Digital pianos can sound disappointing (thin, tinny, nasal, dull) in live settings, even if they sound great in headphones. This is often due to stereo piano samples that have mono-compatibility issues: interference between left and right channels causes distorted timbre due to phase cancellation.
I have an earlier (and even earlier) post with measurements that show this happening on my Yamaha CP50. Those measurements can be hard to interpret. For making comparisons between pianos, I’d prefer one simple measure of how bad these phase issues are. One possibility is a phase correlation meter of the kind sometimes found in DAWs and mixers. This is a quick post to share the results of running my Yamaha DP through such a meter.