Low Ceiling Ideas

i'll be constructing a one room recording/mixing room in my garage in long beach ny. finished room dimensions are roughly 10'6" x 16' with a 7' ceiling. i will treat ceiling with clouds( i think this is standard in most situations) alternate diffusion and absorbtion on walls (bass traps, owens corning 4",and some quadratic difussors i have made). what is best for the floor rug or wooden flooring? also i am decoupling the ceiling from the joist can i benifit from builing the ceiling unparrallel to the floor or will this just add problems ? i was thinking of 2 planes. a high point in the center of the room (or would a 3/4 or 2/3 division be better) dividing the 16' length. can persons more educated in acoustics please discuss the valida ty of my ideas? pros?, cons? thanks for any help. more details about my build will follow as i rethink and fine tune :D :D :D :D :D

been thinking about my idea and i think i can answer my own question. the difference in height over the suggested planes(the ceiling) could only be about 2 - 2 and a half inches. this slight angle could do little to disperse any low or even mid range frequencies whose half wave length is much greater. this still leaves me the question of carpet or wood floor. intuitively i would go with carpet to absorb some highs. but ive seen an interveiw with thomas jouanjean where he suggest a preference for a wooden floor in a low ceiling studio. he gave no reasons and it was left like that. i have learned from research that what one would do intuitively in acoustic room design is often wrong. can anyone discuss some strategies for dealing with a low ceiling. i was thinking of some collapsible 2-3 foot pyramids i could place around the room . would the gains justify the effort?? 8) 8) 8) 8) 8) thanks for any thoughts on my thoughts!!

Hi "seavote", and welcome! :) Lots of questions you have there! I only have a few minutes to answer the most important ones, but the other answers should flow from that, or you cab find them by using the "search" feature of the forum.

dimensions are roughly 10'6" x 16' with a 7' ceiling.

That's a low ceiling, but you already knew that! so probably angling it is not going to be worthwhile: Your idea of using a cloud will work. Angled ceilings are useful, yes (when done properly), but room height is also important, and in your case I reckon height is more useful than angles.

alternate diffusion and absorbtion on walls

Forget diffusion. The room is not big enough to be able to benefit from diffusion. You need a large distance between the diffuser and your head for that, so diffusion is only appropriate for large rooms. Of course, the manufacturers of diffusers don't tell you that...

what is best for the floor rug or wooden flooring?

Forget carpet: it does the exact opposite of what you need for a small room. It absorbs lots of highs, some mids, and no lows at all. What you need is to absorb lots of lows, some mids, and very little highs.

but ive seen an interveiw with thomas jouanjean where he suggest a preference for a wooden floor in a low ceiling studio.

He's right. Wooden floor, or concrete, or ceramic, or anything hard, solid, and reflective is the right choice for a studio floor, provided that the rest of the room is treated correctly. Look at photos of top studios all around the world: How many of the are fully carpeted? NONE! There are several very good acoustic and practical reasons for that.... See above, for part of the acoustic reasons.

also i am decoupling the ceiling from the joist

How?

i was thinking of some collapsible 2-3 foot pyramids i could place around the room . would the gains justify the effort??

Probably not. Look around the forum to find out how studio treatment is normally done. - Stuart -

Sound man thanks for the reply. Disappointed that my diffusers won’t help. I guess I can sell them. Here are more details on my build any suggestions are welcome. Garage is cement block on three sides. Fourth side is block but I’ll be filling in the opening with woodenstud and plywood (standard construction). The height from cement slab to bottom of the existing joist is 7’. Width is 10’ 3 ½”. Length 16’ 8”. The room above is a bedroom so I’ll be decoupling with rc-2channel, 24” on center and ½” sheetrock. On the floor I’ll use felt paper (moisture barrier) ¼” plywood and 1/8 inch floor tiles. This leaves a height of 6’ 10 5/8” Two block walls as well as the wall I’ll be closing in are exterior and I believe the block and my new wall will be sufficient sound proofing. The 3rd block wall adjoins my tenants’ kitchen. I hoping the block and the new wall will be ok. Since I need to get rid of bass energy as well as decouple the walls from the existing structure I was planning on proceeding as follows. ½” between existing walls and new track. Track will be caulked to floor on some type of absorbent material (suggestions???) all walls will remain ½” back from intersecting walls and ceiling. Gaps filled with backer rod and caulk. I’ll use 3 ½” metal stud (need at least this width for insulation) 24” on center and lightweight ½” sheetrock. My reason for this type of construction(correct me if I’m incorrect) is that it was my understanding that a lightweight wall will have more give to it and will resonate and help get rid of some of the low frequency energy.(think I read this in the rod gervais book but I’m not certain. This construction will leave me with a 9’ 6 ½” x 15’ 11” room with a 6’10 5/8” ceiling. I can punch these into a mode calculator and see what comes up. I was planning on floor to ceiling wide range hemlholtz bass traps (ala gervais book) in all corners. As many 2” Owens-Corning 603 cloth covered traps with 2” spacing (hopefully 2 per wall) as I can afford. And four traps above for clouds. Comments, criticism please. Wise me up if I’m headed wrong thanks 8) 8) 8) 8)

Disappointed that my diffusers won’t help.

That seems to be a common disappointment! :) Many studio builders discover too late that most types of diffuser create artifacts that take a lot of space to merge together and even out again. Some types can work (such as polys and slot walls), but those based on numeric sequences are out, unless they are only tuned to high frequencies.

The room above is a bedroom so I’ll be decoupling with rc-2channel, 24” on center and ½” sheetrock.

Depending on how much isolation you need (in terms of decibels), and at what frequency you need it, that probably won't be enough. 1/2" drywall is too thin, too flexible, and too light weight for attaining high levels of isolation. 5/8" drywall is much better, and you might even need two layers (once again depending on how many dB of isolation you need). Two layers of 5/8" drywall on the ceiling would probably need 16" OC, rather than 24" OC, for safety.

On the floor I’ll use felt paper (moisture barrier)

If you have or suspect that you will have a moisture problem in your concrete, then you must get that fixed first, before you do anything else at all. You cannot solve that with just a layer of roofing felt. You must be certain that there is no issue with damp in the foundations, floor or walls before you start building the room. If not, you'll have to tear the room apart at some point in the future to fix it, and by the time you notice the problem, it will have advanced to the stage where is it a major, expensive, big-time problem.

I believe the block and my new wall will be sufficient sound proofing.

Unfortunately, "believing" something to be true will not make it so! :) The only way to find out for sure is to determine how much isolation you need, in real-world objective terms, stated in decibels. Then you can look at the tables and charts to see what type of construction will provide that level of isolation. Just guessing is not a good idea, and guaranteed to be wrong. You need a proper sound level meter in order to determine two things: "How you are you?" and "How quite do you need to be?". The difference between those two is how much isolation you need.

The 3rd block wall adjoins my tenants’ kitchen. I hoping the block and the new wall will be ok.

Most likely not! It sounds like you are saying that you have a common "party wall" between you and your neighbor, so any vibration or sound that gets into that wall will be transmitted straight into his kitchen. It needs to be isolated properly, and "hoping" won't do that. :)

Since I need to get rid of bass energy as well as decouple the walls from the existing structure

You seem to be confusing two concepts here: Isolation and treatment. Isolation is what you do to stop sound getting in or out of the room. Treatment is what you do inside the room to modify the acoustics so that the room sounds good. They are two very different, and mutually exclusive things. First you isolate the room, and you do that for ALL the frequencies that you want to keep in or out. Then you treat the room based on the results of the isolation, once again for all of the frequencies that are causing problems.

Track will be caulked to floor on some type of absorbent material (suggestions???)

That is not the right way to float a wall. Floating a wall is a big deal, and requires careful calculation of many factors, as well as careful study of the characteristics of the resilient isolating material. And you most likely do not need to do that anyway: Once again, that depends on how much isolation you need, in terms of decibels, and the frequencies that you need it for.

and lightweight ½” sheetrock.

Once again, bad idea if you need a high level of isolation. 1/2" is flexible, thin, and low mass. What you need for isolation is rigidity, thickness and lots of mass.

it was my understanding that a lightweight wall will have more give to it and will resonate and help get rid of some of the low frequency energy

Where will it go? The energy has to go somewhere. Yes, you can make a membrane trap (panel trap) like that, provided that you do it correctly, but that is room treatment that you put INSIDE the finished room, and it cannot be part of the wall. If you build a thin, flexible light-weight wall that is tuned to bass frequencies, then that wall will allow those bass frequencies to get through to the other side, where they will be heard loud and clear. So this would destroy your isolation at those frequencies.

I can punch these into a mode calculator and see what comes up.

Ratio is 1 : 1.38 : 2.3. Not looking very good. The bonello diagram looks like a mountain range, and that ratio fails one of the critical tests used by the BBC to determine if a room is usable. There are several large gaps in the modal response at the very low end, then some close bunches further up. I'd try to change that a little, if possible.

I was planning on floor to ceiling wide range hemlholtz bass traps

Not sure what those would be! Helmholtz traps are tuned to very specific frequencies, and by definition are not broad band. They are also very tricky to tune precisely, and not much use if not tuned precisely. They must be tuned to the exact mode that is causing problems, but you won't know what that is until the room is finished and you have tested it. You could build a broadband slot wall, which actually is a Helmholtz device, and could be tuned to several modes, but that's not an easy proposition to get right for corners. It would be far better to build ordinary broadband bass traps, based on absorption, such as superchunks or even plain old ordinary corner traps.

As many 2” Owens-Corning 603 cloth covered traps with 2” spacing (hopefully 2 per wall) as I can afford.

I think you mean "703" not "603"! :) And 4" of 703 would be much better than 2", as it gets down to lower frequencies, which you definitely will need to cover. - Stuart -

thanks for the quick answer. not what i wanted to hear but i need to hear these things. i am dealing with the moisture problem now. the felt paper is somethiong that is always placed under a wooden subfloor. as for the ceiling i was trying to save some headroom. i can go double 5/8 and 16 on center. i dont plan on being very loud late atnight early morning.but i'm sure i wont regret more sound insolation. i will most often be recording myself. guitar, bass (direct if i have to, then reamp at a time that works better for my wife and tenants.) my keys are all virtual. drums are loops and bfd drums. three walls in the garage are exterior walls im not worried about neighbors as there is a good deal of distance between my house and their's. my thought was to let the bass though these walls but i realize thanks to you that the sound will end up upstairs where i just decoupled the ceiling to stop from happening. double 5/8 16 on center, wood studs all around. the adjacent wall is cement block so thats a good start i'll frame in wood and isolate with rc-1. the basstrap i was talking about is a corner trap from 2' off one wall to 3' off the other. 4-6" 703 (yeah i had that mixed up)is then covered with 1x6 wth 1/2" gaps. i believe because the distance the face of the trap varies in relation to the back wall the frequency it is effective on increases?? either way it seems i need to look at the desired ratios and see how much of my spce i should give up on my 16' span to obtain a reasonable ratio. i'll do some research and return to the board. soundman please dont think i have not done my homework on this project. i have searched and read much i guess i misunderstood some of what i've read and havent thought things through enough. thanks for clearing things up for me.

i can go double 5/8 and 16 on center. i dont plan on being very loud late atnight early morning.but i'm sure i wont regret more sound insolation.

Maybe one good alternative would be to try with a single layer of 5/8 first and see how that goes. If it is not enough, then you could add the second layer before you start the treatment.

the felt paper is somethiong that is always placed under a wooden subfloor.

Do you NNEED a wooden subfloor? Concrete is a great surface, acoustically, so if you could just leave bare concrete, that would be simple and inexpensive. If your concrete is ugly or not in good enough condition, then just lay simple laminate flooring. Much easier, and saves you room height too.

the basstrap i was talking about is a corner trap from 2' off one wall to 3' off the other.

Not sure what you mean by "2' off one wall to 3' off the other", but the concept is just to go roughly diagonally across the corner, and make the absorption as thick as possible. Search the forum for "Superchunk" to see how to do the best possible corner bass trap.

is then covered with 1x6 wth 1/2" gaps.

Sounds like a slot resonator. If so, it would be tuned to roughly 200 Hz, assuming average cavity depth of one foot. If it is angled across the corner, and assuming the depth varies from 2 to 18 inches, that would be tuned in the range 155 Hz (or 170 Hz) to 465 Hz. (or 509 Hz) (depending on whose mouth correction factor you believe). But even so, how do you know that's the frequency range you need to absorb? Did you check? It sounds rather high to me. I would expect your modal issues to be lower than that.

i believe because the distance the face of the trap varies in relation to the back wall the frequency it is effective on increases??

The tuned frequency varies according to cavity depth, yes. So it will trap lower frequencies in the middle (deeper cavity) and higher frequencies close to the edges.

please dont think i have not done my homework on this project.

Don't worry! It's clear you've spent a lot of time on this already, but there's still a way to go. :) If you are interested, the equation for your slot resonator calculations is: F = 180*sqrt(r/((d*1.2*D)*(r+w)))

i have searched and read much i guess i misunderstood some of what i've read and havent thought things through enough.

Join the club! :) This acoustics stuff isn't all that intuitive in some ways, and takes a little while to get your head around it. But hang in there: you are well on your way already!

thanks for clearing things up for me.

:thu: That's what we're here for! :) - Stuart -

been busy sealing the slab in my garage and prepairing the floor. ive looked at my options . i cant find any paintable sealer that is waterproof and also tough enough to guarantee they can withstand floor traffic. i found some that will withstandfloor traffic but are only moisture resistant. there are some masonry products that work for both of my needs waterproofing and durability but im not comfortable doing them myself and the cost of having someone else doing it is prohibitive.my proposed plan for the floor will only add 1/2".its a compromise i can live with. as for the ratio of the room. i was planing on using a 36" entry door opening in,at the end of the 15' 8 1/2" length of the room. ive altered my plan to use a 32" door . i now plan i using a second inner door and foyer. i'll use 2 5/8 stud and 1/2" rock on the foyer wall and extend this wall the length of the studio. effectively reducing the length of the room by 3ft. perhaps the space 32" by the remaining length of the room can be used as storage or maybe a vocalbooth (i haven't worked that part out.) the new room measurements are 6'10 1/4" by 9'5 1/2" by 12'8 1/2". the ratio forthese measurement are 1 : 1.39 : 1.85 fairly close to a desirable 1: 1.40:1.90. is it ok to go ahead with these dimensions? as for the bass trap i believe i explained poorly. in this design the face of the trap extends 2 feet out from the corner on one wall and 3 feet out from the corner on the other wall. so the distance from the face of the trap to the rear wall varies from 2 feet out down to zero. so it is effective over a variable range of frequencies. i'll check out superchunk. i think after the room is constructed i can get a better idea of what treatment will be necessary. is it possible that i'll be able to get this room to sound good enough to use some mic techniques that use the room itself? i was looking foward to using some room mic , stereo and non "close up" mic techniques to add space to my mixes. i would not be recording drums in the room although i would not be adverse to trying .