Cabinet speakers use the combination of the speaker itself and the cabinet enclosure to produce an efficient means of sound reproduction. Depending on the requirement the cabinet can be "tuned" to enhance or diminish specific frequencies based on its construction and base materials.
Cabinets designed to promote low frequencies can be tuned by the addition of bass "ports" which are chambers within the speaker enclosure. The shape of the speaker enclosure can also have a bearing on sound dispersal and how far the sound reaches within the auditorium.
Modern systems favour trapezoidal enclosures as they have a very efficient throughput and can be clustered together. Many have internal struts and eye-bolts built-in to reinforce the cabinet for "Flying" clusters which are groups of speaker cabinets that are suspended on towers or hung from the ceiling of auditoriums.