The single most important factor of a great sounding home theater is the acoustic properties of the room itself. Not the brand of speakers, not the receiver, not the bit rate of the movie soundtrack. Unfortunately, room acoustics is usually the area where most people give the least amount of attention. And I can’t blame them, because it’s a lot more fun to shop for electronics than it is to spend hours messing with acoustic room treatments. But if you want the best sound quality possible, room acoustic treatments are an absolute necessity.
It’s almost impossible to get an absolutely perfect room configuration; you always have to make practical compromises. So the list below is intended to be a “menu” of options from which you can choose what best fits your needs. Read them over, figure out what you think you might incorporate into your room, and go from there.
Acoustic Treatment Rules of Thumb for Home Theater Rooms
- Primary Purpose is to Prevent Echos: The primary purpose of acoustic room treatments is to prevent echoes within the listening room. It is not to reduce the amount of sound heard outside of the room. (There is a completely different set of requirements for a sound isolation setup, see the section below for details.)
- Can’t design for both 7.1-channel home theater and 2-channel stereo music. It’s impossible to design a room to sound great for both 7.1 channel home theater configurations as well as for 2-channel stereo music configurations. You have to pick one or the other. This article focuses on Home Theater Room design tips.
- Home theater setups requires a lot of acoustic damping and relies on multiple speakers to create the sound effects throughout the room. If there is too much echo in the room, there is no localization of any of the audio channels and everything get muddied and mixed together, and the advantages of separating sound into 8 (or more) discrete channels is lost. If you want to listen to 2-channel music in a home theater room, you’re much better off using a surround sound mode (such as Dolby Pro-Logic II Music) to recreate the echo effect of a concert hall, rather than having a home theater room with lots of echo that doesn’t work well for movies.
- 2-channel stereo music setups requires a much more lively room with minimal acoustic damping to create a natural echo. So it’s more like a performer on a front stage using the acoustics of the concert hall to amplify and fill the space with sound (not speakers in the rear of the room.) This works great for music, not so great for movies, where the sounds behind you are supposed to be quite different from the sounds in front of you.
- A home theater room needs to have about 60-70% of the surfaces covered in acoustic absorption material. To get the best acoustic performance, you’ll want about 60-70% of your walls and ceiling covered. However, you don’t want the room completely dead. You want some reflections scattered around the room. So some natural echo, but not so much that all of channels start to blend together and can’t be easily localized to a certain region of the room (i.e. the front center and front right channel sound like they are coming from the same spot.)
- Note that I didn’t cover the ceiling at all in my room. I covered about 80% of the walls. A few of my panels don’t have fiberglass in them. I thought panels on the ceiling would be ugly so I skipped it.
- Must use acoustic fiberglass material: It’s critical to use the right type of acoustic fiberglass for it to be effective. If you don’t use the acoustic fiberglass panels, it won’t attenuate the proper frequencies. Typically, these acoustic fiberglass panels are available in 2-feet x 4-feet (or 2-feet x 2 feet) sizes and are about 3/4-inch thick.
- Owens Corning 703 Rigid Acoustic fiberglass panels (and equivalents) are the required density. They are much more compressed than fiberglass insulation, but not as dense as ceiling tiles. This density gives the correct amount of absorption of sound frequencies.
- “Acoustic” ceiling tiles are too rigid and too dense. They are a complete waste of time and money and offer no benefit for a home theater room in terms of reducing echo. Low, medium, and high frequencies bounce off of the surface. Ceiling tiles offer acoustic properties similar to drywall, so they do an OK job of keeping sound from going through to the next room, but do nothing to prevent echoes within the room.
- Fiberglass wall insulation is not dense enough. It’s designed to trap thermal air, not sound. It offers very little acoustic benefit because mid and lower frequencies pass right through it.
- The front wall of the home theater room needs to be completely acoustically dead. The front 3 channels are the most important channels in a movie soundtrack and it is critical that they are properly isolated. To accomplish this, I installed 2 layers of fiberglass panels covering the entire front of the room, as well as the front 3 feet of the side walls (beside the front speakers behind the speaker masks.)
- Air gap between acoustic panel and wall: To get the best absolute performance from the fiberglass panels, they should have an air gap behind them (between the fiberglass and the wall.) 1/2-inch to 1-inch is the ideal gap. This is done to allow the sound to passes through the fiberglass and be dispersed, then continue on through the air gap, hits the wall and reflect/disperse, and then go back through the panel again for more absorption.
- Note that I didn’t do this; there is barely any air gap behind my acoustic panels. It was too much of a pain to mount the panels like that. It’s much easier to just hang them on the wall.
- Panel Placement at Primary Reflection Points: It’s critical that the panels be placed at “primary reflection points” for the 3 front speakers to get the best front sound stage imaging. I primary reflection point is the point on the wall where sound from one speaker hits and bounces directly toward your ear.
- Surround speakers aren’t as big of a concern for reflection points because reflection/dispersion is more desirable with them. Surround speaker should be bi-polar or di-polar designs to increase dispersion and fill the rear of the room.
- To find the primary reflection points: put your speakers in their desired location, sit in your primary seating position, have someone move a mirror along the wall. When you see the speaker reflecting in the mirror, that’s a primary reflection spot for that speaker. You’ll want to do this for each of the front 3 speakers. You will need to repeat this for both side walls. Ideally, you should do this for the ceiling as well. You may want to repeat this exercise for a few other seating positions as well.
- Additional random panels throughout the room: You will need to install additional panels throughout the room to get to 60%-70% coverage. The location can largely be based on aesthetes. Just make sure you hit the primary reflection points and space them somewhat evenly through the rest of the room.
- Note: My panels turned out to completely cover the wall with no gaps in between each panel. I liked that look, so I went with it, but ideally there would be some space between each panel to create some additional small areas of reflected sound.
- Bass Traps in the Corners: Corners of rooms are good because they can make certain bass frequencies much louder. But corners are also very bad because they amplify only specific bass frequencies, creating a very uneven and non-flat bass response. (It’s better to have flat bass response and a more powerful subwoofer.) You needs lots of extra fiberglass in each corner to act as a bass trap. Basically, put as much as you can in the corners. I put small panels at angles across the back corners and loose panels in the front corners behind the speaker masks.
- Note that I really should have much bigger bass traps in the rear corners of my room. But would also start to look weird/ugly, so I didn’t pursue ultimate performance and instead favored visual appeal.
Physical Room Dimensions and Shape
- Big rooms require big power: The larger the room, the more powerful your amplifier and speakers will need to be. So bigger isn’t necessarily better.
- Parallel walls are not good for acoustics as they create standing wave patterns. In an ideal room design, no 2 walls would be parallel. Unfortunately, if you followed this guideline absolutely, you’d have a very weird shaped room.
- Corners are very bad for flat frequency response. Corners create boomy, uneven bass response. Ideally, a room would have no corners. (Think of a circular room, or even spherical room with a dome ceiling.) However, this is not at all a practical design, so it’s much more realistic to use bass traps in the corners, which is described below in the acoustic treatment section above.
Sound Isolation Room Design Considerations
- There are a completely different set of design requirements for a room that isolates sound from the outside environment. (The primary purpose of acoustic room treatments described above is to prevent echoes within the listening room, not to reduce the amount of sound heard outside of the room.)
- To minimize the amount of sound head outside of a room, there are three key parameters to consider: mass, rigidity, and vibration control of the floors/ceilings/walls.
- The walls of the room need to be as heavy and rigid as possible. This can be done by using 2 layers of drywall. Ideally, the 2 layers would be of different thicknesses to isolate different frequencies. The first layer would be perhaps 3/4-inch thick and screwed (not nailed) directly to the studs. The second layer would be 1/2-inch or 5/8-inch thick and would be glued to the first layer (not screwed.)
- There are special drywall mounts that have rubber dampers that go between the drywall and the stud. This reduces the amount of drywall vibration passed to the stud wall.
- There should be two separate stud walls that do not touch each other. So an inside stud wall for a the home theater, a small air gap filled with insulation, and then outer stud wall for the room outside. With this design, when the inner home theater wall shakes/vibrates, the outer wall will not.
- There are special rubber curtains that can be placed between the two walls that are more effective at absorbing sound than is fiberglass insulation. These curtains are also pretty expensive and may not be worth the cost, so it’s up to you.
- Ceilings transmit as much sound as walls. The ceiling should be physical isolated from the floor above, just like the walls as described above.
- Concrete is your friend. Concrete does a fantastic job of isolating sounds from other rooms. If possible, make all walls / floor / ceiling out of concrete to keep sound from passing to other areas.
- Air ducts transmit a lot of sound. You need to isolate the air ducts as well as a lot of sound can pass through them to other rooms. This can be accomplished by using flexible fiberglass covered ducts with lots of extra length and bends, for both the supply and return air.
Where can I get Owens Corning 703 Acoustic Fiberglass Panels to build my own?
You can find the name of an Owens-Corning dealer near you by calling 800-GET-PINK (800-438-7465) or from the Locator page on the Owens-Corning web site. Other companies, such as Knauf, Armstrong, and Delta, make similar products, and they often cost less than fiberglass from Owens-Corning. You can contact them directly to find a distributor near you. In the interest of completeness, here are some other manufacturers that make similar products: Johns-Manville, CertainTeed, Roxul, Ottawa Fibre, and Fibrex.
The most common fabric used to cover home made acoustic panels is Guilford of Maine Acoustic Textiles in your choice of color.
What if I just want to buy some ready-make acoustic panels?
When I built my home theater, it was substantially cheaper to make your own acoustic panels. Since that time, prices have dropped substantially, and it’s probably a better cost/time trade-off to buy ready-made panels. Although I don’t have personal experience with the company, Acoustimac DMD panels appear to be a very good value.
For me, covering the front wall of my home theater with 2 layers of acoustic fiberglass panels made the single biggest improvement in sound quality of anything I’ve done, including using the room correction software within my receiver. After covering the front wall, the front 3 sound channels immediately “came into focus”. Covering the remaining wall gave an incremental improvement beyond that. As with all things, you have to consider the trade off between time, cost, aesthetics, and benefit. The guidelines listed here will give you some ideas to consider. Let me know your thoughts, questions, and ideas. Thanks for reading, good luck, and have fun building your home theater room!
Greetings, I enjoyed reading your post. I am in the beginning stages of designing a new listening / viewing space for our home. I am challenged by the desire to maximize the soundstage with my existing equipment and extend that into the realm of 7.1 with additional speakers. Have you ever used any of the acoustical predictive software in the design phase? I have never had a dedicated listening / viewing space and I understand the need to choose multi-channel vs stereo as a priority, but was wondering if the process needs to be so black and white? My existing mains are Magnepan IIIa’s which are planar speakers and radiate out the front and the rear. They were always sensitive to location and setup to get the best from them and need reflective surfaces behind them to give the sound it’s bloom of spaciousness. What I was thinking would entail a series of sliding and fixed panels at the front of the room that would have varying characteristics of reflective and absorptive. So in a two-channel mode the absorptive panels could be bunched into the middle of the wall revealing the more reflective surfaces behind. They could also cover the screen / monitor. When a theater mode was desired, the panels could be slid to the outside of the wall revealing the screen and limiting the reflectivity. I am not sure if I could get the mass needed to be as absorptive as needed to be nearly dead, but I think my priorities lie with the 2-channel mode. So lies my conflict. Any thoughts or suggestions would be welcomed.
Dan, I think you pose an interesting idea and I think it would work to have removable panels behind the front left and right panels. I don’t think you’ll have a problem with the mass of the panels because the mid and high frequencies would be the focus (bass would need to be addressed separately.) In addition to the moveable panels behind the front left/right speakers, you would also need moveable panels on the left and right walls about halfway between the listener and the front speakers at the primary reflection points. Beyond those two locations, there probably isn’t a huge benefit to rearranging the panels.
Carlton- Do you have a build thread you can link to of this theater? I would be very interested in the construction particulars, such as the front wall design. Is it a false wall? Due to the configuration of my room, I only have 14’9″ of depth to work with as there are balcony doors on the left and another bed and bath on the right in this rectangular bonus room. I’m struggling trying to determine the best way to maximize this space. Using an AT screen or not, etc.
Appreciate your input.
If putting absorption panels in the front using 703 and you also want to black out the front/reduce LR, what fabrics would you recommend? I was looking at something like 8oz Duvetyn, but then other info I’ve read talks about using acoustically transparent fabrics like Guilford of Maine.
Acousticlly transparent fabric is really only important for reflective surfaces or with speakers mounted behind. For absorptive surfaces such as acoustic panels, the fabric doesn’t make a huge difference.
I see that you used the GofM fabric in your theater’s acoustic panels. If you were to do it again, would you choose any reasonably priced good looking fabric at a local fabric store? Are the panels that you have on the wall that are covering speakers just a frame and the GofM fabric or did you cut out for the speaker and left the insulation in the frame?
Adam, the GoM fabric is somewhat thick and textured, so it hides seams in the wooden frame well. That’s the biggest consideration.
For the panels covering the surround speakers, I left them completely empty with no acoustic fiberglass at all behind the GoM fabric.
Awesome information, Carlton. Thank you for sharing it! Do you have an opinion on in wall/ceiling speakers and the use of back boxes (cotton/aluminum) as a sound diffuser? Or would “regular” fiberglass insulation, already installed in ceiling (R38) suffice?
William, I think you’ll get decent results with regular insulation, but the best bet is to make the back boxes out of something heavy, such as 3/4-inch MDF, and fill those with insulation. Mass is your friend. But for movies, the sound profile of surround speakers is generally such that they aren’t too disruptive for adjacent rooms.
Thanks for the wonderful guide.
Some reading with regards to fiber glass density etc…
Carlton, I just found your website and appreciate the time and effort that went into your recommendations regarding HT acoustic treatment and projector screens (I’ve also enjoyed and benefited from your Di2 page!). Many thanks for all of this.
I have a couple of questions about acoustic treatment. You said it’s important to treat the entire front wall of the room. Does that include treating the part of the wall behind a projector screen? I assume yes, but want to be sure.
I also saw a response to another question in which you recommended thick carpet and pad. Do you have any more specific recommendations regarding floor treatment (not for sound isolation, but for acoustics)?
I believe acoustic panels are critical for installation behind acoustically-transparent screens, and optional for installation behind standard (non-perforated) screens. I did install acoustic fiberglass panels behind my screen but I’m not convinced it made a huge different. The front corners of the room and below the screen (where the front center channel is) clearly did. I figured there would be less air movement behind the screen with low frequency sounds, and may reduce screen vibrations. Just be sure it’s not so thick that it presses against the back of the screen and causes a crease/line – I think I used a single 3/4-ince layer behind the screen, and two layers around the screen and beside the front speakers.
For carpet, I don’t think there is a significant difference. Thicker is better, but as long as you have a carpet pad and some pile with the carpet, there probably isn’t much difference. To minimize bass reflections, two-layers of carpet padding and very thick carpet could make it a little better, but probably isn’t worth the incremental expense. (Bass traps make the biggest difference with bass standing way disruption, and they are complicated/expensive/space consuming – unless you incorporate it into a riser platform.)
Hi Carlton. You have an excellent website jam packed with great information. It’s overwhelming. I realize for the best acoustics, I need to treat the walls & ceiling. The floor is carpeted.
My post today is to seek advice what to do about my 7 foot drop down (suspended) ceiling in the basement of my new home. My #1 goal is to create decent room acoustics for at 7.2 Surround Sound Home Theater.
Without giving exact room dimensions (guessing 25-30′ deep X 20-22′ wide). It’s a very large basement that has room for a home theater, with a pool table behind the seating, and a bar tucked in the left rear corner. There are 5 seats in which the viewer’s heads will be 13-14 feet from 133″ 2.35 projection screen. There is a large red brick fireplace on the left wall removed 6-8 feet from left channel speaker (separated by the basement entrance which has no door), and 2 large sets of sliding glass doors on the right side (2-3 feet from right channel speaker) which I plan to cover with heavy black-out curtains.
The entire room has drop down ceilings (6 inches below rafters). The drop down ceilings are only 7 feet in height, not ideal. The ceiling tiles are 2’X4′, old & dingy, probably from the late 60’s. I believe they are plastic coated 1″ fiberglass. I would prefer to install new black ceiling panels to spruce the room up.
My original idea was to place 0.030″ thick black rigid vinyl plastic decorative panels beneath the existing drop down panels to reface our outdated ceiling. After reading this website, I’m not sure this will accomplish my goal. I also have learned that I can purchase acoustic tiles with noise reduction coefficients of .25+, .50+ & .85+. If I went this direction, I’m not sure which noise reduction coefficient to choose. I’m also struggling with brands, quality and of course, cost!
Any advice you can provide would be greatly appreciated.
Lance, I don’t have much personal experience with drop ceilings, so I only offer general advice. Standard “acoustic” tile are generally terrible for home theater. You mentioned some with a noise reduction coefficient of 0.85. That seems like a good solution. That’s slightly higher than Owens Corning 1″ 703 (with no air gap – direct wall mount.) I would go with that option. Unfortunately, I can’t help with cost or brand. Hopefully this helps.
Thank you Carlton. I’ve been doing much research since I posted here. So many options, but I’m fine tuning them and will have a cost effective solution soon.
what an amazing article.. sir i had a query…
I am setting up a 5.1.4 home theatre in a dedicated room in my new flat with Dolby Atmos. Room size is 14.5ft x 10.5ft and height till false ceiling is 8.5ft.
Screen will be on wall measuring 10.5ft. On this 10.5ft wall, 7.75ft x 4ft window is also there, that why I am going for motorised screen. Screen and floor standing speakers (in front of screen) will come in front of this window and centre speaker below screen. My purpose for home theatre is for viewing 70% movies or live sports screening and rest 30% music.
Speaker system will be PSB X2 T – Floor Standing TOWER (PAIR)
PSB XC – CENTER
PSB XB – REAR SPEAKERS (PAIR)
PSB SUB 200
PSB CW 80 R (2 PAIRs) In Ceiling
I want to setup floor carpet matt and acoustics wall panels for getting the best sound.
Please advice me on the same.
How should i go about to get the best sound experience ? I also want a good aesthically looking room like yours.. Do I need Complete Absorbption in the room with Bass Trappers / partial Diffusion etc etc..
One of the acoustic consultant told me that only absorption will be required for your home theatre room as your room is not long enough but just 14.5ft. So he said 2″ absorption with glasswool (50mm) covered with foam(12mm) covered with fabric on ply frame, will do fine. Is it true ?
Please suggest me the best possible solution to maintain the uniform look also and to achieve best possible results.
Just planning on building a new home in WA (Western Australia, not Washington) and am putting in a dedicated home theatre.
I would like to know if having angled walls (think coffin shaped) and possibly raked ceiling helps or hinders with acoustics ? I have done an internet search with absolutely no luck
Or do you think I should just stick with rectangular room and flat ceiling.
Ken, having non-parallel walls as you describe definitely helps acoustics. It counters lower frequency standing waves that can form all throughout the room. The specific trouble frequencies will depend on the dimensions of the room. Rooms that are move of a V-shape don’t have this issue as the distance between the walls isn’t constant throughout the room.
There are trade-offs to having a more V-shaped room, mostly related to practicality and aesthetics. It can look odd and cause adjacent rooms to have odd shapes as well. If you can integrate the design seamlessly with the rest of the house, and like the way it looks, then definitely go for different design. Ideally, the floor and ceiling will not be parallel to each other, and neither will any of the opposing walls.
Thanks for the reply – I have managed to design it into my new home so that the adjacent rooms are the garage and small office so from the outside it will be hard to see that it is an odd shape and it will also have a raked ceiling so from inside it will look just like a real cinema 🙂
Thanks again – Ken
Excellent article – Just the right mix of information for layman and professional alike, I’m a great believer in putting a lot of effort into treating the room – who know when you are going to upgrade equipment, speakers etc… If the room design is done well you are in good stead for whatever you want to throw at it. If I’s OK I’d like to link this article on our facebook page.
Not a problem to link to the article Ben. Thanks for the positive feedback!
Hello Carlton – thanks for the excellent article! I’m in the early stages of planning & design for a dedicated home theater in my basement space, but I’m uncertain as to the acoustic implications of two variables: ceiling & walls. One, ought I leave my ceiling unfinished or throw up drywall? If I should leave the ceilings unfinished, I can choose a space for the HT where the joists run perpendicular to the room’s front-to-rear axis, or horizontal. What would be best choice in this instance, do you think? Also, my builder installed 3″ spongy foam insulation panels around the entire perimeter of the basement, and not only do they not look bad (it’s a new build), but I’m wondering if the acoustics of these wall coverings are worth keeping in place rather than finishing the walls with framing & drywall, only to add acoustic treatments on top of that. Your thoughts are greatly appreciated; cheers! – David
David, you’ll need to balance aesthetics vs. acoustics. Leaving the ceiling unfinished would be better for sound quality as the uneven surfaces would act like an anechoic chamber and diffuse and break-up reflected sound. But it would probably look better with drywall.
The direction of the the joists won’t make much of a difference for sound quality. Go with whatever is best for room configuration and for cable routing (assuming cables will eventually be behind drywall…)
Those panels won’t offer much acoustic advantage on the walls. They are for thermal insulation. They reflect sound just like drywall. You’d be better off to frame over the panels and put up drywall and then acoustic panels.
Hope this helps!
Thanks for your timely response, Carlton – I appreciate the feedback! Aesthetics tell me to finish the ceiling with drywall in spite of the anechoic advantages of leaving it unfinished, but I need to choose whether to finish a 9′ ceiling height for the front 2/3 of the room and box in the lower hanging ductwork & I-beam with an 8′ ceiling for the rear 1/3 of the room, or simply drop the ceiling height down to 8′ (7’10” with drywall) for the entire room. Your thoughts?
So much to consider, but I want to embrace Dennis Erskine’s philosophy that “the single most important component of any home theater system is the room itself.” Do you believe this to be true also?
Next, with an 18′ central axis pre-determined for my room length, I’m seeking your advice to determine the room’s optimal width and balance that width with my desired seating configuration. Golden ratio calculators using Sepmeyer, Volkmann and Boner’s ratios suggest an ideal width anywhere from 10′ to 13’6″, but that’s pretty tight for even a 3-chair front row (the wide-bodied power recliner chairs from Costco I’d like to use can always be returned for narrower models from other retailers, but I don’t want to drop a fortune on chairs if I can use the $500 models I already have). How large a role does the room’s width play in meaningful impact on the acoustics of a dedicated HT space? If I expand the width of my room up to 17′, I have the width I desire for seating, but I question whether I’m coming too close to the dreaded “perfect square” room dimensions (at least along vertical axes) and their accompanying acoustical anomalies. Also, is it more desirable to maintain room width along side walls or is there any discernible benefit to having a narrower wall width closer to the front wall and expand the width at some point away from the screen (ex: 15′ width for front 1/2 of room, expanding to 17′ width for rear 1/2 of room).
My apologies for such demanding questions. I just don’t want to make any avoidable mistakes in this all-too-important planning & design process. Cheers, Carlton!
David, I do believe room design is extremely important. I think wall/ceiling treatments are the single most important aspect; room dimensions are secondary to that.
For the ceiling height, there is some acoustic advantage to not having it the same all the way across. I think higher in the back and lower in the front looks better. But I recommend putting aesthetics first, for all of your decisions. If you think a constant height ceiling looks best, then do that. If you think the room will be too cramped, then make it wider.
For me, I wish my room were wider and more spacious (but I didn’t have the option to choose size.) I think you’ll regret it if you go too small, and it will always feel small to you, but you’d never be able to quantify the acoustic benefit you may or may not have gotten from a narrower design.
So my advice is to design the room for aesthetics and usability first, then do everything you can to make that room size and layout more acoustic friendly. You’ll get pretty close to the same acoustic result either way, but the way the room feels will be significantly different.
Your theater set up looks great! I’m in the beginning stages myself and I have a few questions. Did you build the panels yourself or buy them from somewhere? And if so where? If you did build them yourself did you use the OC 703? I want to panel my walls floor to ceiling because I like the look but are they dense to the touch, meaning if someone pushed into it lightly with their hand or leans against the wall would it make in indent and ruin the look of them? My plan is to make the paneling the entire wall design. Also if you were looking to hang something on the wall could you hang anything on the panel or would you have to panel around it?
Enjoyed reading your post. I was able to collect some ideas.
I am thinking of using brick veneer throughout my home theater room. I know it is a hard surface and will reflect the sound, but it also disperses the sound better than any other surface. What issues do you see, if any, with the brick walls and using about 60% of surface covered with acoustic panel?