The design of the auditorium is a prime consideration in theatre planning. Its formation and decoration should tend to focus attention upon the scene pictured on the stage. The one proportion that regulates the dimensions of an auditorium is the width of the proscenium opening, or vice versa. The width of the opening should be slightly more than half the width of the audience hall. An audience hall forty feet wide should have an opening of about twenty-one feet; a sixty-foot width of hall should have an opening of about thirty-two feet, and an eighty-foot hall an opening of forty-three feet.
The height of the opening should be about equal to three-fourths of its width and the angle of the opening itself about 45 degrees. While a proscenium opening with a greater height than width might present to some eyes a better architectural effect, the reverse proportion is more practicable and in the writer's opinion more artistic.
The manner in which the stage opening is framed usually determines the architectural treatment of the auditorium. Where the top of the opening is arched the ceiling of the room should be curved to correspond. If it be flat the ceiling should be formed flat. An opening with a flattened elliptical top presents the best appearance and suggests a simple, effective design for the ceiling. With amply and properly curved coves for reflected indirect lighting, and with a well-devised central open dome for ventilation that can be opened to the sky in the warm summer months, such a ceiling is ideal. The space immediately above the proscenium opening, usually termed the sounding board, should be low and curved outward to reflect better both sound and heat.
There is no part of a theatre, within or without (not even the auditorium in which the old-fashioned style of defacing its walls with meaningless and inartistic plaster wreaths and ribbons still persists), that is so commonly overloaded with meaningless ornamentation as the proscenium opening. This frame, being the constructive feature closest to the action on the stage, has greater possibilities than any other place for distracting attention from that action. It should, like the auditorium itself, be as simple, harmonious and unobtrusive as possible.
The shape of the auditorium is at present undergoing many changes. The old-fashioned rectangular type of audience hall, with a lyre or horseshoe shaped balcony, has been superseded by the square auditorium with contracting paneled walls approaching the stage opening, curved rear walls with well rounded corners, and a balcony whose front follows the seat line below. In advanced theatres, stage boxes are eliminated for acoustic reasons, and to direct concentrated attention upon the stage. In a truly democratic country it is assuredly not necessary to provide conspicuous boxes for persons of superior rank or social distinction.
It is possible, however, that this square-shaped auditorium may not long endure, as there is already a tendency in Continental Europe toward the adoption of the fan-shaped form employed in the Wagner Opera House at Bayreuth, pictured on Page 21. This is a model affording the best sight lines and* the safest means of escape in case of danger.
The decoration of the auditorium should be chaste in its simplicity and subtle in the harmony of its coloring. Such effects are more conducive to a sense of contemplation than riots of meaningless ornament and brilliant coloring. The aim should be to foster a spiritual mood and to render the senses more susceptible to favorable impression.
One of the most important requisites in designing an auditorium is the establishment of correct sight lines. As no two theatres are exactly alike the sight lines for each building must be worked out separately. This, however, is a comparatively simple operation.
Theoretically the spectators in the last row of seats underneath the balcony should be able to see the top of the proscenium opening, and the angle of vision should never exceed 45 degrees. Errors in sight lines are one of the commonest mistakes in theatre construction. A recently built theatre in New York City, publicly proclaimed a wonderful theatre, shows the result of this miscalculation. The mistake was discovered as the theatre was about to be opened, and an effort was made to correct it by lowering the main floor, a procedure that naturally had to be abandoned, as it meant the alteration and destruction of correct sight lines from the already constructed balcony.
The first necessary step toward fixing sight lines is to establish a proper slope for the main floor. This pitch may depend somewhat upon local conditions. If the natural grade be lower at the stage end of the auditorium and slope upward toward the main entrances to a point equal with, or two or three steps above the sidewalk level, the problem is partly solved. Otherwise it may be necessary to reverse the slope of the auditorium or raise the corridor entrance considerably above the ground level.
If possible a proper slope must be given to the main floor without the necessity of risers by an incline made in the shape of a parabolic curve, as indicated by the diagrams on Page 68. The incline of the first few rows need not be great, as the eyes of the persons in these rows are about level with the stage floor, but it should increase perceptibly from about the fourth to the last row, and be so adjusted that each spectator can easily see over the head of the person in front of him. The old fashioned saucer-shaped main floor, with its seats curving upward on either side, had its commendable points. However, the building laws in many cities regulate the pitch of theatre floors.