5.1.2 Speakers, Dolby Atmos, and a Playstation 5

Dolby Atmos speakers

Does “5.1.2” and “Dolby Atmos” sound like lingo from Star Trek? It’s not; it’s lingo about audio. A pet pieve of mine is that my Playstation 5 audio does — in fact — not sound right. Time for some technobabble.

5.1.what.now?

When Thomas Edison invented the phonograph, it could reproduce sound with one speaker.

In the 1930s, recordings evolved to include stereo sound, using two separate sound channels. As time progressed, more channels were added.

You may be familiar with surround sound. This comes in a number of varieties, but the one you might have at home is probably 5.1 audio: 5 regular sound channels and 1 bass channel. The idea of surround sound is that you want sound from different directions: left, right, front and back. That’s 4. And a separate center speaker is 5.

There’s also 7.1 audio. The 7 in 7.1 is when you add two more side speakers, so in total three to the left and three to the right, instead of two.

The .1 is the so-called subwoofer, which adds low frequency sound (A.K.A. bass). Our ears are not very good at determining the direction of low frequency sound, so you can supplement your surround speakers with a subwoofer, but you don’t need four or six of them. One will suffice, so 5.1, and 7.1.

Head spinning yet? Hopefully the diagram below clarifies this a bit.

7.1 Audio diagram
7.1 speaker setup

Enter 3D

There is one direction we have not discussed: the vertical. In other words, up and down. The diagram above is 2-dimensional, but there is a third dimension. The newest technology allows movie makers to add sound in that third dimension.

But how do you play that sound then? Yes, more channels and more speakers. In this case, height speakers. Height speakers project sound up. And that’s the final third number in the 5.1.2: speakers that send sound up.

So 5.1.2 sound is 5 regular speakers, 1 subwoofer, and 2 height speakers. For an example, take a look at the picture at the top of this post. The height speakers are the small trapezoid-shaped speakers on top of the left and right front speakers.

In short, the speaker notation is <regular>.<subwoofer>.<height>. There’s more to producing sound, though. The other part of the equation is encoding the sound channels.

PCM

When you have 8 to 10 speakers, the question is: how do you get data to those speakers that the speaker can convert to sound.

Sound is a waveform, and with record players, that was encoded with an analog track (a groove in a vinyl disc). For stereo, you use two sides of a groove to encode two signals. The waveform from the groove is sent to the left and right speakers, which transform it into stereo sound.

In the digital age, you encode sound with digital approximations of an analog waveform. Basically, you measure the height of the waveform X times per second and encode that in bits and bytes. You can do that for each speaker separately. That means, for eight speakers, you create eight channels of bits and bytes, that you send to each individual speaker. That’s called PCM (pulse-code modulation).

However, encoding a load of PCM channels is pretty costly in terms of bits and bytes. That means you need a big storage medium to store all the data. Blu-ray has limits, and if you’re streaming it over an internet connection, well…

Even if you could make that work, you’d also need to pump all those bits through the sound output of the Blu-ray player and/or TV set, and then through a cable. It’s possible, but costly, and would require a lot of expensive cable. A different approach is to save on bits.

Dolby Atmos

To solve the bit rate problem, encodings to compress the channels have been developed. Not all sound is equal to human ears, for one, and different channels are a lot alike, usually. By removing sound you can’t hear, or reduce quality for sound you can barely hear, and combining parts of channels, you can save bits. One famous standard is THX, mostly seen in theaters, and another one is Dolby.

Dolby — in fact — is a company that has created several encoding standards: Dolby Surround for surround channels in a stereo signal. Dolby Digital, Dolby Digital Plus, and Dolby DTS which encode true 5.1 sound. And finally Dolby Atmos. Dolby Atmos is the one that encodes height channels on top of 5.1/7.1 sound. So, Dolby Atmos is a way to encode full 5.1.2 / 7.1.2 sound.

One thing to note is that any encoding will only work properly if everything in your setup supports it. For Dolby Atmos, for example, the original encoded audio (from Blu-ray, Netflix, etc.) needs to be in Atmos. The device playing the Blu-Ray or Stream (your Smart TV for example) needs to support streaming Atmos. Your cables need to have a high enough throughput to support Atmos streams,. Then, your receiver (receivers are the devices that take encoded sound and video and send it to the actual speakers) needs to support Atmos to read the data. And finally, you need enough speakers to actually produce the 3D sound.

In my case, the reward of all this is a tiny Atmos icon on my receiver display when it all works.

360 reality audio

Of course, Dolby is one company, with one industry standard. There are other companies in audio land, and they have there own formats. Sony developed something called 360 reality audio, or just 3D Audio. That is another way to encode 3d sound.

Like Dolby Atmos, it produces both stereo and height sound. The difference is not fully clear to me, but if I understand correctly, 360 reality audio is designed with the idea of many individual sound sources in a 3d space, where Atmos is more geared towards audio channels with a limited number of added 3d object tracks.

The difference is not that relevant to us consumers. It’s far more relevant which hardware is capable of playing it. Many receiver vendors support Dolby Atmos. And guess what, Sony is the one mostly supporting their own 3d audio. Sort of.

You see, Sony 3D audio is only supported for television speakers and head phones. Sony can translate their 3D audio to specialized channels for their 3D headphones, and to stereo TV speakers, but nothing else. In theory Sony 3D audio can produce 3D sound on a 5.1.2 setup, but in reality there is no way to translate the encoding to the required 8 channels yet.

Enter the PS5 Tempest

The Playstation 5 will celebrate it’s second birthday in the fall. When announced, Sony explained it had put a dedicated audio chip in the PS5 that allows it to produce 3d reality audio. They lauded the great experience gamers would have with head phones.

They soon explained that, at first, the PS5 would only support those special headphones. Later, they would add stereo and soundbar support, and finally surround sets. Unfortunately, they only produced the stereo/soundbar support late last year. Home theater support is still nowhere to be seen.

So, I have a Playstation 5, and I have a receiver that supports up to 7.1.2 speakers and I have actual height speakers in a 5.1.2 setup. However, I have no real 3D sound with my PS5. The receiver supports PCM (8 channels), and Dolby Atmos, but not Sony 3D audio. No receiver supports spatial audio, of course, because no translation from that to 8 channels currently exists. The best I can do is turn on 5.1 surround sound. That’s still good, but I ain’t using my 2 height speakers.

It’s a bit sad, because my television supports Dolby Atmos, my receiver supports it, and my speakers support it. I can stream Amazon Prime, Disney Plus, and Netflix with Atmos, but not my God of War.

Pass-through confusion

So, when I read stuff on Reddit about this, I see a lot of confusion around the topic, mostly regarding the difference between 5.1 and 5.1.2, but also around Blu-rays. There is a small caveat to the story above, you see. When I say the Playstation 5 doesn’t produce Dolby Atmos or 3D PCM, that is completely true.

However, a Playstation 5 can also play Blu-Rays. And what it can do in that case, is send audio data from a Blu-Ray directly to a receiver. This is called pass-through. The Playstation passes on the audio data without touching it. This means no Tempest chip, and the audio channels are up to the Blu-Ray creators.

So, a Playstation cannot produce Dolby Atmos from a game, but it can play a Blu-Ray movie with Dolby Atmos encoded on the Blu-ray. This leads to a lot of confusion online. You can play Dolby Atmos movies on disc on a Playstation 5, but you cannot produce Dolby Atmos or 3D PCM from a video game running on a Playstation 5. Something that, for example, an XBox Series X can do: it supports Dolby Atmos fully.

So, much to my chagrin, the vaunted audio of the Playstation 5 is in my case worse than that of the competing XBox series X. Still, I can watch my Dune Blu-ray in all its Dolby Atmos glory, and that’s something.

eARC

Finally, a small side note. It gets more confusing when you add video: so-called eARC allows you to send signals across an HDMI cable in two directions so you can send video to the TV and audio back to the receiver. That complicates matters regarding bit rates and encodings even further.

But I’m not going into that today.

And now you know

I hope this gives you some insights into the world of Sony 3D audio, and why Playstation 5 and Home theater don’t always play well together.

And if a Sony employee reads this: go fix your sh!t, I want 3D audio from my PS5. Either that, or start supporting Atmos.

Martin Stellinga Written by:

I'm a science fiction and fantasy author/blogger from the Netherlands