M/S Matrix with Direction Controller and Equalizer for the Treatment of the M/S Signals with Stereo Mastering
The W731 combines a stereo direction controller with base width control, a 3 band M/S equalizer that can be inserted into the M/S-chain of the module with an elliptic EQ. The direction controller regulates the base width and the direction of a stereo signal and can be switched over for M/S operation of the inputs and outputs.
The base width control can be used with a stereo or two mono microphones to produce M/S recordings. The M/S-Equalizer in the M/S path of the module can be used to modify the frequency response in relation to the special effects that are avaiable by the regulation of the M(ono) and S(ide) signals.
The W731 M/S-Equalizer offers outstanding possibilities for the influencing of the spatial image and mono compatibility of a stereo signal. With the base width control the original width of the signal can be reduced or increased, then the stereo basis of the regulated signal can be shifted with the direction fader. The W731 is the ideal device for setting the spatial image of a stereo mix. The M/S-Equalizer can be used to modify the frequency response of the signal separately for the mono and the stereo components of the signal and adjust the base width freqeuncy dependent.
The device is internally balanced and is available with electronically balanced or transformer balanced inputs and outputs. The Headroom of the direction mixer from input to output is +30dBu.
The functional principle
The direction controller can be used with left-right format or M/S format input signals. The output format can also be left/right or M/S. The switches INPUT M/S and OUTPUT M/S select the respective format, and insert or switch off the internal matrix sections. Stereo signals in left/right format are routed the input matrix that converts the signal into M/S format. The input matrix is switched off by the selection on M/S. The M or mid channel transfers a pure mono signal, while the S or side channel contains the spatial information of the stereo signal. With a stereo signal in the M/S format, regulations are possible which are not feasible in normal left/right format. These regulations concern, first of all, the stereo parameters base width and direction.
By the level regulation of the side signal the base width of the stereo signal changes. If the S channel is muted, only a mono signal remains. Attenuatiing the M channel or gain in the S channel increases the base width. Direction control is also possible by regulation of the M channel against the S channel. The effect, which thereby arises, is similar to using a Pan-Pot or balance control. But in the extreme left of right positions a pan-pot or balance control switches off in each case the opposite channel. The direction regulation at the M/S level on the contrary preserve all signal components in all positions of the direction control. In the extreme left and right positions a mono signal appears which corresponds to the addition of both input channels, only the spatial information is lost.
The M/S Equalizer
The equalizer operates at the M/S level of the unit. Therefore the effect of the EQ setting is not only a modification of the frequency respones but a combination of the effects on the frequency response and the resulting changes in the base and direction detection due to the phase shifting of the EQ settings. The low EQ only affects the M chain. If low frequencies are increased, only the mono part of the signal is treatet by the EQ setting. The setting of the mid and high bands however, only affect the S chain. This will result in a modifcation of the base width, that depends on the EQ setting. By increasing the high frequencies only the stereo components will be increased and therefore widen the stereo base in that frequency range. The mono signal is not affected by the settings of the mid and the high EQ.
The elliptic EQ
The elliptic EQ reduces the base width from an adjustable lower edge frequency. This is used to solve mono compatibility problems that are caused by time delay effects and phase displacements in the low frequency range. The side effect of widening the base is increased out of phase components in both stereo channels, therefore, the problem of the mono compatibility increase as the base is widened. Naturally the biggest part of these signal components appears on the basis of the level statistics in the low frequency range. An adjustable, frequency dependent, crosstalk is produced between the stereo channels. The range applies from 31.5 hertz to 3150 hertz for 15 dB crosstalk.
Setting the crosstalk frequency at or below 300Hz cause no audible changes in the width of the stereo signal, with frequencies above 300Hz changes become audible. Which settings are meaningful, one must judge according to hearing by change of the fader position and test of the mono compatibility. The elliptic equalizer is independent of the direction mixer.
The W731 Direction Controller with M/S Equalizer is a standard V700 module and fits into all standard frames.