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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RyanBeta - Wednesday, October 1, 2014 - link
A lot was made of the glass in the run up to this launch but I see no comment about it in the article.I am specifically looking to see if it has changed or information on the materials used over the years. When the original iPhone came out it seemed like they kept with the same glass material through 4s.
As someone who does not use a protective cover and treats my phone well it is frustrating to see the copious amount of minor scratches that have built up on the glass of my 5s in the past year or so. It has probably a hundred or so minor scratches vs the 5 or so scratches I could see on my 4s when I turned it in after 2 years.
ELPCU - Wednesday, October 1, 2014 - link
u kidding me? Yes, RAM has power cost: TINY power cost.That's the worst excuse EVER.
power consumption of RAM is way less than that of display or GPU.
uhuznaa - Wednesday, October 1, 2014 - link
Yeah, but when the display is off and the GPU in deep sleep (like when you don't actively use the phone), RAM still needs to be powered and this can become a major part of standby power draw then. I would like to see standby power usage actually tested though. My old iPhone 4 drains about 10% battery per 24h in standby, which certainly helps with having some battery left when you actually start using it during the day.zhenya00 - Wednesday, October 1, 2014 - link
Then you haven't done the calculations. If your ram draws even 5mA when idle (probably in the ballpark, but we don't really know - this study from 2010 indicates that the 128MB of mobile ram in the test device used ~1mA, 8x that much certainly uses more https://www.ssrg.nicta.com.au/publications/papers/... then the RAM alone will drain the 1810mAh battery of the iPhone 6 in 15 days. If increasing the RAM to 2GB increases that power consumption just 50% to 7.5mA, you lose 5 days of standby time! If it doubles to 10mA, you lose half your standby life, and now RAM alone will drain the battery in 7.5 days.RAM power consumption is important because it is powered 100% of the time so even tiny increases in power consumption have a large effect on the overall battery life of the device.
ELPCU - Wednesday, October 1, 2014 - link
Before reading review, I already started to read comment and it's soo fun to watch everyone arguing whether apple sucks or rocks.TheSlamma - Wednesday, October 1, 2014 - link
it's not fun, it's patheticmjh483 - Wednesday, October 1, 2014 - link
Solid review from Anandtech as always. Would you please elaborate on why you aren't willing to use iPhone 6 as your everyday phone?Torakaru - Wednesday, October 1, 2014 - link
Hello,I really liked so much your iPhone6 & 6+ reviews, but I found something interesting in your comment nowhere else found and for which I would like to have a deeper knowledge experience sharing from your side. Basically you said:
"The only flaw that the iPhone 6 has is a lack of RAM, and this is only an issue if you also felt it was an issue on the iPhone 5s."
I find it very interesting because I have being reading plenty of reviews of the new iPhone6/6+ and you are the first ones to mention it. I think that you are right, but I have an iPhone4, so I dont know. Could you be so kind to be more precise about that feeling that you have? It is due lack of RAM for multitasking, or also for single tasks?
Thanks a lot in advance guys!!!
Torakaru - Wednesday, October 1, 2014 - link
By the way guys, if any of all of you have the iPhone5/5S or the iPhone6/6+ already and want to share also your experience regarding the possible lack of RAM (noticeable) in your daily use, please comment. Thanks! ;-)dmacfour - Wednesday, October 1, 2014 - link
Switched from a Galaxy, didn't notice a thing.