Can You Trap Bass? What is a Bass Trap, Anyway? Room Acoustics 

The short answer is bass traps work to reduce sound energy in a room in the bass region. There are basically two types: velocity and pressure. Velocity is that rockwool or fiberglass or foam and it slows the speed of the sound as it passes through it. Think of waving your hand through water as opposed to waving it through air. It takes more effort and therefore uses up some of the energy the wave has. A pressure trap works by reacting to a low frequency wave in the same way you can feel the floor or walls vibrating when a subwoofer is pumping out dance music. That vibration also uses some of the energy from the sound wave, reducing it. Biggest problem with pressure traps is they are limited to a very narrow band, while velocity traps are more broad-band, covering more frequencies. In an upcoming video I'll measure the frequency the wall panels I made vibrate and get a better idea if they are actually doing anything.

Bass trap? Obviously a fish catching device.

I can't wait. I am so interested in how you finish this room and what speaker design etc. Great Channel!

Wish I lived near this guy so I could pick his brain. Amazing work.

Live sound engineer. Current times mean outdoor venues with power issues meaning portable generators on a budget. Noisy!! Been struggling with building sound enclosures. Reading as much literature as possible and watching RU-vid videos. Glad that I was a drywall metal stud carpenter in my younger days. In some of the literature, I've seen where 25 gauge metal studs are better than wood for sound reduction even with the sound transfer of metal. After hearing you talk about the plywood giving a little (in and out like a speaker cone), maybe that's where a high gauge metal stud would be better than a wood stud, in that it has more give. Just a thought. Carl P.S. I like how you are working through a problem with no perfect solution. I feel your pain!! LOL

As an electrical engineer I find this very interesting and refreshingly free of nonsense and voodoo. Since I haven't really studied acoustics, most of this is new to me (but it fits in well with what I know about wave propagation).

Very well done, John. Semi-retired recording engineer here. Ethan Winer would approve, even though your approach is divergent from his. Good stuff!

Very nice step by step and great results. There are times when I want to rip everything out and just start all over again but there are just too many other projects on the go at the moment.

The train analogy was a good one.

I really dig your content. The mis-understanding of what you're doing and explaining is staggering... and you explained it quite well. Two important characteristics of sound in small room acoustics... that many people are entirely oblivious to is wavelength size, and why that matters, and secondly... behavior in the time domain. Perusing these comments so many that took the time to comment ... just haven't got to the point in their audio journey of being exposed to and understanding the time domain and what you're pursuing here. The muddying effects of latent energy in the bass octaves is one of the biggest issues in HiFi. A room subjectively sounds better when it's reverberation is relatively uniform top to bottom. Most all rooms possess excessive reverberant energy in the bass octaves compared to mids/highs. With the mids/highs, if it's not direct/early reflections, then ideally you want to retain that. So, it's prudent to attack that excessive energy without overly affecting the mids/highs ... otherwise you're not evening out the ratio. Damp the bass as effectively as possible, while working to retain adequate liveliness in the mids/highs. Merely wanted to drop a note in appreciation of your content. Didn't intend to add all this, I know you've got this. All the best

Interesting to see the process, Thanks

I use the sofa. Looks amazing John.

the panels with the holes look great

Audio guy, Musician here. Well done and we'll explained. 😸👍🎶

Very interesting ! Great Insights.

I have 4 bass traps and several panels that I built for my main listening room. I have the bas traps from floor to ceiling in the corners, triangle-shaped and free standing one on top of another. You seem to have gotten good results however. I wanted something quick and easy so I just dampened the hell out of my room :) Edit: some panels are on the sides and I hung two from the ceiling over my listening position.

Could you try a Helmholtz resonator at 40hz to try to fight those modes? I have seen some built that sit in the corner and look like a small trash can.

Great video! In short you can say you don't want the bass to "echo". Like with an empty room you hear the highs echo.

P-R-O-J-E-C-T-O-R I know TV's are big enough these days, but if that room isn't screaming for a projector, not sure one ever will.

I always like it when you really sink your teeth into something, like with the clamps. You talk about little else for a while.

Would love to see a tour of your house with all the before and after photos. That would make an amazing video!

So, John is basically building a walk-in headphones. Nice!

Great work... super valuable that you went thru and measured at each juncture... you know audio folks love to disagree or pontificate about method (I’m not saying it isn’t important) but the results are what matters... and you have certainly improved the response of the room!

For some reason, I'm envisioning you recreating the old Maxell "Blown Away" commercial, the one with the guy in the chair getting "blown away" by the amazing hi fidelity of the cassette tape (amazing that was in 1979, damn I'm old).

Such a difficult task! Cool to see your tests and the results.

Your room is sounding pretty good John, good work. Like what I'm working with right now is targeting specific frequencies, more to learn about that for sure. It gets problematic for sure the deeper down the absorbent rabbit hole you go :)

John really interesting stuf. And although you are not an expert its so worthy for us to see how experiments can work out. Subd!

I have to say your efforts paid off quite well. People may not understand by simply looking at the graphs, but the changes are fairly dramatic for what you can expect.

Fascinating

My first thought when I saw the video title was " Why is John making a video about fishing?" . Then I noticed it mentioned acoustics. Interesting topic, thanks for the video. :)

09:33 Gotcha, it`s Porn :D

Hey John, this was super interesting! Just watched the diffuser build video and I'm glad you put a link to this channel at the end! Cheers!

I think you should put Admiral Ackbar in the thumbnail... 😉

Спасибо тебе большое мужик. Очень полезное видео, все понятно. Удачи с работой!!!

Little know fact, John is the guy from the front of the old Maxell tapes.

Thank you for not just making us rely on you habilities to form complex phrases full of subjective interpretation and add some proper measures.

"Hole-y Diffuser" is my favorite Dio album.

Thanks for the video. I cringe when I see folks use the cheap studio foam and claim "we are now sound proofed, neighbors can no longer hear us" :( I'd love to know how you are treating isolation though, your thoughts on tube/tuned traps, and if you've tried making waterfall graph (which are my go to personally). Also, have you considered shortening one wall to avoid the perfect square, or angling it slightly.

Small room acoustics is a secondary professional interest for me. Most of your room treatments are good, but I was surprised to see the TV on the wall at the end. You need the Diffusers on the rear wall not front for best imaging. Read up on mirror points, Haas effect, etc. if you had more Diffusers where the TV is, that would be a good design for the rear wall. From what I can see on the brief plots, you did a good job on reducing bass modes. A waterfall plot shows this better than the spectrogram in my opinion. I have never built a QRD, for work I just buy them. You might consider improving your design with a scaled version in each cell to extend the range higher. I have seen plans for doing that with strips of MDF.

Very Cool John... Makes Perfect Sence! lol

Wow, really nice! What about a ceiling like in your shop? Or is the fiberglass also cheaper than those tiles? I guess they worked pretty well in your shop.

John, I’m wanting to learn more about acoustics like you did. What literature and resources can you recommend? Thank you.

This is so interesting.

Good luck with getting rid of standing notes with in a 8 foot tall sailing But you do give some really good tips an you do have a really good understanding of how acoustic works

Hey John, Great video! I find your woodworking videos fantastic because I used to be a carpenter and now I'm a sound designer working in film and TV. I used my construction 'skills' (Not so great anymore haha) to build studios and currently on my 5th and last one. I am no physicist but I am in love with acoustics and I do know the fundamentals fairly well, though, like you said it's an extremely complex topic. You mentioned that your room is too small for the waves to bounce around but that isn't true. A 80Hz wave is roughly 14 feet, which explains your RTA readings as well as the harmonics. You can also prove this in your shower, just make a high end to low end sweep with your voice and you'll hear the tub mode pop as you get really low (Mostly a harmonic of a higher frequency but its a fun test). The trick to stopping modes or standing waves is to cut the frequency off 1/4 into the wave, so a trap that's 3.25ish feet would stop that pesky 80Hz mode, practical? NOPE so to get around this is you find material that soak up the frequencies that are being an issue, Rockwool is great because it is relatively good at soaking up lower end frequencies, at least in its coefficient tests. Though the thicker you make a rockwool panel the more low end it will reduce (but like you said take away the high end). The resonant absorbers that you've made are a great way to save space. The issue with modes is that only the lower end ones are a problem because they are the ones that fit in smaller rooms and they are the most noticeable, there are so many higher frequency modes in your room but they all are un noticeable as they are too numerous. So the theory that I build into my studios is, use as much rockwool as possible to soak up the low end, then treat the high end with quadradic diffusers. A reason I don't like resonant absorbers is that they are tuned to a specific frequency and any change in the room, like a couch will change what happens and the math gets out of hand. I'm a really big fan and I hope you take this information well! Great video again John!

Oh, I thought this was about fishing!

Me: I put an old patched subwoofer on my television to get something better J.H.: Bass traps #6, it's a work in progress

Wow it shows how the decay times is decreeing in your measurements. Well done 👍

All measurements and techno details aside are you pleased with how it is working/sounding to the naked ear? It looks great by the way...

Man you need to go with a 85 in 4k sony

Sounds like you want to listen to, Gagrakacka Mind Zones, Disaster Area.

What if I built a free standing panels, in a roundish cubicle around my desk. No corners. Leave gaps so pressure can escape. A cloud above my desk. With gap. So pressure again can escape. So my room can remain a live room, it’s all wood. But when I mix, I pull the absorbing panels around me, in a circle ⭕️

Thanks, Your explanation is easy to follow.

You should try to move your sitting position a bit forward or backwards from the center. The center of a rectangle room is bad to start with and probably worse in a square room. I tend to move backwards from center in smaller rooms because speakers need room to breath, but I'm sure you know that you can't get too close to the back wall, or it will open up a bunch more problems.

Spacing of the panel off the wall is basically allowing you to get almost the same absorption as if the entire area depth was treated. There is a big misunderstanding going on where many people are claiming that an air gap is better than full depth absorption, when in fact it is the opposite. However, using an air gap can reduce the cost considerably (if you build several panels) while attaining almost the same performance.

The one thing that this video gets across well is just how large you really need to go to get significant taming of modes as low as 40hz. Most videos have no measurments and make exagerated claims as to how big a difference a couple of panels will make to the bass response

Wow. That’s amazing. Are you Canadian ? - Nick from Toronto

Lol I have been playing rust...i thought this was a different type of vid haha

Can you not use an equaliser, or something similar, to drop that 37-40Hz range?

Very interesting. What. program and test mic and sound source are you using? I use a homemade dodecahedron speaker and an Earthworks M30 mic. Just FYI your room is too small to develop a true statistical reverberant field. You are dealing with cumulative spectral decay. And yes you have a massive amount of modes in the small room plus flutter echoes. Some of you assertions are not 100% correct but close enough. You might consider a Helmholtz resonator trap in each corner at the fundamental freq of the lowest room modes. You also need add diffusion to the rear wall. You should get tbe book Master Handbook of Acoustics by Alton F. Everest. Keep it up and i enjoyed the vid

so glad i discovered you and your channel. its inspiring in so many ways.. thanks

Theater is looking good. I don't know anything about bass traps, but have used dynamat for car stereo installations in the past, of course the purpose is different. My Denon AV receiver has a multipoint EQ that is set up with a microphone, would adding bass dampening via panels improve the curve then, or what if the room already has drywall. Interesting stuff.

Did you have those panels mounted with caulk? Pretty much made them fully isolated.

Turn down the bass? Only joking, love your work.

This is really interesting, although I don't understand a lot of it.

Ffffffffffffffffffff... thank you for all the information, anticipation away makes it dificult for us. inother cases :1)

Have you done any work on reducing shop noise?

What’s the thickness of the plywood you used for the diaphragmatic absorber, and what would you suppose would be the affect of using a thicker plywood? Thinner?

what is wrong with using an equalizer and speaker placement to achieve this? that is what I have done in the past to even the sound to the room.

Does the TV panel add any bad reflective noise? And would a projector screen be acoustically transparent like cloth? Very interesting video I love the new channel addition to your lineup.

Can fiberglass be replaced by denim insulation?

John, does the open ceiling affect the results of the tests for frequency response to the tester?

Great video! One suggestion: use hemp wool instead of glass fiber! Same effect but doesn't kill you slowly when breathing it in! You can use wood fiber as a substitute for rock wool, but rock wool isn't as deadly as glass fiber (still not great to breath the stuff) and its harder to come by in the US.

Great video… easy to understand and explained in layman’s terms !!!

After watching maybe 100 videos, this is the one that best seems to capture every aspect of acoustic treatment and "sound proofing" in a coherent and easy to understand way. I love the professionalism of Acousitc Fields, but between the sales pitches and abrupt end of each video, I had to watch dozens to get this much information. Great job, and to anyone else poking around, this is a great place to start and get a solid understanding of how sound works in a space.

I am not sure if you are using the same equipment you do for the shop videos but the sound from this is very clean, easy to tell that the room is well treated. Hope everything lives up to expectations.

It's a challenging room the way you describe it. Graphs are showing progress though.

When the room is as good as you are going to get it, are you going to utilize electronics to try to get the rest of the way? Starting with maybe an equalizer?

And how did you deal with fiber glass and rockwool dust in the air?

You can't trap bass but you can make bass trap

Honestly, Anything under 100hz can be completely fixed using multi-sub and DSP. In a small, square room with low ceiling, you have no chance in hell of ever getting rid of modes in the low frequency region using just room treatment. Good luck..

You're on the right track. But if you want a "warm" room sound but block out bass travel to the exterior I've got one word for you - Acoustiblok. Hang it like drapes around all of your outer walls - then put up the baffles and panel you have leaving about an inch airspace. Concrete. The floor is going to be a resonance problem. This is what I did - I have a metal building behind my house. Half is storage, half is my practice room. The walls are coated with spray rubber undercoating (the whole building) - seals, helps keep vibration down, minimal soundproofing. Jam room is built room in a room. Outer walls and divider wall are insulated with rockwool then 2 hanging layers of Acoustiblok from ceiling (8ft) to floor inside a 2 inch airspace. The inside wall is another layer of rockwool. Foam tape on all studs including frame to floor. 5/8 plywood walls, floor and ceiling. Floor has a layer of Acoustiblok between the concrete and a layer of plywood. I did this after the fact when I found out that carpet alone wasn't gonna do the job. Doubled door entry with both doors layered. Building has 12ft side walls and 14ft peak. Ceiling (or attic floor) has Acoustiblok, rockwool, Acoustiblok between ceiling studs then plywood on top. Used as extra storage space in building. Interior is cover with sound absorbing foam with foam corner bass traps. I'm a bass player so If I don't rumble no one else will that comes to jam. I wanted as "dead" a room as possible so it doesn't bother neighbors. The most vulnerable part is the entry. Testing at the door is 47db with a full band inside at a db level of 147! 20 ft away - nothing. My house 40ft away. Nearest neighbor to building 90ft. Mission accomplished! Nice room you've got going John. But if you're looking to keep bass travel down you'll definitely need to cover that concrete and ceiling and some corner traps which a panel across the corner about 12" wide with holes half the size you have on the others and then an 18" wide panel with the same size may create a catch in the corners for you. Currently helping my brother build a studio and that's an idea out of many we've had to keep the main room "warm" and "live' for recording. Anyone interested in keeping sound travel down should definitely check out Acoustiblok. Good product and very helpful people there. PS Putting Acoustiblok and a layer of plywood under the carpet made a 26db difference.

How about a Helmholz Resonator as absorber tuned to 37 Hz? This could help with your Room modes

The size of your room is 14x14 after all your added traps or before? Because I have a 15x11 and would like to understand my continued battle. Thanks for really breaking things down, because like you stated in the beginning, months and months of research. Seems like you hit circles at times.

First thing is you need speakers that produce the sound, you need an equalizer, and a true microphone to measure the sound waves, I would suggest that instead of trying to make the room conform to your speakers, I would make the speakers conform to the room by proper equalization, lot less work and better results. I would suggest instead of spending money on wood I would spend the money on a Klipsh horn speaker, or if you like room shaking bass a set Electro voice 18 to 30 inch bass speakers. Then use stuff like mirrors and carpeting in your room with the true mike and equalizer to set up the room, you will also need a decibel meter to set up the separate frequencies. Used to do this years ago when I was younger, set up one disco with Electro Voice speakers and told him do not go past 1 watt, you may deafen people, on opening night he went past one watt and shook the color show glass box light out of the floor. Gave me a call the next day and said you where not kidding, I told him that was my job. And yes people no matter what they say today about sound, what we know today will be obsolete tomorrow. Me I will stay with the mighty Klipsh Horns for real sound, and Electro Voice for speakers that will bring down the walls of your house. There was another speaker I believe they where B&W that gave amazing sound but you needed 1200 watts of power to power up that speaker.

I totally transformed my square room’s horrible low-freq sound by doing it via the CHINA method….cheaper, simpler, most effective method i hv encountered. No need to buy lots of fiberglass, rockwool and no need to fill the room with such a huge qty of panellings. In my country, we call it “plaster ceiling” which is the American drywall done on the ceiling with a huge airspace behind it. In short, simply create a slanting, fake ceiling (from drywall material) so that your entire ceiling is sloping in any direction. It will totally transform and normalize the horrible low-freq behaviour of any smallish squarish room. If you dont wanna slope the ceiling, then you can slope/cant/slant ONE wall…any wall. The results are amazing and the room’s size doesnt diminish much while looking so clean. The above were done to 2 highly problematic videoconferencing rooms during the Covid lockdown as taught by a China-based German acoustics specialist, and he simply calls it the China method….clever, efficient, cost-effective…thinking out of the box👍

where do you buy pressure traps?

Something you don't mention, and most people don't understand, is that most sound you hear indoors is from reflections. You hear the initial sound from the speakers, and then 100x as much sound being reflected off of surfaces as it bounces at 700-ish mph back and forth, reducing in strength every bounce. Your efforts are redirecting or reducing the energy of those reflections, and therefore the amount of times they continue to come back to your ears at a significant level. What's left over is easier to listen to, and more accurate to the original recording in the case of music.

What diagram you used to get the circles for cut out you got

I don't know if you shot your whole room this way, but @ 2:34 you have your measurement microphone pointed at the ceiling. You need to point that microphone head on facing towards the speakers otherwise your data will be inaccurate and you'll be treating the wrong things.

Hey John; serious question... what would you charge to build two of those Quadratic Residue Diffusors for me?

I dínd't think this was gonna be a fishing vid.

If you don't want to drill all those holes, I hear you can also put up panels with slits between them. Like slim vertical boards with space between them.

I know there is technology to counteract loud machines by inverting the sound wave and essentially canceling the noise. I wonder if it could be adapted for home theaters?

Great video thanks. I see perforated panels on the front, they act both like basd trap and diffuser.... on side wall I.dont't understand the approcch. Is diaphragmatic panel.?

Best way to treat a room is to hoard newspapers.

I am curious about how well your plywood wall membrane will work for low frequency capture and /or diffusion. Whisper wall uses a similar approach, but the material they use is much lighter than wood. To capture anything below 800Hz, I would suggest leaving gaps in the wall panels along the rear wall, that are covered with acoustically transparent cloth. If possible I would have these openings run from floor to ceiling and be at least 2' wide. This should work as a bass trap down to about 80Hz, and diffuse a portion of the the frequencies below that. *Edit- My apologies, It would have helped if I had finished the video before writing my comment. You pretty much did what I was suggesting, but you placed two on the front wall and have a semi-reflective surface on the front of the trap. I like how you approached it though.

Great video, very insparing. 👍

Put oc 705 in your bass trap

I am personally designing / building my "Dream" wood workshop. I have been down the rabbit hole of sound in an effort to to reduce the sound that is inherent to a shop and also for music. I can listen to this video and without question "hear" that the room is "treated" ( it sounds good, and I am sure will only get better ) and looking back at your shop videos its now amusing to watch one of your videos from say 2015 vs your more recent ones. Could you maybe do a video showing / explaining the treatments you have in place in the shop? GREAT VIDEO!!