The W730 combines a stereo direction mixer with an elliptic equalizer. The direction mixer regulates the base width and the direction of a stereo signal and can be switched for MS operation. In this mode the device can be used with a stereo or two mono microphones to produce MS recordings.
The elliptic EQ is used to reduce the base width at low frequencies and improve the mono compatibility.
The W730 direction mixer offers outstanding possibilities for the influencing of the spatial image and mono compatibility of a stereo signal. With the base width regulation 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 W730 direction mixer is the ideal device for setting the spatial image of a stereo mix, and the elliptic EQ can be used to maintain mono compatibility.
The direction mixer has a totally symmetric, ground-free circuit and is equipped with high-quality output transformers. The Headroom of the direction mixer from input to output is +30dBu.
The functional Principle
Stereo signals are routed into the direction mixer 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 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 base 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 theside/width information is lost.
The elliptic Equalizer
The elliptic equalizer reduces the base width from an adjustable lower border 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 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 elliptic equalizer is independent of the direction mixer.
The W730 direction mixer is a standard V700 module and fits into all standard frames.
