DAB and DAB+. Mono, low bitrate audio is more common than you might think

Hello again. Now, you may remember, in years past, how I tried to fill the lengthy commute with some music that I’d actually enjoy rather than the bilge that was being offered on my car radio. It was a fair few years ago now, so I had a car full of CD’s and a few FM radio stations. That was it.


This was a time before DAB radio – which gives us a wider choice of radio stations, and before DAB radio kit could be found in any car. So, once I’d exhausted my CD collection and I’d grown tired of having to copy MP3 files onto my phone each night, I decided to get a 3.5mm audio plug wired into my car radio.

Nowadays there’s endless FM broadcasting gadgets like this which will pair via Bluetooth to your phone and then output a very low-powered FM signal so that your car radio can tune in. They’re very clever and I’d recommend that you get one if you’ve got an FM radio in your car as it’s cheaper than getting a DAB radio plumbed in. You simply pair your phone with the clever Bluetooth / FM gadgets and play your local or streaming audio. It comes out your speakers and you’re ready to rock.

In years past I’ve given this whole thing a test with internet radio streams. This was back in 2011 when DAB was still fairly young and the signal in my local area wasn’t great. So instead, I used TuneIn radio on my phone and listened to a 128k MP3 stream. This then fed into my car stereo via a 3.5mm hook-up (you could use a Bluetooth connection now though).

The phone data connection was fast enough and the 128k audio stream was very clear. It opened the door to a vast range of live internet radio streams from all over the world. I could listen to stations from out of my area, from other countries and, of course, to music supplied by streaming services.

That 128k stream used around 1MB of mobile data per minute, which is obviously 60MB per hour.

Now, however, I’m lucky enough to have a DAB radio at home and in the car. DAB radio works in a broadly similar way. It’s a digital stream which you receive in your car.

However….

That 128k audio quality isn’t always what you get. Also, just to add some complexity to the mix, there’s now different methods of encoding the audio stream. So, are you sitting comfortably? :) Then we’ll begin.

First, the “original” DAB audio signal. This is actually encoded in MP2, which is an ancestor to MP3. A lot of stations on DAB will have their signal encoded as 128kbps. It’s considered a bit “old school” now.

In addition, there’s DAB+. This is encoded in aacPlus. This is a standard which uses less bandwidth whilst delivering a similar audio quality. A 48kbps DAB+ stream, roughly speaking, will sound similar to a 128kbps DAB signal.

Because the DAB+ system is three times more efficient, it means that more stations can be carried and the audio quality, to the human ear, is the same.

So great digital audio quality and more choice, right?

Err… well, not always, no. A 48kbps aacPlus service will sound great, but there’s stations out there choosing to use far lower bitrates.

People switch to DAB partly for the increased choice. So, stations are stepping up to fill that requirement but reducing the signal quality to make it cheaper

I compare it to the days when my dad used to listen to his “60’s Classics” station. It was on Medium Wave and, although it was in mono and the audio quality wasn’t overly amazing, it offered the choice that wasn’t available on traditional (and popular / cluttered) FM stereo broadcasts.

So, some of the digital stations broadcasting on the supposedly superior DAB and DAB+ system are making their existence worthwhile by using lower bitrates or switching to mono.

Station Bitrate Audio
Absolute Radio  80 kbps Mono
Absolute 70s 64 kbps (L) Mono
Absolute 80s 80 kbps Mono
Absolute 90s 80 kbps (L) Mono
(Absolute) Classic Rock N/A N/A
Absolute Radio Extra 64-112 kbps Mono
Ahomka Radio 64 kbps (L) N/A
Awesome Radio 64 kbps Mono LSF
BFBS Radio N/A N/A
Capital FM 128 kbps (L) Joint Stereo
Capital Xtra  112 kbps Joint Stereo
Classic FM 128 kbps  Joint Stereo
Desi Radio N/A N/A
EWTN N/A N/A
Fun Kids 32 kbps Stereo (DAB+)
Gold 128 kbps (L) Joint Stereo
Heart 128 kbps (L) Joint Stereo
Heart extra 80 kbps Mono
Heart 80 80 kbps Mono
heat 80 kbps Mono
Jazz FM 32 kbps Stereo (DAB+)
Kerrang! (UK only) N/A N/A
Kiss (UK only) 80 kbp/s Mono
KISS FRESH (UK only) 64 kbps (L) Mono
KISSTORY (UK only)  64 kbps (L) Mono
Kanshi Radio N/A N/A
Khushkhabri N/A N/A
LBC 64 kbps Mono
LBC News 64 kbps (L) Mono
Liberty N/A N/A
Magic (UK only) 80 kbps Mono
Magic Chilled (UK only) 32 kbps Stereo (DAB+)
Magic Mellow (UK only) 80 kbps Mono
Panjab Radio 56 kbps Mono LSF
Planet Rock 80 kbps Mono
Premier Radio 64 kbps Mono
Radio X 80 kbps Mono
Rainbow N/A N/A
RNIB Connect N/A N/A
Share Radio 64 kbps Mono
Solar Radio  N/A  N/A
Smooth Radio 128 kbps Joint Stereo
Smooth Extra 80 kbp/s Mono
Sukh Sagar N/A N/A
Sunrise Radio 64 kbps Mono
talkRADIO 64 kbps Mono LSF
talkSPORT 64 kbps Mono
talkSPORT 2 64 kbps Mono LSF
The Hits N/A N/A
TWR N/A N/A
UCB1 UK 64 kbps Mono
UCB 2 UK 64 kbps Mono
Union JACK 24 kbps Stereo (DAB+)
Virgin Radio 80 kbps Mono
WRN Europe N/A N/A

As expected, there’s not a great deal of information around the internet telling you this. The information above is from this Astra2Sat page, which had the bitrates for a lot of the DAB stations. From this, we can see that Fun Kids, Jazz FM and Magic Chilled are all broadcasting 32k streams. Panjab radion runs a 56k Mono stream and Union Jack, which is proving to be quite successful at the moment, runs a 24k stream. All of these, apart from Panjab, run on the DAB+ system. It’s interesting to see that Union Jack has recorded the fastest-growing audience in the UK, despite (from the evidence we have) it using the lowest bitrate stream anywhere on digital radio.

What also gets me, and again I’m using the only evidence we have (from this page) is that new digital stations like Absolute Radio, Absolute 90s, Heart extra, Heat, Kiss, Kiss Fresh, Magic, Planet Rock, Radio X, Smooth and Virgin, are all broadcasting in glorious mono.

In your car you might notice the lack of stereo, but we live in strange times. The big broadcasters who run these stations know that…

1 – DAB+ is still quite “young” and doesn’t quite have the reach of DAB, so they choose mono on DAB even though it might be more cost effective to switch to stereobon DAB+.
2 – Most people use single-speaker DAB radios, or “smart speakers”, or Bluetooth speakers. So stereo isn’t a consideration. People only have one single speaker.

So right now, mono and lower-bitrate radio stations are actually more common than you think.

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