Since our initial turn in testing smartphone audio, I’ve had a lot more time to play with the APx582 from Audio Precision. I’ve also received far more feedback than I ever expected to on this subject. I have made a few changes to the testing method that I’m going to outline along with discussing some of the reasoning behind the changes.

All tests are now run manually instead of automated over USB

For most phones, running over USB and running them manually provide the same results. For a few, the commands sent with adb to adjust volume result in a higher maximum volume than you can select with the volume buttons. This causes results that are not correct for real-world use.

Note that non-Android phone testing will be identical. The test tones can be manually selected and used regardless of platform. I will try to determine why this happens, as there is the potential for other software to also set the volume control too high. I’m most concerned with results that match real-world usage and this does that better.

Using standard dummy loads

Before I used common headphones (Apple earbuds, Grado SR60s, and AKG K701s) as my loads. While more real-world than resistors, they also present more issues. They have a nominal impedance, but their impedance might be low in the bass and high in the midrange. If you only base results off the nominal impedance numbers, you can mis-interpret charts.

Duplicating the results also becomes a challenge. The parts used in headphones can change during production. Someone trying to match up their results to ours may not be able to achieve the same data with what they believe are the same headphones. A resistor has a tolerance as well, but with fewer variables it is easier to interpret the data and replicate the results.

For the dummy loads, I selected 15 Ohm, 33 Ohm, 150 Ohm, and 330 Ohm loads. During testing I load each channel with the same value of resistor. The Audio Precision software calculates the wattage from the resistor and voltage.

Fewer charts

The standard Audio Precision smartphone project produces lots of charts. Seriously: a lot of charts. It is easy to include every chart in there but most often they aren’t needed. Instead I plan to summarize the data into a nice table form and include the charts that are indicative of performance. If a chart shows nothing new or unusual, I likely will not include it. If a new chart helps to explain what is going on, I will include it. So sometimes you will see a chart and sometimes you won’t depending on what it shows.

I will pull almost all charts from the 33 Ohm loads. This is the the closest to real-world earbuds for most people. There are a lot of earbuds that drop down into the 16 ohm range, and you should look at the 15 Ohm results for those. Since this is a harder load to drive you are most likely to see worse results than with easier loads. People using over-ear headphones with impedances in the 150-300 Ohm range should use those results. This is easier to drive, but also is going to output far less power in watts so you need to pay more attention to those numbers.

This first round-up includes the HTC One M8 and the Samsung Galaxy S5. This is also purely objective listening. My time with the phones is usually short and I don’t have the time to offer my subjective opinion on the audio quality. I will leave that up to the original reviewer.

HTC One M8 Audio Testing
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  • bigboxes - Tuesday, June 3, 2014 - link

    I never use the headphone out. I use Bluetooth to connect my Note 3 to my Alpine and the sound is great. The only issue I noticed is an occasional tick in the sound which I assume is when I receive data (texts, e-mails, etc.). Not sure how to eliminate that. If anyone has a suggestion, please let me know.
  • The1Metallian - Tuesday, June 3, 2014 - link

    @bigboxes I never have any noise due to notifications. I use a sound profile manager so when I start the music I choose the profile that has notifications muted, media almost all the way up, phone half way up (for emergencies!).

    I must add that the poor quality is more evident depending on the type of music being played. When the music is mostly guitars, bass, drums and vocals (metal) I don't notice it, but if keyboards come up front then it sounds kinda garbled. The same with sustained cymbals.

    You have a Note 3. That device is newer than the GS3. Maybe it has better bluetooth?
  • bigboxes - Wednesday, June 4, 2014 - link

    Probably. However, I came from an HTC 4G EVO LTE. The Bluetooth on that model sucked. I RMA'd a Jawbone headset thinking it was bad. When I got the Note 3 I realized it was just the HTC handset and not the Jawbone. It could be the Bluetooth or it could be the antennas or both. I'm not AnandTech where I have labs and access to different equipment. I can tell you that the audio over Bluetooth sounds amazing. Of course, the Alpine could have something to do with that. :)
  • Jimster480 - Tuesday, June 10, 2014 - link

    I had an EVO 4G LTE and I never had any issues with the bluetooth! My father has one too and his bluetooth never acts up. it could have been your phone specifically!
  • cheinonen - Tuesday, June 3, 2014 - link

    Bluetooth testing is something I plan to add in the future. I need to decide what I want do with it, but likely something similar to this. There is also a legibility test for talking that can be done over Bluetooth which will be interesting to see. Hopefully Bluetooth doesn't have issues with USB control as analog does, but I will test both ways to be sure.
  • Jimster480 - Tuesday, June 10, 2014 - link

    I think that the sound via bluetooth would depend on the DAC of the device on the receiving side? I'm pretty sure bluetooth is a digital signal and therefore the receiving device would have to convert it.
  • haukionkannel - Tuesday, June 3, 2014 - link


    It would be nice to see some pro portable flack player compared to these phones.
    What is the best audio phone and are they even near or a far, far away distance compared to high class portable audio players or real hifi DACs?
  • cheinonen - Tuesday, June 3, 2014 - link

    If you want comparisons to some really high end gear, I've been testing the Auralic Vega DAC ($3,500) and the Auralic Taurus headphone amplifier ($1,900). Since the headphone output here is a combination of a DAC and headphone amp, these numbers aren't exactly comparable.

    The Vega has 0.000345% THD+N, a frequency deviation of 0.002 dB, Dynamic Range of 125 dB, and Crosstalk of -130 dB.

    The Taurus does over 5V into 15 Ohm, and nearly 20V into 33 Ohm, 150 Ohm, and 330 Ohm. It has 0.0004% THD+N, deviation of 0.007dB, 124 dB of Dynamic Range, and -70 dB of Crosstalk. IMD, which isn't measured on the phones, is also below -100 dB at maximum gain.
  • haukionkannel - Thursday, June 5, 2014 - link

    Thanks to this info! But the comparison to real portable devices would be more important. I am in situation where normal phone does not produce good enough sound compared separate mobile music player. I am just wondering if we are getting near the situation where phone is good enough compared to dedicate high-end mobile music player?
  • cheinonen - Thursday, June 5, 2014 - link

    I don't really use any portable DACs and amps, either for work or for my daily life. If I get my hands on one I will measure it, but it's an area I don't really venture into.

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