How does an IB compare to a sealed or ported sub?
Sealed and ported subs are enclosed systems where the enclosure and rear-wave coming off the cone impacts it’s operation. In the case of a ported alignment; the rear-wave coming off the cone interacts with the air-mass inside the enclosure to create a Helmholtz resonator (like blowing over the top of a bottle). The vibrating mass of air colors the sound. In the case of smaller sealed box systems; the box interaction of the rear-wave and the compressing air-mass inside the box changes the ‘Q’ of the system. This too colors the sound. In poorly designed or inadequately built ported or sealed box subs, the walls of the enclosure itself can be excited by the rear-wave coming off the driver. If the walls of the box are vibrating there’s a detrimental effect on the sound quality. With an IB sub there is no Helmholtz radiator effect, no compression of the air-mass and in most cases no box walls to negatively impact the output of the driver.
