it for the profit. To be clear, I'm FINE with people making a profit. They SHOULD make a profit. That's the whole point of capitalism! But I just don't like it when people are basically duped into paying way more than what most people would consider a "fair" profit. That's why companies like Bose and Monster and SpeakerCraft get such a bad rap. A lot of the times, it's because their products are utter junk and not worth ANY price due to bad performance. But mostly, their products are fine - it's just that they're priced about 10x what they should be - or for what would buy you comparable performance. A lot of people seem perfectly happy paying 10x more. But if you educate yourself, you can save A LOT of money. Or better yet, pay the same price and get WAY better performance - that's really what I would like to see people do.
Anyways! Enough about that. So far as your center speaker installation goes, I'd recommend a horizontal install so that you can get the tweeter as close to the height of the front L/R speakers as possible. Use the SMPTE recommendation of the top of your TV being 15 degrees above your eye line in order to maximize the height of your TV's placement without greatly reducing the image quality. And then install the center speaker underneath the TV as high as you can.
Hope that helps!
And Merry Christmas!
