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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  • akdj - Thursday, October 02, 2014 - link

    The 'little SD expansion slot' that reads and writes at about 6-8Mb/second vs, the onboard NAND speed tested within the review should be enough to tell you why samsung and ....hmmm ....are offering the micro SD slot. Android is moving 'away' from accessibility to and from the 'off board' storage. I've got a Note 3 and with each update I've been able to do less and less
    Apparently you didn't bother to read the review ...at all. You also mention 'good LCD ...at least as good as the competitors.'
    Then you quite DisplayMate. The S5. And the single point difference between it and it's LCD runner up. From Apple. If you'd have bothered to have read this review ...or the S5 review on Anand's site when it dropped you'd know A) how impressed the author was with the evolution of AMOLED, it's continued refinement and accuracy, brightness and viewing angles. B) you'd notice in EVERY possible measurement. Each one in the review are 'objective measurements'. It (6) tops the display's characteristics in each area someone that knows what a 'great display' entails. At 400+ PPI, you nor any of your freneds will distinguish the difference between it and the new Note 4 or any other 2540 display. It's silly, it's a waste of energy and its detrimental to fluency of the UI (with today's SoC GPU and that many pixels) and the ever important 'battery life'
    To be fair, NO OTHER vendor offers 128GB, & 64 is extremely rare. I waited six weeks for a Note 3 w/64GB to show up at AT&T. Never happened and I settled for 32. At the same price as the 64GB iPhone 6.
    And from what I've read the 2014 model will have the same. 32GB with a caveat. Buy a micro SD card. Hope Google allows support in the future and keep your fingers crossed. 1080p on my Note chews up space. 4K is quadruple. And it will NOT shoot to the fastest SD or microSD card on the market.
    As an ambidextrous owner and user since their inception, I enjoy both Android and iOS. But silly comments like yours shows your ignorance. It was IN THE review! The actual (& damn near identical testing method used by DisplayMate's team will use) 'proof' it's 'LCD ....(IS) @ least as good as its competitors.
    Reply
  • Caliko - Tuesday, October 06, 2015 - link

    A good phone runs its own OS.

    You and that moron don't understand HD so your obsession is invalid.
    Reply
  • echtogammut - Tuesday, September 30, 2014 - link

    He isn't wrong about anything he said, but I just can't imagine getting worked up enough to say it. As a current Apple user/developer, I have every Apple product. I like their stuff, but I can't say I am obsessed about it. I also have a lot of the competing products, so I am constantly toying with all of them. When my current iPhone breaks, I will probably replace it with a Sony Xperia Z3 compact, because it looks like a perfect phone for me. I am not interested in a bigger phone and I would like something that is waterproof, because I run or ride a rain, sleet or shine. I personally think Apple is falling behind in the world of business and multi-use devices. I am seeing a lot of customers whom I developed business apps for iOS coming back and wanting to move to Microsoft or Android platforms because the devices are more powerful and offer more robust features. Reply
  • GerryS - Wednesday, October 01, 2014 - link

    I agree. He makes some good points, though most of them are seriously overstated. For most users (yes, nearly everyone in my experience) a "pretty dang good" display is about as good as we can be bothered to look for. I actually like the display on my iPhone 4s. I've never had a complaint, except that it is small, so I got an iPad.

    See, I don't actually like it that Apple went for big phones. I carry my phone in my pants pocket. The 6 might be about the limit of the size phone I want. If I could get an updated 4s with the processor and other basic features of the 6, that's what I'd buy.

    So, for most consumers, we want something that works. I had 4 Android phones before Verizon got the iPhone. I liked them pretty well, but they kept breaking. I went to Apple for dependability, and have not been disappointed. I've only had a couple of problems (even with my jailbreaks), and they've always been easy to fix.

    I do like it when Apple leads the way, but it would be silly to expect them to have all of the advances. So many people compare the iPhones to Android phones, listing all of the things that came out first or "better" on Android phones. They seem to forget that there are dozens of companies making Android phones. The best of them have only one or tow innovations at a time - about the same as Apple manages. Apple continues to be one of the leaders, as long as you compare them to one company at a time.

    If you want the universe of advances coming from Android manufacturers, then go buy an Android. We really won't hold it against you. For me, I like my iPhone and iPad. My wife has Android (at my recommendation) because we could get some features that were important to her.
    Reply
  • Actius - Wednesday, October 01, 2014 - link

    Lol, he is wrong about his engine analogy! Seriously, none of that makes any sense. Haha, and what's a "V8 compressor"? My goodness...people shouldn't talk about things they really don't know. Just reading that was cringe worthy. Reply
  • sigmatau - Thursday, October 02, 2014 - link

    I'm going to guess you are not so dense as to be picking at the spelling but instead don't know what is a v8 Kompressor. Not only one of the best engines that Mercedes made, but also award winning by 3rd parties. Reply
  • techconc - Thursday, October 02, 2014 - link

    Actually, he is either wrong or extremely misguided in almost everything he's said. Feel free to pick your argument of choice. He starts off by saying how the iPhone 6 launch was disastrous. As compared to what? What other vendor will sell 10 million devices on a launch weekend? Even for Apple, it broke their own previous records. I'm genuinely grateful for people that prove they're an idiot right up front. It lets me know I can either skip the rest of the post or read on for purely amusement purposes.
    That's just the conceptual part of the post. His technical observations were equally misguided. Especially with regard to screen quality, etc. Clearly he didn't bother reading the Anandtech review he's commenting on.
    Reply
  • shm224 - Thursday, October 02, 2014 - link

    @techconc: Sure, what other products you know starts to bend, or totally crap out after the first buggy update, or even have features withdrawn due to more bugs all within the first week of release? Reply
  • akdj - Friday, October 03, 2014 - link

    Really? You're still convinced the iPhone (6 OR 6+) actually and easily 'bends' in the first week? Buggy update? The one available for about two hours that few downloaded and within ten hours of pulling it a fixed update was released? Features withdrawn? I'm intrigued ..as an owner and realist like techconc, the person you responded to... I've GOT to know!
    I'm patiently awaiting my pair of 6+s for my wife and I. We just returned from the mall and the Apple Store specifically playing for almost two hours with them. I built a two minute movie and. Rendered in 1080p in about 35/40 seconds, air dropped to myself. Un. Believable phone. It's. Amazing
    We ordered launch day through our business representative. Lol. Silly me. Ship date estimate is pretty specific, actually a bit ambiguous with the latest update. 11/2-11/28/14:-)
    Oh well. Plenty of time to allow developers to continue updating their apps.
    Between my Air, rMBP 15" and the iPhone 5s /6+, my business of 27 years has been revolutionized. Literally, over the past half decade, as a pilot and sound/video producer...weight savings alone are enough to double our profits. And ½ our setup snd break down times. Even my 'flight bag' of nearly fifty pounds isn't necessary. With three retina minis in the cockpit for redundancy, the 'paper' is still there, but unnecessary any more for updates to plates and Jep charts, winds aloft and weather/traffic ...even diversion airports, filing my flight plan and telling me how thirsty she is! Fuel calculated, with a GPS dongle a tenth the price and 100 fold quicker to lock n track than avionics just a half decade ago provide incredible accuracy. ADSB and TCAS (3D terrain, weather and other traffic/with their specific info; altitude, speed, heading, and Xspnder --- TCAS, a warning system that 'tells you what to do' in conjunction with other planes fitted with the system including all commercial traffic and many GA pilots with ILS certifications ...Alaska can get nasty quick and having to 'duck down' these two systems alone are incredible and 'reasonably priced' advancements!).
    I'm not sure there's a place in my life iOS has t changed. As a father, business owner and operator, little league and wrestling coach, and pilot...each iteration has improved signficantly enough in 'most situations' to justify yearly updates for me. iPhones hold their value. Until the 4s, AT&T was generous and 'allowed' a 12 month subsidized update. With the business I also provide 17 full time employee iPhones so we've been lucky enough to 'recoup' some of the money spent each update
    I just sold an employee's iPhone 5, 32GB AT&T with a cracked screen, scratched to hell and working perfectly. With excellent battery health and perfect camera lens (only scratch-less area of the phone!) for $235 to a local repair guy. He saw me in the mall with the Gazelle box (more than a hundred bucks less) on my way to the USPS. Asked what I was sending. Told him. Showed him a 'picture' or seven before I unboxed it, but he was adamant ...he was able to shine it up with his pieces n parts for $45 or less! Told me it would cost a customer about $210 to do the work but parts were 20% the cost ...labor and time is the price. From there he was confident he could sell it for $325-350 at his kiosk within 24 hours.
    My son has had his fifth generation iPod touch for two years. He's nine. No scratches. No scuffs. Clean a booger or twelve off once a week but other than that, it's completely 'perfect'. These iPhones are built damn near the same. Sleek, thin and well balanced ...no bugs, incredibly quick and unless you're a dumbass and put your $800 pocket computer in your rear pocket of your jeans and SIT on it, you're an idiot ...and you've got to be SIGNIFICANTLY overweight AND hit the precise angle in order to 'mash' 100 pounds of pressure to a 'single point'/torque.
    Can you bend em? Yep. It's been proven and EVERY piece of proof we've seen visually demonstrates the incredible amount of force necessary and in such a way not indicative of daily use or situations a consumer would find themselves in 99.9% of the time.
    Don't. Be. Silly. I respond not only to you but to all those talking like you. Until you've used one. Felt one. Actually spent time with it, it's difficult to understand.
    These are absolute and unequivably the BEST two phones on the maket at this time. With the best and most abundant apps/software optimized to its specs. Support to back it up. And resale value when Ya get bored and ready for a new one. You'll recover your 'down payment' plus fifty percent in many cases ...if you take care of it. Seemingly, they're even more valuable than a same year flagship Samsung Note 2, as I wasn't able to get more than $125 for that joke. Note 3 got it right. But it took twice the cores, clocked at twice the speed with three times the memory ( ⅔ to ¾ of which is in use even without an app running! I've got one though and don't take me wrong, I love it) to get 'close' to the GUI fluency of the iPhone & iOS
    That's. SAD. That's. Buggy. I'd much rather have a phone that bends with a hundred pounds of torque in a certain and specific area than I would gambling I'll get an update, deal with carriers and OEM bloat and shitty aesthetics and design. Lack of support or resale, lack of apps and software ...& the apps and software in parity are incredibly more enjoyable and stable on iOS. I like my Note for browsing and the SPen. I think an active digitizer would put the six plus over the top but as it is, it's perfect.
    Indeed, I'll continue using (& owning) my N3. But I'm not the least bit compelled with the '4' and its 2540 display. While I'm sure there's noticeable and 'obvious' benefits to having 550/600+ PPI ...I'll warn ya when you're 38-42, speaking from experience...you'll need 'cheaters';) ...like our ears, our eyes deteriorate as well ...the elasticity of our lens and ability to change and 'maintain' up close focus just ...goes away! Hence the incredible benefits I've found witg the HiDPI display technology. 3D? Good riddance! It was a joy to see 4k/Ultra HD and even examples of 5/6 & 8K motion display AND capture gear instead of dumbass glasses and crappy off center viewing with limited content.

    Apple lead the way and destroyed multi billion dollar monsters in the industry with the iPhone. They then changed consumer display technology's availability. HiDPI and increased resolution is awesome. But to a certain point. Your 1080p 65" LED LCD IPS or AMOLED TV in the living room at 10-12 feet or typical viewing distances is around 100ppi. Quadrupling the resolution (4k) while not exactly linear, will amount to approximately an increase of 100%. To 200ppi. Not four foukd as you may think.
    The 'new' ipad(3)/4 -- iPhone 4 -- the rMBPs --- ALL Game Changing home runs. Putting a certain 'joy' back into 'work' again. With SUCH an accurate palate and the ability of OS X'es scaling of the UI (& third party apps the same ...utilizing pixel for pixel when necessary or quadrupling for the GUI simultaneously and without 'glitches' or latency is a marvel in engineering. Coupled with the IrisPro 5200/750m and PCIe SSD at a TB with read and write speeds exceeding a Gb/s, Thunderbolt 2 and its 'one' cable capabilities and abilities to run multiple 4K displays ...shoot man. Seems like yesterday I was hunting the wax pencils and cutting my fingers slicing tape ...now it's immediate and fast as hell in a four pound package at a dozen times the resolution.

    Times are good if you're an Apple user. And thats JUST the hardware!

    OS X and iOS's march to marriage is incredible. Continuity and Handoff. Air drop between iOS and OS X, as well ...the aggregation and integration between the devices you're using is revolutionary. Period. Only Windows has the power and support vertically and horizontally to compete with what Apple's doing. Vertical & Horizontal backbones.

    No one that needs to 'work' is buying a Chromebook

    J
    Reply
  • elajt_1 - Friday, October 03, 2014 - link

    This must've been the longest and weirdest Iphone ad I've ever read. ;-) Reply

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