If you’ve been looking at modern surround sound receivers and Blu-ray players lately, you’re probably wondering what all the new nomenclature means – it can be very confusing! It was hard enough to determine the difference between 5.1 and 7.2 surround sound, but now we seem to have grown another term. Modern systems are now shown with a second decimal point and a third digit, such as: 7.1.4. What exactly do these extra numbers mean?! The objective of this article is to give you a top-level understanding of these new surround systems and their associated numerical nomenclature!
Surround sound has come a long way since it was introduced as “Dolby Surround ® ”, over 25 years ago. As it has evolved, though, it has seemed to grow more speakers! The original surround sound setup consisted of 4 speakers: 2 in the front and 2 in the back. But then “Dolby Pro Logic ® ” came around and added a center channel and a subwoofer. “Dolby Digital ® ” went a step further and gave each speaker a discrete, independent channel of sound. So at that point we had 5 speakers, plus a subwoofer that only handled some of the sound – so not quite 6 independent speakers. Thus, someone decided we needed a numerical code to address this new configuration. The new systems would be designated as a “5.1” system. The “5” indicates the number of main and surround speakers, and the “.1” indicates the number of subwoofers.
…Additional improvements over the years have added both side and rear surround speakers (“6.1” and “7.1”) and even additional subwoofers (“7.2”).
Dolby Atmos ®
So, we should be done, right? Certainly 8 or 9 speakers is enough for a proper theatrical experience? Well, if you ask the folks at Dolby, the answer is an emphatic “no!” The problem is that, if done properly per Dolby guidelines, a 7.1 surround system has speakers in front, to the sides and in back of you, covering all areas. But they are all at your ear level. This adequately covers two dimensions - width and length – but it doesn’t cover height. So, enter a new system called Dolby Atmos ® . This object-based surround processing system adds 2 or more speakers in the ceiling and gives the sound engineers the ability to use that missing dimension – height. Now they can place objects anywhere in the virtual space in your home theater.
There are several speaker combinations for an Atmos ® surround system, but the typical scenario uses an additional 4 speakers in the ceiling, in front of and behind the audience. So, once again, the experts decided we needed to change the code to signify the new configuration. And, hence, the second decimal and third digit were added. A full 4-speaker Atmos ® system with both side and rear surround speakers and a single subwoofer is thus referred to as a “7.1.4” system. 7 main and surround speakers, 1 subwoofer and 4 Atmos ® or “height” speakers.
Modern surround sound systems continue to evolve and are more impressive than ever. Although the configurations and nomenclature can be confusing, you owe it to yourself to go audition one of the new Atmos ® systems. Most critics agree that the addition of object-based decoding and height speakers has been the most significant advance in the theatrical sound experience in over a decade. Modern movies can now fully immerse the viewer with things going on above, behind and all around them. It’s really fun – go listen for yourself!