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Baffle Wall Case Study: Acoustic Frontiers Demo Room

This article is a case study of how we designed and built the THX style baffle wall in the Acoustic Frontiers demo room. A baffle wall can be thought of as a false wall into which speakers are ‘flush’ mounted and can be built in front of the existing wall in a home theater or instead of the front wall. There are many acoustical benefits to baffle walls including reduced increased low frequency headroom and smoother frequency response due to reduced speaker boundary interference and diffraction.

 

Step 1: Speaker Selection

The first step is to select the speakers that will be installed in the baffle wall. There are obviously many ways to select loudspeakers. For a home theater that replicates the commercial cinema experience narrow down your selection based on loudspeakers that can reproduce THX reference level 105dB peaks. You might also want to choose loudspeakers that are designed to be baffle wall mounted (many are not and have baffle step compensation circuits that cause bass boost if mounted in a baffle wall).

Speaker size dictates baffle wall framing requirements. Deep, heavy speakers may require special shelves or thicker studs to support their weight. In wall speakers will require a more standardized framing approach.

In our demo room we selected the Procella Audio P610, a full range speaker capable of 105dB peaks in our room and expressly designed for baffle wall mounting.

 

Step 2: Speaker Lateral Layout

The next step is to determine where the left, center and right speakers will go since the baffle wall needs to be designed around their locations. This is done by following the speaker layout rules.

In the Acoustic Frontiers demo room we used a large screen for a 50 degree viewing angle (see our home theater viewing angles article). Because of the narrow width of the room we chose to place the left and right speakers inside the edges of the Seymour Screen Excellence 4K acoustically transparent screen rather than outside, which would have resulted in the speakers being located close to room corners (an acoustically sub optimal location).

 

Step 3: Subwoofer Selection / Layout

The subwoofer system must be designed to provide consistent, THX reference level bass (115dB peaks) to the primary seats in the home theater. Typically this means two or four subwoofers, some of which will be located at the front of the room. A baffle wall provides a great opportunity to hide subwoofers and so the subwoofer selection and layout process should be done before completing the baffle wall design.

The demo room has four subs, two front and two rear. The two front subs are shallow format Procella Audio P10. These are dual 10″ driver subwoofers, 7″ deep with side input cabling. Procella Audio also make dual 15″ and dual 18″ subwoofers.

Subwoofers are typically the deepest object in any baffle wall and most high performance 12″ subs are 20″ deep with rear entry cabling. This means the front of the baffle wall ends up maybe 22″ off the front wall without using shallow format or in wall subwoofers. Alternatives to shallow format Procella Audio subwoofers are few and far between – our extensive search has led us to in wall subwoofer from Triad and Artison.

 

Step 4: Screen Selection / Speaker Vertical Location

The fourth step is to determine the screen size and vertical location. This must be done in order to position the speakers appropriately relative to the screen center.

The vertical location of the screen is chosen such that the top of the screen does not exceed 15 degrees from the position of the viewers. Once this is done we can locate the left, center and right channel speakers relative to the screen. We do this by placing the speakers such that their acoustical center (typically midway between high frequency and midrange drivers) is between 1/2 and 5/8 of screen height.

 

Step 5: Baffle Wall Design

Now that we know the locations, dimensions and weight of speakers and subwoofers we can layout the framing such that they are supported and sufficient clearance is left around them.

In wide or tall rooms the baffle wall can be built as three individual sections around each speaker, or can have cut outs to allow the space behind the wall to function as a bass trap.

Baffle wall design is one of our consulting services, typically following on from theater design. Done correctly it should allow any competent craftsman to build a baffle wall optimized for your specific room, speakers and subwoofers.

 

Step 6: Baffle Wall Build

It’s important to build a mechanically solid wall without gaps between framing members to avoid buzzes, rattles or resonances that can result from a poorly assembled structure.

 

Step 7: Baffle Wall Finishing

There are many options for finishing the baffle wall including paint, foam and fabric. In this particular room we installed fabric track and stretched black speaker grille cloth fabric over the whole wall.

33 thoughts on “Baffle Wall Case Study: Acoustic Frontiers Demo Room”

  1. What fabric track did you use? I’m making a baffle wall and like the final picture on the way yours turned out. Did you put anything over the frame except the fabric track and speaker grill cloth? Any sound absorbent or dampening material? Foam etc?

  2. Nyal, thank you for the very informative write up on the baffle wall.

    In situations where the baffle wall is built upon a decoupled stage ( to minimize vibrations from the sub woofers) how is the attachment of the baffle to the room walls and ceiling handled? Is there a method of decoupling employed such as the use of DC05 clips, so as not to overide the stage decoupling efforts?

    Thanks
    Steve S.

    1. Hi Steve,

      Yes, there are a number of RSIC isolation clips that work for the purpose of isolating baffle wall from wall and ceiling structures. If you are using hat channel in the walls and ceilings we generally tie into this.

      We don’t normally specify decoupled stages, though I know quite a few designers that do. The reason is that we like to spread the subs around the room to smooth out the low frequencies. If I was designing a baffle wall to sit on top of an isolated stage then I’d tie the baffle wall into the stage and then use the aforementioned RSIC clips to decouple the baffle wall from the room walls and ceiling.

      Thanks,

      Nyal

  3. Any chance we could see a few pics of the finished baffle wall?

    What did you use to cover over the speakers?

    Thanks,

    Rob

  4. Are the speakers simply placed in the spaces? Are they attached in any way? What is the gap between the speaker sides and baffle wall space? Do you fill that with anything and some type of refraction still obviously occur at the interface? If you could literally attach the speaker to the baffle wall with no gap, would that be a benefit or a problem?

    1. If you are using box speakers, then you just place them in the openings, and use something to decouple them from the shelf that they sit on such as sorbothane or foam feet. I’d also advise adding some foam around the speaker edge to prevent it moving over time resulting in hard contact of speaker cabinet to baffle wall, which will lead to buzzing and rattling.

  5. IF……you were to use rear ported speakers, would the insulation behind the baffle wall simply absorb the majority of the port sound? Or would you plug the ports?

    IF….. you used a regular speaker with baffle step compensation, would this be mitigated or improved if you set your small speaker rolloff frequency at 80 or 100hz, assuming that the baffle step occurs below these frequencies?

    1. Ports are used to extend the LF performance of a speaker. Port tuning is normally below 60Hz, so if you are using subs and crossing over the main speakers to the subs (i.e. bass management) then you can plug the ports.

      Baffle step compensation circuits are normally set with corner frequencies quite high, say 800Hz or more depending on the speaker’s baffle width. In a baffle wall there is no loss from the transition from half to full space, so you’ll now have a boost below the baffle step compensation corner frequency. This site has some good basic info on baffle step compensation circuitry and how it works: http://sound.whsites.net/bafflestep.htm

  6. Nyal, thanks so much for posting so much great info. Learning a lot.

    Some questions. If I am understanding the baffle wall concept correctly, the speakers used should NOT be regular in-wall speakers (those designed with dog legs), rather on-wall, boxed or floor standing types? The idea is to decouple the LCR from the baffle wall area, attaching them to the wall itself would defeat that purpose or am I confused? lol

    Further, when you refer to the “baffle wall”, is that the area around the LCR layered with gypsum and MDF and the cavity wall directly behind them stuffed with R19? Is the area above and below the LCR (anything outside the AT screen outline) left uncovered and unstuffed? Is that what you did in your showroom?

    Thanks again for your help.

    1. No reason why you cannot use in-walls. The baffle wall in this case is just a more “beefy”, low resonance version of a typical wall.

      A baffle wall can take many forms. Some are solid wall-to-wall and floor-to-ceiling, others may be partially open to let the air get behind the wall and use the space available as a bass trap of sorts.

  7. For a flat baffle wall with dome tweeter speakers (e.g., Triad in-walls) can you toe-in the speaker around 15 degrees without significant negative effects (e.g., diffraction) and retain the intended 2pi gain? Or does that require an angled baffle wall? Thanks.

  8. Hi,
    first of all: excellent information on your website – thanks for sharing!

    I´m about to start building my own home cinema soon.
    With regards to the baffle wall: what would the construction look like for a curved screen?
    Plan is to have a 1,3′ width screen with a 10% curve.
    Would you build a curved baffle wall behind that or would you stay with a straight one?
    Regards, Thorsten

    1. Most curved screens are designed to mount on a flat wall, so I would build it flat. You could do a curved wall, in which case I would do a separate screen wall to the speaker baffle wall.

      1. Thanks for the quick reply.
        First: of course it should read 13′ in my post above, not 1,3′ 😉
        I´ll build the curved screen by myself, it will be a curved wood construction.
        So i guess i´ll go for a curved baffle wall as well. I think i´ll build it as a couple of angled, flat segments.
        Is there any detail that would need special attention in your opinion because of the curved design`?

  9. Hi Nyal, I have a question regarding your response to a post. You were saying the wall (baffle wall) is built within the outer wall of the room. I plan on building a THX style baffle wall once my 15’x22’ dedicated ht room is completed (framing, drywall, soffits, etc). I thought I would then build the baffle wall within the room, obviously at the front. Because of where I am building the room in my basement, the outer wall essentially is outside the house. I guess my question is will my baffle wall build compromise acoustic guidelines since I am building it within the home theater rather than within the outer wall? I suppose I would be building it outside the inner wall. I could take out the drywall down to the studs which would expose the foundation concrete and start the baffle wall from there. Would love your thoughts and suggestions. Always appreciate hearing your feedback.
    Thanks Nyal!

    1. Baffle walls should be built within the sound isolation envelope, not outside it. I think that answers your question.

  10. Nyal,

    Sorry, one more question. What are your thoughts on building a THX style baffle wall with duel subwoofers outside/directly outside the baffle wall. I plan on purchasing 2x SVS PB4000’s and aesthetically, I feel they may be too big to incorporate in my baffle wall thus changing the design I had in mind. Of corse I could find a way to build the wall with them but again because of their size, it would also shorten the room. I was thinking the baffle wall would be built in reference to the length and width of the screen and on the ends of the left and right sides of the baffle wall/screen I could incorporate angled mini chunk bass traps and position the subs in front of each. Again, would love your thoughts and expert opinion.
    Thanks again.

    1. Yes you can certainly do that, the other option is turning subs sideways and putting them into the baffle wall but keeping the area in front of the driver open.

  11. Would it be possible to provide some kind of side view? I have a hard time understanding what is actually holding the speaker. Is that a platform mounted on the 2×4 horizontal beams? That doesn’t feel very sturdy?

    1. Correct – platform on the stud, with a couple of angled supports at the back of the platform diagonally back down to the framing. It’s extremely sturdy.

  12. Hi Nyal,

    Sorry for a dumb question but how do I tell if a speaker is designed for baffle wall use or not?
    I am after all in theory any speaker can be mounted or placed behind a false wall or furring with a hole cut into it where the speakers are located and then covered up with acoustic transparent material (like wall paper) for aesthetics right?

    Most speakers do not specifically say they are designed for baffle wall installations.

    1. Speaker should be front ported or sealed, and probably should have a rectangular front baffle for a nice transition to the baffle wall. Beyond that, you can use anything.

  13. Thanks so much for the responses. Since then I’ve decided to change the location of my ht. I’m now going to be building it in an interior room in the basement. Only problem is the length of the room. I plan on knocking down the outer wall with doorway and basically extending the length of the room out from there. That being said, the front of the ht where the baffle wall will be will have the open basement behind it. Will this be an issue as far as acoustics for baffle? I plan on decoupling the 2 layers of drywall with staggered framing behind the baffle wall as well as build a small equipment closet outside of the ht/baffle wall. Do you see any issues with this? I guess this goes back to your response regarding the baffle wall built within the sound isolation envelope. Would love your thoughts.
    One other question, my LCR speakers are Klipsch KL-650 THX and have length/depth of 11” which is quite a bit larger than most baffle wall speakers. That being said and in reference to your response in the other acoustic frontiers case study. The space behind these speakers and the baffle wall should be filled with strategically hung rigid insulation with air gaps. Could you elaborate on this?

    1. On your first question, I don’t see any issue with building the baffle wall in free space without a supporting sound isolation wall behind it.

      On your second question, you can do either the hung rigid fiberglass or filling the space with batt insulation. The best approach depends on the specifics of your situation.

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