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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grayson_carr - Tuesday, September 30, 2014 - link
I own an iPad and my wife uses an iPhone. I hate lightning connectors. They're expensive, they die or stop being recognized far too frequently, and I can't use them with any of my other electronics so they add more cable clutter to my house and cars. So your statement is false. There are people who own Apple devices and still hate lightning connectors. Also, check out the lightning cable reviews at Apple's website (1300 1 star reviews vs 130 5 star reviews... hmm)... http://store.apple.com/us/product/MD818ZM/A/lightn...blackcrayon - Tuesday, September 30, 2014 - link
How are people killing these lightning cables? I've never had one die, the first one i got from my iPhone 5 is probably still working (can't tell them apart really, but they're all still working).shm224 - Thursday, October 2, 2014 - link
you are the exception, not the norm. the 1.5 star, out of 5, on Apple review clearly demonstrates that @grayson_carr isn't the only one with unhappy with Apple's charge cables.mrochester - Wednesday, October 1, 2014 - link
It sounds like you're being incredibly careless with your cables. Personally I think people who don't look after their things deserve to see them broken. I've never had any Apple or micro-USB cable break. Maybe try looking after you're stuff a bit better?dmacfour - Wednesday, October 1, 2014 - link
A lot of people think it's normal to bend the connector ends of the cable at obscene angles. I've never done thing with any kind of cable, and I've never had a cable fray.akdj - Friday, October 3, 2014 - link
I agree. We've got a dozen ipad fours. We use them in the field. All over Alaska and from extreme to extreme temperature wise. Had the iPhone 5&5s'es for 17 employees and my wife, nine year old son iPod touch fifth gen and not a SINGLE lightning cable since their release two years ago has crapped out. Two dozen at least with backups for vehicles, desks and homes.This is ridiculous. Whoever 'breaks' a Lightining cable does it intentionally. They don't. Just. Break. Good Lord!
michael2k - Tuesday, September 30, 2014 - link
Apple has more cash on hand than the US Treasury:http://www.bizjournals.com/sanjose/news/2014/04/14...
Not sure why you think they needed to compete in the mid and low end three years ago, do you really think they need that much more cash?
Hemlocke - Tuesday, September 30, 2014 - link
Exactly. Every other OEMS competes there, and the only one who is even playing in the same sport as Apple is Samsung, and they have been sent back to the minors over the last year. Competing on the low-end/price is a race to the bottom that nobody wins except Google, much like Microsoft did in the PC business. In the end, Apple proved that model to be inferior, as well.techconc - Thursday, October 2, 2014 - link
Lightning connector is not defective. We all wish USB would have put nearly as much thought into their connectors as Apple has. I can't exactly blame Apple for raising the bar here and showing others how it should be done.It's funny, people see jacka$$ on youtube putting lots of pressure on an iPhone 6 plus and assume it's a real issue. Those that I know with a 6+ don't seem to have any trouble with it in their pockets, etc. Also, why no mention of devices like the HTC One which bends under considerably less pressure? According to consumer reports, it bends under 70 lbs of pressure whereas the iPhone 6+ doesn't start to bend until 90 lbs. of pressure.
supgk - Tuesday, September 30, 2014 - link
Wow.. I sincerely hope it's just Samsung paying you to write that. The thought that anyone would truly believe it is depressing.