How to Fix Speaker Boundary Interference (SBIR) Issues 

Room modes don't change depending on where you put the microphone and the listener position; they are inherent to the room geometry and the boundary conditions (and air properties), and are independent of sourcing and mic position. What changes is the driven response, and so you might see renonances appear and disappear as you move things around, but each mode has it eigenvalue (the frequency) and eigenvector (the pressure distribution across the room) stay the same, as long as the room stays the same.

Brilliant! You guys have given a world of knowledge on these live streams! Thank you!

Extremely informative! You've convinced me that I need some absorbers behind the left and right speakers, and potentially move them closer to the wall to increase the frequency where SBIR happens

This is good stuff for me to learn. I feel like I've reached the top of the line for speakers for the time being. Now it's time to start putting some real time into room treatments. My room is treated, but content like this is great to move forward for do it yourselfers like me and others.

Thank you guys, great information! I see too many forum members give advice to others with no idea of what the real problem is.

I intentionally responsibly avoid any meetings at work following the morning of an Audioholic live stream, one must have priorities.

Great and informative presentation! Thank you.

Great video. Keep up the good work.

Love the video. Any time Grimani is on the channel, it is like a masterclass from a guy who has been doing this for decades, and having him and Matthew Poes in dialog is fantastic. Matthew takes all this knowledge and translates it into real world realistic practical approaches for those of us that cannot spend six figures on our home theater! That said, they have both been pretty transparent about naming names in the past, companies and products worthy of praise. But this time although they mentioned that SOME in wall (baffle mounted) speakers have solved the imaging depth problem, a few times, they didn't actually mention which those are. I found that disappointing, since that would solve SBIR without the one key stumbling block (less depth to the acoustic image) that people trot out. So it seems likely that one of the best solutions could be achievable without a lot of sacrifice......if we were privy to what these two titans have learned with real speakers.

Great video! There's actually a good trick I've employed in a few rooms that I don't hear very often. Speakers close to the wall with thick abortion can indeed help the SBIR null but Ive seen it exagerate other room modes. On the other hand in many residential sized rooms pulling out over 3 feet can be a bit obnoxious. Especially in home theaters. There's a third solution. If you bass trap most of the wall to wall and wall to ceiling corners and throw the subwoofer in the front corner you'll probably get fairly even response after EQing unless you have reallt poor dimensions or a tiny room. So in this SBIR trick you'll pull your speakers just a bit out from the wall. Say somewhere around 18" from the rear of the speaker. With most speakers this will usually put the SBIR null somewhere arpund the 100-120 htz range. It's important to measure here to pinpoint it. Then you just set the crossover to the sub a little higher than the null. The Negative here is the subwoofer might sound a little directional this high. It won't be very noticeable but if it bothers you just put a second sub in the other front corner and voila... diectionality gone. The most successful residential room I treated employed this tactic and it was small. About 10.5 ft x 13 ft. I had all corners trapped with 4" 2'x4' panels. I had a 6" panel on the ceiling's first reflection. 2" panels on the walls first reflection. 2 4" panels on early reflections. All of these panels being materials with OC703 like absorbtion . Then I put two 4'x4' panels on the rear wall with a foot of mineral wool, specifically Owen's Corning Fire and Sound batts. The room was a bit dry but after I utilized Sonarworks EQ I was shockingly really close to a mastering rooms frequency response. So I went completely overboard and built a desk where the desktop was made of OC703 and then I put a screenlike material over that to protect it. Amazingly, This brought the REW measured response to within 6 dB across the full range after Sonarworks EQ. Voila, mastering room frequency response in an average sized bedroom. People will harp how dry the room is. Even sub range was fairly dry. But for super critical listening I was a fan! Any little flaw was audible. After spending enough time in the room you adjust to the dryness and learn how much verb to apply. The awesome thing about that room is the bass was so tight it just smacked you right in the chest. Even snares could be felt well. The staging and separation was also excellent. I didn't realize that "Blood On The Dancefloor" would become one of my top 5 favorite mixes until I heard it on that super accurate staging.

It was really good help to me :) Thank you so much guys!!

Amazing video Gene, Matthew Poes and Anthony Grimani !!! This really should be added to that Audioholics youtube playlist: Room Acoustics 👍

Just the video I needed.

Hey Matthew Poes, I'm glad to see that the advice you requested from me regarding binaural audio was of use to you. It was cool to have those guys from Sonic Presence on during last year's HiFi Summit. Remember the one thing I asked for in our email in exchange for my help. 👊😎

Great stuff. Going to soffit mount my LCR in the wall with a custom baffle.

This is one reason why subwoofers will always improve a system, even if the speakers are full range. Pull the speakers out from the front wall, put the subwoofers against the wall, and cross over at a frequency whose quarter wavelength is shorter than the distance from the speakers to the wall. Problem solved.

Sub sections: ALWAYS in the corners are my mantra. Sooo much easier to integrate and to help cancel nulls. And ofc. 4 of them minimum. I also run my sides and rears (1m high good sizes) with proper amps and full-frequency. To me that sounds way better than cutting them off at 80 or similar. I am starting to think cutting off decent sized speakers at f.ex. 80hz is for puny receivers as they do not have enough power...

Another Great Video Thanks. I sit at home thinking about stuff and have been wondering about reflections from my sofa. Its leather with a metal frame and has recliners on the end. I noticed the other day when I was leaning back on the sofa it lifted up created a gap underneath, my bass response seemed to improved. I think this was because I had allowed a gap under the sofa and the bass wasnt rebounding back towards the speakers. I recently decided to get rid of my coffee table for this reason. Im now thinking of getting a new sofa that's on legs to allow a flow underneath. Im I being silly and imagining things. Ive yet to get out the mic and try measuring it. Thanks.

Really enjoyed the video Gene, Matthew and Anthony. A question I would ask would be about the increase effectiveness by using standoffs to mount acoustic panels and how much surface pressure zones come into the that effect.

I guess matthews binaural mics and earbuds were feeding back.

B.t.w, as far as the 3 voices go, the most unnatural sound came from Anthony with reverberance at mid range frequencies. In 2'nd place was the binaural microphone sound with slight reverb at all frequencies & the most natural lifelike sound by far, came from Gene. Sorry to go off topic.

Gene's room measurement, with 1/24 smoothing, would you EQ that? Or would you just use more smoothing to cover it up if you couldn't use absorbers and room treatment?

Old Sony Trinitron. Fits in perfectly with the rug and the clock.

Anthony Grimani a man to my heart. Laphroaig Scotch (Ps. it's law all Whisky made here in Scotland is labeled as Scotch) Whisky 🏴󠁧󠁢󠁳󠁣󠁴󠁿🥃 and Dark Chocolate 🍫 a great combination 👌🏾

In-wall/soffit mounted monitors only address front wall SBIR, and do nothing to address every other wall and reflective surface. In fact, because they are often mounted high on the walls in the case Augspurger’s, ATC, PSI, Adam and many others, they often substantially increase often untreated, very near ceiling related SBIR. Other issues with in-wall is often poor imaging due to a lack of actual or virtual open baffle and related support. When you couple that with strong structural/wall coupling that quite often is the case, and strong in-wall resonance and reflections back to the monitor due to constrained in-wall areas, these are the reasons why even in many (albeit not all) of the top recording studios, the in-soffit mains are the “limited use party” speakers and NOT the critical listening, mixing or mastering speakers.

How do you know, or could you tell if it’s a front/back, side or ceiling reflection, or if it’s a dip or even room mode?

Use inwalls where possible. Modern inwalls are great in small/medium rooms. Lol. Watched further. You said that.😎

I have a idea I want to try. What if I built 12 inch thick front wall Rockwool bass traps and in the middle I put MLV ? I think against the Rockwool sandwiched that it might act dysgraphamatic across lower frequencies.

Thank you so much for this so informative video!! I have a question as are room modes just about the reflection and interference? As I understand they increase or weaken the direct energy itself also while there are no reflections yet or almost won’t be due to the room is dry. Because when the direct energy is spreading before the reverberation it is like vibrations of speaker on the frequencies of power having while it’s own frequency causing resonance (the forced mode). Thank’s for the someone’s answer!

Does anyone know what the blue software that calculates SBIR is called?

My system: 10" woofer 3ft from either wall, sub: 6" forward from the common plane of the woofers. Room: 20ft x 12ft x 8ft sound only gells near to 15+ ft from speakers. I do enjoy, but could it get better?

Could you use cheap passive radars in thin enclosures to use as bass traps

Wondering if 3d diffusion right behind the rear speakers could also help resolve SBIR? Like in Blackbird Studios.

43:32 DIY diaphram solution. If I get it right. I will take 4" deep wool and on it I will glue on 8" width but thin layer of ply wood to create some kind of membrane which will work better for some low frequencies then wool alone.

For SBIR big speakers is a issue. That is what I am saying: "That optimal placement of tweeter and midrange driver is not always the exact optimal position for the bass." In other words if we could sepperate/remove the bass parts from Gene big speakers and put those in a much better position then problem solved. So THAT is a point why a bookshelves and subs is "better" when they can be placed optimal in the room for each type of duty they have. (If well integrated). Floor standers can give you issues that bookshelves and subwoofers can fix.

Great video- very well done. OMG the sibilance and distortion on Mathew’s end is HORRIBLE. I had to take out one of my earbuds to get rid of some of that weird phase distortion. Please get a decent mic of some sort. It doesn’t even cost much to get a better mic nowadays.

Wouldn't ceiling (and floor) reflexions also be significantliy reduced by the line array speakers?

Ever try the sumiko speaker placement?

Instead of absorbers behind the main speakers, why not a hard reflective board that is at an angle (say 20 degrees) to the wall. The pressure waves causing the SBIR would have to follow a different path to the listener and would no longer cancel. Effectively, it shifts the phase of the bass hitting the board so no cancelation.

Gene 🧬 here’s an idea that I’m 100% serious about. It’s about using brute force-hear me out. Get a third RBH 400 LB full range tower and use that behind your screen as a center channel and run all 3 front channels full range. I don’t know what but full range large speakers just sound different and foe dialogue, they take things to a mew level

What are the 2 USB mic's recommend for REW?

My SVS subs point at the floor. I think that's a great way to do it. It also shakes the couch without butt kickers.

Any thoughts on open baffle speakers?

Too late now, i would have had Anthony provide an acoustic analysis of the room and have it built to his design. Plan it, build it, enjoy it.

I am curious what you found as a solution. My KEF R11 measure well close to the wall but no imaging. 4-5 feet off the wall big dips in lower bass and rise in middle bass. Great imaging though!

Can you stack SBIR peaks and dips on top of each other? Like distance to the front wall would be half of the distance that is between the speaker and the floor? I figured stacking LBIR and SBIR dips might be a bit out of whack since your head moves all the time.

1:01:07 -- sound stage depth mystery -- negative feedback in the amplification.

Why not move the xover up a little on the subs?

Matthew come visit South Africa 😊

Ceiling SBIR @ 30hz ? Height of Gene room ? distance of listening ?

What would the measurement graph at 31 minutes look with PSY smoothing? This would more accurately resemble what it ‘sounds like’.

Great info, But Gene, where did you get that shirt? I want one!

Why not a Anechoic Control room/studio. Theoretically, is not that the optimal space?

Buy saddle then the horse or buy the horse then a saddle for horse, which one is right

Now big question is: if Dirac can narrow this dip to few Hz - does it matter if exists? I mean from psychoacoustic side we would most likely not hear that dip. Nothing in the movie will play specifically that frequency flat out. So spending too much time or money on room treatment just to make a line flat is not worth IMO. I’m not against room treatment but against over doing it.

It was only on the third attempt I got the subwoofer EQ better figured out. SVS "only" gives you 3 bands of free EQ to tinker with, so perseverence paid off but I was going pretty nutty and disapointed at the meager results of the two first attempts. I'm dumb enough to have 2 subwoofers still in stereo mode so they can play individual material, this is not recommended. I have a mic + REW 1st attempt I kept getting frustrated by only having 3 bands and so many peaks and valleys to correct... results was poor. 2nd attempt I thought I'd deal with it "scientifically", I opted to correct one sub as best I could before moving on to the other. When I was done he L and R sub response curve was really good with only 1 needle thin drop + minor valley. Then I drove L and R together = complete disaster, the subs where interacting really poorly! Very sad day. 3rd attempt, I nulled all settings, deleted 50-75 of sub sweeps graphs. Time to think outside the box: instead of letting surround processor stay at "typical" 80Hz, I let main speakers play down further and sent full frequency signal to subs. By doing that I could set a difference during cross over point and that solved some issues. Then the EQ strategy is to only work with L and R playing at same time, that way you can see if any changes has unintended consequences elsewhere. When you apply EQ's you are also imposing a phase shift that effects adjacent frequencies - for better or worse! So, I worked through applying EQ but it wasn't going great, I had an insane peak at 37Hz. I could get a 4th EQ band by using SVS "room boom correction" however that dragged the frequency response of 17-24 Hz down. It was a necessary sacrifice. 37Hz still had a massive peak. Then I tested correction on each sub but still sweeping in stereo, this made me realise which sub made the largest effect for same correction magnitude (and didn't screw up something else). This tactic worked so much better, takes hours though. I also looked back at the largest offending frequencies, used the tone generator and figured out where the largest null spots where located, by moving seats a foot forward I avoided some large issues.

Whole setup should turn angeled in the room so the spk gap from walls are different lenghts, then standing-waves not occure same ferg

Is there a reason why acoustic diffusers weren't mentioned as a way to mitigate SBIR?

I just bought a Marantz RS8015 I have no Speaker interference problems but that is probably because i dont have any speakers.I think it will take me a year to buy some decent speakers untill that time i will have no speaker problems i guess.

What does the 'r' stand for in that acronym?

How about Anthony Matter ?

The acoustic dream team, love it guys! So if in wall speakers eliminate the SBIR issue, why all the talk that they are inferior to cabinet speakers? Or is that an old myth at this point?

Wouldnt a DSP help out far more then just moving speakers around in hopes of finding a sweet spot

You need to have your absorption panels away from the wall makes them more effective how far not sure maybe a couple of inches try it out see what your measurements are Plus you can have thin absorption panels like half an inch of wool fleece and leave gaps between the panels would work the best better than having one 4-inch absorption panels on its own what the measurement factor I'm not sure tested out. I would have thought it would give you a equivalent to 8-inch panel or more Try mixing materials up different fibres works better, like with half an inch of fleas half an inch of cellulose foam some natural cotton underlay and with the gaps and to the wall. the different material work better with different frequencies fleece is best for lower frequencies below 100 Hz Papers good as well that's why they use in offices paper panels or tiles. You could use some office paper panels used as dividers your speakers like a false wall extending the baffle. What I would do Glen some natural wool fleece half an inch folding over and then behind that put the half an inch paper panel would work the best You talk about fibreglass rockwool is a lot better than fiberglass that's what's used in Studios. The place them in the Wall in studios to achieve infinite baffle. You could make your own active absorbers if you place a speaker in a tunnel long funnel just a little slit against the side walls pointing towards your main speakers with DPS you could tune the Frequency to cancel out the Frequency from your main speakers just have to get the phase correct out of phase

I have a very small room 10 x 10 with very large speakers for it's size and I have a huge 80-90 hz dip, it's very annoying because I can move my head around and the dip goes away. I can't really move my speakers or my furniture because my room is so small, I have my couch as far is I can off the wall without running into the TV.

Now you know... When a reviewer says something about a new product "improving the bass" its all Bullshit. The only way to "improve bass" is to improve or optimize the position of sources and the acoustic performance of the room. "The kick drum hits harder" my ass.

Guy in the middle smoke some good ganja? lol

If only there was a type of speaker that didn’t radiate bass to the sides and top🧐……… oh wait

Tip: The Echo is because Mats Mics are directly to his AirPods ;-)

I really enjoy these videos, but at the same time i'm often disappointed about your audio quality in these videos. Matthew's binaural mic setup is fun and all, but when they're so close to his earbuds, it's asking for problems. Gene has the right idea, boommic and headphones. And strangely, Anthony's setup didn't cause any problems. I guess he had his monitors volume low enough and maybe a gate on his mic. Do you guys test for problems before going live?

Do you have any idea how bad your audio sounds

I don't get it why Gene needs such huge speaker in that thiny room , Solution will be moving speaker from the wall , LOL, it will be huge speaker in front of face , Gene you need bigger house or smaller speaker, these guy they don't know what they talking about, very irony solution from experts, 🤣🤣🤣🤣

Ridiculous acronym

The comments in the video about why speakers can sound better when moved away from the walls actually has a lot of engineering and science behind it. One of the key areas is directivity. (secure.aes.org/members/insidetrack/201911/) This is a set of articles going back for over 40 years on this area of acoustical concern. Another mention in the video why some in wall sound great and others do not is also highly influenced by phase alignments (in the time domain ) and the radiation patterns of the drivers over their operating frequencies. Good luck resolving your suck out issues...... there are active methods also that can help reduce the issues (noise canceling methods).

If they only knew as much of materials and manufacturing as they know audio they wouldn't force their customers to pay $2000 for a 4" wide panel of acoustic material.