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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dylan522p - Sunday, December 8, 2013 - link
Just because you have a good DAC,doesn't mean you have great audio. S4 has a great DAC but it can't even power high impedence headphones.cjl - Monday, December 9, 2013 - link
The S4 powers moderately hard to drive headphones just fine - sure, it won't drive something like an HD650 adequately, but the majority of consumer headphones out there will go plenty loud driven straight out of an S4. That having been said, it would be nice if it had a bit more power for hard to drive headphones.oktrav - Monday, December 9, 2013 - link
I can't believe how many people on the internet are singing this song... Does it really matter who makes the DAC if the output sounds like crap? The DAC is just one of many components that affect the sound quality. You can have the best components in the world and still produce absolutely dreadful sound. Ask any wannabe audiophile who's dabbled in assembling home systems out of separates. This is akin to saying that your car must be very powerful BECAUSE it has Bosch coil packs --and Bosch makes the BEST coil packs (just play along for the sake of the analogy, I'm not actually asserting that Bosch makes the best coils --I don't know).nomopofomo - Sunday, December 8, 2013 - link
So glad you went into such depth.Best case scenario, the public and manufacturer are both made aware of the flaws.
drwho9437 - Sunday, December 8, 2013 - link
This has been needed badly for some time. Phones displacing media players this matters a whole lot. To me far more than actually anything else about a phone.probedb - Sunday, December 8, 2013 - link
You also have to remember with some measurements about what is actually audible and what isn't. It's crazy seeing people moaning about nanoseconds of jitter on DACs yet they're quite happy with milliseconds of the equivalent of jitter on vinyl. Then again some of these companies sell ethernet cable at £1600/m and claim it makes a difference to sound ;)matagyula - Sunday, December 8, 2013 - link
Great to see something like this on anand!I would like to see some older high-end phones compared to the ones we have now - for example the Nokia N900, or maybe even some of the ooold Sony-Ericsson Walkman phones (W810 and up). I'd find such comparison interesting ^^
chubbypanda - Monday, December 9, 2013 - link
Great stuff Chris!I was also wondering if it's possible to add some ancient phone with cult following from audio geeks. You know, Nokia N91 and similar. According to some, sound quality on the phones were never better, so that'd be nice to see what is really happening.
wrkingclass_hero - Sunday, December 8, 2013 - link
So, how long before Arstechnica "discovers" the audio problems with the Nexus 5?crabperson - Sunday, December 8, 2013 - link
YES! Thank you so much for doing this, its awesome. I didn't realize audio/amp quality was a huge thing until I upgraded my headphones. Being able to hear the difference between the same audio file on two different devices made me realize how little manufacturers care about audio quality.Then using an FM transmitter in my car showed me how some devices can't pump out enough power over the headphone jack. My Galaxy Nexus has pretty good audio quality (and does optical audio out through the dock, also awesome) served me fine for pumping up music through the FM transmitter. The Galaxy S3 I'm temporarily using does not though, and produces noticeable clipping at max volume. It also isn't properly shielded and when charging there is interference on the headphone jack (something you should also test if you haven't thought of it). I'm looking at upgrading if I can't fix my Nexus, and hope the HTC One is as good as it in terms of audio quality (with Beats disabled of course).