Small Room Acoustics: Small Room Treatment Basics - Part Two

Small Room Acoustics series includes info on:
• Traps and Frequency Response
• Small Room Treatment Basics
www.jhbrandt.net
Music: "What Makes People" by Jimmy D.Lane
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[@acklin83]

That's my room! :) Thanks again for your great work, turned out fantastic!

[@MarcoCastilloWorld]

I like the blues at the end! Great video, thank you again!

[@YHRS]

So glad to see that you're doing these videos! This is all really valuable stuff, and I'll certainly be pointing people to these videos every chance I get. I'm about to move away from my beloved home studio and into a new house. So I might be coming to you for a consulting job in the near future.

[@joebione]

I'm surprised to see membrane traps away from the rear wall where the pressure would be maximum. Is the wavelength large enough at 30hz for it not to matter?

[@armansrsa]

Hi John. Good videos please keep em coming. I am treating my room and out of all the different designs out there, I want to do something a-la-John Brandt. Can you please do a video on slats and how you use them in your designs. Cheers!

[@samibefree2410]

Thanks for that amazing video! Could you please tell us more about the waveguides, why they have been angled like this and when they perform better than superchunk traps?

[@JHBrandt]

Wave guides, properly done will always out-perform the 'superchunk' style traps. Reason: rigid glasswool or rockwool becomes reflective past 4" thick. So after a certain depth, it doesn't really help anymore... It just COSTS more. :P Wave guides can actually 'guide' the waves, or turn them. There are air channels that allow the sound waves (and rays) to enter... They check in, but they don't check out. :D

[@mubute]

Hi John. I’d love to hear more about these too. I know this is a fairly big topic though and that research is still being done, but I know you have spent a lot of time thinking about them and using them. I’ve actually been racking my brain and research abilities trying to understand them. Even reading Newell and sources like that get confusing with edition addendums, etc ;) Though they have pointed me to interesting studies like the array concept you mentioned. And then there are the late Desarts interesting discussions on diffraction effects, tests, etc. Not sure I quite got my heard around the reference to the “reflective past 4 inches” above, unless you’re referring to higher frequencies. Otherwise they would make for great low frequency isolation devices if they reflected. Though it did make me put some thought to why their efficiency decreases past a certain point like you mention. Lots of paths I’m trying to venture down as to how these waveguide “traps” work: maybe it has to do with gradual impedances changes, maybe keeping absorber thickness narrow but spread along the wavefront presents more tortuosity potential, maybe that same spreading also helps prevent a sort of “saturation” effect that would cause thicker absorbers to eventually move as a more solid mass, maybe because they get redirected/reflect and cause more paths through absorption, maybe there’s some phasing through these paths, maybe…..well…it feels good to blurt random things out. Ha. There are a dozen more maybes. This will take a lot more time on my end to even remotely understand. Maybe one day we get to hear your thoughts too :) Thanks for keeping discussions and thoughts open and out there though John! Take care.

[@umusachi]

John Brandt: Thank you so much for sharing your knowledge. This is amazing! I am learning so much. I, like Sami Befree, would like to know more about the waveguides. How do you calculate the angels? I'd love to see a video specifically on this style of bass trap. Seems like it would be far better than panels in the corner, or super chunk bass traps

[@JHBrandt]

Liminal, Thanks so much! That is a very good idea. I'll work on that. Meanwhile: Wave guides are not so much calculated as they are arrayed. The 12 degree relative angles have been found to work best. Note: latest testing indicates that it is edge diffraction that increases absorption dramatically. More to come on that subject. All the best!

[@umusachi]

Thank you John! Keep up the great work. I've always admired your work. Can't say thank you enough 👍

[@aelucif]

7:14 does anyone know what this effect is called or know some papers that may clarify this principle? "a coupler before an absorber doubles the absortion"

[@Dobrovinskiy]

Maybe he talks about air gap?

[@manamimnm]

Search: space coupler acoustics

[@lgmnowkondo938]

are membrane traps tuned to the frequencies of the room modes or are they just a more general construction? ALso..did you say the side wall traps are 8" or the cloud traps were 8" thick?

[@JHBrandt]

Yes, the membranes are tuned to the axial modes. And yes, the wall treatment is 8" deep... More on larger builds. 😊

[@HaNguyen-kn2tg]

Dear Mr. Brandt, Thank you for your information. Can you share with us some information about the cloud ceiling panels? How deep they are and what kind of insulation, density you used?

[@JHBrandt]

Ceiling panels.. it really depends on what trapping you are already using for the ceiling trap. The ceiling trap is just about the MOST IMPORTANT trap in the Control Room. If a cloud panel is all you've got, I would recommend making is as deep as possible. I use lightweight fiberglass, Dacron, and 1", 40 kg/m3 rockwool. - Mostly lightweight Fiberglass.

[@HaNguyen-kn2tg]

Dear Mr Brandt, you saved my life! Thank you a lot.

[@davebeeboss]

Great video, very helpful. I am wondering if the waveguides are fixed with a solid core or if they are hangers?

[@JHBrandt]

No Hangers! We do Fixed wave guides and they are solid 3/4" or 18 mm MDF. They are to 'guide' the sound waves.. or at lease move the wave direction a bit. The mass of 3/4" MDF is good but it's not THAT much, yet it has an effect. We used to use fiberboard, but a fiberboard system does little to re-direct the sound waves at low frequencies. The massive MDF is much more effective. ;)

[@davebeeboss]

Thank you for the information, very interesting. I may try and build some of these for my studio.

[@qrdaudio]

Hello sir, waht if I only have 3m W and 3m L and 2.8 m slanted ceiling, I already add 4 10cm bass trap in each 4 corner, but still no ggod response below 150 hz. Thank Sir

[@JHBrandt]

That's because, good response is not going to happen in a room with the same dimensions for lenght and width. That is the uncomfortable but honest truth. Is there any way to change either of those dimensions?

[@qrdaudio]

may I sent you message at your facebook sir?

[@JHBrandt]

Cahyo Baskoro, of course! :)

[@ZXCVBNMZ819]

Very nice videos. They really help allot. I do have a little bit off an oddball though. I am trying to treat a room that a friend of mine uses that has carpet on the floor and on the walls. The room is 15x14,6x8,5ft and has a dropped ceiling. The problem I am facing is that although I am allowed to hang stuff on the wall and maybe place a hardwood floor in over the carpet, the owner of the building does not want me to actually remove the carpet. What would you recommend for a room like this?

[@JHBrandt]

I would recommend a LOT of portable traps. Is this room framed or stone/brick construction?

[@ZXCVBNMZ819]

John Brandt : Thank you for taking the time to reply. This is a constructed room made out of wood panels with rockwool inbetween. We are already planning on taking out all the carpet and putting in a hardwood floor. That should be a good start from what i've gathered.

[@JHBrandt]

Marten, It's always difficult in those situations to get exactly what you want, but like song says, you can get what you need. ;) Hardwood is good. Most music is enjoyed listening to with a hard floor surface; from classical to rock band performances. That's the way we hear it. Removable acoustic walls. There are ways to do it where you get the optimal acoustics and portability. Remember that you can't have both so something has to give. But it's not so bad. Even in the top pro studios there are compromises made. It's a real world. Send me an email. :)

[@jesperzeng]

Hi Mr Brandt, your videos are extremely informative and I really appreciate it. May I ask you how does space couplers affect the first reflection since you place them at the position which i assume them to be the first reflection point off ceiling? I often see you use them in your design. By the way, I am a huge fan of your designs and works. =D Thank you very much sir!

[@JHBrandt]

Space couplers will effectively double the absorption of the cloud or ceiling traps. They do this by redirecting sound rays/waves upward into the traps. When a ray or wave is re-directed by the space coupler, it also loses energy, reducing the level of that reflection.