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# Building A Home Theater? Start Here. (1 Viewer)

#### Brian Dobbs

People come to the Home Theater Forum as a resource, and I think it’s time to consolidate as much information as possible concerning the construction phase of building a home theater.

Many folks have questions regarding acoustics, sound control, wiring and calibration. The purpose of this thread isn’t to endorse specific brands, only to highlight the techniques and type of products available to the consumer of which they can greatly benefit from.

I will be updating this thread periodically, touching upon best practices in home theater construction, focusing primarily on sound control and wiring, and extending out here and there.

After all, this is the construction board, so the discussion will be construction-centric.

Please refer to this thread in conjunction with the “Things I wish I would have done differently in my project.”

A great general resource to educate yourself on sound control is an E-Book developed by the E.P.A. in 1978. It’s titled, “Quieting In The Home” and can be read here.
http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9101AJ9Q.txt

The thing to keep in mind when soundproofing a room is the STC rating. The higher the rating, the more sound will attenuate.

STC Ratings For Various Wall Assemblies

In this first post I will keep a Table Of Contents as well as a running list of websites that cater to the ideas and technologies presented.
In no particular order, listed below are websites that provide solutions to sound control.

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#### Brian Dobbs

Room Ratios

It all starts with the room dimensions. There are good dimensions, and bad dimensions.

Why?

It has to do with how "modal frequencies" resonate and reflect in a given space.

From RoomModes.com...

"Room modes are caused by reflections between room surfaces. There are three types of modes in a rectangular room: axial (sound waves reflecting between two parallel surfaces), tangential (sound waves reflecting between four surfaces), and oblique (sound waves reflecting between all six surfaces). Axial modes have the most influence on the acoustical characteristics of the room. Oblique modes have less effect than the other two.

In a studio or home theater, a mode is heard as a coloration of the desired sound by emphasizing the modal frequency. If a certain modal frequency is isolated from its neighbors (more than 20 Hertz separation), its effect is more likely to be noticeable. If modes are widely separated, then the sound will be abnormally weak at the notes between the modal frequencies. At frequencies above 250 Hertz individual modes are seldom distinguishable. Speech coloration below 80 Hertz is rare because so little speech energy is in that part of the spectrum. If there is no spacing between modal frequencies (called a coincident) they would tend to overemphasize the sound at that frequency.
"

A basic rule of thumb is that you want to avoid room dimensions with similar measurements. The worst example is an 8' x 8' x 8' room.

Also avoid room dimensions that are simple multiples of one another, like 24' x 16' x 8'.

There is no consensus as to what the "Golden Ratio" should be when designing a home theater, but there are a few accepted ratios that you can consider.

From TheHomeTheaterBook.com...

"In Alton Everest’s Master Handbook of Acoustics (which is the best reference on these subjects) lists the ratios of four industry experts. Here are the four ratios:

Sepmeyer: 1.0 : 1.28 : 1.54
Louden: 1.0 : 1.4 : 1.9
Volkmann 1.0 : 1.5 : 2.5
Boner: 1.0 : 1.26 : 1.59

You’ll notice that even with these four experts, there is no one single Golden Ratio that everyone agrees on.

In almost all home theaters, the limiting dimension is height, we simply don’t have unlimited vertical space to work with. So when you are calculating your room, using one of these ratios, the 1.0 ratio will be your height, and you work out the other dimensions from there.

An eight foot ceiling height is average for many home theaters, so below are the dimensions using the ratio of height : width : length, and using eight feet as the ceiling height.

Sepmeyer: 8.0 : 10.24 : 12.32
Louden: 8.0 : 11.2 : 15.2
Volkmann 8.0 : 12.0 : 20.0
Boner: 8.0 : 10.08 : 12.72

Using this example and the Volkmann ratio, you would have a room that is 8 feet tall, 12 feet wide, and 20 feet deep.
"

At the end of the day, you have to work with what you have, so at the very least, do your best to avoid similars or multiples.

Here are some additional resources on the subject.

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#### Brian Dobbs

Room Within A Room

If you have the room, walls, ceilings (and sometimes floors) should be mechanically isolated from the rest of the house.

Why?

Nothing prevents the transmission of vibrations from one room to another better than the rooms simply not touching each other.

If you have the room, construct double-wall assemblies.

If space is an issue, a staggered stud configuration is the next best thing.

For ceilings, install your own joists to avoid using the floor joists of the upper floor.

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#### Brian Dobbs

HVAC

This is probably the one aspect of home theater that gets the least amount of attention. It's very important, however, especially if your theater will be sealed off from the rest of the house.

A lot of people simply have one side of their home theater open to a common area, so air flow isn't as important. But if you're trying to soundproof your theater, then it will most likely be walled off and accessed only by a heavy duty door with rubber sweep at the bottom.

If you can build in your basement, the temperature will not fluctuate that much due to the surrounding earth insulating the house foundation. The biggest challenge will be heating the room in the winter. If your electronics are placed inside the room, then they can act as a small heater in addition to whatever ducting supplies the room.

If you are building on a 2nd or 3rd floor, the HEAT IS GONNA RISE!

In any case, take the time to install both a supply duct and return duct back to the main system.

Room exchanges are fine, but they won't suck air, and will allow noise from an adjacent room to creep in.

This is also an area were getting some professional advice would be of great assistance, since the concept of heating and cooling is generally not understood well enough.

Most of us just tap of the main system without regard to how it affects the entire system.

Me? Guilty as charged. But at least I added a return.

The idea is that not only do you need to heat and cool the space, but to keep the air moving to prevent the room from getting stuffy. Electronics like moving air.

Given this, it would also benefit you to reduce the amount of noise the airflow actually makes. The last thing you want is to be watching a quiet scene only to have the air system kick on, which then makes you reach for the remote to turn the volume up and then back down again when the air goes off.

There are a few different types of duct silencers, which reduces the noise generated from the main blower unit that reverberates through the duct work and out through the register. Sometimes vent covers whistle.

I found this inline duct silencer to be of great help.

There are also products you can use to wrap duct work, to reduce noise generated from the vibrations. See my first post for more products.

Projector fans produce noise, and it quite often is an irritant for people sitting right underneath. You may want to think about building an enclosure for your projector and run flex duct to and from its location.

Centrifugal bathroom fans are really quiet, and you may be able to incorporate one in your designs.

Here are some
inline versions that may be of help.

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#### Brian Dobbs

Electrical

Have you ever had someone blow dry their hair or turn on a space heater only to trip the circuit, thus shutting down the movie you were watching in another room?

Ever turn on your equipment only to hear humming coming from the speakers?

All of that really sucks!

Home theater components can easily draw a lot of current, especially when you're watching a big action movie.

So let's give them room to breathe.

The goal should be to run multiple circuits for the room. Keep the circuit for lighting & general purpose separate from the circuit that will power the components.

The last thing you want is to dim the lights slightly and have noise creep into the speakers or distortion show up on the projected image.

You also want to run electrical wire as far apart from low voltage wire (speaker wire, coaxial, HDMI, etc.) as you can. A few feet at least.

15 amp circuits are standard for general purpose outlets and lighting, but 20 amp circuits can be used for extra breathing room for higher current amplifiers.

Generally, 14/2 wire is for a 15 amp circuit and 12/2 wire is for a 20 amp circuit.

I decided that I wanted to have the option of using powered speakers in my setup. GoldenEar towers have up to a 1600 watt amplifier built in. I talked to my local A/V shop Gramophone, and they recommended no more than two GoldenEar Triton Two's per circuit.

So what if you're ambitious (crazy) like me and want the option for a fleet of GoldenEar towers? Gotta run multiple circuits! Especially if you want to include additional powered subwoofers!

For my home theater, I supplied the following circuits
• Lighting / General Purpose Outlets
• Subwoofer
• Subwoofer
• Speakers
• Speakers
• Speakers
• Speakers
• Speakers
• Speakers
• Projector
• Equipment Rack
The issue of grounding is a tricky one, especially when you have components powered by one circuit sending signals to components on another circuit.

Here's an article by Martin Logan on grounding. In essence, if you are running multiple circuits, run an independent ground wire through all of the outlet locations. You may need to utilize it for a different grounding configuration in the future, especially if you get a ground loop hum turning your system on for the first time.

Pre-wiring a Home Theater: Eliminating Grounding Related Hums

When pre-wiring for a Home Theater, it is critical that the ground connections be wired in a very specific way. If you are planning to run a dedicated power line (or multiple dedicated power lines), proper grounding is critical to ensure that noise and hum are reduced to an absolute minimum.

Typically, when an electrician wires a home, each power outlet has a ground wire (along with the hot and neutral) that runs from the outlet, directly to the service panel (see figure 1). When multiple ground wires of different lengths are connected to the service panel ground, 'current eddies' are created due to the different lengths of the ground wires (differing Ground Potentials). These 'current eddies' create the infamous 60 cycle hum! Do not use hospital grade outlets in the dedicated power line, as hospital grade outlets require separate grounds and cannot be tied together.

The key to reducing hum and noise is to have the electrician wire only a single ground from the audio / home theater system to the electrical service panel (see figure 2). If you are installing a dedicated or multiple dedicated lines in the Home Theater it is critical that all outlets that will be attached to the A/V system be wired with the same single ground wire, and run directly to the service panel. 'Hot and neutral' wires are attached directly to the service panels dedicated power line. Do not attach anything other than the Audio and Video system to this special dedicated line. Be sure to plan for enough outlets for the electronics, speakers, sub-woofers, video and video accessories as well as the location of each outlet (subwoofers in the rear, etc). Lighting, fans and anything not directly related to the A/V system, should be attached to a separate circuit with it's own ground, connected to the service panel.

The net result will be noise and hum free power with a 'deep black background' in which to enjoy your audio and video presentation. Please note, before trying any of the above mentioned suggestions, please check your local electrical codes.

Don't forget to run power to any potential wall-mounted television you might install. You also really need to think about where your components will reside. In other words, inside or outside of the room? Make sure to provide them the circuit that they'll need in the location that they'll be.

As for lighting, if the goal is to minimize the amount of holes you are cutting into your ceiling to reduce the potential of noise transmission from the above floor, opt for sconces instead. Better yet, floor standing lamps.

Be sure to watch this video as it relates to power conditioning, voltage regulation, and electrical noise filtration. There is also some helpful hints relating to running electrical to the circuit panel.

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#### doug zdanivsky

##### Supporting Actor
Very nice!

Will you be covering seating options?

#### Brian Dobbs

doug zdanivsky said:
Very nice!

Will you be covering seating options?
Hmm. I'll have to give that some thought.

#### Brian Dobbs

Audio / Video Wiring

One simple rule. Wire EVERYTHING EVERYWHERE.

Wire is relatively inexpensive. Then install conduit for future wiring.

Before you pull wire anywhere, first determine where your electronic components will be placed. Call this the 'home run.' After you pull a wire, label it at both endss and carefully coil it up..

For every TV, projector, speaker and subwoofer location, print out a list of all of the wires you want to run to those locations. Then install an electrical box. As you run the wire, cross it off the list.

For in-wall or in-ceiling speakers, you must position the wire between the studs without the use of an electrical box. The idea is that you want to be able to cut a hole for the speaker without the stud or joist getting in the way.

Unless you're really concerned with the aesthetic quality, don't terminate your wires at a wall plate. Pull wire 6-10 feet out from the wall and coil it up. That way, you can make a direct connection to your device, bypassing a potential failure point in the signal.

Purchase wire that is certified for in-wall or in-ceiling use.

Speaker And Subwoofer Wire
Surround sound has historically shown us that the number of channels increases every few years or so. Stereo, then Pro-Logic, then 5.1, 6.1, 7.1, height channels, wide channels...will it ever end? How do you future-proof?

With Dolby's most recent release of their new Atmos system, the future of surround sound will most likely stay consistent for a long time to come. So as of this writing, my suggestion would be to wire for the maximum capacity that Atmos has to offer, which is 24.1.10.

24 floorstanding / wall mounted channels
1 subwoofer channel
10 ceiling channels

Don't stop with 1 subwoofer location either. Run more than you think you'll need. In fact, go ahead and run a subwoofer wire everywhere you run a speaker wire. This will allow you to maximize the number of subwoofers you may choose to use later, in addition to their placement options.

As for the speaker wire itself? For long distances, thicker gauge wire is best. 14 gauge or thicker. As for me? I ran both Belden 5T00UP 10 gauge and a generic no-name 12 gauge wire to all of my predetermined speaker locations.

Ray Kimber, President of Kimber Cable, talks about the effect cable can have on audio.

Noel Lee, founder of Monster, talks about cables, and physics.

For subwoofer wires, you can run twisted pair, but most people run coaxial. I ran Belden 1694A.

How much wire should you order? Measure the distance in the walls through which your wire will be pulled. Then add 10-15 feet on each end of every pull. Best way to keep track of it all is in a spreadsheet.

TV And Projector Locations
To every TV and Projector location, run...
• HDMI
• VGA
• Coaxial
• Cat5
• Conduit
Run multiples of each wire. Keep in mind you're running from both the home run (from the components) and your cable/phone/internet distribution box (for cable TV). Coaxial and Cat5 are versatile. They can be used for many different purposes.

Miscellaneous
Perhaps you can consider wiring to a console, or a command center, constructed at the seating location. A way to plug in any multimedia device quickly, without having to get up and connect it at the home run location. Don't forget USB extension cables. You may choose to incorporate a computer into your system.

The bottom line is that you should spend as much time beforehand trying to think of all the wires you wish to have and in what locations. Print it all out, tack it up, and start running. As you wire, more ideas will come to mind.

You never want to rip out drywall to install more wires. It can be done, but it's messy and a big pain in the neck.

Check out RiteAV's custom wall plate builder.

Be creative.

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#### Brian Dobbs

Insulation

In addition to temperature control, insulation can also be used for sound control for both walls and ceilings. But it is best to use the blown-in variety.

Double Wall Construction and Blown-In Insulation

According to all the research I've done, blown-in cellulose is the way to go because it will yield a higher STC rating for the wall assembly.

Cellulose vs. FIberglass Insulation Sound Proofing Demonstration

Here's a white paper from National Fiber.

#### Brian Dobbs

Decoupling

The best way to stop the transmission of unwanted sound vibrations is to mechanically isolate the structure of the home theater from the rest of the house, as mentioned in my earlier post.

If it is not possible to do so, the use of isolation clips and resilient channel are the next best thing.

RSIC Isolation Clips

Resilient Channel

#### Brian Dobbs

In order to truly soundproof your home theater, you must add mass to your walls. I've seen recording studios fill concrete walls with sand, but we don't really want to be doing that in our homes.

So let's look at some more practical methods.

Before you hang your drywall, consider installing Acoustiblok (A.K.A. Mass Loaded Vinyl).

A common weak point in wall and ceiling assemblies are the outlet boxes and recessed lights. For these, it's best to use putty pads and quiet boxes on the back side.

When installing drywall, consider two layers of different thicknesses. Apply Green Glue between the two layers.

Consider using QuietRock instead of standard drywall.

And don't forget to fill those gaps with acoustical caulk!

#### Brian Dobbs

Room Colors And More

Here's a great interview Scott Wilkinson of TWIT conducted with Alan Brown of CinemaQuest on the Home Theater Geeks Podcast. The basic idea is that you want to use neutral colors and lighting.

#### Brian Dobbs

Room Acoustics

Here's a great interview Scott Wilkinson of TWIT conducted with Anthony Grimani of MSR Acoustics and Performance Media Industries about the importance of room acoustics and acoustic treatments on the Home Theater Geeks Podcast.

The basic idea is that you want to cover 20% of each wall and ceiling with absorptive material and 25% with diffusive material.

Here's an older, audio-only interview between Scott Wilkinson and Anthony Grimani.Scott Wilkinson chats with Paul Hales of Professional Home Cinema about the science behind optimizing audio for a room on the Home Theater Geeks Podcast.

Scott Wilkinson chats with Bob Hodas about room acoustics and speaker placement on the Home Theater Geeks Podcast.

#### Race Bannon

##### Supporting Actor
Room Acoustics

The basic idea is that you want to cover 20% of each wall and ceiling with absorptive material and 25% with diffusive material.

Is there any discussion somewhere about ways to add the absorptive and diffusive material in a stealth and decorative way? My home theater is not a dedicated room. It is big, and if anything could use more dampening in it (it has parquet floors). I have rugs and furniture, but are there wall treatments or fixtures designed to help improve acoustics? (Besides the black studio foam that is obviously for this purpose).

Any replies appreciated, and move post to appropriate thread as needed.

#### Brian Dobbs

Is there any discussion somewhere about ways to add the absorptive and diffusive material in a stealth and decorative way? My home theater is not a dedicated room. It is big, and if anything could use more dampening in it (it has parquet floors). I have rugs and furniture, but are there wall treatments or fixtures designed to help improve acoustics? (Besides the black studio foam that is obviously for this purpose).

Any replies appreciated, and move post to appropriate thread as needed.
Might want to check out http://www.vicoustic.com/. They have some really nice looking stuff.

#### Bob Bielski

##### Second Unit
wonderful collection of information Brian. Thanks for posting so much helpful info.

#### Bob Bielski

##### Second Unit
I went to the building inspector in my town yesterday and asked him if I could use any wire in wall or ceiling as long as I ran it in a conduit. He told me a metal conduit should allow me to run the speaker wire of my choice. I figured with time I may want to swap out my speaker wire for an upgraded wire. Easier to snake if a conduit is in place. Settled on Roxul Safe and Sound for the inlulation and Quiet Rock. Still not sure about the electrical wire. Any help from electricians would be greatly appreciated. Need an explanation about seperating audio and video room circuits and rest of the house electrical circuits.

#### Ben kirk

##### Auditioning
I'm a complete n00b at this, and had no idea there was so much involved. I'm having a house built and the media room will be included in the basement. Some questions for you guys and gals.

1. I saw a video where a guy had a hidden room behind his tv and I think that would be a god idea, any issues? Maybe 3' deep and the width of the room.
2. My room can be almost any size but I was thinking, 9' Ceiling, 25' long and 15' wide. So with the hidden room, the room will be 22' long, or should I keep it 25'?
3. I'm going to have a 200 AMP fuse box will I need another one just for the media room?

Anything else that's required, of have any other suggestions I need to think about?

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