Past the 100 hour mark on my Mills MRA-12 resistors and it was time to evaluate the sonic difference. I had to do this in mono, comparing the upgraded speaker to the OEM version. Not ideal but the only other choice was to upgrade both speakers and rely on sonic memory. I used Roon DSP to mix the signal into mono. This allowed me to use my “reference” recordings rather than rely on rarely listened-to mono originals (which I also tried). To minimize room effects, I put the speakers close together in the middle of my room, about one foot apart (ie, each speaker had the “same” room interaction). In this position, I simply shifted a couple of feet one way or the other on my couch so that I was directly on-axis. The on-axis energy shifted the balance from what I’m used to (my normal arrangement has the speakers just under 8’ apart with no toe-in) but both speakers were equally handicapped.
Anyhow, I’ve now done two comparative sessions. My impression from both sessions is that the Mills has a fuller, richer sound although my perception of this varied from song to song. I heard little, if any, difference on solo trumpet but a pronounced difference on the well-recorded 2L Mozart violin concerto. Guitars and voices were more "full-bodied" on folk-rock, blues, and bluegrass. More “tonally-rich” might be another way to describe it. On a Chesky test recording, percussions were more emotionally engaging, toe-tapping. The Mills also seems to have a bit more texture or, at least, it was easier to hear into the microdynamics. I think this is related to my initial impression of a "lower noise floor".
All-in-all a worthwhile upgrade - audible benefits and at a reasonable price. I think Tom Thiel’s upgrade path is off to a good start.
