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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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!