I tried a few hp before in the past. At some stage I do listen to some music at night etc. After using a decent earphone I do noticed a couple of good audio reproduction hp. I tried Sony, nokia pureview 808 and 1050, iphone, huawei p9 and now a nexus 6P. 

I noticed that 6P's audio quality is rather below average although it has two front facing speakers etc. So I stop listening to music with my device technically. Since then I start to take note of audio quality with earphone on HP. I encourage you all to take note on this too. Huawei p9 was only just average. Sony is really good. Samsung too I heard (never owned one).

Its something good to know.

Go for LG V30 if audio is your number 1 priority. But the software ain't great I heard. Lag and stutter.
HTC also not bad. But you have to use the supplied earphones to take advantage.
There is no perfect phone though.
CD is using 96kHz/24-bit sampling. Better than normal MP3 but not audiophile grade I think.

Yeah, agreed. The HTC U11 with the Boom Sound earphones is hard to beat as far as phone audio + stock accessories is concerned.