Complex sentence: In 1964 the proscenium was removed to accommodate the installation of Cinerama widescreen and a new projection room was constructed under the balcony to accommodate 70-mm projectors.
Split into simpler sentences: In 1964 the proscenium was removed to accommodate the installation of Cinerama widescreen. A new projection room was constructed under the balcony to accommodate 70-mm projectors.