MK Sound MPS-5410, MPS-5310 operation manual Wave Acoustics in Rectangular Rooms

One might ask, won’t I perceive a difference in imaging if the sound of one channel originates from two sources (subwoofer and satellite)? The answer is actually no. Bass Management works by taking advan- tage of the ear’s inability to determine the direction of frequencies below approximately 150Hz. Provided there is no audible distortion or sonic artifacts at higher frequencies (port noise etc.), and the sound ema- nating from the subwoofer is limited to below 100Hz, it will be impossible for the listener to identify the location of the subwoofer in the room.

This lack of auditory acuity is based on the fact that the wavelengths of frequencies below 100Hz are much greater in length than the distance between the listener’s ears. However, our ears can easily identify the source of high frequency information as coming from the main speakers. Because the sound of the main speakers is the listener’s primary audio location cue, the listener’s brain believes that the bass is actually emanating from the main speakers and not from a separate subwoofer (even when it is behind the listener).

With a properly designed satellite/subwoofer speaker system using Bass Management the response and overall accuracy of a monitoring system can be greatly improved. These benefits apply to any type of monitoring, whether two channels, 5.1 and beyond.

One additional point that is important to understand is that Bass Management is done as a function of the monitoring system and in no way affects the actual encoding of the mix.

Wave Acoustics in Rectangular Rooms

•From wave equation (stated by Rayleigh in 1869) for sound in rectangular enclosures.

•Calculation of the permissible frequencies corresponding to the modes of the rectangular enclosures:

where p, q, r = 0,1,2,3... C is the speed of sound (1130 feet or 345 meters per second at sea level), L is the length of the room, W is the width, and H is the height.

•Axial modes involve reflections from two surfaces of the room.

•Tangential modes from four surfaces. 1/2 of the energy of axial modes.

•Oblique modes from six surfaces. 1/4 of the energy of axial modes.

•Axial modes have the greatest effect to the room response, and at low frequency.

•But tangential and oblique modes have some effect on the room's sound pressure pattern.

10.THE 4 MAJOR ADVANTAGES OF USING BASS MANAGEMENT OVER FULL RANGE SPEAKERS

Most “Full-range” speakers do not go down to 20 Hz.

Most “full-range” speakers (even those with dual 12" or dual 15" drivers) in reality have a low frequency cutoff in the range of 40 to 50 Hz. This puts them about an octave short of the low frequency response of an M&K Professional subwoofer. Because these speakers are the standard that is used in many studios, many modern stereo recordings have bass information below 40 Hz that the recording engineer never heard. When these recordings are played back on a properly calibrated multichannel audio system, the music sounds bass heavy or even worse has information in the sound track that was never intended to be there, such as truck rumble or other artifacts.

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