Bass combo

A bass amplifier or "bass amp" is a musical instrument electronic device that uses electrical power to make lower-pitched instruments such as the bass guitar or double bass loud enough to be heard by the performers and audience. Bass amps typically consist of a preamplifier, tone controls, a power amplifier and one or more loudspeakers ("drivers") in a wooden cabinet. While bass amps share many features with the guitar amplifiers used for electric guitar, such as providing an amplifier with tone and volume controls and a carrying handle, they are distinct from other types of amplification systems, due to the particular challenges associated with low-frequency sound reproduction. This distinction affects the design of the loudspeakers, the size and design of the speaker cabinet and the design of the preamplifier and amplifier. Speaker cabinets for bass amps usually incorporate larger loudspeakers (e.g., 15" speakers are more common for bass than for electric guitar amps) or more speakers and larger cabinet sizes than those used for the amplification of other instruments. The loudspeakers themselves must also be sturdier to handle the higher power levels and they must be capable of reproducing very low pitches at high sound pressure levels.

Bass amp speaker cabinets are typically more rigidly constructed, with thicker wood and more heavy bracing than those for non-bass amplification. They usually include tuned bass reflex ports or vents cut into the cabinet, for increased efficiency at low frequencies and improved bass sound. Preamplifier sections have equalization controls that are designed for the deeper frequency range of bass instruments, which extend down to 41 Hz or below. Bass amplifiers are more likely to be designed with heat sinks and/or cooling fans than regular guitar amplifiers, due to the high power demands of bass amplification. They are also more commonly equipped with audio compression or limiter circuitry to prevent overloading the power amplifier and to protect the speakers from damage due to unintended clipping in the power amp.

...
Wikipedia