Home Theater Sound Considerations
After finalizing the room layout and seating plan, I need to answer some important questions about which type of speaker to use, the appropriate speaker setup, and where to place the speakers. These decisions can significantly impact the room's layout. Some of these considerations may seem obvious, but I want to ensure the room is compatible with the desired sound configuration. ​The relevant surround sound information and decisions are covered in the sub-sections on this page. The next page describes the decisions made regarding subwoofer usage.
Selecting the Basic Surround Sound Configuration
Last Updated: 09/02/2024
When deciding on the speaker configuration, it is advisable to use Dolby's speaker placement configurations and recommendations as a guide and match the configuration to the limitations of the room. When the initial room design was done, the concept of ATMOS for the home had not yet been invented. ATMOS, so it was added later. This is described in the next section.
Dolby's speaker setup guides are posted on the dolby.com website, Speaker Setup Guides (web).
These should be treated as guidelines and not rules. If speakers could not be placed precisely, they were placed as close as practical. Since this room is a dedicated theater, meeting the guidelines was not difficult, although squeezing in a second row caused some minor compromises. ​
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Dolby has defined about seven base-layer speaker configurations (no overhead speakers). I considered 4 of these.
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2.1/3.1—Front speaker configuration is usually used when it is difficult to place or connect the surround speakers, typically in a multi-use room. It provides upgraded sound over TV but no side/back sounds.
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5.1—This configuration gives excellent envelopment; 7.1 adds some ambient rear sound but is incremental over 5.1.
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7.1—Adds rear surrounds, which is helpful if there is room behind the primary listening position. If seating is close to the back wall, use 5.1.​
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9.1—This adds speakers between L/R and side surrounds to fill in sounds between the two, called Front Wides. Very little content encodes 9.1. The benefit of a smaller room is debatable.
Note: See Figure 1 in this section for the definition of the Dolby numbering scheme.
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There were a couple of generic considerations before deciding on the exact speaker configuration.
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If the budget is limited, one can start with the front speakers and add the rest of the speakers over time, which is what I did.
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Wire is cheap; therefore, designing and wiring for the maximum expected configuration is preferred.
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Being a dedicated room, there were few speaker placement limitations.
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Using all these considerations, the theater was designed for 7.1. I would have also wired for ATMOS, but it was not an option then. 7.1 was chosen because we have enough room behind the seating for speakers. It was also decided that front-wide speakers were unnecessary.
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Figure 1. Dolby Placement Recommendations for 5.1 and 7.1
More Regrets on Not Doing a False Wall
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Again, in hindsight, it would have been worth the extra effort to create a false wall, place the screen on the false wall, and place speakers behind the screen.
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A clean look up front.
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Flexibility in speaker choices and placement
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A way to hide equipment in the room.
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Allow for additional (hidden) acoustic treatments in the room.
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Added expense for an Acoustically Transparent Screen and increased build complexity.
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Speaker Distances and Heights
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The Dolby Recommendation (and PDF)provides more details on speaker placement but notably does not specify a distance for each speaker. This is because it states that all speakers should be equidistant from the listener or that the system can compensate for audio delays. Since most AV receivers provide distance calibration, very little consideration was given to speaker distance.
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The height recommendations currently are that all listeners should be at the same height (3.9 feet). All speakers should also be at the same height. This seems impractical for a room with multiple listeners and seating rows; hence, some tradeoffs were made. At the time of my initial design, these documents weren't available, nor did I follow them. The guidelines for speaker height used were as follows:​
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Position the left/right front speakers so the tweeters are at ear height. This helps ensure a good frequency response from the listener.
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Place the surrounds ~5-6 ft. high. This was done partly to move them out of the room's traffic and to give each row of listeners direct sound from each surround.
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Since height speakers did not exist at the time of the original design, it was a general recommendation to place speakers so each listener had a clear view of their ear from the surround speakers. Placement about a foot above ear height accomplishes this. However, placing surrounds lower with ATMOS distinguishes the base layer speakers from the overhead speakers. I placed surrounds at ~5.5 ft. for this home theater and left them for ATMOS.​
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Adding Dolby ATMOS Height Speakers
Last Updated: 09/02/2024
With the advent of Dolby ATMOS (and similar recommendations), a "standard" method for adding overhead sounds was defined. Since most video media is distributed with ATMOS mixes, only the Dolby recommendations (and PDF) were considered for this theater.
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Dolby's recommendations specify ATMOS speaker placements for 2, 4, 6, or 8 overhead speakers. Some considerations for deciding which option to go with are:
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Two overhead speakers can only pan overhead sounds left and right, but this is the least expensive option.
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Four overhead speakers can pan sounds left, right, and front and back.
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6/8 overhead speakers can pan like four speakers and better spread the sound across multiple rows. This option requires a much more expensive receiver and, of course, more speakers.
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From the above, it was apparent that I should plan for four speakers. For this small home theater, I focused on the best placement for the primary listening position and felt that the extra cost of 6-8 overhead speakers was not warranted.
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Dolby provides several placement diagrams for ATMOS. For the top-down view (see Figure 2), I referenced a 7.1.4 placement. For the side view, Figure 3, which shows the placement options, I chose Top Read/Front for the primary listening position. To achieve the desired 45/135-degree angles, the speakers are about three ft. in front of and behind the main listening row.
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One slight confusion is how far apart the height speakers should be relative to the room width. In most Dolby diagrams, the ATMOS speakers are shown aligned to the front left/right speakers, but this does not work depending on the placement of the front speakers. Another guideline is that the ATMOS speakers should be placed such that the distance between them is between 0.5 and 0.7 of the room width and within the listening area. This is shown in green in Figure 3.
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The Dolby diagrams only show one row of seats, so how should I set up when I have multiple rows of seats? The ATMOS speaker placement for this theater was optimized for the main (back) viewing row. The front row's speaker positioning was somewhat compromised but still quite acceptable.
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As mentioned in the previous section, the surround speakers were placed vertically higher than recommended, resulting in a less-than-optimal separation between the rear surround and top-rear overhead speakers.​
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Figure 2. Dolby ATMOS Placement Recommendations for 5.1.4 and 7.1.4
Figure 3. Overhead Speaker Placement Recommendations
Useful references.​​
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Dolby ATMOS Speaker Setup Guides (Web site)
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Dolby ATMOS Home Theater Installation Guidelines, 2018 (PDF)
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ITU R BS.775-4-202212-1 —Multichannel stereophonic sound system with and without accompanying picture
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ITU-R BS.1116-3-201502—Methods for the subjective assessment of small impairments in audio systems
Selecting Speaker TypeÂ
Last Updated: 09/02/2024
After deciding to implement a 7.1 system initially and later upgrade to a 7.1.4 system, several considerations were made regarding the types of speakers to choose from before selecting the final speaker model(s). Choosing the exact speaker model/brand is covered later in this section.
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Relative Importance of Each Speaker
The amount of sound contributed by each speaker is not equal. Most of a movie's sound comes from the front speakers (LCR), whereas surround and height speakers usually are focused on ambient sounds. Here is my subjective list of speaker importance:
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Center—Plays nearly all dialog and contributes much to music and sound effects.
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Left and Right Front—Plays sounds from the left/right side of the screen, provides stereo music, and is used to pan dialog.
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Side Surrounds—Ambient sounds and sound effects are typically mixed to the side and behind the viewer.
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Heights—Ambient overhead sounds and overhead panned sound effects.
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Rear Surrounds—The same job as side surrounds except for sounds behind the viewer.
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One benefit of prioritizing the importance of each surround sound speaker is that it helps determine how to prioritize spending.​​​
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Floor-standing vs Bookshelf
A tradeoff in the design of the surround sound system is whether to use bookshelf or floor-standing speakers. We'll discuss these first.
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Pros for floor-standing speakers:
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Better low-frequency response (as mentioned), but when using a subwoofer, this is mainly a "don't care."
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Higher efficiency (speakers play louder for a given input power). This may be helpful if one sits far away from the speaker or wants to play very loud.
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Aesthetics: One might like the looks of floor-standing speakers.
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Pros for Bookshelves:
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Typically, it is smaller and less expensive than similar floor-standing speakers.
There are a few options for where to use floor-standing speakers.
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All base layer speakers are floor-standing
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Additional space and expense, especially for surround speakers.​
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Debatably better timbre matching than #2.
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Check if higher efficiency is needed.
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Front speakers, floor standing, and bookshelf surround speakers. ​
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Potentially better performance and higher efficiency for the more important front speakers.​ Check if extra efficiency is needed to meet loudness requirements.
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​​Bookshelf speakers everywhere.
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Most space-efficient, typically at a lower cost. Less volume ​efficiency.
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Based on the above rationale, I arbitrarily decided to go with bookshelves all around, but I probably should have double-checked to ensure the bookshelf speakers played loud enough. Afterward, I calculated this as shown in this section. From this analysis, a typical bookshelf speaker and a ~100W amplifier should be loud enough.
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​Considering In-Wall SpeakersÂ
In-wall speakers are another possible design choice that can perform similarly to bookshelf speakers and could impact specific wiring locations. As the name suggests, in-wall speakers are mounted flush to the wall, and the speaker cabinet is located inside the wall. In-wall speakers are attractive options because they can be hidden. However, there are some downsides to using this type of speaker.​​​​​
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In-wall speakers tend to be more expensive.
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The selection of in-wall speakers is more limited.
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Due to size/engineering constraints, in-wall speakers are known for not sounding as good as similar bookshelf speakers.
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In-wall subwoofers typically perform lower than stand-alone subwoofers.
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In-wall speakers must be located between existing wall studs, limiting placement. This is less of an issue for the surround and ceiling speakers.
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It is challenging to adjust the placement of an in-wall speaker.
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In-wall speakers can make sound isolation more difficult.
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There are other ways to hide speakers.
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Front speakers can be hidden behind a false wall.
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Side and rear speakers can be hidden in a decorative column
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Due to my unwillingness to spend extra money, in-wall speakers were not an option for this build.
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Timbre Matching Considerations
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Another consideration was to decide how important timbre matching between speakers was so that I could create some guidelines regarding mixing and matching speakers.
Timbre matching is important because when a sound moves around the room (between speakers), we want it not to change tone as it moves between speakers. Some argue that speakers must be identical to ensure timbre matching, yet in my experience, discerning tonal differences between different (albeit similar) speakers is challenging. Surround speakers make it even more difficult (for me) to discern timbre differences.
Additionally, Harmon research indicates that when listening to multiple speakers, listeners are less able to differentiate between speakers. Thus, based on this research and a little experimentation, my guidelines for timbre matching are summarized as follows:​
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It is important to match the front left, center, and right speakers and use the same manufacturer and model line.
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The surround and ATMOS speakers are less critical. It is desirable to match the timbre of the LCR speakers; however, it is OK if different manufacturers make them from the front speakers and each other.​​​
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Personal Speaker Matching Guidelines
Spend more on the front three speakers and carefully match them. The other speakers do not require exact matching; being better suited and having lower costs are priorities.