Should I use sound deadening, diffusers or fibrefill inside my enclosure?

The debate on whether to use sound deadening material, diffuser panels and fibrefill inside an enclosure has been around for a long time. However, this debate needs to be broken down into two areas because you're actually addressing two separate issues when asking about these materials. The first issue is regarding standing waves and the second is regarding the delaying of sound waves and the smoothing of resonance. Well start with standing wave issue first. Standing waves Standing waves cause violent response fluctuations inside the enclosure but for a standing wave to exist the distance between parallel boundaries (the enclosure walls) must be half the wavelength of the frequency at which the standing wave exists. Considering that sub-bass waves vary from 17.19 meters (@ 20 Hz) to 3.44 meters (@ 100 Hz) the generation of a standing wave is going to be impossible in an enclosure designed to fit in your average sedan or hatchback. People often install sound deadening and diffuser ...  more