There is one guy on youtube who posts some very high quality speaker comparisons. The recording quality is very good, the sound level is matched, and you can really hear the difference between speakers. Here is his most recent comparison. He has a bunch of comparisons of various high quality speakers, and some other videos of various speakers.
https://www.youtube.com/watch?v=NWNW2C2ZQQ4
https://www.youtube.com/watch?v=NWNW2C2ZQQ4