Maybe your system is not wide-range enough or dynamic enough for you to tell the difference. There definitely is an audible difference. Record companies don't record at 45 rpm just to take up more space on the record (and charge you more on top of that).
Are you comparing versions of the same recording(s) on 33 and then 45??? If so, then you could have reached the limitations of your playback gear... or your ears.
Are you comparing versions of the same recording(s) on 33 and then 45??? If so, then you could have reached the limitations of your playback gear... or your ears.