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.

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  • Scootiep7 - Wednesday, December 11, 2013 - link

    Wonderfully well thought out and written article. Thank you! FFora future article my one request would be for a llcomparrison of all phones on each test parameter instead of only comparing 2 or 3 on some metrics. Again, thank you!
  • qualitycounts - Wednesday, December 11, 2013 - link

    Thank you so much for doing this testing. It would also be very helpful if your wrap up section did some side by side comparisons, kind of like they do on Consumer Reports. It's very hard from this article to tell which one comes out on top. Also, it would be nice to see an audio/phone quality report on the HTC One since it is also one of the most popular smartphones available.
  • sergoliv - Wednesday, December 11, 2013 - link

    In my opinion, audio quality testing is a very welcome adition to Anandtech. I am maily a classical music listner. Good dynamic range, wide and flat frequency response and capacity to respect all harmonics present in recordings are very important for classic music. Can you broaden your testing to in order to give an idea of what smartphones are more capable with classical music?
  • mike8675309 - Wednesday, December 11, 2013 - link

    A major use case for me and my phone is as a spoken language playback device through a speaker (not headphones). Be it podcasts or audible books, a good percentage of my "audio" listening on my phone is via powered "stereo" speakers plugged into the headphone port. Often with the volume on the phone at max so the powered speakers have more range especially if in the garage doing noisy stuff or taking a shower. What if any weight should be placed on these results for such a use case?
    Additionally, I've historically found phones unable to provide enough power for the various headphones I use (currently Klipsch S4) when using them with mowing the grass or such. Thus I have added a small personal audio amplifier for some uses of my phone and listening to things. In that case I usually have the phone at mid or lower levels and control most of the sound at the amp. Any thought to testing some of the more common portable audio amplifiers?
  • skynet11 - Wednesday, December 11, 2013 - link

    Could you please test on-board speakers in like manner?
  • BobN - Wednesday, December 11, 2013 - link

    Anyone know of an app that improves the call quality of the Galaxy S4? I know about Adapt Sound but it doesn't give my phone good phone call sound. Thanks.
  • AnnonymousCoward - Wednesday, December 11, 2013 - link

    What a good article. I'd love to see this data for sound cards vs integrated, and MP3 players, using only high quality reference headphones (or speakers).
  • hmaarrfk - Friday, December 13, 2013 - link

    Interesting article.

    From the stepped response, it seems that they are all using 16 bit DACs (16 bits would give you close to 96dB of dynamic range if the only source of noise was quantization for a signal at full power).

    Can you confirm this? Does this mean, that having 24 bit encoded music is simply wasteful on a mobile device?
  • hmaarrfk - Friday, December 13, 2013 - link

    Or did you simply use 16 bit audio? Have you tried your tests with 24 bit audio?
  • panda-fu - Thursday, December 19, 2013 - link

    24 bit encoded audio for end-user listening purposes has never been shown to have any advantage or difference from 16 bit in double blind tests. The potential advantage of 24 bit DACs lies in being able to use digital attenuation for volume control without losing any dynamic range. However, with proper dithering after attenuation, you have quite a bit of leeway even with a 16 bit one before it gets audible. So, don't worry about that spec!

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