Baffle Wall for your Home Theater

[@xburgos1]

Great video Super useful and true science that actually worked in my room imminently Especially the front and ceilings Thank you Matt. Now my dedicated vinyl room is truly a live event 🎉

[@peterorr9798]

Thanks for another informative video, Mr. Poes! What I don't understand is whether a full baffle wall is built with a hard surface attached somewhere to the point that it changes the fundamental dimensions of the room. If the room were 15ft deep and I built a full size baffle wall that ends 1 ft off the front wall, for room mode and acoustic treatment purposes is it now a room that is 14ft deep? Then I need to figure the right viewing distance from screen which will be different than the distance for acoustic purposes behind the screen to the speakers - complicated job you got! 😁

[@PoesAcoustics]

That’s exactly right. The baffle wall shifts the in room shell by the depth of the baffle wall. And yes we design rooms exactly like this. We take the outer shell, identify the final finished inner shell dimensions, and then figure out the screen size, seating distance, and thus viewing angle. It’s all a balancing act. What I try to share is that every theater at every budget is full of compromises. The key is for those to all be carefully considered compromises.

[@EverythingHomeTheater]

Ohhhh...didn't know you had a YT channel! Yayyy

[@PoesAcoustics]

thanks for watching!

[@KASmonkeys]

Thanks - Did you get a chance to test the towers vs your in-walls?

[@frankvee]

How do you deal with speakers that are ported in the rear, or have a passive radiator in the rear? One can't really build a baffle wall and isolate the entire back side of the speaker from the room.

[@PoesAcoustics]

Yeah that doesn’t really work. In my opinion a home theater LCR should be sealed. From a system design perspective that is a better approach. Having said that, a ported speaker could be sealed. It’s very likely that this would work fine in a bass managed system. I’ve done this many times. In fact when I use Klipsch towers in particular I usually plug their port and bass manage them. It’s a popular speaker but I’ve had trouble integrating them unless I do that. I have a talk years ago around optimal bass optimization at AXPONA where I specifically covered this topic and uses the Klipsch tower speaker as my stand in for the discussion.

[@mx96288]

Hi Mathew, would you use the same approach (plugging bass reflex port) in a genelec coaxial speaker setup, say 8341AP and upwards? For context, the idea was to create a mostly digital signal path from a jbl sdp-55's dante out going then to genelec's 9401A AoIP box doing the dante to aes/ebu conversion and bass management. Speaker distance being near to mid-field with low to medium volume listening habits. Since they are fairly compact and offer good mounting hardware, positioning them close to the wall with said 6" absorber behind them to mitigate the boundary effect should work fine and get close to the signal phase correctness of a real bafflewall/in-wall install? Kind regards, Max

[@bingdong8571]

Man, with all of the knowledge you have about acoustical engineering you should try to create fantastic audio things.

[@PoesAcoustics]

I like to think I do. I design private home cinemas. I am doing theaters with Anthony Grimani and on my own. These are all highly engineered and beautiful audio things.

[@geickmei]

@@PoesAcoustics Grimani has no clue about direct and reflected sound either. He uses inwall speakers all around.

[@geickmei]

Speakers pulled out into the room produce some reflected sound for depth and spaciousness. Inwall speakers cannot do that. We do speaker positioning for spatial reasons, not frequency response.

[@miscreant1739]

Did you toe in the front left and right in-wall speakers? I'm not sure what the right approach is or how difficult it would be to do with in-walls, but I assumed you would since you have promoted time intensity trading in the past.

[@Lowkey_nxthxn]

In walls don't really get toed in unless you have a wall that's designed for it or the speaker itself

[@northeastcorals]

I basically asked the same question on one of Matt's previous videos & heres a copy of his reply if you're interested: "I am not putting a toe angle on the speaker, it’s not ideal but it’s workable. I did it for convenience of design. For many speakers a toe is required for good sound. The speakers off axis response is seriously compromised and the Hf would be very rolled off. It would also place the extreme seats in a much worse listening axis. The Perlisten speakers have a very wide area in which the response remains smooth and consistent. This isn’t true or many other speakers. As such, you can keep them pointed forward and still get good sound at all deals. There is about a 2dB difference in treble level between on axis and the extreme off axis seats in my theater. There are a tiny number of ultra wide dispersion speakers, like Grimani Systems, where the difference is 0dB. The dispersion is so wide that over a 90 degree window there is simply no change in the HF response. So basically aiming only matters when the dispersion is fairly narrow or the DI is not smooth."

[@northeastcorals]

I'm building my theatre from scratch so will be toeing mine in 😀

[@miscreant1739]

@@northeastcorals Thanks for sharing his response!

[@northeastcorals]

@@miscreant1739 No probs 😀

[@andreemilsen369]

It kind of make sense to do uneven absortion on the back wall. I gues, that if you absorb parts of the wave, you also change it? And that might make it less of an inerference? Maybe 🤪

[@PoesAcoustics]

When you say back wall do you mean the wall behind the speakers? You don’t necessarily want to change the reflection to be different from the direct sound. That doesn’t make less interference. It only makes the reflection sound colored. It’s also not what I did here. However all absorbers have a non-flat reflected response and the reflection response will look nothing like the direct sound or the absorption rating. The way we “measure” absorption relies on a statistical phenomena of waves that averages out fine peaks and dips. It’s also done at course intervals. As such we don’t get to see the true response of a specular reflection. If we really cared about this we would use big wedges. I’ve long speculated that a curved front absorber could be useful as well. In any case, what I did here was used different materials in layers. So if you imagine the layers from the actual baffle the speaker is mounted to our to the room, it goes like this. MDF and plywood CLD sandwich that the speaker attaches to. A layer of 1/2” high density acoustic PET felt. A 2” layer of medium density acoustic foam. Covered in a layer of foam backed acoustic rated suede headliner material. The way this works is that when a soundwave begins to move toward the CLD layer, it passes through layers of material that gradually change acoustic impedance. The acoustic impedance goes from very low at the air layer to slightly higher at the suede layer to very high once it eventually hits the baffle itself. This gradual transition leads to a lower probability that the incident wave will reflect. It becomes more likely to pass through to the CLD layer where it can be absorbed. This really only works down to maybe 500hz. Maybe lower but that is a good conservative guess. However the goal is to minimize comb filtering which is mostly only an issue above 2-3khz.

[@andreemilsen369]

@@PoesAcoustics First mr. Poes; I really apreciate the detail in your answers. Not many take the time to actually answer with this kind of involvment😊 With backwall, I mean the wall behind the listener, oposite of the frontwall😊 It sounds like a really complicated build🙊 What do you do foe sub 500hz then? Massive absortion?

[@PoesAcoustics]

@@andreemilsen369 ah I see. My back wall consists of 2” absorber panels, 6” QRD diffusers, and bass traps. My bass traps are a steel membrane type. I bought some 6” panels I had made with 8lb density insulation. Those are for the back wall below the diffusers.

[@andreemilsen369]

@@PoesAcoustics There is some rather serious investment in that room🙊 Must sound amazing😊

[@PoesAcoustics]

@@andreemilsen369 well absolutely. But remember that Poes Acoustics is my company and I made a decision to make this room a demo space and lab for my work. It has the equipment I sell in it, it used techniques I most wanted to try out for sound isolation (for example Hushframe was new to me when we decided to try it), and the acoustic treatments are brands I knew to have a good reputation but had not used a lot myself. It’s hard to sell someone an acoustic treatment plan and recommend specific products when you aren’t sure the products are actually any good. Artnovion has dozens of products and I’ve only had hands on time with a fraction of their total products. Using some of them in my room allowed me to expand what I could give first hand experience with. Same for the Real Acoustix products.

[@runebjrnjensen8874]

Have you had the chance to test the jbl synthesis scl 2, if so how did they compare to Perlisten?

[@PoesAcoustics]

Not really. That would be a hard comparison to make. I have heard the SCL-2’s in a theater of all synthesis speakers. I often find JBL Synthesis products to sound bright and even at times harsh. Some of that may be the speaker itself but I often suspect it’s the tuning. The demo I got was a poorly setup showroom theater with inadequate treatments and a calibration that I strongly suspect was overly flat in the high frequencies. Otherwise clearly the two are comparable speakers. They have the same rated sensitivity and the JBL has slightly lower power handling. My guess is that they play about the same max output. Both designs are held back by their woofers and not their tweeters. The Perlisten uses all aluminum construction. Even the back boxes are aluminum with a significant damping layer. That would tend to make the Perlisten a more expensive enclosure to build and would have superior transmission loss within the enclosure. The Perlisten would have superior vertical directivity with a symmetric lobe. The 2.5 way JBL design would create a lobing error in one direction that is different in the other. It also appears that the Perlisten has wider horizontal dispersion by about 10-15 degrees. I am not sure that is very consequential. Kef now also has a Dominus rated in wall speaker. I have not heard this new version. It’s tough. Even if I did, no way I could compare. It would need to be in my room in a direct comparison to make any judgement. Not really readable.

[@runebjrnjensen8874]

@@PoesAcoustics Thanks for the great respond, are you using S7i-LR for all speakers or only for LCR, and what are you dimension of your HT.

[@PoesAcoustics]

@@runebjrnjensen8874 no I used the S4i for the surround speakers. It would have been quite expensive to do S7i for all channels. I had considered doing S5I for surrounds. I may upgrade at some point to see if it changes things. It’s a big expense for a likely modest return. The main advantage is the better vertical directivity. I don’t think the increased output is of any meaningful consequence.

[@steakhoux]

One question: When I want to tame side wall SBIR (of front wall SBIR) do I have to put absorbers on all of the front wall or is a sufficient area (like 2x2 meters) also going to do it?

[@PoesAcoustics]

It would depend heavily on the frequency in question. Covering some but not all of the area would help a lot. Covering all would help a lot more. It also has to be efficient at absorbing in those frequencies. If the SBIR effects are 150hz or less the typical 4” or less of fiberglass won’t cut it. FRK faced fiberglass might be a better cheap option.

[@steakhoux]

@@PoesAcoustics It is mostly 120,150, 170Hz that show drops because of SBIR. Unfortunately ceiling/floor/front/sidewall. Cant do anything in my living room about ceiling and floor SBIR. But I could do something about side walls (120Hz) and front wall (150Hz). Maybe I could use GIK monster traps. They are about 6.5 inches thick. I would still have to dig a bit deeper to find out what I can do about the somewhat jaggy response 120-400Hz though. Only partly those drops can be attributed to SBIR. I use 4 subs optimized by MSO and crossed at 120Hz to circumvent the first SBIR dip. It is a bit annoying that my response is looking really good until 120Hz, then is messy till 400Hz and is looking good again. The transition region above my subs XO till Schroeder frequency is really hard to come by.

[@geickmei]

Matt, you need to study live sound acoustics. That is what we are trying to replicate. The reverberant field comes from reflection off the walls all around, and needs to do the same in the reproduction. It should not come from the same points in space as the direct sound. To accomplish this, speakers need to be a combination of direct and reflected sound, just like the Bose 901s, Infinity IRS, all dipoles and bipoles, and omnis. Inwall and on wall speakers cannot do that. Instead of SBIR, study image modeling and speaker positioning.

[@mrbendel]

Nice looking theater