The W731 combines a stereo direction mixer with Base Width Control ,an 3 band MS- equalizer that can be inserted into the MS-chain of the module. The direction mixer regulates the base width and the direction of a stereo signal and can be switched over for MS operation of the inputs and outputs.
In this mode the Base Width Control can be used with a stereo or two mono microphones to produce MS recordings. The MS-Equalizer in the MS 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 MS-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 MS-Equalizer is the ideal device for setting the spatial image of a stereo mix. The MS-Equalizer can be used to modify the frequency response of the signal separately for the mono and the stereo components of the signal.
The MS-Equalizer device has a totally symmetric, ground-free circuit and is equipped with highquality +30dBu.
The functional principle
Stereo signals are routed into the unit by an L-R format matrix and then encoded into MS format. The input matrix is switched off by the selection on M-S. While in the normal stereo mode, both channels are transferred to left and right outputs separated, in MS mode The M-or middle channel transfers a pure mono signal, while the S-or side channel contains the directional information of the stereo signal.
With a stereo signal in the MS format, regulations are possible which are not feasible in normal left/right format. These regulations concern, first of all, the stereo parameters base width control and direction. By the level regulation of the side signal the basis width of the stereo signal changes. If one interrupts the S signal, only a mono signal is left. If one strengthens the side signal so the basis width grows, a direction regulation is also possible in which one regulates the side signal against the middle signal. 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 switch off in each case the opposite channel. The direction regulation at the MS level on the contrary gets all signal interests of the input signal. In the extreme left and Right positions a mono signal appears which corresponds to the addition of both input channels, only the side/width information is lost.
The MS-equalizer
The equalizer operates at the MS 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. The mono signal is not affected by the settings of the mid and the high eq.
The elliptic equalizer
The elliptic equalizer reduces the base width below an adjustable lower limit 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 30 hertz to 1000 hertz for 15 dB crosstalk.
Setting the crosstalk frequency at or below 300Hz cause no detectable 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 W731 MS-Equalizer is a standard V700 module and fits into all standard frames.
