If it cannot be moved
A master bedroom in the north puts the household’s settled centre in the lightest direction, which the tradition reads as unsettled rest. Where it cannot move, the bed goes in the room’s south-west corner with the head to the south.
What the ಉತ್ತರ governs
North is Kubera’s direction, the one the tradition associates with wealth and with opportunity arriving. It is kept light and unobstructed: openings, windows and low, empty corners rather than heavy storage.
Where the ಮುಖ್ಯ ಶಯನಕಕ್ಷ belongs
The master bedroom is meant to sit in the heaviest, most settled part of the house, on the theory that the person carrying the household should sleep where the building is most grounded. It is a placement about stability rather than energy.