 This is corrected by (1) mounting the midwoofers as close to the tweeters as possible (so that the listening distance is much larger than the distance between the drivers) and (2) operating the midwoofers and tweeter in quadrature, i.e., achieved by ensuring that the tweeter lags the midwoofer by 90° in phase at the crossover frequency, and this in turn can be achieved if the crossover has a 3rd order Butterworth characteristic.To achieve the smallest distance between the mids and tweeters requires the drivers to have the smallest possible size - but there are design limitations to this (lowest mid-range frequency, for example, will place a lower limit to the mid's diameter).Another problem with the MTM configuration is the interaction between the two midwoofers.