06.04.2016: Just listen to my favorite album The Best Of The Art Of Noise (1992),
2. Title: Yebo (Mbaqanga Mix). This is ideal for testing low-frequency reproduction! Further Answers: 7. Title: Legacy.
This is a synthesizer sound that is not objectively suitable for testing the sound quality of a music player - electronic music sounds good on every device. But I know this album inside and out, and I've heard it quite often on MP3 players (constant-quality coding, dynamic data rate up to 320 kbit / s).
For the objective test of the sound quality I have used musical titles with acoustic instruments and very often heard musicians.
Also the hearing test CD of the audio magazine HiFi was very helpful in the objective test of the acoustics.
The Apple iPhone 6s Plus can show correctly that it has pulled down to the low-frequency range a frequency as with the ruler. Otherwise, the bass would not be so abyssed, undistorted and clear (I can not measure it unfortunately - no test magazine has published measurements).
Only gsmarena.com tests and always publishes the frequency response diagram!
My hearing is confirmed - the 20 to 20,000 Hertz lineal-slit frequency response is better than most other smartphones.
The signal-to-noise ratio is also excellent. Because the latency is extremely low, the iPhone is liked by musicians and DJs.
Bottom line: the best high end music player - but not with the included Apple Earpods!
These have a too weak bass reproduction, but otherwise offer quite linear reproduction (writes the press).
Since I do not think of such gimmicks, I have not even unpacked the Earpods.
My audio test equipment: As headphones I use the Sony MDR-EX90LP on the Bluetooth audio transmitter Samsung Level Link.
This in-ear earphone in studio quality ensures unadulterated playback.
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