Samsung Galaxy S 2 (International) Review - The Best, Redefined

• 0:00 to 0:02  sound card noise only.
• 0:02 pop on codec power up, music start to play. EDGE activated, Volume 1/15
• 0:02 to 0:35 music playing, you can hear GSM and CPU noises despite the signal
• 0:35 Volume set from 1/15 to 0/15. Music keeps playing in background but is silent
• 1:03 WiFi enabled, EDGE is automatically disabled. Moving some UI elements

Due to its bursty nature, this flaw is hard to expose in measurements and fortunately less audible with medium sensitivity headphones, not at all with low sensitivity ones.

You can solve this issue by using an attenuator or amplifier: maximizing digital Android output level and adjusting the volume to your need with the amp.

DAC Distortion

With today’s Android audio implementation, all kind of media are sent to the DAC as a 44100 / 16bit / Stereo stream. Despite the usage of a fixed rate, Yamaha’s codec is not able to provide a very clean output.

Galaxy S II DAC output quality is limited by several kind of distortions. So far, no firmware was able to fix those despite early Korean updates describing “audio clarity improvements”.

When playing music, those artifacts are perceived as “lack of clarity”, “reduction of stereo separation”, “loss of detail” and “lifeless sound” (opposite of lively).

From 20 Hz to 20 kHz, dB: -0.42, +0.04
Galaxy S II Frequency response: no load (line in)

Not the best ever but reasonably flat. The slight oscillation in frequency response starting at 1kHz gives a clue about what we’ll see in the next graphs.

Noise Levels
RMS power (A-weighted), dB: -95.1, -95.6
Peak level, dB FS: -71.7, -74.4

Dynamic Range
Dynamic range (A-weighted), dB: +95.4, +95.9

On Noise Levels and Dynamic range graph, I added measurements of Apple iPad and a reference sound card for comparison puposes.

What we see here is good performance. In theory and measured in ideal conditions Galaxy S II has low noise levels and very good dynamic range. However, if noise levels are remarkably low on high frequencies, they increase on lower frequencies which is not something expected nor a good sign as those are more likely to be heard.

Total Harmonic Distortion
THD, %: +0.0036, +0.0035
THD + Noise, %: +0.0390, +0.0388
THD + Noise (A-weighted), %: +0.0425, +0.0424
THD + Noise (A) equivalent: -67.4 dB
Same Graph adding iPad results

THD is calculated by measuring harmonics generated by the electronic circuits when a signal at 1kHz is played. As you can guess by this graph’s shape, there’s an issue here.

In terms of sound and perception, harmonics add colour to the sound; sometimes pleasing like the kind of distortion tube amps add.

This graph show all kind of distortions introduced by Yamaha’s DAC, ie:

• Jitter-like frequencies distributed around 1kHz
• All sort of unexpected spikes at higher frequencies

As the noise and other distortions are high, the THD measurement itself becomes kind of irrelevant. Unfortunately the value of  0.0036% is not of the actual performance here.

Other reviews might have use this THD value as base for invalid conclusions.

InterModulation Distortion 
IMD + Noise (A-weighted), %: +0.0655, +0.0655
IMD + Noise (A) equivalent: -63.7dB

What IMD + Noise means needs an explanation: I believe it’s safe to describe it as “all kind of noise and distortions happening when you play a signal” − at the opposite of the signal itself.

IMD + Noise importance is often underrated, like it was useless as we already have another distortion value (THD). Still, it’s often more representative of the general performance and of the sound quality perceived.

No matter how low is the theoretical noise floor, Yamaha MC-1N2 DAC has issue when playing signals. As you can guess by this latest comparison graph and the number of spikes indicating some sound that shouldn't be there. iPad DAC is not perfect either, still it provides a much cleaner sound. The reference DAC shows how the graph should be.

-63.7dB level for “noise and distortions” is far from the level of performance expected from a last-gen audio IC.

InterModulation distortion + noise (swept freqs)
IMD + Noise at 5000 Hz: 0.0108, 0.0109
IMD + Noise at 10000 Hz: 0.0108, 0.0109
IMD + Noise at 15000 Hz: 0.0108, 0.0109

This test consist of a single sine played going from a very low frequency to 22kHz.

Actually, when playing something as simple as a single frequency at one time result is not so bad; music is rarely made of simples sines.

Stereo Crosstalk.
dB: -82.3

My guess is that Yamaha’s codec internal behavior is perturbed by a jittery clock source (being Exynos AP PLL clock). If not? it  would mean the DAC design is flawed. The first hypothesis is more likely: implementation on small very low power board is always tricky.

You cannot avoid the distortions described here by using an external amplifier or any other equipment.

Exploring sound with spectrograms

A spectrogram lets you “see” the sound, why I’ll use this colorful presentation to show you some examples of Galaxy S II audio output.

Udial

Galaxy S II udial output sampled at 96kHz (FLAC sample)

Reference, re-sampled to 96kHz with sox
For comparison: Apple iPad udial output (FLAC sample)

udial is a very interesting sample circulating in forums for more than ten years. I didn’t manage to find its author to thank him for his clever idea. udial is a very efficient stress test that enables an easy test for clipping, re-sampling and some types of jitter.

Galaxy S II performance is not terrible but not good either. Artifacts are audible and can be seen in this spectrogram. I must admit some are a mystery to me like the “delayed” ones.

Bass sines

Simple bass sines allow to check a few things: clipping, unwanted EQ, Bass Boost or Dynamic Range Compression but also buggy DC Servo setups.

The sample used here contains 7 tones: 100Hz, 80Hz, 60Hz, 50Hz, 40Hz, 30Hz, 20Hz.

Galaxy S II bass sine waves output (FLAC sample)

For comparison, Apple iPad bass sine waves output (FLAC sample)

Once again Galaxy S II exhibits artifacts. If you download the associated FLAC record phone’s output you may be able to hear those appearing as lines on the spectrograph (more noticeable on last 2 notes).

But it’s not all bad: Samsung’s phone spectral representation exposes a nice hardware feature called Digital Noise Gate.

DNG analyzes the signal played and quickly shut down parts of the codec. It helps reducing the perceived hiss and reducing power consumption a little.

Eventually (after about 2 seconds of nothing played) the entire audio hardware is shut down by Android OS but the best part is that Digital Noise Gate feature is extremely efficient as anti-pop.

MC-1N2 performance is class leading on this regard.

Headphone amp

Galaxy S II built-in headphone amp is able to drive in-ears or full size cans to satisfying levels. I know for sure mobile devices are never LOUD enough. Samsung’s flagship is louder than iPhones, iPads, a first-gen Galaxy S.

This part may become a dedicated article but here are some facts already:

At Max level (15/15):

AC Tension, no load (line-in): 0.703V

Driving Sennheiser HD 650 (300 Ω)

• AC Tension under load: 0.621 V
• Power (left+right): 2.11 mW

Driving Head-Direct RE0 (64 Ω in specs, mines measured at 58 Ω)

• AC Tension under load 0.381 V
• Power (left+right): 4.14 mW

Question is: Is it loud enough? When driving HD 650, it reaches comfortable listening levels but won’t reach “loud” levels. For RE0 and most consumer headphones, yes it's loud enough.

Remember isolating headphones are recommended when in loud environments rather than pumping volume too high and damage your hearing.

To me the quality of the amp itself is average-to-okay. Its hard to speak much about it as it’s most of the time amplifying the signal sent by a flawed DAC.

As distortion amount rises at highest levels, its probably MC-1N2 amp power stage implementation on Galaxy S II board does not have much headroom. More measurements may be welcome here.

High output impedance

One characteristic of Galaxy S II's headphone driver is its relatively high impedance: higher than competitor chips. Power efficiency diminishes when the output impedance grow: energy lost in heat. This is why Yamaha’s choice of design is surprising.

I measured mine at 49 Ω.

A notable side effect of this characteristic is that the headphone output becomes less loud with low impedance cans. 

Output impedance doesn’t have much effect on 300 Ω gear, but on common 16 Ω earphones:

• Gain is lowered, hiss level is reduced: nice bonus
• Frequency response shift: less bass, more highs. Okay if the tiny speakers was too bassy, terrible if the headphones were bright already.

As a result, Galaxy S II might play well with some equipment but also reveal the worst side of other with harsh and aggressive rendering.

This output impedance is why opinions about Galaxy S II audio are so contradictory in forums: experience can vastly differ depending on your choice of headphones.

Appreciation note

There are many issues or flaws listed and demonstrated in this article. However it doesn’t mean Galaxy S II is unable to play music.

Compared to the average Android phone it probably sounds better already. Explanations mean to show where there’s headroom for improvement on the next devices.

We're more than willing to discuss audio testing methodology with manufacturers to help improve the next generation of phones.

Samsung Music Player

Samsung updated their Google music player replacement look and feel with TouchWiz 4.0.

It still supports FLAC natively, which is a nifty feature for audiophiles and its simple interface and efficient will satisfy most users.

This pre-installed music player still lacks a much desired gapless feature, which means listening to mixes, concerts records or classical music won’t be as pleasing as it should.

You’ll find an 8 band graphic EQ in settings as well as EQ presets and additional sound effects adding reverberation, spatialization or stereo enhancements. Some effects are interesting if you’re not looking especially for an hi-fi accurate sound reproduction. However I would suggest to stay away of the EQ presets as much as possible:

The way the EQ engine uses a suboptimal DRC implementation makes constant volume changes audible.

If you really need to use this EQ, one workaround in using the graphic EQ manually instead: only attenuate but never increase some frequencies, those you find too present. This is in general the best way to use an EQ and find a more balanced sound response to correct headphone or speaker response.

This tip will avoid triggering the DRC.

Typical graphic EQ setup using only negative gains for frequency response correction

As usual with Android OS, you’ll be able set an alternative music player as the default one without any restriction, adding gapless , more compression codecs  support or a different UI.