Covered Plywood Panel Style Bass Trap

Hi, I've been reading some articles about bass traps, and actually I'm considering using Ethan Winer's design of bass traps. But, if I'm not mistaken, John Sayers said that the bass trap would absorb bass, but because its plywood surface, it would reflect highs. So, if I cover the bass trap with cloth to kill highs, would it defeat the purpose of the bass trap itself? Ari

Ari, > the bass trap would absorb bass, but because its plywood surface, it would reflect highs. < Yes, which is often a good thing. You don't want to make any room completely dead, which is what happens when you cover the walls with foam or fiberglass. As I explain in my article, wood panel traps alternating with mid/high absorbers made of fiberglass gives a nicely balanced sound. --Ethan

plywood surface can be replace by drywall? krish

Well, I don't know. Maybe Ethan would answer that question. And to Ethan, first thanks for answering. It's a pleasure to be able to talk with one of the experts here in this forum. But that doesn't mean the others are not experts though, we all learn together, and maybe with everybody's help, I can be an expert too. :) My question is, is acoustic treatment need really detailed calculation? I mean if a room is already calculated, then treated accordingly so the room provide the best sounding room with balanced absorption and everything, but if the person inside is varying between one, two, and maybe ten, the room will sound different for each condition, because a person also works as an absorber. Another example, if I buy the RealTraps, the RealTraps working frequencies are fixed (right?), and although they might be designed to work on wide band frequencies, I don't think that they work at the EXACT frequencies that my room is needing. But if the RealTraps DO work in my room, so any not-so-detailed-absorber would. Are my assumptions right or not? I need some insight on this. P.S. And although I would love to buy those RealTraps, unfortunately I can't afford them. :( Ari

Ari, > is acoustic treatment need really detailed calculation? < I don't think so. If you absorb from about 80 Hz. and up, that's perfect for most rooms. Unless the walls are made of cement or brick, or three layers of drywall, lower frequences pass through them and are also absorbed to some degree. > I don't think that they work at the EXACT frequencies that my room is needing. < Your room does not have exact frequencies that need trapping. All frequencies need to be trapped, because standing waves and acoustic interference occur at all frequencies in all rooms. It is a myth that only a room's modal frequencies need trapping. --Ethan

It is a myth that only a room's modal frequencies need trapping.

Here Here :D

I just dowload the MODECALC software, but to be honest, i dont have a clue...can you explain me or give me a tutorial link to learn how to use it? something like Modecalc for dummies,,,, :lol: ....i`m setting up a little studio, with brick walls, it`s a perfect square...so, i want to prevent some reflections and of course, avoid bass problems...can u help me ? :(

Aziel, > can you explain me or give me a tutorial link to learn how to use it? < A tutorial is built into the program. Press F1. Note that I added this tutorial about a week ago, so if you have an older version download it again. At only 57 KB it's a very small program (long live DOS!). Here's the link: www.ethanwiner.com/MODECALC.EXE > brick walls, it`s a perfect square < A square is not good, so you are sure to have problems. This is explained in the tutorial too. The good news is it's still possible to make your room acceptable, but you'll need more bass trapping than usual. --Ethan

Sorry, i realize is not a perfect square...it`s a rectangule...my control room is around 7.38 x 11.81 and 8.79 of h...the recording booth have the same measures...what do you think? how i said before, i have brick walls with the exception of the right wall of the booth that i cant decide the material i`m going to use to build...may i use drywall? or maybe mazonite estructure? :roll:

Aziel, > my control room is around 7.38 x 11.81 and 8.79 of h < That is typical of small rooms. That ratio is not terrible, but the small size definitely requires you to add sufficient bass trapping. > i have brick walls with the exception of the right wall of the booth < Brick walls are worse acoustically than sheetrock, but I wouldn't add new inner walls because that will make the room even smaller. --Ethan

Ethan, Thanx for your advice, the right wall of the booth gonna be added because is the entrance hall of the place...what you recomend me? i mean, the material...and, i have to use the kind of absovers and bass trapps for that side? sorry if i`m bothering you, as you can see, i`m a totall neophyte in the matter... :roll: PS: sorry about my english :lol:

i mean: i have to use the same kind of absovers and bass trapps for that side? :oops:

Aziel, you can use a drywall construction for the new wall - Masonite is NOT very good for sound control. If you need the new wall to be sound proof, you would need to use one of the accepted methods of construction for sound proofing. This is typically two layers of wallboard on each side of the wall frame, well sealed. It helps if you add a layer of Homosote between the two layers of wall board on one side (either side) of the frame. If you are using wood framing, you should either use staggered stud frames or add Resilient Channel to one side of the frame. Light weight steel studs are flexible enough not to need the Resilient Channel in order to decouple the wall. Each layer of wall board should have its seams offset from the others so you don't get sound leaks. The wallboard wall will give you some bass absorption, but you will need more traps in the room than that. Positioning of mics and instruments will also be somewhat critical in that small a room... Steve

Aziel, You are not bothering me. I come here voluntarily to help people! And your English is fine. :) Steve gave you good advice on the wall construction. As for bass trapping you need to treat all the corners, and possibly add more trapping on the walls and maybe even the ceiling. --Ethan

Well, It`s just incredible the rich knowledge i discovered here!!! and i have another question...i`m making my own basstraps (thanx Ethan) i dont know nobody down here in Venezuela who own`s a basstrap or something...so, i`m doing my version...50cm x 10cm and 220 cm tall (please do the conversions) i`been thinking...if i have some paralel wall...may be i can bend the basstraps plywood a little...then, the high frecuencys gonna be reflected in diferents angles, so i can avoid ringing or something...the question is: the resonator inside gonna work in this way? does the low frecuencys gonna impact the fiberglass and stay right there between the wall and fiber? thanx for youe answers in advance... :?

Aziel, > bend the basstraps plywood a little < I wouldn't bend the plywood panel into a curved shape, but you can angle it to have the panel deflect mid and high frequencies in different directions. --Ethan

There is a studio here in SE Michigan that has a curved rear wall bass trap. However due to the curve of the wood, they have a very annoying 5K problem that shows up on any mixes done in this room. Bryan Right on Ethan

thanx for the advice...my basstrapps are in the corners...in the rear wall i`m using absorbers...beacuse the size of the room (very little) i`m uusing absorbers in the sidewalls too...but leaving some clear places of the walls cause and dont want to kill all the high frecuencies, they are very little, just between the absorbers....and of course the window that is way big...(was a gift, so...) i hope i won`t have too many reflections problems with that....maybe i`ll post a picture when it`s done...so you can critizice (construct) it... :roll:

I have been planning to put curved panel asorbers on the ceiling in the studio room - to also add diffusion. The SAE site details curved panel absorbers - what is the reasoning to not use curved ones?

Andrew, Nice avatar photo. I dare you to do that with a $50, or even a $20. :D > what is the reasoning to not use curved [face panels]? < When you curve plywood it becomes much stiffer, much like the arched supports under a bridge. But with a wood panel bass trap the panel must be free to flex. Barefoot Thomas explains a way to make a curved panel work as a trap in another thread, but to me it looks a lot more complicated to build that properly. --Ethan

Ok, you mean that the plywood must be bend without a support to bending? just floating? thats what barefoot told me...how can i avoid a broken plywood? haw can i float this plywood? :?