– the demos!

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Be­tween last is­sue and this, we’ve heard two demon­stra­tions of Dolby At­mos, the lat­est and ap­par­ently the great­est in mul­ti­chan­nel sur­round sound (see also p79 and p92). The sec­ond was in a proper home cin­ema demon­stra­tion room with acous­tic treat­ment and fixed in-ceil­ing speak­ers, whereas the first was a tour­ing show set up in a ho­tel func­tion room, with ceil­ing speak­ers hung from an im­pres­sive con­struc­tion of lad­ders and beams hired from the lo­cal Bun­nings.

This is not to den­i­grate the first demo — in­deed we were hard pressed to pick a pref­er­ence be­tween the au­di­ble re­sults (they used the same Dolby demo Blu-ray, so com­par­i­son was mean­ing­ful), which speaks well for both demos, and for this new height-en­hanced for­mat in gen­eral.

For the record, the first demon­stra­tion was from Qual­iFi, us­ing Jamo speak­ers and a Marantz SR7009 ex­panded with an MM7025 stereo power amp for the ad­di­tional height speak­ers. The sec­ond was from Am­ber Tech­nol­ogy at their War­riewood HQ, us­ing NHT front speak­ers, 6.5inch two-way in-ceil­ing speak­ers (most prob­a­bly So­nance) and an Onkyo re­ceiver.

Adding height

Adding ob­jects

We de­tailed the At­mos con­cept in a fea­ture last is­sue. In brief Dolby At­mos adds ei­ther two or four ceil­ing speak­ers to an ex­ist­ing or new mul­ti­chan­nel audio sys­tem. If you cur­rently have 5.1-chan­nel sur­round, you could add two ceil­ing speak­ers to have a 5.1.2 Dolby At­mos sys­tem, or four to make 5.1.4. You needn’t stop there — home sys­tems can have up to 24 speak­ers on the floor and 10 over­head (see Dolby’s di­a­gram, right).

This abil­ity to scale is at the heart of Dolby At­mos, be­cause At­mos is not about adding chan­nels, it is about cre­at­ing a near-sphere of sound us­ing how­ever many speak­ers you have. And here’s the thing, re­mark­able as this propo­si­tion sounds — the fi­nal audio mix­down hap­pens in the AV pro­ces­sor, in the At­mos decoder, not in the stu­dio where the sound­track was fash­ioned. There are still audio chan­nels — nine of them, now be­ing called ‘beds’. But the sound en­gi­neers can then add audio ob­jects, their sound sep­a­rately en­coded along with meta­data that de­scribe their po­si­tion in three-di­men­sional space, their phys­i­cal spread, and the sound’s in­ten­sity. Only at the decoder will th­ese audio ob­jects be placed into spe­cific chan­nels, this de­pend­ing on how­ever many speak­ers are avail­able, and how they’re set up. So ex­actly the same sound­track used in the cin­ema can be used at home, with Dolby At­mos able to scale down to home lay­outs — in­deed, we gather, all the way to mono if re­quired.

This shows the re­mark­able com­put­ing power that lies within to­day’s AV pro­ces­sors and re­ceivers, for one thing, but it is most re­mark­able in de­liv­er­ing an en­tirely new way of stor­ing and trans­mit­ting audio, as sep­a­rate frag­ments tagged with meta­data to be down­mixed at the end user. With 128 audio ob­jects avail­able, the sound­track guys can have a fair bit of stuff whizzing around the au­di­to­rium — or so you’d think. But there is a sig­nif­i­cant lim­i­ta­tion on this, which we thought was audi­bly ev­i­dent in both the At­mos demon­stra­tions we heard.

Does it scale? Just a bit — here’s Dolby’s di­a­gram for a sys­tem with 34.1 speak­ers At­mos cer­tainly adds an ad­di­tional di­men­sion in pro­vid­ing height chan­nels, and of course the demo ma­te­rial comes steeped in ceil­ing sound to show off the new abil­i­ties; you get bom­barded with sounds fly­ing above and around you. But what it doesn’t do is come at you, like an axe in a 3D hor­ror movie. The most sur­pris­ing thing about the At­mos demos was that while stuff was whizzing around ev­ery­where from front to ceil­ing to rear, there was noth­ing in the room. Ev­ery­thing is around the room. The sec­ond demo de­liv­ered some fairly lo­calised po­si­tion­ing be­hind us, but never did any­thing go right in front of our face, buzzing like a fly be­fore our nose.

Why? Be­cause in a cin­ema, if you mixed a fly to be an audio ob­ject in front of your nose, then it would ap­pear to be in front of the noses of those in the dead cen­tre rows, but pro­gres­sively out of po­si­tion for ev­ery­one else in the cin­ema. Ditto for front to back move­ment. In the cin­ema that’s an un­fix­able prob­lem which can only be ad­dressed by not al­low­ing it — no flies in front of your nose. So At­mos seems to de­liver a sphere. The sound moves around, but it does not en­ter far inside.

Home cin­e­mas have far fewer seats — even just one sweet-spot seat, if you like. So At­mos could po­ten­tially de­liver a far more lo­calised sonic ex­pe­ri­ence at home than in the cin­ema. But it won’t, pre­cisely be­cause the ex­act At­mos sound­track from the cin­ema is be­ing scaled down to the home with­out en­gi­neers remix­ing it for a dif­fer­ent en­vi­ron­ment.

At­mos cre­ates a trun­cated sphere of sound

It’s all around you

It’s not be­low you

And the sound is not quite a sphere but a trun­cated sphere. We were con­scious that the sphere was cut off at seat level, ef­fec­tively the tweeter level of the front speak­ers. There’s not much to be done about that, and it’s not new — there’s never been any sound down there. But gain­ing the sound above seemed to cre­ate a con­trast with the lack of sound

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