I can't explain this in any scientific way, I just think the frequencies between 200 and maybe 2000 Hz seem to be very important for piano waveforms to be fully transmitted. And if you look at how the speakers are designed, it isn't surprising that two db K300 speakers deliver more mid frequencies than a system like the Nano 300 or Bose Compact. The K300 have two 6.5 inch speakers each, whereas the Nano 300 has a subwoofer for very low frequencies and two 3.5 inch speakers with an emphasis on high frequencies. So I guess the K300 put more emphasis on the mid range.