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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Friendly0Fire - Sunday, December 8, 2013 - link
The Nexus S has some of the best DAC in the industry, actually... Most phones these days use the built-in Snapdragon DAC, but the S has a Wolfson DAC which is way superior.I think you either had a dud or you have another issue somewhere because the S was lauded for sound quality (just like the original Galaxy S).
tedders - Sunday, December 8, 2013 - link
I must have had a dud Galaxy S then too because my Captivate had abysmal audio.Samus - Monday, December 9, 2013 - link
The captivate and epic 4G (sprint variant) were substantially different from the galaxy s, although I remember the epic 4G touch (S2) having decent audio quality.tipoo - Sunday, December 8, 2013 - link
So I've heard, but I'm not the only one with shit audio on it, the running theory is they put in a good DAC but didn't bother properly making drivers or something for it.tipoo - Sunday, December 8, 2013 - link
Or perhaps improper shielding of the audio circuit from the radios, since the static seemed to be radio related. Even modern phones have some of that, even the best sounding ones like the iPhone 5S, but it's much much reduced.cheinonen - Sunday, December 8, 2013 - link
The DAC really means nothing without knowing everything else that goes into the circuit. Yes, the DAC might have superior SNR and THD+N but if you use an amplifier, or a volume control circuit, that are worse than other phones, you've now mitigated that advantage. It's there in the DAC but by the time it gets to the output stage it's been buried by noise elsewhere in the system.Using a better DAC is nice. But you can't just drop it in and get better results, everything else needs to be engineered around it as well.
Friendly0Fire - Sunday, December 8, 2013 - link
Using a higher end separate DAC hints that the manufacturer at least somewhat cares about sound quality. Using the built-in SoC DAC says that it's an afterthought.It's not a guarantee, but it's certainly an indicator.
Galidou - Sunday, December 8, 2013 - link
Totally agree with cheinonen, any high end audio stereo setup is as strong as it's weakest link. Take the excellent nuforce DAC-100 at ~1200$CAD, use it with a poor sub 400$ multi channel receiver and you won't get much out of it. The nuforce got plenty of amazing review, but it always depends on what it is paired with.The galaxy sure got a nice DAC but it's amplifier section is poorly engineered.
cjl - Monday, December 9, 2013 - link
Actually (and I know audiophiles everywhere will disagree with me on this, but whatever...), you can get audibly perfect sound with a dac worth only a couple hundred dollars at most, and an amp of similar cost. There's really no point in buying a >$1k dac, and the same goes for an amplifier (though expensive multi channel receivers can be justified, not for the quality of their amplifiers, but for the quality of their DSP, room correction, video upscaling, and variety of inputs and outputs). For an audio system, by far the most important component is the speakers. You should spend the vast majority of your audio budget on the transducers (speakers/headphones), then buy an amp with sufficient power to drive them to whatever level you need without distortion/clipping (which is almost always less power than recommended by audiophiles). The rest of the system can really be quite inexpensive - the built in DAC in most modern audio products is audibly flawless, and it's impossible to improve on 14AWG zip cord for the cables (from an audibility standpoint) unless you're running your wires over an extremely long distance.Now, that isn't to say that modern smartphones have reached that audibly flawless point yet - many of them haven't (especially when they have such blatant flaws as the single channel clipping shown in the review above), but many of them are a lot closer than people realize, and it really doesn't cost much to make a product audibly flawless. I remember seeing testing done on the latest iPod, and it was good enough to not contain any audible flaws. I would assume that the iPhone is similar, and the GS4 looks to also be audibly perfect in the review above (so long as 500mV p-p is sufficient to drive your headphones - this may not be the case for some less sensitive models).
speculatrix - Tuesday, December 10, 2013 - link
+1A lot of audiophile ideas simply don't stand up to basic engineering principles, and blind A:B tests show it.