Opening Note
I previously disclosed that many audio enthusiasts lack a basic understanding of audio concepts, such as stereo audio. It holds for multi-channel surround sound, which was built on the foundation of stereo audio.
If you’re interested, select this LINK to confirm the definition of stereo audio.
Kickoff
A friend disclosed that his interior decorator (read wife) had given him a ‘permission slip’ to install a home theater surround sound system. He was pumped and ready to ‘set off into an audio/video adventure.
The permission slip safeguards my friend and his audio/video dealer from injury.
However, his enthusiasm was ‘short-circuited’ by the barrage of speaker layout options and their acronyms. Confused and discouraged, he sought help. This blog is for him and others in a similar situation.
Before we ‘forge ahead’, let’s chart some pivotal dates in the history of surround sound cinema
Cinema Sound
The origin of surround sound lies in ‘cinema sound’ of the 1930s.
Monophonic cinema sound systems of the era annoyed many with sound emanating from points different from the screen image. Included among the annoyed sat Alan Blumlein, the inventor of binaural audio (stereo). He created binaural stereo audio to address the issue.
Stereo audio was great for those seated at or near the stereo equilateral triangle ‘sweet spot’.
However, if seated well left or right of and closer to the ‘sweet spot’, a screen-centered actor’s voice emanated from the edge of the screen. Multi-channel audio solved the problem.
Multi-channel Audio
Multi-channel cinema audio synced the audio with the screen images and added enveloping sound effects. Here’s a sample of multi-channel audio highlights.
1940 – Disney’s Fantasia introduced multi-channel audio with surround effects.
1952 – Cinerama Theaters featured seven surround sound audio.
1953 – 20th Century Fox’s ‘The Robe’ included surround sound audio.
However, these were elaborate installations limited to select major city theaters.
That was the case until Dolby Surround arrived.
1976 – Dolby Labs introduced an economically viable multi-channel system for neighborhood theaters.
Bring It Home
Dolby multi-channel audio was an exclusive movie theater format until the HiFi Stereo VCR landed on retail shelves. The Stereo HiFi VCR and the forthcoming DVD player, partnered with a surround sound receiver, created what we now call home theater.
1982 – The HiFi Stereo VCR brought Dolby Surround Sound home.
1997 – The DVD introduced digital surround audio formats.
I provided this slim slice of cinema history to add perspective to the evolution of multi-channel audio.
Now let’s rescue our discouraged friend from his home theater blues.
Forge Ahead
What was the lead source of our friend’s confusion?
The answer is Dolby Labs.
The Dolby website offers 36 home theater layout options and acronyms.
That alone is enough to bend the mind of any budding home theater enthusiast.
But the confusion is compounded by component options, his floor plan, room acoustics, and installation obstacles such as doorways, windows, furniture, and cable/wire paths.
Yet, my lead concern is speaker placement.
Speaker placement is critical to a successful outcome.
However, a typical home floor plan is often a challenge for even stereo audio placement, let alone
multi-channel audio. Our friend’s floor plan falls into this category, which can jeopardize his home theater investment. Given this, I recommend limiting his system to a Dolby 5.1 layout.
The Dolby 5.1 Layout
A Dolby 5.1 surround sound speaker layout radiates the sound of screen images from their screen location via the front left, center, and right speakers. As the name implies, rear speakers create enveloping sound effects. The number 1 in 5.1 represents a dedicated subwoofer channel of low-frequency sound effects.
‘Star ships’ fly front to back, left to right, diagonally, circularly around the room, and reinforced by exploding concussive sound.
The above illustration specifies the Dolby 5.1 speaker layout.
• Five speakers on the floor plus the subwoofer.
• The front left and right speakers are located at 22° or 30° from the sweet-spot seat.
• The center speaker is ‘centered’ between the left/right speakers.
• The subwoofer is placed where it is most effective. (More on that later.)
My 5.1 Modifications
My advice differs slightly from the official layout as follows.
Understandably, the layouts focus on cinema sound.
But my modifications also address the interests of the stereo music enthusiast.
Stereo
• Select the 30° front left/right speaker location option.
• Place the listener’s ‘sweet-spot’ seat in an equilateral triangle with the front left/right speakers.
Cinema Surround
• Sketch a circle with a radius from the front left/right speakers to the ‘sweet-spot’ seat.
• Place the rear left/right speakers at or within the 110° or 120° locations.
Maximize Fidelity
• Place all speaker midrange/tweeters at or near ear level.
• Place all speakers at points that minimize room mode distortion. (See links below)
Minimize the Compromise
The above assumes a perfect audio world.
I know, we don’t live in a perfect world.
However, at a minimum, place the front left/right speakers as I specified.
Then address remaining issues, such as compromised rear speaker plus subwoofer placement, or distorting room acoustics, with the help of the following ‘how-to’ links.
• Minimize room mode distortion: The Mounkes Method
• Easy acoustical solutions: Sonic coloring
• Not so easy acoustical plus and video solutions: The Room, Speaker, & TV.
• Minimize the compromise of the architectural speaker
• Baffling custom speaker installation
• Auralex Acoustics 101
Dolby Atmos Layouts?
This is for the Dolby Atmos 5.1.4 & 5.4.2 fans.
The #4 and #2 of these layout options add ‘above speaker locations’.
Atmos creates additional enveloping sound effects.
The ‘above speakers’ perform best if hung from or installed in the ceiling.
That’s It
He did it.
Our friend replaced chaos and confusion with an organized plan.
And with his permission slip in hand, he’s ready to set off into a home theater adventure.
Give him a standing ovation.
.
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