Ten ways to improve Android audio
Not happy with the sound quality coming from your Android device? Darren Yates has 10 ways to fix it to suit all budgets.
Boil it down and there’s not much smartphones can’t do. These powerful and portable hand-held computers are already playing high-performance games, recording and playing 4K video, there’s not much left for phone makers build in. However, while ‘more battery life’ is always at the top of everyone’s wish list, one area phone makers are now targeting for improvement is audio quality. That’s fine if you’re ready for a new phone, but what about your current phone if its audio quality is, well, not up to scratch? We’ve come up with ten ways to hack audio quality and some of them don’t cost a cent.
HIGHER-QUALITY SOURCE
Before we start trying more involved hacks, there’s arguably not much point if the original source’s audio quality isn’t up to scratch. Granted, in some circumstances, you may not have a choice, but basically, if you’re still listening to 128Kbps stereo MP3 audio, you have to question whether you’re really serious. Anything less than 256Kbps MP3 is pointless in my view because you’re throwing away too much audio data to make the most of your hardware — you’re relying on the MP3 codec and your ears to ‘fill in the gaps’.
These days, there are much better alternatives to MP3. For the highest quality, WAV audio can’t be beaten because it is the raw pulse-coded modulated (PCM) audio format. However, when factoring in storage space, FLAC becomes the perfect choice (think of it as ZIP file compression for audio) as its native to Android since Honeycomb/3.1. And then there’s the ‘Hi-Res Audio’ (HRA) standard, audio recorded with 96kHz/24-bit sampling or better, that’s been slowly gaining fans over the last year or so as new phones arrive with supporting hardware.
Going the other way, use a lossy audio compression format to save space if you must, but at least try a high bit-rate MP3 or Opus. Google added support for Opus in Lollipop/ Android 5.0 and in listening tests, it’s proven to offer the best perceived audio quality for a fixed bit rate compared with a range of other lossy codecs.
All up, you can’t blame hardware for poor audio quality if your source audio isn’t great to begin with. And if you have a choice, it shouldn’t include 128Kbps stereo MP3 audio.
EXTERNAL USB DAC
We can now establish that audio quality is a combination of the source audio and playback hardware you listen through. When that hardware is your smartphone, however, there aren’t always options for hardware-hacking. But if your device supports USB-OTG, you can bypass the on-board
“These days, there are much better alternatives to MP3. For the highest quality, WAV audio can’t be beaten because it is the raw pulse-coded modulated (PCM) audio format.”
audio chain entirely and use your own external audio digital-to-analog converter (DAC). Some audiophiles will demand you spend $200 or more on a decent DAC to get gold-plated quality. However, there are goodquality options using the excellent Burr-Brown PCM2704 DAC chip online for under $20.
Android supports USB audio DACs as standard from Lollipop/Android 5.0, so provided you have at least this OS and your device is USB-OTG ready, you just plug in the DAC via a USB-OTG adapter cable, the phone should recognise it and re-route your audio through it. The beauty of this is your phone sends the audio digitally through to your DAC, ensuring the phone no longer controls the actual sound you hear.
The downside is that the DAC’s power comes from your phone’s battery, so there’ll be a corresponding drop in run-time. But if you’re not ready to upgrade to a new phone just yet, this is one way you can overcome below-par on-board audio quality — and provided your next phone also supports USB-OTG, you can take the DAC with you. Just check for any compatibility issues before you purchase.
EXTERNAL BLUETOOTH AUDIO RECEIVER
What if your phone doesn’t support USB-OTG? The next option is Bluetooth. Now Bluetooth is commonly used with speaker bars, but you’ll also find Bluetooth headphone adapters — a little larger than a USB flash drive, these devices contain a Lithium-ion battery, Bluetooth receiver with built-in amplifier and headphone socket. Instead of connecting straight to your smartphone, you pair your smartphone with the adapter and stream music wirelessly.
You’ll find them starting from around $20 or so online, but if you’re using powered speakers, you can choose a $5 USB-powered receiver that basically looks like a USB flash drive, while more audiophile-grade models go up to $200. Either way, you plug the USB port into a USB power source, plug the audio cable in between the receiver and your amplified speakers, pair the receiver with your phone and away you go.
The idea, again, is to remove the phone’s analog audio circuitry from the quality equation and make the results external to the phone.
EQUALISE YOUR MUSIC
Headphones are a major factor in audio quality, but if your budget won’t spring for a new headset, try attacking the problem from the other direction. How you perceive audio quality is a function of your phone hardware, your headphones and your ears — and none of them are perfect. Using EQ (equalisation) allows you to vary different frequency components of the audio to equalise or balance out perceived peaks and troughs in the audio spectrum and get a better sound.
The great thing about EQ is there’s no right answer — only what sounds right to you. However, if you’re correcting budget headphones,
“The downside with using EQ is that, depending on your phone, it may well be the CPU that has to do the work, which may also affect battery life.”
chances are the bass levels will need boosting below 300Hz, the mid-range somewhere around 2–4kHz will need minor trimming and the high frequencies above 6–8kHz will need minor boosting. Start there and see how you go.
The downside with using EQ is that, depending on your phone, it may well be the CPU that has to do the work, which may also affect battery life. However, more modern phones outsource EQ processing to dedicated chips, reducing power consumption. Try some ‘ before’ and ‘after’ testing to see how your phone performs.
CHECK AUDIO SIGNAL LEVELS
OK, this may sound weird, but go with me for a bit. To get sound from your phone to your ears, the last stage it passes through before reaching the headphone socket is the audio amplifier circuitry. Now without diving deep into audio amplifier design theory, the sound you hear coming from the headphones is a function of the output signal voltage from the amplifier and the impedance of the headphones. All headphones have an impedance, or resistance to audio signals, but it varies between models — 32ohms is common, but you’ll also find 250ohm and 600ohm headphones. Lower-impedance headphones are easier for smartphones to drive, meaning you will likely get a higher output level than using higher-impedance headphones. You’ll also likely try to push the output level higher on these higher-impedance headphones to get a listenable audio level.
Just beware that, the higher you push the audio level, the closer you may get to creating clipping distortion. This occurs when the digital value of an audio sample reaches ‘full scale’, with no room to move higher and ‘clips’. If you use software tweaks that allow you to boost audio levels, for example, using EQ with added gain, it’s possible to push those levels into this ‘clipping’ territory, adding truckloads of distortion. So be wary using EQ gain — too much doesn’t always help.
CHANGE YOUR MUSIC PLAYER
This sounds pretty obvious, but many users just stick with the default music player app and think “That’ll do!” However, few default players include equalisation and if you’re hoping to improve your phone audio at zero cost, EQ has to be on your must-try list.
Everyone seems to have their favourite player, so here’s mine. The Onkyo HF Player on Google Play from audio specialists Onkyo gets my vote because it has one of the best equalisers you’ll find in an Android app that doesn’t require root access. It’s build on a digital-signal processing (DSP) technique called ‘finite impulse response’ (FIR) filtering, which effectively lets you specify the frequency band and amplitude change of the audio you want to modify. The Onkyo HF Player takes this to the extreme by incorporating up to 16,384 bands and turning them into a fully-customisable equaliser you create by drawing the precise frequency response you want on the screen. Compared with most fixed full-octave EQ options that might give you ten frequency bands to play with, this is the ultimate in frequency-response control.
Again, the downside is that the mathematics required to implement those FIR filters requires extra CPU cycles, so your device battery life might drop a bit, depending on the CPU and battery capacity of your device. But if you want to try to overcome poor audio with little--
to-no outlay, FIR-filter equalisation is the best way I know.
TRY SOME AUDIO MODS
If you’re seriously hard-core about your audio and you have an Android device that has root-access, you can try some of the audio effects libraries floating around specialist Android websites like xda-developers ( xda- developers.com). Two popular options are Viper4Android and A.R.I.S.E. SwanSong.
Viper4Android provides a dizzying array of audio filters and options, including different forms of surround, such as field and differential, as well as reverb. It includes FIR-filter equalisation like the Onkyo HF Player, but also adds extra features such as automatic gain control (AGC) to auto-adjust levels when listening on speaker.
Swansong takes Viper4Android a step further, bundling a whole new series of audio FX and profiles. This is as hard-core as audio-modding gets and isn’t for the feint-hearted or those who count down the remaining days of device warranty.
WARNING: SwanSong has to be flashed to your device and, once installed, it can’t be completely uninstalled unless you re-flash your phone ROM. In other words, try these options at your own risk. In both cases, read up on their install requirements before proceeding.
AVOID TOO MANY FILTERS
But on the other hand, you can’t guarantee adding a bunch of audio filters will somehow result in perfect sound. It may colour it, it may mask it so that you perceive it to sound better, but every time you fiddle with audio, you are modifying it and you can’t guarantee it’ll actually help.
When it comes to audio amplifier design, the ideal is to pass the audio through as few stages and through as few processes as possible, so that you have fewer opportunities to affect the audio quality — whether it’s by adding electrical noise, total harmonic distortion (THD), intermodulation distortion (IMD) or just straight-out clipping. But equally, passing the audio through numerous filters can also change its flavour.
The purists will always tell you if you want the cleanest audio quality, do as little to the audio signal as possible.
GET BETTER HEADPHONES
Now please don’t read this as ‘get expensive headphones’. While many earphones supplied with smartphones are probably best left to landfill, it’d be fair to say that a number of headphone models available on the market appear to focus on style over substance. If you want to look like a rock-god with a hip brand, fine, go for your life — but don’t assume more cash always buys you better sound.
From a technical perspective, I avoid headphone models with extra bass or top-end boost — the ideal headphones reproduce all frequencies equally (or have what’s called a ‘flat frequency response’). Any audio engineer worth their salt will create the right mix without requiring peaky headgear.
And finally, open-back headphones don’t block sound, so remember your fellow bus or train passengers when setting the audio level.
GET A BETTER PHONE
But if none of that works, it might just be time to fork out for a new phone. Yep, that sounds like the mother of all copouts, but there’s been quite a bit of work going into some recent high-end Android phones. For example, LG’s recent V20 smartphone features a new audio DAC design called a ‘Quad DAC’, which combines four 32-bit DACs in parallel for each audio channel. According to chipmaker ESS Technology, the ES9218 audio SoC delivers increased signal output and reduced background noise as a result, pushing the signal-to-noise ratio (SNR) to an impressive 125dB.
Rumours are the new LG G6 phone also features quad-DAC tech. But another less-known feature in these chips is the 2-volts RMS output amplifiers. This higher-level output provides greater drive for premium high-impedance headphones, something some phones struggle with.
At the end of the day, there’s really no excuse for listening to dodgy audio. Regardless of your budget, there are a number of techniques available that may just help squeeze some extra enjoyment from the gear you’ve already got.
And some of these tweaks will cost you nothing to try.