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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psuedonymous - Monday, December 9, 2013 - link
Any chance of a test/roundup of bluetooth receivers?Impulses - Monday, December 9, 2013 - link
I'd love to see that.deathdemon89 - Monday, December 9, 2013 - link
I do hope you consider providing the audio tests in the main review on the day it's published, as opposed to tacking it on later. I usually read reviews only once, i.e. on the day they are published and don't keep returning to individual reviews looking for updates, so this would be a major data point readers like me would not be able to take advantage of.DanNeely - Monday, December 9, 2013 - link
I wouldn't hold my breath. Chris H isn't a typical smartphone reviewer. As a result getting these results at initial launch time would require either buying additional sets of test equipment for the reviewers, buying an additional phone for Chris H to do audio testing on, or delaying the article to ship the phone to Chris H after completing the rest of the testing work.Audio precision won't let you see pricing information without creating an account on their website. That suggests it's painfully expensive and that getting multiple copies of the hardware won't happen. Getting multiple copies of the phone isn't cheap either and is probably not going to happen except perhaps for a few halo devices. With the peanut gallery raging about any reviews that don't make it out on release day, I'm doubtful that anandtech would choose to delay reviews for a few days for a specialized test.
Impulses - Monday, December 9, 2013 - link
Ehh, I agree, if it's not realistic to have this testing the day the review is out it's no big deal... If it's a deal breaker for you then you'd wait the same amount of time either way, and if it's not (probably the majority of readers) then there's no point in making the rest wait.xaml - Saturday, December 14, 2013 - link
"Chris H isn't a typical smartphone reviewer. As a result getting these results at initial launch time would require either buying additional sets of test equipment for the reviewers, buying an additional phone for Chris H to do audio testing on, or delaying the article to ship the phone to Chris H after completing the rest of the testing work."Or buying an additional Chris H...
cheinonen - Monday, December 9, 2013 - link
Having this on the day-of is going to be a challenge for a number of reasons.- Brian is in Arizona, and I'm in Oregon. If there is only a single review sample, I have to get it from him.
- As mentioned, the Audio Precision is ridiculously expensive. I think the APx 582 used starts at $19,000 before adding the HDMI, Bluetooth, and Digital modules I use (I need it for receivers as well). Audio Precision is just a few minutes from my house and they've been nice enough to let me come in, test everything there, and endlessly bother their QA people to get this right. However, as I have to come in I have to schedule that, and it takes time.
- That also makes it far easier to do a batch of these at a time than one at a time. If I had at APx at home it would be easier but right now that's not possible.
So we will try to get all the data, as fast as possible, into the system, but day-of is going to be a logistical challenge. I'd rather have it be accurate than be fast.
cheinonen - Thursday, December 12, 2013 - link
OK, I shouldn't say ridiculously expensive. However, the instrument we use costs enough that it's not feasible for us to have them for myself, Anand, Brian, and everyone else that needs one for testing. The Audio Precision gear ranges from $6K to $50K+ depending on what you need and the price still means we can't outfit everyone with one. So testing will happen as fast as possible, but likely won't run with the reviews when they are initially posted.Bobs_Your_Uncle - Monday, December 9, 2013 - link
This audio bench is a tool of truly significant value to anyone hoping to arrive at the best, most fully informed purchasing decision possible. Given the respect & high regard that AT has earned throughout the tech sector, this audio initiative raises the bar for more than smartphone manufacturers alone.Along these lines, does AT have any plans to initiate a similar audio bench for the various motherboard lines that have recently implemented enhanced audio capabilities?
These are very positive steps toward driving advances in fundamental, yet long neglected platform capabilities. However, as improvements in audio reproduction are realized, there will still remain one critical, & seemingly intractable obstacle to overcome; What's it going to take for the recording industry to give up on compression & adopt a regimen of decent mastering.?
It'd be a shame if the only thing audiophile-grade tech revealed was just how badly most studios butcher great music through compression & lousy mastering.
Impulses - Monday, December 9, 2013 - link
I think that battle's beyond Anandtech'srealm, though the more cognizant the average reader/listener is the better.