We spend a lot of time watching and listening to our smartphones and tablets. The younger you are the more likely you are to turn to them for watching a movie or TV show instead of an actual TV. For a lot of us it is our primary source of music with our own content or streaming services. Very rarely when new phones or tablets are announced does a company place any emphasis on the quality of the audio.

Display quality also used to receive very little attention. As more and more people reported on the display performance, more companies started to take notice. Now benefits like “Full sRGB gamut” or “dE < 3” are touted on new products. So now we are going to introduce a new set of testing for smart phones and tablets, audio performance.

To do this right we went to the same company that all the manufacturers go to: Audio Precision. Based out of Beaverton, OR, Audio Precision has been producing the best audio test equipment out there for over 25 years now. From two channel analog roots they now also test multichannel analog, HDMI, Optical, Coaxial, and even Bluetooth. Their products offer resolution that no one else can, which is why you will find them in the test and production rooms of almost any company.

Just recently they introduced a brand new set of audio tests for Android devices. Combined with one of their audio analyzers, it allows us to provide performance measurements beyond what has been possible before. Using an Audio Precision APx582 analyzer we set out to analyze a selection of Android phones to see what performance difference we can find. More phones and tablets will follow as these tests can be run.

The Test Platform

The test platform is the Audio Precision APx series of audio analyzers. For this initial set of tests I used an APx 582 model, which has two analog outputs and 8 channels of analog inputs. The outputs are not necessary as all of the test tones are provided by Audio Precision for playback on the devices. For each set of tests we can add a load, simulated or real, to see how the device handles more demanding headphones. For this article I am sticking with only a set of the updated Apple Earbuds. They are probably the most common headphone out there and easy to acquire to duplicate testing. For future tests the other loads will be AKG K701 headphones and Grado SR60 headphones. Both models are popular, and I happen to own them.

There are a few main tests we are going to use for all these reviews. Those key tests are maximum output level, Total Harmonic Distortion + Noise (THD+N), Frequency Response, Dynamic Range (as defined by AES17), and Crosstalk. These tests are the exact same ones that manufacturers will be running to verify their products. Most of these tests will be run at maximum output levels. Most amplifiers perform best at close to their maximum levels, as the residual noise compared to the signal decreases, and so that is what they are typically tested at.

We might add more tests as we decide they are relevant to our testing. I will also attempt to go back and fill in as much data as possible from previously reviewed devices as time permits. Now to look at the tests and see our results for our initial set of phones.

THD+N
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  • Impulses - Wednesday, August 13, 2014 - link

    It wouldn't really be a factor, the Bluetooth device's amp would be what's driving your headphones, not the phone's circuitry. Reply
  • blade 7 - Monday, February 17, 2014 - link

    while quality of music playback is certainly a major issue, one primary quality question hardly gets any mention, not to speak of objective examination: the quality of the phone call audio itself !
    it you conduct crucial negotations over the phone - or even if you just flirt with someone on you portable, the quality of voice call transmission can make a huge difference in how you - your message, business proposition, etc - are perceived on the other end of the call, and what impression yout gain from someone calling you. so where in the respective media is a systematic phone-call audio quality assessment ? ( and no, phone call audio quality is not equal to music file playback audio on a smartphone. we are talking much more elements of the phone involved and influencing phone call audio qu. compared to file playback quality.) a lot of modern smartphones sound very poor on voice calls ....
    Reply
  • Excerpt - Wednesday, February 26, 2014 - link

    Represent RIP city main! You did an amazing and scientific report I have high hopes for future articles and I'm really behind your trailblazing (another reference) the audio quality topic on our electronics!

    I did a wedding gig with a decent firewire audio interface, ran out of music (as the crowd wanted more current hip-hop) Hooked up my friends iphone and I was a little awestruck. My speaker amp was at about 80% and the iphone 5 was at about 90% volume and the distortion and quality did not seem to dip down at any noticeable amount, through the head phones or the floor speakers. WOW.

    I personally just bought the nexus 5 and yes, even at low levels being hooked up to my home stereo (which i do often) the quality and total max dBs are defiencent compared to the iphone. Crap-tastic infact, the left and right speakers even seem noticably out of phase or somehting to that effect. (I'll start using the S.O.'s ipad air if i need an emergency audio source in the future)

    Just verifiying this man's findings with real world examples. Thanks!
    Reply
  • Excerpt - Wednesday, February 26, 2014 - link

    Good point and I think there's some information to be discovered on that topic. However, I wanted to add, carriers are really responsible for increasing the quality of voice. The local recording of a mobile device is much better than the transmitted voice (not withstanding software enhancements eg. noise canceling). Check out, 3GPP and the ITU (International Telecommunications Union). There's some benchmarks that are measuring voice quality calls, but assisted with network simulators, as the network is also an important factor. Reply
  • @paulkind3d - Thursday, March 06, 2014 - link

    Call and sound quality are a huge part of mobile phone tech. I'm currently looking into the HTC One as it appears to have set a precedent on sound quality. Personally I am absolutely sick and tired of having to ask "huh, what?" over phone calls due to the crappy little garbage speakers in most cellphones. They are either a) loud enough to hear but are not clear or b) too quiet to hear and are not clear either. Either way hearing calls on cellphones is painful and difficult on every cell phone ive owned to date. I can live with a bulky cell phone if it means better sound personally. Sadly no one else thinks this way. Apparently till a phone is the size of a thumbnail and useless for calling people cellphones makers will not be satisfied.

    I know that this test does not compare that and is more of a DAC question as the test is geared to headphone sound quality (bonus that one of the test subjects is a grado headphone... grados are amazing... i love my sr325's). None the less, the fact that someone is out there testing audio quality of cell phones means that eventually we may be able to actually hear phone calls when we make/answer.

    BTW head-fi.org has many user posts on this same subject. If line level quality is important to you definitely search headfi too. This and many other compares can be found there... http://www.head-fi.org/t/685103/best-phone-for-mus...
    Reply
  • H0rtOn - Thursday, May 08, 2014 - link

    I read Anandtech alot and have never posted a comment before, but I signed up just to make this post. Please make this a standard part of your phone reviews. I specially missed this part in the review of the HTC One (M8). Reply
  • notsure123 - Friday, April 29, 2016 - link

    Old article. I would just like to point out the difference between driving apple headphones (or any headphones for that matter) vs a line input. Not to say this data is inaccurate, it is just not particularly useful in comparing smartphones audio quality. Firstly because I hope no one actually uses their smartphone with headphones at volumes even up to 80% where it might also start distorting. This is too loud and is damaging your hearing. I would like to see the distortion figures when connecting the headphone jack to an auxiliary input rather than a headphone and see how these phones compare (willing to bet its much more similar) Reply

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