6 Loudspeaker cabinets

6.2 Cabinets

Bass loudspeakers don't work well in free air. They need a cabinet to absorb the sound radiated from the back of the loudspeaker, or else it would cancel out much of the sound radiated from the front. A properly designed cabinet drastically improves the bass response of the loudspeaker driver. Below is a list of common ways to achieve this:

  • Closed: A closed system is a cabinet with nothing more than an enclosed air volume, in which the compliance of the driver and that of the air interact to improve the bass response. Often the cabinet is loosely filled with damping material.
  • Ported: This type is defined by the use of a port, a hole in the cabinet wall; often a tube or rectangular channel, extending into the cab, is attached. This port will make the cabinet resonate at a certain frequency. This frequency is chosen just below the point where the loudspeaker's response starts to roll off, effectively improving the bass response. The far majority of (bass guitar) cabinets apply this principle. It has numerous advantages over a closed system. It is, however, harder to design, and the sound is usually less tight than a closed cabinet.
  • Horn loaded: The driver is coupled to a funnel-like duct, either on the front or the back of the cone, to create a horn. The function of the horn is to better couple the stiff cone with the air in the room and thereby channeling the sound into a beam, increasing the on-axis efficiency of the system enormously, while unfortunately also increasing its size enormously. With today's cheap high power amplifiers and higher efficiency drivers, the need for highly efficient cabinet designs is diminishing rapidly.
  • Transmission line: The driver is coupled to a slightly narrowing duct, making the system act as a resonator, much like the ported cabinet.
  • Band pass: Completely enclosing the driver into a 2-chambered cabinet, with each side working on one chamber, this system provides a narrow frequency band 2.7.3 Frequency to be reproduced by 1 or more ports in one or both chambers.
  • Di-pole: The driver is mounted in a cabinet, but the back of the cabinet is left open for the better part. This type of cabinet needs to be electronically corrected, requiring substantial power and drivers with large Xmax 6.11 Distortion figures.

© Joris van den Heuvel 2001-2009