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THX baffle walls – design, build and benefits

What is a THX baffle wall and why do I want one in my home theater?! This article explains what a baffle wall is, covers the acoustic and audio benefits and finally provides tips on how to design and build them.

A baffle wall is essentially a false wall into which the screen speakers (i.e. left, center and right) are mounted. It is a core component of a THX certified cinema.

“Unique to every THX Certified Cinema is the THX “baffle wall.” If you were to peel away the screen at any THX Certified Cinema, you will see a massive wall of speakers housed in an acoustic baffle. The baffle wall is approximately the same size as the screen, providing a solid, smooth and uninterrupted surface to distribute sound throughout the auditorium. It produces a large sound image and accurately tracks sound elements with the onscreen action. This makes panning shots and off-screen sounds more believable and natural, helping to pull audiences into the storyline. Without a baffle wall, sound is uncontrolled – producing a weak, uneven image.”

Acoustical and sound quality benefits of baffle walls

Baffle walls have a couple of major acoustical benefits which translate into sound quality benefits:

  • No speaker boundary interference from the front wall behind the speakers, since the speakers are mounted flush with the surface.
  • Increased low frequency output. The baffle wall essentially removes the ‘baffle step‘ which happens when the speaker radiation transitions from half space to full space as the frequencies exceed those which can be controlled by the baffle. If your speakers are designed for flush mounting in a baffle wall, as Procella speakers are, then you gain 6dB of headroom in terms of the ability of the speaker (or sub) to reproduce reference levels.
  • Reduced diffraction. There is little to no diffraction as the front baffle of the speaker is flush with the wall.

From a sound quality perspective these things mean that the sound tracks cleanly from left to right with no jumps, we have more headroom at low frequencies and we have better bass free from boundary interference suckouts.

Note that very few speakers are designed to be baffle wall mounted – most are designed to be used in free space and hence incorporate baffle step compensation circuits or are otherwise designed to counteract baffle step losses. When placed into a baffle wall the frequency at which the baffle step occurs is moved significantly downwards, to 80Hz or lower, which results in a bass boost. It is possible to equalize out this boost using a low shelf filter.


Visual and aesthetic benefits of baffle walls

baffle wall allows you to hide the screen speakers and front wall located subwoofers so that they are no longer visible. This provides for a very neat and visually attractive installation.

If shallow format speakers and subwoofers are selected baffle walls can be made very shallow. The baffle wall in our demo room uses Procella Audio speakers and subwoofers which allow the baffle wall to be only 8″ deep.


How we design and build baffle walls

  • Speaker’s acoustical center optimally placed. Typically this means 1/2 to 5/8ths of screen height but will vary depending on the vertical off axis response of the speakers in question as we want the relationship between speakers and audience to be within the angular range where the speakers sound good.
  • Multi-layer construction using constrained layer damping techniques. A proper baffle wall is at least 1.5″ thick and comprised of multiple layers of material, primarily to stop the baffle wall from resonating and becoming a giant speaker. This might happen if thin material were used as the speakers sit in the wall and hence transfer energy to it.
  • Absorbent covering. The front of the baffle wall behind the screen should be covered with a 1″ layer of light and sound to absorb light transmitted through the screen and sound reflected back from the screen to the wall.
  • Speakers and subs decoupled from the wall using appropriate isolation pads. These are used to prevent transfer of energy into the wall from the speakers.
  • Void between the baffle wall and structural wall filled with absorbent material to prevent resonances developing in the space. In wide or tall rooms cutouts in the baffle wall can be made to allow the area behind the wall to function as an effective bass trap.

We have written an in depth case study of the design and build of our Demo Room baffle wall which explains the steps in the process and how it fits in the overall theater design process.

78 thoughts on “THX baffle walls – design, build and benefits”

  1. Hello.

    Thank you for the tipps.

    Can you tell me what material are the three layer damping construction?`

    best regards


    1. Using a combination of drywall and plywood works great because both materials will have different acoustical properties. Therefor they can’t resonate together and kinda help each other to not do anything unwanted or weird.


    1. Hi Mike, thanks for your comment!

      The wall does not have an STC rating because it is not designed for sound isolation. The wall is built within the outer wall of your room. It’s the outer wall that does the sound isolation. The baffle wall has holes in it for speakers and subwoofers so doesn’t offer any sound isolation.

      Hope that makes sense!

  2. I understand that you need absorptive materials on the front of the baffle wall to absorb light that leaks through the acoustically transparent screen. I also understand that this material needs to be sound absorbent if you use a perforated vinyl screen, but do you still need the baffle wall to be sound absorbent if you use a woven textile screen? A woven screen should have a lot less audio reflections from the back of the screen compared to a perforated vinyl screen.

    Also, if you clad the entire front wall (the baffle wall) with a thin layer of sound absorptive material, won’t this cause other acoustical problems? You will get very non-linear dampening of the sound. You will have a lot of dampening in the high frequencies and very little in the mids and lows. Won’t this be a problem?

    I also have the impression that the old hi-fi concept of dead-end / live-end is not the best acoustical solutions anymore. It is better to place the absorption on strategic places elsewhere in the room. Based on this, why would you still want to use a baffle wall in a home theater?

    Please comment.

    1. Hi Lars thanks for reading and leaving a thoughtful comment! The material should be sound absorbent regardless of whether the screen is woven or perforated, since even woven screens reflect sound back towards the baffle wall.

      You are right on point that cladding the whole front of the wall with a thin absorber is generally bad, since you only absorb the highest frequencies. A better approach is to use thick absorbers around the speaker and leave the upper and lower parts of the wall outside the screen reflective, or add diffusors. If you think about it from the perspective of the surround speakers the front wall is an major reflection point. However this needs to be balanced with practicality, and dealing with thick absorbers and diffusors on a screen wall can be challenging.

      The point of a baffle wall is to reduce diffraction, increase the low frequency output of the speaker and prevent the sound energy from wrapping around the speaker baffle and bouncing off the front wall [aka speaker boundary interference or SBIR]. All the top studios still have baffle mounted speakers (they call them soffit mounted speakers), and you will see that they often clad the wall in stone for diffusion.

  3. Hello great info here. Obviously the LCR should be mounted directly behind my micro perf screen but my question is can the front 2 subs be built into the baffle wall below the screen. Or do they need to be built in so they they travel the the micro perfs as well? I hope that makes sense. Also how high should you mount the main drivers on the LCR’s? ear/ listening level ? thanks in advance. jj

    1. Hi JJ

      Thanks for reading!

      Rule of thumb for LCRs is acoustical center (typically between midrange and high frequency driver) to be at 5/8ths of screen height. This comes from commercial cinema best practices.

      A baffle wall is a great place to hide subwoofers. As long as what covers the subs is acoustically transparent then they do not need to be behind the screen. In fact putting subs directly behind a screen can sometimes cause problems as subs can move a lot of air and this can actually cause the screen surface to vibrate!


  4. Lars says: "I also have the impression that the old hi-fi concept of dead-end / live-end is not the best acoustical solutions anymore."

    • Still likely my favorite solution I’ve heard!
    1. The live end / dead end (LEDE) approach was designed for two channel monitoring in professional recording studios. LEDE was never conceptualized to provide an ideal acoustic environment for multichannel reproduction. For surround speakers you don’t want the front of the room to be completely dead and the back end completely live, you need in my opinion a more balanced approach in order to achieve great surround sound envelopment and effects localization.

  5. What are your thoughts on the tradeoffs between the benefits of baffle walls and the benefits of broadband or low bass absorption on the front wall, especially for small room applications (1000-1800 sqft)? For the same 8" depth of a baffle wall, you could also treat the entire front wall with 8" of treatment, providing huge amounts of absorption to quite low frequencies. You would also eliminate SBIR (right?). You are then only left with the benefits of effeciency and lack of diffraction when considering a baffle wall. Add in the fact that small rooms need significantely more bass treatment(?), and also lack the wall real estate of a larger room for bass absorption/trapping, and I would lean towards the opinion that baffle walls only make sense in rather large listening venues/rooms, especially considering effeciency is much more important for said venues. What are your thoughts?

    1. Hi Brian,

      Thanks for your message. A very good point!

      1000-1800 sq.ft would be a very large home theater, do you mean cubic ft?

      Small rooms definitely need all the help they can get with bass absorption, so your position is a valid one. Most speakers need more than 8" of depth, so in reality the face of the speakers is going to be further into the room and the SBIR frequency lower. SBIR is hard to kill with even very deep absorbers. One option is to incorporate bass trapping into the baffle wall. I’ve done a few walls like this recently, where there are essentially cut outs in the baffle wall to expose deep bass trapping behind.

      There is a relationship between how large the baffle is around the speaker and the lowest frequency to which it controls sound waves. Below this frequency the sound wraps around the baffle. So one option is just to build large baffles around the speaker and leave the rest of the wall open. Or you can build a continuous baffle wall and then have cut outs towards the ceiling or side walls to expose deep bass trapping behind.



      1. Any advice on the cut outs and where to absolutely not put them?
        I’m in a hard spot choosing between the two.

        Baffelwall or open with absorption

        Thank you so much

  6. Thank you for unveiling the mystery of the THX Baffle wall. More importantly thank you for expounding on the knowledge and science behind it.

    I am in the process of building my home theater. I decided to go with a AT screen so that I can maximize the screen size. Further research led me to your website. I would like your opinion on implementing a thx style baffle wall in my build. My LCR speakers are CLearwave Dynamics 4TSE and 4TCC They are rear ported. I know that since these speakers were not designed for in wall use their may be some complications implementing them into a baffle wall. If they can not Ill just place them behind the screen.

  7. Hi, great article. I see you recommend placing the HF 1/2 to 5/8 of the way up the screen. My question is what if 1/2-5/8 up the screen is significantly over ear level? I have heard to try and keep the tweeters (or compression driver in my case) around ear level. I am using JTR Triple 12’s as my LCR and they will be standing on top of Seaton Submersives which puts the CD at about 45" off the ground. I was also going to try and incorporate a 10" high front stage but that is then putting the CD at 55" high and seating level will just be on a couch on the ground, not elevated by a platform or anything. I could lower the screen to accommodate for the -5/8 height but there will also be a secondary elevated row on a platform behind the main listening position. If I lower the screen too much then that increases the height I have to make the riser so they can view all parts of the screen. Any advice would be appreciated!

    1. Hi Devon

      Thanks for reading the article and posting a comment! There are a couple of home theater design principles that are at play here.

      1) Keep speakers within their operating window
      2) Tie on screen action to sound

      In more detail:
      1) Most speakers have a narrow vertical ‘operating window’ where the frequency response does not deviate significantly from the on axis sound. That’s why you see the advice about trying to listen on the speaker axis. The only real way to know how wide the operating window is is to take measurements. I’m not sure if there is an official definition of operating window but I’d say you want to position the speakers vertically so that the response is within 3dB of the on axis sound. Most speakers will only have 5-10 degrees of vertical operating window, so placement is constrained.

      The only real way to know is to measure your speakers vertical off axis response and use CAD modeling or trigonometry to figure out the vertical angle from head height / listening position to the speakers.

      2) The ventriloquism effect is strong if you are watching video with accompanying audio. 5/8ths screen height is the commercial cinema recommendation. If you move off the 1/2 to 5/8 recommendation then you are starting to compromise tracking but still your adaptation to angular differences in video/audio location is good up to about 15 degrees, so theoretically there is some good flexibility with speaker positioning.

  8. Hi Nyal,

    thanks for the great posts and answering the questions.

    I have a rather annoying question. Does it make sense at all in constructing a baffle wall if I use 2 THX down fire sub-woofers?



    1. Yes definitely, you can build a partial baffle wall around the LCR speakers and then leave the bottom part of the wall open where the down-firing subs will be. Another option is to turn the subs on their sides so they fire forwards.

  9. Great article!

    I do have a question, though. The article’s “How we design and buld baffle walls” section specifies that the “Void between the baffle wall and structural wall filled with absorbent material to prevent resonances developing in the space.”

    Could you be more specific about the type of materials which can/should be used for this and how full the space needs to be? If a baffle wall is deeper for some reason, such as if the front structural wall is not flat, would the entire space need to be filled with absorbent material? In my case, there is a recessed section of the front wall about eight feet wide and two feet deep, right in the middle. I am trying to decide whether I should just wall that space up, or if some other treatment might be effective.

    Thanks in advance!

    1. The answer, as usual, is “it depends”.

      In a solid front baffle wall the filling is there to prevent resonances. Even a thinnish layer of pink fluffy (R13) will do the job. If you have a baffle wall design which incorporates open areas to allow the space behind the wall to function as a bass trap then what and how you fill the space with is critical. In this application the type of material needs to be selected based on the depth it needs to fill. Over a certain thickness even low density pink fluffy fiberglass becomes internally reflective (as in you increase the depth but absorption DECREASES). That effect is due to GFR or gas flow resistivity. A good technique for deep cavities is to hang sheets of semi-rigid insulation from the ceiling, spaced with air gaps. With these they should be strategically positioned in areas of low pressure, high velocity.

      1. Nyal, with this application, would LCR speakers with more depth that require a larger space require a more thicker acoustic filler?Since the space between the existing structural wall and baffle wall has increased perhaps filling the back wall with OC703 or ATS would be sufficient? My Klipsch KL650 THX’s are over 11” in depth. Besides the semi rigid insulation with gap from the ceiling, what would you suggest in this case?

  10. Great article.

    Can you clarify th placement of the surface of the absorption versus the plane of the flush mounted speakers and the plane of the baffle wall? Are they all flush causing a need to recess the absorption?


    1. Ideally front of speaker baffle should be flush with absorption. Baffle should not be significantly recessed into absorption.

  11. Great article,

    “Speakers and subs decoupled from the wall using appropriate isolation pads”
    What pads ?
    Speakers decoupled, are the platforms that support speakers screwed into the wall?

    Thanks in advance!

    1. dont want any vibration from the speakers transferred to the wall.
      Smalers speakers can be mounted on the beams but largers speakers need more support and one way to fix that is with a platform.
      My own solution was to build a box thats 5 mm larger then the speakers (inc damping feets).
      Then i used cinder blocks to get correct height (inc damping) and mounted the boxes in to the wall.
      Since i have 0.6met off space behind the wall that was realy the only solution.

    2. Hi Louis

      Platform to support speakers is part of the baffle wall. For speaker isolation you can use a number of things including rigid fiberglass (OC705), high density foam (Auralex Platfoam), Auralex MoPads, etc.



      1. Hi,

        I have built a baffle wall but made some mistakes. I screwed the speaker with the baffle wall (vibrations), now i want to rebuild the Baffle Wall. I Decouple the speakers and i make a multi layer construction.
        Now my Question:
        In the moment i have only a 0.8″ mdf Layer. I can make a three Layer (Multi-layer construction) construction. First Layer 0.8″ mdf, second Layer 0.5″ gypsum Board , third Layer 0.5″ gypsum Board. Icant make gypsum, mdf, gypsum. Can i do this?
        In Austria i dont have Green Glue, what can i take?

        Here you can see my Baffle Wall:

        Thanks, Horst

        1. I have forgotten to write, the vibrations are not great (very little/light) but easy to hear in certain scenes.
          Sorry for my bad english.

        2. MDF–>Gypsum–>Gypsum will be fine. Not that much different to the way I normally do it.

          If you don’t have GG you can use construction adhesive. Again not as good but probably 80%. You may find some local version of GG (damping compound used for sound isolation) which you can substitute.

    1. It’s there to provide a different set of material properties than gypsum board, to control resonances when used in the sandwich with the gypsum board.

  12. Nyla
    What’s your thought on ideal spacing between the baffle wall and AT screen? Does it depend on speakers? thanks!

      1. In what capacity?

        Procella make very good speakers. They sound good, use one of the workable high frequency transducer designs for high SPL home theater (compression driver), have great form factors, are sealed, offer a fully timbre matched solution for spatial audio and are reasonably priced.

    1. Depends on the screen. If you have a woven screen then you may only need a few inches. If it’s a perforated then you might need 18″. Of course there are variances between the various woven and perforated materials, that’s where it helps to have measured the screen at different distances from the speaker, and at various off axis angles to determine what a good minimum distance is.

  13. Hello,
    What would be the alternatives to glass wool for “filling” the wall and avoid resonances ? Can high density polyethylene foam work ?
    I am doing a “mini baffle wall” (kind of inside a custom furniture) and i don’t really want use glass wool (not very health safe).
    Thank you!

    1. You need a low density product if you go > 6″ or so. I haven’t researched what alternatives there might be for a non-fiberglass product. Maybe long haired wool or polyester batt.

  14. Mr. Mellor,

    I appreciate your blog, there is a lot of useful information here that I’ve found very helpful! I will try to be brief. I am building a multi-use home theater room in my basement and would greatly appreciate your input and recommendations to help me make the best of my situation.

    I have a Seymour AV acoustic screen (100″ wide) and the seating area is about 13 feet from the screen. The wall that the screen will go on divides the living/theater area from a fairly large storage and mechanical room. I decided to get DefTech UIW RLS ii in-wall speakers for the L/C/R behind the screen. Because there is a furnace and water heaters relatively close behind much of the wall behind the screen, I decided it would be too difficult to mount anything other than in-wall speakers. I have an SVS SB-16 ultra subwoofer which I am hoping to put behind the wall on a DIY stand that will be about a 20x20x20 inch cube mounted solidly to the concrete and put the subwoofer on it with subwoofer isolation feet. I am planning on cutting a hole in my drywall behind the screen for the subwoofer and filling the space between the sub and the wall studs with acoustic foam to prevent the sub from causing rattles in my wall.

    My question is whether there is anything else that I can do to make my theater sound better or anything that you would recommend doing differently. For example, adding horizontal reinforcements to the studs in the wall or adding insulation between the studs or a different subwoofer location.

    I really appreciate your comments and suggestions!

    1. Hi Ben

      Seems like a good start!

      You will likely find that seat-to-seat response is not great with only a single sub, but with an SB-16 you may not have room to add another. We developed a shallow depth, high output sub system with Power Sound Audio for exactly this application. It uses a rack mount amplifier and 12″ deep ported sub cabinets with 15″ high excursion drivers.

      Other than that, you should consider a basic set of acoustical panels at reflection points, being careful not to overabsorb. Simplistic rule of thumb, aim for 50% coverage at the reflection points.

      Finally, I would strongly advise finding a good professional to do a proper audio and video calibration instead of relying on the auto-EQ.

      Have fun!


  15. Hi,

    Thanks for all the great info on building a baffle wall. However, I still have a couple of questions.
    1) If I am supposed to decouple the speakers from the wall, using isolation pads and/or absorbent material, so that they don’t transfer energy to it, then why do I need to add the two layers of dry wall and one layer of mdf? Wouldn’t it be sufficient to fill all voids in the wall with absorbent material and cover it all up, except for the speakers of course, with a black layer of cloth, and be done with it. The speakers would be flush with the wall like they’re supposed to, plus the entire wall will be a giant absorber preventing sound to reflect off it, and not just the highest frequencies either, right? No? Would it be too much dampening?
    2) Also, the filling of the voids in the wall should it be material of high or low density? Should it be packed hard or softly filled?

    1. Hi Anders!

      The drywall / MDF layers are the “baffle wall”, whose main function is to stop the sound waves wrapping off the speaker baffle causing phase cancellation from the bounce off the front wall (i.e. speaker boundary interference or SBIR). If you just add absorptive material then your wall is no longer a baffle wall, it’s just absorption around the speakers, and it’s unlikely to be thick enough to absorb the bass wave that comes off the front of the speakers.

      The fill for the baffle wall should generally be low density fiberglass batt so that it works effectively in 12″ thicknesses. If you use a higher density material then they generally do not function as well as lower density materials from a bass absorption perspective in that depth of application.

  16. I designed my theatre room according to Sepmeyer ratio – 2700h x 4320w x 6290d (all in mm).
    I was wondering if a baffle wall would work in my room as it would effectively reduce the depth of the room to 5690mm. Would this adversely affect the acoustics that way or would the baffle wall compensate for it ?
    Can I just wall mount my speakers either side of my screen (I have 2 tall skinny windows that I can remove and then box in the speakers outside the room) and get a similar effect ?

  17. with my limited Knowledge I presume that the screen is acoustic transparent screen what will be the minimum distance for the non display of the holes of the screen

    1. Yes, the screen is AT. Minimum seating distance depends on the physical characteristics of the screen – some have larger holes or gaps in the weave, other smaller. Most screen material manufacturers provide minimum seating distance recommendations.

  18. Just wondering about the bass trapping and thinking of the following possible designs:

    1) Build baffle wall as you outline (partially at least) with enough space left on the sides to place R13 or R19 insulation in the corners, still in bags, stacked to ceiling. These would end up same depth as baffle wall. If not the bags of insulation then superchunk corner stacked OC703 perhaps?


    2) Build the baffle wall as you outline but with air conditioning grills on the sides to open the wall for bass absorption; like I’ve seen people do with riser bass traps.

    Hope this makes sense.

    1. Our current designs typically incorporate some open areas to allow air to circulate into the space behind the baffle wall, which is filled with low density fiberglass batt insulation. You could use HVAC registers to allow air to circulate, or you can just leave sheet goods off the wall in certain areas and then cover with fabric to hide the opening. You can see an example of a hybrid design here.

  19. Hi! I’m looking to build a baffle wall but am unsure about the outcome when using speakers with passive elements in the back. I have a LCR set of Amphion two15’s

    How tight should the speakers be packed whitin the wall and how much air/insulation behind them?


    1. If you have speakers with radiating elements that would end up behind the baffle wall face when installed, then you are blocking free air flow by putting them into a baffle wall. This will have a measurable acoustical effect, and obviously is not what the designer had in mind.

  20. I enjoyed your interesting and helpful article. Thank you.

    I have a small two-row 7.1.4 home theater with a fixed 106″ Dragonfly AcoustiWeave screen. The original L/C/R speakers were in-walls installed behind the screen. I would like to replace them with three 12.5″ x 14.25″ JBL L810 on-wall speakers that are only 5.5″ deep. In the case of the left and right L810’s, my plan is to simply install them on the wall on either side of the screen at an appropriate distance apart given the size of my theater. (Because of stud locations behind the wall, it would be complicated to mount them behind the screen and they would not be far enough apart. Maybe I need a bigger screen!)

    Here is my challenge. I would like to place the L810 for the center channel behind the screen at the same height as the left and right L810’s. The wall is standard 0.5″ gypsum board, behind which is a 4″ deep space to a concrete wall. My plan is to cut out a 12.5″ x 14.25″” hole in the gypsum board and mount the L810 on the concrete wall using its brackets. Of course, the 5.5″ deep L810 will protrude out about 1″ beyond the front for the gypsum board. Here, my plan is to build a 1.75″ thick wooden frame for mounting the screen out from the wall that will provide space for the L810 plus 0.75″. Based on your article, it seems I should also install a 1″ thick layer of absorption material around the speaker covering the entire area of the screen.

    By the way, my subwoofer is free-standing and four other L810s are used as surrounds mounted on the side and rear walls. The other four channels of my Atmos setup are JBL l226c’s mounted in the ceiling.

    I would greatly appreciate your comments on my plan and any suggestions or changes you would make. Thanks so much. George

    1. Sounds like a good plan! Any reason not to stick with the in-walls and simply install some better ones? There are some pretty good in-walls out there, we like the Martin Logan Electromotion series and the higher end Revel.

  21. Extremely useful article, and remarkably nice of you still answering questions five years later!

    I had this, probably crazy, idea: as a “lazy man’s” version of a partial baffle wall, could one use bookshelves? I’m thinking either a) place each speaker inside a bookshelf and cover the front except for a cutout for the speaker, or b) place a closed-up bookshelf on each side of each speaker (speakers between them). The advantage being that you only need to build and mount the mdf-gypsum fronts, not the entire wall skeleton.

    What say you?

  22. Hey,

    My home theater is underway and I wanted to see if you see any issues with the baffle wall design I have here? Post 80 has my design.

    I am going to build the wall with a 2×6 frame, 2 Layers of 5/8″ drywall and 1 layer of 3/4″ MDF with 1.5″ Duct liner on the face of the wall… The baffle will house 3 x HTM12’s and 2 x 18″ MBM (VBSS). 2 x 18″ MiniMartys will be below the wall in an open cavity.

    I only have 30″ of room behind the wall with 2″ of space for the screen to mount in front of that. I am planning on filling the gap behind the wall with R13 bat insulation from bottom to top with a bass trap hole on the top portion of the wall between the soffits.

    Any suggestions would be appreciated!

    Thanks in advance!


    1. Sounds like you’ve got the basics figured out. I’d go much deeper on the insulation though, like two layers R49.

  23. Hi again – I have just reread the article, comments and replies and I am still a little confused. My understanding is that a baffle wall is basically 2 walls with a small gap in between and the speakers protrude a small amount in front of the second wall. The speakers are then made flush with sound absorber ??
    If that is correct is there a minimum or maximum thickness of the absorber material or protrusion ?
    I have a double brick cavity wall and I figured the internal brick wall will be the baffle wall and I just need to cut holes in it and mount some absorber to it. But the cavity is 50mm, the brick and plaster are 100mm and my speakers are 280mm. This would leave the speakers protruding 130mm. Is this OK if I mount 110mm insulation 20mm from the baffle wall or should I move the speakers out 20mm then mount 150mm
    fibreglass insulation ?
    Am I on the right track or should I consider in wall or shallow mount speakers instead to flush mount them with the internal bricks or would they still need to protrude and have just 25mm of foam absorber ?
    Or should I build a 3rd wall as the baffle wall and build it as per recommendations ?
    Thanks heaps 🙂

    1. Think of the baffle wall as an extension of the speaker baffle (front face of the cabinet). There’s no minimum or maximum thickness, more good practices to follow: at a minimum two layers of material, with a constrained layer damping compound between. It’s also good to have absorption on the baffle wall, especially if you are doing an acoustically transparent screen as there will be some reflections off the back of the screen material back onto the baffle wall. If you are adding absorption, then 1″ is the absolute minimum, but 2″ is better, and if you have space 4″ is awesome. Thicker the absorber the more of a full frequency effect it will have.

  24. Hi Nyal-
    I’m considering building a hybrid baffle wall for all the good reasons above.(stealth aesthetics, bass trap, defraction reduction, Low Frequency Enhancement, etc.) However, it poses a dilemma in my situation. My LCRs are Geddes Abbey’s, which are large, constant directivity waveguide speakers designed to be cross-fired, or toed-in, at about 35-45 degrees. My drop-down screen only gives me about 15″ of depth to with which to work, so it’s tight. This amount of toe-in seems difficult with a FLAT baffle wall and large speakers. It seems they’d need to protrude significantly from the baffle. Alternatively, to accommodate this, I’m considering either an elliptically concave or 3-section baffle wall with the left and right sections toed in and the center section flat. If sectioned, the center would need exposed absorption on its sides to reduce early reflections from L&R. Do you have any suggestions regarding FLAT/protruding speakers versus concave versus multi-section, toed-in baffle walls?

    1. The baffle wall should be multi-sectioned, toed in. If they are protruding and angled you are not getting one of the main benefits of the baffle wall – that is the wall acts as an extension of the speaker baffle. Instead you’ve created a close surface behind the speaker that will create phase cancellations from the backwave coming off the speaker baffle. You don’t NEED to toe them in as much as 35-45 degrees, as long as you are less than about 20 degrees off axis from the speaker you’ll still be within the ‘cone of coverage’ (-3dB at 4kHz).

  25. Hi, I have an AT screen. I didn’t build a baffle wall, as I just hung the screen from the ceiling using hinges, so I could have easy access behind it, and plus I have a door on the left side that I need to have access to. I use bookshelf speakers, or speakers on a stand. Should I build individual boxes filled with roxul, to place each speaker in? I’m wondering if that would help with dialog… Thanks

    1. No. I’d recommend adding thick acoustic treatment across the front wall behind the speakers. Boxes that you put the speakers into won’t do anything – no real increase in baffle area if you do that.

  26. Hello. I see in the photos that you have a black material between the floor and the bottom of the baffle wall. I’m assuming this is an isolation material of some kind. What did you use for this?

  27. Great article! I was baffled with some of the nulls I had in my HT and after reading this article, it got me to look into baffle wall. Total helped me reduce a couple big nulls. Thank you!

    I didn’t go the full extend, I made noticeable improvement (between 8db to 15db) on nulls with a simple 1/2″ thick plywood that’s flush to my speakers.

    Documented some of it here in case people are interested.

    Net is try it out, and crawl-walk-run, even a little goes a long way!

  28. Hi Nyal.

    I read your reply ‘March 5th’

    “You are right on point that cladding the whole front of the wall with a thin absorber is generally bad, since you only absorb the highest frequencies. A better approach is to use thick absorbers around the speaker and leave the upper and lower parts of the wall outside the screen reflective, or add diffusors. If you think about it from the perspective of the surround speakers the front wall is an major reflection point. However this needs to be balanced with practicality, and dealing with thick absorbers and diffusors on a screen wall can be challenging”

    When you say “A better approach is to use thick absorbers around the speaker”. How thick are we talking?

  29. HI

    This is an amazing site and Ive learnt so much. I want to build a baffle wall into my loft conversion cinema. Due to the limitation on height the max width screen I can fit in on a 16:9 is around 3m. This leaves me around 0.75m free space each side.
    I’m not sure why if I’m honest but i like the idea of being able to gain access to the rear of the baffle wall and maybe even putting some of the AV equipment behind it. If I left that 0.75m on each side as a empty space and covered it wit a hanging curtain, ie the baffle wall would sit in the centre of the front of the room and would not butt up to the side walls, does that have any detrimental effect on the baffle wall ? I hope that makes sense !

    1. It really depends on where the L/R speakers are. The idea of a baffle wall is having an extended baffle around the speakers to reduce the baffle step frequency. If you have the sides open you are probably not going to get that benefit for the left/right, just for the center speakers. You can learn more about baffle step frequency here. There’s a formula on this page – f(3) = 380/W(B) – you can use to estimate the -3dB point for any size baffle. Using that formula, to get an f3 of 80Hz your baffle would need to be 4.75′ wide…ignoring driver width this is 28-1/2″ from the center of the driver to the edge of the baffle.

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