M and S meters are normally aligned to the 'M6' standard in which M = (L + R) − 6 dB and S = (L − R) − 6 dB. In other words, the sum and difference signals are each attenuated by 6 dB before being displayed on the meter. As a result, signals of identical amplitude and phase in the left and right channels make the M meter show exactly the same deflection as for the individual L and R meters. This is because summing two identical signals produces a result 6 dB louder than either source, but the M and S meters show summed signals attenuated by 6 dB to compensate. The M6 standard means that dual mono sources (e.g. a presenter panned to the centre of a stereo sound stage) can be peaked to 6 in both channels, with the M meter also showing 6.