I wouldn't place an HDTV over a fireplace for two reasons.
First, placing it over a fireplace will make the height too great for optimal viewing.
Second, the heat generated by a fireplace, even a sealed one, will adversely affect the TV.
Now, for the components.
I have never understood why people have to hide their components after they have spent all that money.
They aren't ugly and, to the contrary, are quite attractive, at least when they are being used. This is just a personal viewpoint.
Heat is the main enemy of electronics and airflow is important both around and through them. Placing fans behind the components convered by louvered doors might be an option but even with proper ventilation fans I would never even consider "solid" doors to cover my components, if that's what you are thinking of.
First, placing it over a fireplace will make the height too great for optimal viewing.
Second, the heat generated by a fireplace, even a sealed one, will adversely affect the TV.
Now, for the components.
I have never understood why people have to hide their components after they have spent all that money.
They aren't ugly and, to the contrary, are quite attractive, at least when they are being used. This is just a personal viewpoint.
Heat is the main enemy of electronics and airflow is important both around and through them. Placing fans behind the components convered by louvered doors might be an option but even with proper ventilation fans I would never even consider "solid" doors to cover my components, if that's what you are thinking of.
