Complex sentence: In 1656 Davenant turned a room of the house into what was, at first, a private theatre performing his own plays, soon the performances were advertised and semi-open to the public at a cost of 5 shillings per head.
Split into simpler sentences: In 1656 Davenant turned a room of the house into what was, at first, a private theatre performing his own plays. Soon the performances were advertised and semi-open to the public at a cost of 5 shillings per head.