The iPhone 6 Review
by Joshua Ho, Brandon Chester, Chris Heinonen & Ryan Smith on September 30, 2014 8:01 AM EST- Posted in
- Smartphones
- Apple
- Mobile
- iPhone 6
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.
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Drasca - Wednesday, October 1, 2014 - link
Less workload = longer charge.Since we don't know the actual workload your teenagers are inconclusive. Given literal different Apple to Win Phone app economy systems, the usage model is further blurred. For all we know, your teenagers could be using the iphone more / intensively, but no conclusion can be drawn.
Personally, I think all your family should be spending less time on the phone, but that's me.
cknobman - Thursday, October 2, 2014 - link
No doubt they should be on the phone less and I try my damnedest to get them off.My wife is the problem and unfortunately that is a battle I wont win. Since I dont wont a divorce I have to make concessions somewhere.
If it were up to me my kids would not even have smartphones. Right the farthest I can go is to take them away when they are making poor grades and/or get in trouble.
Parhel - Wednesday, October 1, 2014 - link
I couldn't exactly tell from your comment if you have the 5 or the 5s. If you have the 5, though, check if your phone is part of the battery recall. Mine was, and after the replacement, the difference was night and day.cupholder - Wednesday, October 1, 2014 - link
I have a Note 3 that would last between 10 and 48 hours on a single charge. Yes, android is that annoyingly variable in that regard. The higher numbers tended to occur once I got AutoStarts and Greenify(rooted).With the iPhone 6+, I'm getting 36+ hours. I haven't done a full rundown outside of the first day, but I was actively trying to kill it to properly calibrate the battery for the first use. It was at 36 hours of use with 14 hours of "Usage" time. No idea how much of that was screen time. With the Note, I never got more than 6-7 hours of screen time.
Note during a day of work: Come home ~30-40%.
iPhone 6+ during a day of work: Come home ~70-85%.
This includes an hour break of constant screen on time and YouTube/Crunchyroll/Netflix viewing during that hour.
So, no, the battery life on this phone IS awesome.
dmacfour - Wednesday, October 1, 2014 - link
Why do you think the performance of the previous generation is indicative of the performance of the 6+?Stimpak_Addict - Thursday, October 2, 2014 - link
I got an iPhone 6, and I can attest that the display is very impressive.One thing that does bother me is the scaled apps that have not been optimized for iPhone 6's larger display. Mainly the fact that it makes the size of the keyboard inconsistent with apps that have been optimized for the larger screen. Of course, this will be fixed in time as developers update their apps.
beggerking@yahoo.com - Thursday, October 2, 2014 - link
i don't know why you would attest a 720p screen as being "impressive"...imo iphone 6+ screen is much better.
ufarooq - Thursday, October 2, 2014 - link
Hey guys...how did you estimated SPECINT2000 score? Did you run these workloads?Ryan Smith - Thursday, October 2, 2014 - link
Yes. We have built a version of SPECint2000 to run on iOS. These are estimated scores because SPEC CPU2000 is retired, which means further scores cannot be submitted as official.SunnyNW - Thursday, October 2, 2014 - link
Interesting Apple has been able to consistently deliver a die shrink (whether half-node or full-node) each year and if Samsung delivers like promised I guess can continue that next year with the A9 but I wonder if that will be the end of the year over year improvement...