Why a Dummies guide to Dolby Atmos and DTS? Because 99% of the reviews we read get it wrong and 100% of users are equally confused by the terminology.
So we developed the ‘Dummies Guide to Dolby Atmos and DTS’ to demystify and clarify just what you are getting when you buy a Dolby Atmos TV or a soundbar expecting that it will magically have Dolby Atmos 3D sound. Chances are that it will be nothing more than a stereo device.
Audiophiles can stop reading the Dummies guide to Dolby Atmos and DTS now. This guide is about Dolby Atmos TVs and soundbars – we will add dedicated Dolby Atmos AV receivers later.
What is Dolby Atmos sound?
Think of Dolby Atmos as 128 microphones spread around, up, over and back from a movie sound stage. This allows movie makers to capture sound movement as it goes at the speed of sound from microphone to microphone (phasing sound). So, if a plane flies overhead you hear it tracking its course ‘up there’ while other sounds on different ‘planes’ still occur. It is 3D, immersive sound.
Technically it expands on existing surround sound systems by adding ‘height’ channels, allowing sounds to become 3D objects. Creators have a total of 128 channels routed to up to 64 speakers.
But I can get Dolby Atmos on a smartphone – even a toaster!
Dolby Atmos has become the gold standard in 3D sound and it has expanded its reach from movies and music to smartphones, gaming and even appliances – yes you can get a toaster with Dolby Atmos.
But it has become one of the most misused and abused marketing terms. Something with Dolby Atmos does not have to do anything more than decode the Dolby Atmos metadata stream and allocate it to the physical speakers it has.
It is ridiculous to think that a Dolby Atmos equipped smartphone with two mismatched speakers (earpiece and down-firing) can produce an expansive sound stage. Sorry but that is Easter Bunny territory.
Similarly, a TV with Dolby Atmos processing simply down-mixes content to the physical number of speakers – usually 2.0 or 3.0 channels. Again it is marketing BS to claim it has Dolby Atmos sound when all it has is a decoder chip.
But I want better sound
TVs universally have poor sound because that is all they need to deliver free-to-air TV that has PCM 1.0 (mono) or stereo 2.0 sound. Most have tiny 50mm speakers that on the 20Hz to 20kHz frequency response scale get around 1-6kHz (mid-to-upper mid) for clearer dialogue.
Any non-Dolby Atmos TV can benefit from a 2.1 (stereo and sub-woofer) or 3.1 (stereo, centre and sub-woofer) soundbar that uses its own digital signal processor to add a bit of volume and some bass from say 60Hz and treble to 10kHz.
But as we start streaming content more to 4K TVs that now cost the same as 1080p TVs we are starting to realise that TV sound is CRAP.
Enter the world of Dolby Atmos, Dolby Digital, DTS:X and DTS and more. And you know what – 99.99% of these so-called Dolby Atmos TVs only have a decoding chip and down-mix to whatever the TV speaker system handles or pass through the signal to an external soundbar./.
But my TV is Dolby Atmos. How do I get true Dolby Atmos sound?
Remember that few if any Dolby Atmos TVs come with a Dolby Atmos speaker system capable of 3D sound. You have to upgrade by adding a Dolby Atmos soundbar or AV receiver and speakers.
That means a choice of Dolby Atmos 5.1.2, 5.1.4, 7.1.2, 7.1.4 and now 9.1.4.
By the way, the .1 stands for a sub-woofer that is for frequency cut-over handling low and mid-bass. It is the same way that tweeters don’t count as Dolby channels as they are frequency cut-over handling upper treble. Read more later.
The Dolby Atmos soundbar chip down-mixes the 128 channels to the number of prime channels, e.g. 5, 7, or 9 and the number of height channels, e.g. 2 or 4.
Dolby Atmos is different from other Dolby standards that are simply audio channels – e.g. have no Dolby Atmos metadata.
True HD (7.1 channel audio and the default if an Atmos metadata is not present)
Digital Plus (7.1 used by Windows, macOS)
Digital 5.1 also called Dolby AC-3
What is DTS (Digital Theatre System)
DTS:X is alternative technology to Dolby Atmos
DTS-HD is similar to Dolby Plus 7.1
DTS is similar to Dolby Digital 5.1
We won’t go into which system is best – just that they try to achieve similar things and most soundbars handle both formats.
Why bass (Sub-woofer) and treble (Tweeter) are not Dolby Atmos or DTS:X channels
Human hearing maxes out from a low of 20Hz (bass) to high of 20kHz (treble). Many older Australians may only hear from 1 to 3kHz, so they hear more muffled sounds requiring clear voice amplification!
Few speakers can reproduce 20Hz-20kHz so dedicated speakers help to fill in either end. These are not Dolby audio channels but simple frequency cut-over.
Sub-woofers amplify any bass below a cut-over frequency (usually between 80-110Hz). So, when you add a sub, you both hear and feel more bass (a combination of volume and air movement). Subs are worth adding to enhance the overall Dolby Atmos movie experience. Without it, you get whatever bass the soundbar can produce – reasonable but not room-shaking.
To get Dolby Atmos or DTS:X sound you need metadata encoded content and a whole lot more
Content comes from Blu-ray, some games consoles and some streaming services. It does not come from DVDs, free to air TV, or 700/1080p streaming.
If you look at the 4K Blu-ray above you will see HDR: Dolby Vision and Audio: Dolby Atmos.
Now if you have the right TV with eARC, 4K Blu-ray player, HDMI 2.0 cables and soundbar you will get this. If not all you will get is stereo 2.0!
Cables: You must have HDMI 2.0 cables connecting all devices (information here). These are Premium High Speed (HDMI 2.0) or Ultra-High speed (HDMI 2.1) although most Dolby atmos soundbars abdn TVs are still at 2.0. Gamers with the PS5 may object to the lack of HDMI 2.1 ports!
TV: The TV must support Dolby Vision/Atmos/HDR10/DTS:X metadata via eARC to the soundbar (only late model 4K and 8K TVs do this). Some soundbars have additional HDMI 2.0 inputs to connect external sources and will pass through a Dolby Vision image to the TV.
BTW – If you have an older TV with ARC it will pass through compressed Dolby Atmos signals, But whenever you compress something you lose things in the translation.
What is Dolby Atmos (and DTS:X) home theatre?
We will come to the issues of all-in-one soundbars later. For this table the terms overhead, up, up-firing and ceiling speakers are the same and refer to adding overhead sound, e.g. height. The .1 is for a Sub-woofer.
Base 5.0/1, 7.0/1 and 9.0/1
5.1 (and 2/4)
7.1 (and 2/4)
9.1 (and 2/4)
1. Left front
2. Right front
3. Centre front
4. Left surround
5. Right surround
6. Left rear surround
7. Right rear surround
8. Left wide surround
9. Right wide surround
Dolby Atmos must have at least two overhead channels.
If not, it becomes more of a faux surround sound reproduction and you may as well buy a straight 2.1 soundbar.
.2 Left front overhead
.2 Right front overhead
.4 Left rear overhead
.4 Right rear overhead
Here is an illustration of the current top home spec 9.1.4 or nine audio, one sub and four height channels.
Confused – most are. Remember Dolby Atmos needs a .2 or .4 overhead speakers!
Dolby Atmos can work on as little as a 3.1.2 soundbar like the LG SN7Y or a Samsung HW-Q70T. It just means the 128 channels are down-mixed. As spoilt audiophiles, we cannot recommend 3.1.2 (Left, right, centre, left up/right up-firing) but if you have never had Dolby Atmos before it sounds pretty good. BTW if a soundbar advertises it is Dolby Atmos 5.0 it is really 3.0.2 (plus a sub).
A single 5.1.2 uses front up-firing or side-firing front speakers (we call this psychoacoustic trickery) to bounce/reflect sound off the ceiling or wall and drop it somewhere behind the viewing position where you would normally have speakers 4 and 5 (in our table and #6 above in Dolby parlance) – left and right surround.
Exception: Sennheiser’s $4000, 5.1.4 has nailed it for an all-in-one soundbar. It does depend on the room setup but has one of the best calibration systems I have every used to tune the bar to the room.
If a single soundbar is 5.1.4, it is 5.1 and uses another four up-firing speakers to provide the .4 channels (#8 in Dolby image). JBL Bar 9.1 is really a 5.1.4.
It is very hard to get 7.1. let alone 7.1.2 from a single soundbar. Samsung’s new 7.1.2 Q900T or has no separate L+R rear speakers. But if the room has the right surfaces and dimensions, you can do it (not tested).
It really depends on the quality of the Dolby or DTS decoder to phase the sounds across the 5/7/9 channels and 2/4 height channels. For most users, a 5.1.2 system is pretty good.
If you have a non-Dolby Vision/Atmos TV buy a low-cost 2.1, 3.1 or 5.1 soundbar for sound reinforcement. This is perfect for free-to-air and HD streaming.
If you have a Dolby Vision/Atmos TV (and all the gear) buy at least a true 5.1.2 or 7.1.4 Dolby Atmos and set it up properly. Soundbars with dedicated rear surround/up-firing speakers are best as they don’t rely on psychoacoustic trickery.
We will keep adding to the Dummies guide to Dolby Atmos and DTS guide as we get more questions from readers?