The problem at 50dB is not the speaker but the human ear. The sensitivity of the ear varies with volume and treble and especially bass are way down relative to mids at low level. Flat response comes around 100 dB(too damn loud) and at low levels bass can be over 20 dB down relative to mids. The only solution is equalization.
But my question is why would you listen to a high quality system at such low levels? It's a waste of money and of a hi fi system.

