Audio Quality

The iPhone 6 is the first non-Android phone to be put onto the Audio Precision APx582 for audio testing. The exact same test tones are used as with Android devices, but they are played back through iTunes at maximum volume. We use the same four static loads as we did with the HTC M8 and Samsung Galaxy S5 for the results you see in the table below.

  15 Ohm 33 Ohm 150 Ohm 330 Ohm
Dynamic Range 84.155 dB 92.281 dB 92.223 dB 92.160 dB
THD+N 5.873% 0.0054% 0.0032% 0.0032%
Crosstalk (L) -49.608 dB -56.239 dB -71.721 dB -77.966 dB
Crosstalk (R) -49.831 dB -56.459 dB -72.191 dB -77.983 dB
Output Power 44.04 mW 26.39 mW 6.614 mW 3.072 mW
Output Voltage 812.7 mVrms 933 mVrms 997 mVrms 1,007 mVrms
Relative Level (20Hz - 20kHz) ±0.088 dB ±0.088 dB ±0.089 dB ±0.088 dB
The first thing to notice is the 15 Ohm load test. At maximum volume, with a -0dBFS signal the amplifier section in the iPhone 6 enters clipping. You can reduce the volume to avoid this, but it does not do as well with really hard loads as the M8 does. You can see the 1kHz sine wave for that below, with the amp clearly clipping at the bottom.
iPhone 6 997 Hz Sine Wave 0dBFS, 15 Ohm Load
For most testing I focus on the 33 Ohm load, as most in-ear headphones have a rated impedance around 32 Ohms. A data comparison to the HTC M8 and the Galaxy S5 is in the chart with the S5 as the clear loser.
  HTC M8 iPhone 6 Galaxy S5
Dynamic Range 92.074 dB 92.281 dB 91.921 dB
THD+N 0.0152% 0.0054% 0.0505%
Crosstalk (L) -64.780 dB -56.239 dB -44.767 dB
Crosstalk (R) -64.329 dB -56.459 dB -44.804 dB
Output Power 47.63 mW 26.39 mW 10.63 mW
Output Voltage 1.254 Vrms 933 mVrms 592.4 mVrms
Relative Level (20Hz - 20kHz) ±0.664 dB ±0.088 dB ±0.081 dB
Compared to the M8 the iPhone 6 isn’t quite as powerful, but it has lower THD+N and a much better relative level. The relative level isn’t a big deal, as a variation of 0.5dB is unlikely to be heard by most. That the THD+N is 1/3rd the value of that on the HTC M8 is more important, as the FFT below shows a very low noise floor on the iPhone 6 when compared to the one in for the M8.
iPhone 6 997Hz 0dBFS Sine Wave FFT
HTC M8 997Hz 0dBFS Sine Wave FFT
The crosstalk is also lower on the HTC, which is an area the iPhone 6 could certainly improve in. Digging into more depth on the THD+N results provides a bit more context. The HTC M8 has THD+N levels that start at 0.03% but after 2kHz it begins a steady rise up to 0.1% at 10kHz and past 0.2% at 20kHz. In contrast, the iPhone 6 THD+N is 0.03% until 500Hz, rises up to 0.06% at 5kHz, then back down to 0.03% at 9kHz, and peaks at 0.1% by 20kHz. The iPhone 6 will have slightly more midrange distortion but less treble distortion.
 
iPhone 6 THD+N Ratio Frequency Sweep
HTC M8 THD+N Ratio Frequency Sweep
If we leave noise out of it and look only at distortion then the iPhone 6 does even better. It has a distortion level of -95dB out to 10kHz and then it rises up to -82dB at 20kHz. The HTC M8 begins at -77dB for 20Hz, falls to -95dB until 2kHz, and then rises up to -56dB by 20kHz. The bass and midrange distortion is about equal, but the HTC M8 has far more distortion in the treble.
 
iPhone 6 Distortion (Noise) Frequency Sweep
HTC M8 Distortion (Noise) Frequency Sweep
Is one phone superior to the other? With the iPhone 6 and M8, I don’t believe so. The M8 is more powerful with lower crosstalk while the iPhone 6 has less distortion and better frequency response. Most notably the iPhone 6 has no results that indicate odd behavior, which we have seen with the Galaxy S5 and other phones. It is a well engineered headphone amplifier provided you do not need to listen to something at maximum volume with a 15 Ohm load.
 
Can Apple improve this? They could improve crosstalk, though some headphone companies like more crosstalk to help create an image more like a pair of stereo speakers than headphones. They could also support 24-bit audio which can improve on the SNR values here. The test tones are only 16-bit in nature, so the SNR maximum value is around -98dB. The HTC M8 may perform better given 24-bit test tones but would need a retest to verify this. Apple seems to have decided on using Lightning with an external DAC to push beyond 16-bit audio so we will have to wait for devices using that to see.
 
Audio hardware on phones can still improve a lot to get closer to where the best stand-alone products are. Those are capable of Signal-to-Noise ratios of -120dB or greater, and crosstalk of -110dB or more. How much those would be audible with headphones is uncertain, but when used as a source device with a stereo it may be audible. However, unless high-resolution audio downloads, like Pono or HD Tracks, really start to catch on I don’t see this being a main focus for most of the companies out there. The iPhone 6 is more likely what we will see going forward: good audio quality, but most importantly free of any major issues.
Video Quality Software
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  • Gondalf - Tuesday, September 30, 2014 - link

    To be fair, a >$600 phone deserves a good LCD.....at least good as competitors, more ram and a little SD expansion slot. Plain and simple. This is not a matter of "idiocy" Reply
  • Samus - Tuesday, September 30, 2014 - link

    Too many people define "good LCD" as having high resolution. In the real world, that just isn't true. There are so many terrible 1920x1080 panels on the market, and I'm not just talking mobile devices.

    Look at desktop LCD's. To get one properly calibrated you need to spend $500+ for a 24" HP Dreamcolor or NEC Multisync PA Spectraview. Some Dell's with Samsung LCD's are pretty good out of the box but almost nothing is 100% RGB until expensive calibration.

    So back to Apple. They're all about balance. They don't push the envelope in any direction like Samsung (and others.) What bothers me lately about Apple is they are "too" safe with their design language and technology that their products are actually becoming boring. As the company that pioneered mainstream unibody mobile devices and multitouch\gesture driven interfaces, it's interesting the competition has essentially been perfecting it for them to just copy back.

    At least Apple isn't suing everybody anymore...seems like Steve's thermonuclear crusade is finally dying along with him.
    Reply
  • Omega215D - Tuesday, September 30, 2014 - link

    I do have a problem with people constantly trying to push AMOLED as the ultimate display tech due it being featured on DisplayMate with the Galaxy S5. People forget that you lose the efficiency of OLED once you start using something that displays a lot of white like web browsing. Also, turning down the brightness still has the tendency to give it a "soggy" look to it, though it is much less on the Galaxy S5.

    The burn in effect can be easily avoided unless the clock/ dock locks up for whatever reason and leaves the display static.
    Reply
  • darkich - Tuesday, September 30, 2014 - link

    The burn in can be easily prevented also.
    Download an utterly simple burn in tool app, and leave it working for couple of hours, every few weeks or so.
    Reply
  • nevertell - Wednesday, October 01, 2014 - link

    This is exactly the kind of thing that people DO NOT WANT TO DO.
    It's a phone, it must just work, I shouldn't worry about any specific technical part of the phone, let alone do maintenance work on it to keep it functional.
    Reply
  • elajt_1 - Friday, October 03, 2014 - link

    Nah, thats for bad image retention. If you already got a burn-in you can't do anything about that as of now. Reply
  • Toss3 - Wednesday, October 08, 2014 - link

    In my experience AMOLED displays look a lot better than their LCD counterparts with the brightness turned down. They also give you the option of having even lower screen brightness which is ideal if you want to use it in bed at night (night mode on android looks great on the S4, but not so much on my Nexus 5). Reply
  • hoelee - Thursday, December 04, 2014 - link

    IPhone white balance not accurate, how you proven your point said iPhone had good display? At least I saw on mine eye compare between mine z3 with the so call iPhone... Besides, you calculate by yourself, iPhone 6 latest phone less 1x pixels to push compare to android FHD screen. Benchmark alway unfair in mine point of view... Reply
  • braveit - Friday, December 12, 2014 - link

    Apple hasn't really done much on it's new iPhone 6 release. Source: http://berichinfo.com/reasons-iphone-6-sucks/ Reply
  • Caliko - Tuesday, October 06, 2015 - link

    Who else is innovating in design?

    All phones today are iKnockoffs.

    Steve's thermonuclear attack has juat started buddy!! Droid is making manufacture lose billions. Can't wait to see who goes bankrupt first!!
    Reply

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