I've been running active (3 way) speakers for years. After running different crossover slopes and points on different drivers and different speakers over time, I've come to a couple of conclusions:
1. Phase is audible. Steep crossovers like LR48, Butterworth 48, LR24, and Butterworth 24 all have messed up phase which eventually ends up bothering me. Shallow slopes like Butterworth 6 or Butterworth 12 just sound better.
2. Steep slopes sound cleaner. Face it, if you cross a driver at 2khz, you don't want 3khz resonances poking through into audibility. Steep slopes cut off out of band crap very effectively.
Hi Tyson,
Sorry I missed this earlier. Way to go with the measurements

.
However, I must urge caution. When conducting experiments, it is important to account for
all the variables and confounders, lest one arrive at erroneous conclusions. You are indeed changing phase. But that is not the only variable changing, so when your conclusion of audibility (in a stereophonic reverberant environment) conflicts with established thresholds, it is prudent to examine other possibilities...such as polar response. What is happening
off axis when you vary the slopes? In a reverberant space, this has an impact on the perceived sound. The greater overlap of the drivers might be filling in holes off axis, etc.
There is also the issue of driver non-linearities vs excursion. That is changing as well and may or may not be audibly benign due to masking.
This is my abbreviated lunchtime answer. If you care for a more detailed explanation, drop by Rm 2012 when you make your 2nd floor rounds at RMAF.

cheers,
AJ