Sound frequency and reproduction
Sound frequencies produced in a concert environment are identified as: sub-low, low, midrange, mid-high and high frequencies. To provide a balanced sound, each frequency must be isolated using an electronic crossover unit set by the sound engineer. Crossovers filter and separate total frequencies, and the signals are routed to dedicated amplifiers. The amplified filtered signal is sent to speakers, intended to effectively reproduce the specific frequencies.
Lower frequencies require more amplifier power and larger speakers to reproduce. As frequencies range from low to high, power and speaker sizes are reduced proportionately. It is not uncommon to find four- and five-way transmission systems in place at large concerts, with separate amplifiers and speakers for each frequency. Smaller arenas use simpler two- or three-way transmission speaker systems, as critical reproduction of all frequencies is not necessary or justified.
Subwoofer or subwoofer speakers are usually 18 inches in diameter. Since very low frequencies are more often felt than heard, lower cabin cabinets are placed on the floor for maximum power and the speakers are often mounted to the back of the speaker cabinet, which is set to produce improved sub-bass tones. Smaller concerts can use one or two sub-bass housings, while the large concert hall will use 12 or more. Low frequencies are not very accurate, which makes speaker placement in relation to the audience not as critical. Subwoofer frequencies are generated by bass guitars, bass drums and keyboard notes with lower level synthesis.
Speakers used to reproduce bass frequencies are normally 15 inches in diameter and are ideally placed at the chest level audience. The bass frequencies are heard in the sound range, but are physically lower than high frequency speakers in an attempt to distinguish the sound in the most efficient and comfortable way for the listener. Bass speaker frequencies are also generated by bass guitars, drums, lower frequency synchronizers and other keyboard brands, but in a higher frequency range than subwoofer.
Midrange concert speakers are usually 12 or 10 inches in diameter and reproduce sound in the middle of the frequency spectrum. The speakers are located above subwoofers and under high frequency drivers. Midrange frequencies are produced by vocals, guitars, keyboards, drums and other instruments. The dominant sound we hear is in the middle, because these frequencies are audible and easy to understand.
High frequency horn
High-frequency reproduction requires small speakers with tight diaphragms to limit bass-inducing air movement. Because these speakers, called drivers, use diaphragms with a diameter of 1 to 2 inches, they will not handle high-watt amplifiers. Their inherent design also means that the sound levels are low and must use an appendix called ‘horn’ for the project sound to be heard at audible concert levels. Horns produce high-medium and high-frequency sound and are usually aimed at the main level of the audience. Cymbals, guitars, keyboards, vocals and other instruments produce sound in the high frequency domain.
Concert speaker cabinets
Most of the cabinets used in large concert halls are full-scale cabinets that contain bass speakers, mid-range speakers and high-frequency horns. These cabinets are usually suspended by wire rigging, at different angles and placement arrays. Separate bass and sub-bass shelves are placed on the floor, and other full-range cabinets can be placed on the stage, depending on the location setting and performance type.
The monitor speakers are placed in front, and sometimes to the side, by artists so that they can hear themselves and other band members. The screens are connected to separate mixers and amplifiers and allow custom sound mixes for each artist. Monitors are usually two-way systems, which include a 12- or 15-inch speaker and high-frequency horn. Speakers used in live concerts come in different types and sizes. While there is no real universal standard speaker, there are standard configurations, selected for the type of music and concert venue. The main function of concert speakers, also called drivers or speakers, is to let the audience enjoy high quality sound wherever they are located in the arena. Practitioners must also hear themselves and other band members and demand that the monitoring speakers be positioned correctly.