I think something at play here is the cabinet. It is only .75 inches thick even on the front baffle. It is NOT the most inert. At db levels of 110 dB they will undoubtably cause all kinds of vibration induced distortion and smearing. That is very, very loud and not something I would ever recommend for mere mortals. Anyway, put Star Sound Apprentice platforms under the DIs and you will hear a very different speaker at both low and very high listening levels. These speakers really need a footer of this quality to sound their best. I highly recommend Star Sound Apprentice platforms. I have no doubt they would have cleaned and sorted out the music much better. Food for thought.
Secondly, as I have said before the DI is a tad, just a tad, forward in the upper mids in stock form. I use Roon DSP and shave 1.75- 2 dB off the upper mids and find that perfect. I find this is needed more the louder the speaker is played. I understand the builder is now putting a resistor in series with the 6.5 inch mid drivers to accomplish the same thing. I find this interesting as I have been doing this since day one.
We don’t know the value of the resistor, but it is most likely 1.8-2.2 ohms. This would shave some 2 dB on an 8ohm speaker.