Dolby takes sound above and beyond

Home theatre has come a long way over the last couple of decades. One company that has been the driving force behind it, and with a history spanning 50 years — is Dolby.

Founded by Ray Dolby in 1965, the company soon became known for its noise reduction technology used in audio recording and playback.

It was only a matter of time before that technology was put into practice in film making.

The groundbreaking anti-culture film, A Clockwork Orange, was the first film to use the Dolby noise reduction process, with the blockbuster Star Wars using Dolby Stereo in cinemas.

Flash forward to 1982 and Dolby Surround is perfected.

Further developments saw the creation of a surround sound format with a dedicated subwoofer channel — 5.1 becomes the standard for home theatre.

Movies are released with the expansion of Compact Disc. Called DVD or Digital Versatile Disc, lasers read and decode the embedded signals. Blu-ray goes further, with more room for a better picture and enhanced sound.

Receivers become available that process 7 channels, even 9 and 11 channels, however these are effectively project sound at ear level.

Dolby Atmos takes that surround sound and applies it to a higher plane — literally.

This next level of sound processing allows movie makers to further envelop the listener and viewer in sound that is not just around, but above.

Dolby refers to the idea as a “dome of sound”, in the way the atmosphere is a dome over our location.

Consider a movie with a World War II aircraft battle. The sounds of the engines, or guns firing, are around the viewer’s location, and as a plane flies overhead, the sounds follow the plane.

This brings that aural envelopment to an extra level which makes the watcher feel as if the plane really has flown over them.

Home theatre receivers can distill two, or four, discrete Atmos channels.

And a new development in home theatre and stereo sound is the addition of an extra subwoofer channel. 

In a 5.1 or 7.1 system, the .1 is a dedicated LFE or Low Frequency Effects channel. In simple terms, it’s the channel that brings the BOOM to a movie.

Because the range of sound is low in frequency it allows a subwoofer to be placed almost anywhere in a home theatre as the source can’t be pinpointed.

However, some subwoofer units are large in size and take up a lot of room. Sonic development has found that two smaller subwoofer units can actually enhance the quality, and depth, of the low end sound.

That single channel may not be suitable for all viewing and listening environments, whereas a twin subwoofer system will fill in, in a sense, the audio hole a single sub cannot fill.

When it comes to stereo music listening, a pair of subwoofers can provide that extra lower end fill without losing the “image” or the soundstage of the recorded piece.

Think of a thumping bass line from a rock band, and that sound has more punch, more depth, without blowing the lower frequencies out to a point where it sounds “muddy” or indistinct and lacks clarity.

A visual indication on the shop floor may now read something like 7.2.4. This decodes as 7 surround channels (centre, front left and right, surround left and right, and rear left and right) with two subwoofer channels, then four Atmos channels for that overhead sound.

Those two subwoofer channels, by the way, is more marketing speak. The “2” actually indicates two physical subwoofers outputs on the back of your AV receiver, each sending out the same LFE signal. 

Scott Sauer from The Digital Picture says: “When utilising only a single subwoofer, most rooms will have only a few small listening positions that offer good bass response.

“By using two subwoofers correctly placed in the room, the sweet spot listening position will increase to a much broader area which will allow more seats and more rows to enjoy great powerful bass without hearing any of the modal nulls which present themselves as sometimes massive drops in power at particular frequencies. 

“In a multi-subwoofer setup, correctly placed subwoofers should in almost all instances be connected to a single sub out with identical time and phase settings in order to realize any cancellation of room peaks and nulls. This will provide a smoother pre-calibration bass response at the listening position which allows the system to be easily calibrated.”

It is also highly recommended that in a dual sub setup, for enthusiasts the best results are easily obtained if both subwoofers are the same sub of brand, size and model with their volume settings set to the same level on each sub.”

With movies being released in ultra-high definition video with Atmos sound processing, the home theatre experience is ever closer to that seen and felt in the theatre complex.

(Picture credits Scott @ The Digital Picture, online sources)

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