 Despite this, the 604 continued to be widely used - mainly because many engineers and producers were so familiar with their sonic signature that they were reluctant to change.In a BBC white paper published in January 1963, the authors explored two-channel stereophony, and remarked that it was at a disadvantage compared with multi-channel stereophony that was already available in cinemas in that "the full intended effects is apparent only to observers located within in a restricted area in front of the loudspeakers".The authors expressed reservations about dispersion and directionality in 2-channel systems, noting that the "face-to-face listening arrangement" was not able to give an acceptable presentation for a centrally-located observer in a domestic setting.