Rear Wall Bass Trap Question

ok i hope im posting this in the right section but if not please dont kill me its my first post, lol. ive been reading through the SAE site and this forum for about a month now trying to accumulate as much info as i can. im going to be building a fresh building from block in my backyard. right now the plan is 60 ft by 25 ft. this dimension has to do with my backyard and the space i have. i could change it by a few feet on either end but thats basically what im planning on. now i have a bunch of questions but there is one thing im just not getting. when building the control room, i want to do the rear wall hanger approach, and do it broadband to kill the whole low end spectrum. or even the variable resonator method to the the same. i understand you hang the insul and put a wall in front, but what i dont get is the details on the wall IN FRONT of the hangers. drywall? mdf? studs with cloth over them? i mean if you did dry wall, would that actually pass the freqs good enogh so they could be absorbed? do you seal that wall? put holes or vents in it? im just not understanding the fine detail of constructing it. what my plan is, is the broadband bass trapping wall (which will act as a diffuser as well) in the rear, angling the shape of the room. false ceiling with lo mid hanger absorbers panel resonators on side walls tuned to the 2 worst lo mid modes, and also for high diffusion angles corner traps in front that will be added after construction (probably broadband low absorbers, but maybe resonators) a few high freq absorbtion panels if nessesary hard wood floor all of which i will be constantly checking with an rta after each addition now i only use nearfield moniters because i just dont see the point of farfeilds except to impress clients, but if i do decide to add them, im going to make it easy for me to add those in the future if i want by putting removable bass traps in the front. if any one has any ideas or critisism, pleeease respond. im in beginning phases of planning and i dont want to screw up. also with the dimensions i gave, can someone reccommned a general size for the control room, i def dont want it too small. perhaps 13ft wide 20ft long??

Most of the designs I've seen use a false wall in front of the bass hangers, built out with studs with insulation (703, rockwool, cotton) installed, covered with cloth. They do NOT use drywall, though there are ways to build a wall like this with bass hangers behind it that do use drywall.

well i dont want anyone falling through the wall, lol. plus that sounds a little hokey. I was really hoping to go with diffusion in the back, perhaps putting slats or peices of wood over the studs and cloth, then attaching more peices of wood to those slats, each being different thickness and what not to resonate over a broader freq band. or would that just be too much and work against itself? here is an example of a studio i found online that uses some kind of resonaters. I like the look of them, there portable which is good. but do you think these could cover all the way down to 50 hz and so on in either a control or a live room?

I'm not sure what "hokey" means, but I do know that the false wall design is very common for one reason.... it works. Take from that what you will. I'm not sure what the design is of the photographs you show. They look like diffusors, but I can't quite tell. Either way, I'd be quite surprised if they are effective down to 50Hz, mostly because of their size (or more accurately, their lack of size). They certainly wouldn't be as effective as an absorptive false wall in front of bass hangers, presuming your goal is to establish some control over the low end in your room.

well id like to have low end control in any room, but especially the control room. basically the idea why i dont want a cloth wall behind me is that i do like to feel comfortable in the room, and i like the look of diffussers and nice wood on the back wall. plus i reaaaaly dont want some rock musician to lean againt it and fall through, lol. is there another option with the hangers but with wood diffusers/resonators in front of them? also, guitar amp/dead iso drum rooms need low end treatment too, and the hangers seem a little unrealistic for that application. what is the best method for those small isolation rooms? small hangers chamber, resonators, or plain thick ass mineral wool?

TangoCash wrote:

when building the control room, i want to do the rear wall hanger approach, and do it broadband to kill the whole low end spectrum. or even the variable resonator method to the the same.

Standard broadband using rockwool, 705 is your best bet - it's the least expensive - good looking treatment you can build.

i understand you hang the insul and put a wall in front, but what i dont get is the details on the wall IN FRONT of the hangers. drywall? mdf? studs with cloth over them?

Typically you would do a fabric wrap over the rigid insulation and then hang it off the wall by a few incles (for general broadband) or straddle the corners (to maximize LF benifits.

i mean if you did dry wall, would that actually pass the freqs good enogh so they could be absorbed? do you seal that wall? put holes or vents in it?

Now you are building a membrane device - which would be depending on the density of the drywall what frequency it was - and even with insulation behind it (after an air space - you can't touch the panel) it is only good to about a 1/2 octave abover and below it's center frequency.

broadband bass trapping wall (which will act as a diffuser as well) in the rear, angling the shape of the room.

I could be dense - but i do not see how a broadband absorber is going to act as a diffusor as well.

panel resonators on side walls tuned to the 2 worst lo mid modes, and also for high diffusion

DOn't waste your time with panel resonators - you will never have just 2 problem frequencies to deal with - you are MUCH better off sticking with broadband -

angles corner traps in front that will be added after construction (probably broadband low absorbers, but maybe resonators)

Like I said - stick to broadband

a few high freq absorbtion panels if nessesary

figure some 2" 703 2" off the walls at all of your mirror points.........

hard wood floor

Good choice

all of which i will be constantly checking with an rta after each addition

Yu can if it amuses you - but if I were you I wouldn't waste my time - believe me - you haven't described anywhere near too much treatments in the room. I would treat it completely as described - and THEN test it to see where I was..........

can someone reccommned a general size for the control room, i def dont want it too small. perhaps 13ft wide 20ft long??

If it has ceilings in the 8 to 10' range then it's not bad ratios........ still a small room - so stick with the broadband - best bang for the buck in small rooms..........

WOW thats so weird! i like just bought your book right before you posted that, lol. the reason i was saying the broadband absorber would act as a diffuser, was because if i put different size slats and boards across the studs in front of the hangers, it would be variable and diffuse because its random hard surfaces. also, i didnt think 13 x 20 was small. i definetly do not want a small control room that automatically puts me at a disadvantage, because i do alot of mixing as well as recording. what would be a min. size for a decent control room if say the ceiling was 10ft, or even 12ft? and would extra thick mineral wool do as well as 703 or 705? that stuff is retardingly expensive! like perhaps if i used 6 or 8 inches of mineral wool instead of a 4 inch think 705 board? or wrap the hangers with 2 inch mineral wool around twice?

TangoCash wrote:

the reason i was saying the broadband absorber would act as a diffuser, was because if i put different size slats and boards across the studs in front of the hangers, it would be variable and diffuse because its random hard surfaces.

Nope - various width boards across the face - with varying slot width would makeit a helmholtz trap - not a diffuser..........

also, i didnt think 13 x 20 was small.

well if it had an 8' ceiling height (which wouldl be a real good ratio for a small room) it would have 2080 c.f. of volume - which is a smallroom by anyone's definition. 10 feet would only push it up to 2600 c.f. - which I consider really minimum size for a contol room. A good room would have ove 5,000 c.f. of volume.

i definetly do not want a small control room that automatically puts me at a disadvantage, because i do alot of mixing as well as recording. what would be a min. size for a decent control room if say the ceiling was 10ft, or even 12ft?

12 feet would make it 3,120 c.f. (a medium sized room) but now you don't have as nice a ratio for the room...........

and would extra thick mineral wool do as well as 703 or 705? that stuff is retardingly expensive! like perhaps if i used 6 or 8 inches of mineral wool instead of a 4 inch think 705 board? or wrap the hangers with 2 inch mineral wool around twice?

Re-read my first post - didn't I mention mineral wool (which is rock wool) in my comments thre? Rod

for the diffusors to be effective, you'd want your CR to be at least 20 feet long. given you want your building to be 60' x 25', this shouldn't be a problem. plus you could control the ceilign height to get the volume and ratios to work. then if you take jwl and Rod's advice on constructing the back wall with the broadband controls and trapping, you could still add some diffusers and some slats to keep musicians from falling through your walls (although I would think unless its someone paying big bucks you're probably not inviting them back if they did that... :-)) also you could put furniture along the back (shown here) to prevent people from leaning on the walls...