The PM8.4.1 features an 8" woofer, 4" midrange and 3/4" tweeter powered by a 60W, 18W and 18W independent amplifier, respectively, for wider frequency range reproduction - a first for a Fostex PM-series monitor. The built-in channel divider provides ideally overlapped frequency crossovers for smoothest connections between the drivers. The midrange and tweeter are positioned symmetrically on the Left and Right to minimize the physical height of the enclosure boxes as well as to minimize the affect of diffraction. The woofer and the midrange are housed in an individual chamber respectively inside the enclosure box to have little interference between the drivers.

Three-step level adjustments are provided for HIGH at +1/0/-1 dB and LOW at +3/0/-3dB. The diaphragm for the woofer and the midrange is highly rigid with moderate internal loss being made of highly elastic Kevlar papered by Fostex's original engineering to reproduce any type of input source. The tweeter diaphragm is UFLC (Urethane Film Laminated Cloth) soft dome type to reproduce any types of high frequencies keeping its own transparency.