Smartphone Audio Quality Testing
by Chris Heinonen on December 8, 2013 5:15 PM EST- Posted in
- Smartphones
- Audio
- Mobile
- Tablets
- Testing
In many of the examples you have seen so far, you notice that the Nexus 5 has a large issue with the left channel at peak volume levels. As Brian mentions in his Nexus 5 review, it is based on a similar platform to the LG G2 but it isn't identical. Because there are similarities I want to test it out and see if it has the same issue that I see on the Nexus 5.
The test that is causing the large issue on the Nexus 5 is a 1 kHz sine wave, at -0dBFS, at maximum volume. This is the loudest sound that any device will be asked to produce. If you're familiar with the trends in music mixing the past two decades you'll know that a peak of -0dBFS is not all that uncommon now. This chart at NPR shows the average and peak levels for the most popular songs over the past thirty years. Two decades ago testing for -0dBFS might not have been important but it is now. So lets look at this image from the Nexus 5 again.
Now for comparison, we will look at the LG G2.
This looks much better. However the LG G2 is still putting out 0.546528% THD+N into the left channel while only outputting 0.003338% into the right channel. So there is still some imbalance going on here. So why is the issue so much less on the G2 than on the Nexus 5?
The key to this is looking at the scale on the graphs here. While the Nexus 5 peaks are up close to 1.3-1.4V, the G2 has peaks that don't even reach 700mV. Looking at the actual numbers the G2 has a Vrms level of 475.3 mVrms while the Nexus 5 checks in at 843.6 mVrms for the left channel and 982 mVrms for the right channel. The G2 is placing far less stress on its headphone amplifier and keeping it from the output levels that cause this excessive clipping in the Nexus 5.
To look in more detail, we have THD+N Ratio charts for the stepped level sweep that we looked at earlier. First, lets look at the Nexus 5.
We see that the first three volume levels, 15-13, have THD+N distortion over 0.3% for the left ear, while they are below 0.01% for the right ear. From level 12 and below the THD+N levels are practically equal. Now to see how this data on the G2 looks.
We see the first volume step has 0.55% THD+N or so for the left ear, but the right ear is down at a similar level to level 14 on the Nexus 5. The next step drops it to 0.03% which is way, way below where it is on the Nexus 5 at that point. By step 13 they are equal.
The conclusion I pull from this is that both the G2 and the Nexus 5 have the exact same flaw right now. However, the G2 has attempted to hide it by reducing the maximum output level of their headphone amplifier. The Nexus 5 can play louder, but only with far more distortion. Given this I would expect there to be an update to the Nexus 5 at some point that lowers the maximum headphone level to something closer to the G2.
However this doesn't mean that the Nexus 5 is certainly worse to use with headphones. The top 3 settings are ones I would avoid due to the left channel issue, but I might avoid the top 1-2 settings on the G2 as well. If we consider 1% THD+N to be the maximum allowable level, that leaves 8 volume steps on the Nexus 5 that are usable. The G2 has 9 steps that are available to you, and 10 if you consider 0.03% THD+N in one ear to be OK (it probably is).
In the end, the G2 won't play as loud as the Nexus 5 will, but you don't want to play that loud anyway. It has more usable volume steps than the Nexus 5, and otherwise very similar numbers. I'll be interested to see if either of them make further changes to their maximum output levels to remove this issue.
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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.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 ....
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!
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.@paulkind3d - Thursday, March 6, 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...
H0rtOn - Thursday, May 8, 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).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)Photosynthecis Media - Friday, March 6, 2020 - link
It is important here to differentiate between the microphone and the rest of the audio system if you will because if the microphone is providing the input then its intrinsic response curve will apply kind of like a coefficient to what the audiio sys output is. Whereas an aux input other than the microphone would offer an output only affected by the frequency response characteristics of the amplification system, primarily the speakers, but not the microphones.