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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.
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.
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).
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.
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.
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.
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.
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.
Nyal Mellor, Founder, Acoustic Frontiers