REL S/510 subwoofer initial impressions

Hi there,

Purchased a single REL S/510 subwoofer, installed 3 days ago but with only ~ 15 hours burn-in time. First impression, at this stage, is more clarity in the highs & mids and a slightly “weightier” sound (Tool - 46&2). 
Have other owners have the same experience? What can I expect with another 50 hours play time at various volume levels?

Using a HL connection to both monoblocks. See photo for REL placement.

Thanks,

Charlie