Absolutely. In fact in most of our installation a majority of the electronics are either in a central closet or in cabinetry behind closed doors. Be careful though. There are some things to consider when doing this. Since you are putting them in a confined space heat dissipation needs to be considered. Passive ventilation will almost never be enough and we need to install a thermally triggered fan system to help out when the system gets too hot. Also serviceability can be an issue. Finding a way to get to the back of the equipment will need to be considered. Use of a roll out rack or removable rear panel in the case of cabinetry can both be acceptable solutions