We therefore do employ rectangular shapes in our subwoofers. The key to designing a good subwoofer is to make sure that the cabinet is very rigid. We use 1 inch MDF covered in 3mm of Teak. The internal structure is braced. Making a speaker two small will reduce the amount of low frequency information it can produce.
Most loudspeakers are low budget, low performance designs.
Constructed of particleboard, plywood, or low-grade hardwoods, resonance problems and instability make these products unsuitable for quality loudspeakers. The cheapest loudspeakers are built from vinyl covered pressed wood. These loudspeaker cabinets will nearly dissolve in water. Usually the back of the speaker is simply painted. I have seen many well-known speakers that cost hundreds of dollars built this way.