Mounting TV Above Fireplace

Ideally for movie watching your TV should be where the center of the screen is at eye level at your seating position.  In your case that most likely is not possible so my suggestion would be to mount as low as you are able. 

If for movie watching often mounted high may cause neck strain.  For casual TV watching/sports while in kitchen or entertaining then a little higher should work.

Bill

Make sure you have a heavy duty plywood backer board mounted to studs for your TV arm mount to attach.

Our TV is mounted about 45 inches above the floor and works fine

Google the available “tv mounts over fireplace pull down”

the swing both out AND down to be positioned lower over the mantle and/or fireplace to lower the screen height position 

Chief makes a great high quality TV mount

I put in a great Heat N Glow gas insert, puts out a lot of heat.  It gave minimum distances to flammable material specs.  You don't want to get your TV too close.  My TV was up high but tilted down a little.  When reclined in my chair with my head laid back, it was just right.  Standing in the kitchen was good, too.

Place all your speakers at ear level. the video display can be higher. it is the sound that makes a difference not the display positition.

I destroyed my entertainment center furniture to get the audio right.Just bumped the display up a few inches and got the center channel same height  as mains and the improvement was sooooooo good. Please try this.