1.2 Sufficiently Steep Rolloff Slopes between the Filter Outputs
The filter rolloff slopes must be fast enough to prevent driver damage. Even a small amount of LF energy can rapidly wreck a tweeter. The slopes must be steep enough to not excite areas of poor drive unit frequency response, such as resonances outside normal band of usage; this applies only to mid-range drive units and tweeters, as the LF drive unit resonance will always be used. In addition, the linearity of drive units is very often worse outside their intended frequency range, so steeper slopes will give less non-linear distortion, and that has got to be a good thing.