ABSTRACT
Investigations that have been done tend to be conducted under very controlled circumstances, most involving computer simulations of both the problems and the solutions. Those investigations were in the frequency range above the transition frequency, where reflected sounds were an important factor. Audible differences appear to be near or below the threshold of detection, even when experienced listeners are exposed to isolated low-frequency sounds. Bass sounds is stripped from all channels in which the loudspeakers have been identified as "small," and is reproduced through those identified as "large," as well, of course, as the subwoofer(s). The design of bass traps came later, and fit the general pattern of acoustical treatment being synonymous with acoustical absorption. Acoustical absorption has been around since the 1930s, when dozens of companies were manufacturing versions of resistive absorbers. Narrow-band, tuned membrane absorbers are a logical solution when only a few modes are problematic, placed so that they address the offending modes.
