Marshall Amplification is a British company that designs and manufactures guitar amplifiers, speaker cabinets, and related accessories. Many Marshall speaker cabinets use a bass-reflex design, which means they have a port or opening in the cabinet that allows air to move in and out, enhancing the low-frequency response of the speakers. Other Marshall speaker cabinets use a sealed design, in which the cabinet is completely sealed and there is no port or opening. Sealed cabinets tend to have a more controlled and precise bass response, but may not produce as much low-end output as a bass-reflex design. It is also common for Marshall speaker cabinets to use a combination of both sealed and bass-reflex designs, known as a bandpass enclosure.