I am a music listener, and have never mastered a recording. But, I find this topic interesting. Today there are a plethura of re-masters, but they do not always sound better than the original recording. Case in point, Brothers in Arms by Dire Straits. I have the original CD. The first time I listened to it on Spotify it sounded different, worse, to the point that I thought there was a problem with my audio system. I put the CD in and the magic came back. After looking into it, Spotify was streaming a re-master. I don't know if the person who did the re-mastering had bad equipment, didn't know what he/she was doing, or what. I am curious as to what speakers were used for mixing the original master. The result speaks for itself.