Three principal types of theater spaces predominate: a traditional proscenium theater, a thrust stage, and theater in the round (think of ancient Roman arenas). For music, the thrust stage has certain advantages because the audience surrounds the performers on three sides. This seating configuration puts them in the same space as the performers, which is good for intimacy and acoustical coupling. But the seating rake in a theater with a thrust stage tends be overly steep in order to optimize sight lines. The steep rake compromises acoustics.
Theater in the round, or arena seating, has similarities to the thrust stage, but for acoustics it’s even worse, because the audience is on all sides. A thrust stage allows for the possibility of a sound-reflecting wall or shell, which is not a possibility in theater in the round. For music, this configuration is rarely successful. The most noteworthy exception is the Berlin Philharmonie: a concert hall in the round reputed to have good acoustics. It works because of carefully calculated seating rakes and walls, designed by Lothar Cremer.
The traditional proscenium theater shares most of the same features as an opera house, except that it may lack an orchestra pit. Both proscenium theater and opera house stages require wing space adjacent to the platform. Wing space provides ‘visual masking,’ concealing actors prior to stage entrances and after exits. Adjacent space is necessary to furnish storage for scenery, which is often housed in the fly loft above the stage, outside audience view. Of course all theaters have backstage facilities as well.
All these ancillary spaces—particularly wing space and flylofts—drink up sound, making theaters favorable for the spoken word but unfriendly for music. The human voice, which is directional, can project speech through the proscenium into the audience area. The more omnidirectional sound of a violin or the backward-facing directionality of a French horn rely on multiple reflections in the ‘sending end’ of the room to project their sound to the audience areas. The proscenium functions as an acoustical barrier for the projection of music. Ideally, musicians want their sound to project out to the audience chamber, where the sound has the best opportunity to reflect off all available surfaces—walls, ceilings, floors, balconies, even the smaller architectural accoutrements of the chamber—to yield a warm, rich, and reverberant acoustic. Musicians also often want their performance space to be integrated into the audience chamber, rather than separated by a proscenium. Acousticians call this concept ‘acoustical coupling.’ This principle is especially important for smaller performing ensembles, where intimacy is a crucial element of the listening experience. The more integrated the performance platform is to the space the audience inhabits, the better the acoustic for music.
While a small theater may have the potential for acoustical intimacy, the psychological separation effected by a proscenium theater, and the practical problems presented by theatrical wing space and flylofts, are essentially at war with a good acoustical environment. Many orchestras renovate old theatres to use as their performance space. Old theatres share the same drawbacks. For optimal acoustical coupling, the proscenium opening should be similar in width and height to the audience chamber. This is never the case, because proscenium openings are designed to enclose a stage ‘room’ with three enclosed walls and the audience viewing in through the fourth ‘wall.’ The bigger the difference in the proscenium dimensions and the audience chamber dimensions, the worse the acoustical coupling will be.
One stop-gap measure that has long been used not only in theaters, but also in multi-purpose spaces, is the acoustical shell, which should be designed to reflect sound out to the audience chamber and prevent it from getting lost in the cavernous spaces that necessarily surround a dramatic stage. Shells do not solve the problem of acoustical coupling, which is endemic to the architecture of a proscenium stage. Shells do assist the musicians on stage in hearing one another better. They also assist in projecting sound out into the hall, but that is a double-edged sword, because different instruments respond differently. The strings, placed farther forward on the stage and often downstage of the proscenium, benefit less—if at all. Brass and percussion benefit more from the reflective capability of the shell. Almost inevitably, balance problems are the result.
In the audience chamber, a drama space favors a lower ceiling than music. From an acoustics standpoint, the lower ceiling minimizes reverberation that could render the speaking voice unintelligible. At the same time, it maximizes clarity and the impact of the spoken word. These qualities are advantageous for theater, but obviously undesirable for musical performance.
Many theater spaces have a steep seating rake, ostensibly for two principal reasons, sight lines and sound. Sight lines are important so that each audience member may observe the actors on stage, including their movements, gestures, and facial expressions. These crucial elements of theater are a lower priority in music. Therefore theater rows will generally be steeper than those in concert rooms to ensure that the actors are visible from all audience vantage points. This arrangement fulfills an acoustic function as well. Sound reflections in a steeply-raked room travel directly to the seating area, which improves the clarity and intelligibility of the spoken word. This occurs at the expense of additional sound reflections arriving later in time. These additional later-arriving sound reflections generate reverberation, a crucial component of optimal acoustics for music, but detrimental to clear and understandable speech. The result is a better acoustic for theatre, but—again—one that is correspondingly less satisfactory for the performance of music.
From a purely architectural standpoint, the principal difference between a conventional proscenium theater and an opera house is the pit. Most plays do not include live music, therefore the space for an ensemble of musicians is unnecessary. Musical theater, opera, and the occasional play with incidental music do require pit space.
From Out of Place: A HyperHistory of the Elusive Acoustics of Concert Hall Venues
By Laurie Shulman
© 2002 NewMusicBox