Hi, tbh I don't care much about frequency response or accuracy, I only care about the sound: if it's enjoyable to listen to then I'm all for it! Having said that I'm sure that more drivers can be integrated and the 1.5 is not that bad after all, it's just that the single driver approach has a purity to it that it's difficult to replicate (I think Kondo San has said that the combination of SET amplification + single driver speakers brings the most realistic result).
+1 this is what is really important, a beautiful music reproduction that please the audiophile.
I'm using the 47 Labs 4722 in a small room and in full honesty I don't feel I'm missing anything on the low end, it's a spectacular speaker.
There is no much music under 50Hz in most musical works, Zarathustra opening are 60Hz, most of electric bass energy are around 70Hz.