Smartphone Audio Quality Testingby Chris Heinonen on December 8, 2013 5:15 PM EST
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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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porphyr - Monday, December 9, 2013 - linkThis article is fantastic. I love that you are going to be testing audio quality. Obviously testing anything takes a lot of time, but I think it would be nice to see how these phones perform at "reasonable" listening levels. It would be great if you could pick dB level that is pleasant through the apple earpods and test a 2nd time at that, sort of how you use 200 nits for panel tests. That would give a more helpful representation of performance. Another thing that I would really appreciate is an explanation of how bad (or good) performance needs to be for most people to hear the difference (with bad and with good headphones). Thanks for the piece.
99sport - Monday, December 9, 2013 - linkThanks for the great article.
Can you add built in speaker testing? I have an HTC one, and while I prefer to turn beats audio off when I use my phone in the car (listening to music on the car's speakers), I much prefer the sound of the built in speakers with beats audio on. As others have pointed out, all of the pieces in the chain are important to sound quality. My guess is that the frequency response of the built in speakers is much less at low frequency, and the beats audio increase in gain shown in your chart (below 100Hz) is designed to compensate for the frequency response characteristics of the built in speakers. In other words, if you tested the frequency response of the built in speakers (using a microphone with a known linear frequency response to gather the data), would the curve be much flatter when using the built in speakers with beats audio turned on versus turned off? Would the HTC one with beats audio on in fact have a much better (flatter) frequency response through the built in speakers than other phones do through their built in speakers?
It would be very useful to be able to compare the sound quality of the whole sound reproduction chain including the built in speakers – for me, the built in speaker sound quality and volume level is a major discriminator between phones – right up there with display color accuracy and camera quality.
dishayu - Monday, December 9, 2013 - linkExcellent initiative. The HTC One frequency response looks dreadful. I'm looking forward to graphs with beats enhancement off.
As the next step, I would really like to see where different types of audio devices compare to each other... smartphones, ordinary media players (ipods), audiophile media players (HM-801), entry level/top level PC sound cards, realtek onboard chipsets.
NeoteriX - Monday, December 9, 2013 - linkI'm not sure if it's necessary to go through the effort of including PC soundcards, motherboard solutions, etc., but including media/MP3 players would definitely be a nice addition. The place that mobile phones have now as media consumption devices in addition to being phones came as an evolution from the original media device.
However, the media device, given its singular purpose, prominently had sound quality as a major review component, and consumers did look at the DACs and opamps used. When they evolved to all-purpose smartphones, suddenly there were a lot of other features that took precedence, including processing power, display quality, etc.
Now that AnandTech is shepherding in a new look at audio quality, comparing the state of mobile phones to the heyday of media device would definitely be useful.
stunta - Monday, December 9, 2013 - linkExcellent article! It would be fantastic to see results from commonly used mp3 players. iPod, Sandisk Sansa (Clip, Fuze etc.) etc.
How do you feed the test tone into the phone? Does the Audio Precision device come with test files you simply drop on the phone and play?
Also, do we know if these phones use the same amplifier for the built-in speakers and headphone outputs?
Impulses - Monday, December 9, 2013 - linkI'll second this and dishayu above, it'd be a great reference.
Hell, if we could get you to test output of a few BT receivers out there that might also be interesting and valuable to readers... I know BT's another can of worms as it introduces more compression etc, but it's actually gotten quite decent and those receivers end up replicating (and thus bypassing) many of the same components in phones.
There's not a lot of in depth reviews out there for those things but seeing as you can use them with any pair of headphones they'd fit right into your testing and they can be a suitable solution/alternative to a phone's line out. Something like the older Sony MW-300, or the newer models, or three equivalent Samsung/LG models.
Panzerknacker - Monday, December 9, 2013 - linkPlease test the Oppo Find 5! I use that phone and it should have good audio capability. Wonder how it does vs iPhone 5.
juhatus - Monday, December 9, 2013 - linkNow if only apple would enable their audio tech (noise-cancel atleast) on bluetooth.
I downgraded from nokia 800 to iphone5 and atleast using the in-car-bluetooth the audio on calls went really bad.
On other comment, the graphs are huge in this article, maybe little scaling or something? some bare flatlines there and very big size graphs.
Nice article :)
Impulses - Monday, December 9, 2013 - linkGreat article, though I have a quibble with the headphones to be used for future testing... Nothing against either as I've owned both, and the SR80 are a fine candidate (common entry level open headphone recommendation). The AKG have a reputation for being hard to drive and they aren't exactly very portable anyway, plus they represent another dynamic open headphone. I think a popular IEM (Ety, Shure, even Apple's dual driver IEM) might be a better second alternative, if it's at all possible with your rig... I know IEM are a pain to test due to seal issues and whatnot. Failing that maybe some other dynamic headphone that's more likely to be used with a mobile device (V-moda M-80? Senn HD25-1 II?), or something cheap yet extremely popular and good for the $ (Koss Portapro or KSC75).
Impulses - Monday, December 9, 2013 - linkAlso, if you could test and report output impedance for the phones that would be a HUGE help for people trying to figure out what kinda headphone would work best... Relatively high output Z isn't uncommon and it can wreck havoc with some lower impedance headphones, particularly sensitive IEM (and specially the multi balanced armature models that are so prevalent now).