It doesn't if the receiver crossover is set lower than 100hz and the sub is left in bypass since you continue to get output above the receiver crossover point and below 100hz. Setting the processor crossover at 100hz or more, means no rolloff just the brickwall response at the sub. There is no output above the brickwall DSP low pass filter unlike the typical rolloff you see with fourth order filters. You can see the steep clifflike drop in amplitude from the FR graphs.
So running the sub hot and crossing at 100hz or close to it means a steep drop in response at or slightly above 100hz, a discontiuity in overall FR if you will depending on how hot you run the sub above the speaker level. Its less of an issue the lower you cross and not a factor at 80hz receiver crossover having a 24db slope with the sub crossover bypassed. However, it is an issue as you cross closer to the 100hz brickwall because, except for some nominal port resonance, their is no output above 100hz.
Discontinuity in response may be a problem if you are trying to blend small speakers that are rolling off above 100hz because there is no output coming from the sub to fill in above 100hz. A firmware revision which raises the low pass brickwall to 120hz will mean more of the output from the sub above the receiver crossover point. In addition higher crossovers help when blending two way speakers or bookshelf monitors.
