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Building a room - need help with ratios Modular Synthesizers
Old 8th March 2014
  #1
Gear Head
 

Building a room - need help with ratios

Howdy!

I´m building a control room and have a possibility of building walls to choose the size of the room so I´ve been pondering the room ratios.

Here a pic of the plan. My room is the red one. My brother has his room on the other side of the lounge/hallway. (kinda like when we were kids :D )

https://dl.dropboxusercontent.com/u/...0rooms%201.jpg

Since the ceiling is 3m high the most suitable well known ratio for the room would be 1:1.4:1.9,
but i came up with a ratio that seemed to work well according to Bob Golds modecalc and it would use the space more efficiently

1 : 1.6 : 1.833

heigth 3m
width 4.8
length 5.5m

The Bonello curve seemed good, it passed all modecalc tests and the low end seemed ok. Any thoughts?
Old 8th March 2014
  #2
Lives for gear
 
avare's Avatar
 

You did you your homework well. Use it and enjoy.

Andre
Old 9th March 2014
  #3
Gear Head
 

Thank you Andre!!! Good to know I´m on the right track.

Few things still bothering me. About the wall that I have to build next to the angled wall (one layer brickwall, theres an office on the other side). Can I get away with building just a single stud wall with drywall (maybe doublelayer) only on the studio side and maybe make the insulation (rockwool) behind it thick, say 100mm to 200mm? Of course the empty space acts like a room in a sense so I would throw some fluffy insulation bales in there with wrapping on them to act as bass trapping.

Would this suffice to make the room acoustically valid and at the same time also lower the sound transition to the office side behind the brickwall?

Oh and the room´s wall next to "lounge" is going to be double stud wall with first drywall then 2" x 4" studs with rockwool insulation, an 2,5" air gap (should the airgap be wider for better bass reduction?), 2" x 4" studs with rockwool insulation and again drywall on the outside.

Should i have double drywall on both sides of the wall or is there acoustical reasons to maybe have only one drywall layer in the studio side and then have a 2 layers on the outside?

So many variables here... :D Thanks in advance for any further advice.
Old 9th March 2014
  #4
Gear Head
 

Heres a picture with the same questions.

Old 9th March 2014
  #5
Gear Guru
Priority

You have chosen room ratio as a primary priority. These calculations are based on hypothetical solid boundaries. Also sound travels slower through fibre, so if you have significant depth of traps, the dimensions will be acoustically wrong.
When undertaking a fairly major acoustic build you have two big choices. Learn to be an Acoustician, or hire one.
DD
Old 9th March 2014
  #6
Gear Head
 

I guess I´ll have to learn how to be one. Keeping on learning.

I chose the room ratio as a first priority since I actually have the possibility to get a good starting point. And the ratio hypothetically is a good one.

I have a friend who is an acoustician and will help with the room measurement and treatment once i´ve built the walls. The idea is indeed to have solid boundaries. The question is how to deal with the leftover space so that it won´t create a problem inside the room? Double drywall? Triple drywall to the studiowall next to the leftoverspace?

Any help much appreciated.
Old 9th March 2014
  #7
Gear Guru
Hypo

Quote:
And the ratio hypothetically is a good one.
It would be in an entirely concrete room. But not here.
The calculators work on the basis that all the boundaries are hypothetically fully hard. In your case they are not. Also the treatment will change the acoustic dimensions.
DD
Old 9th March 2014
  #8
Gear Head
 

Quote:
Originally Posted by DanDan View Post
It would be in an entirely concrete room. But not here.
The calculators work on the basis that all the boundaries are hypothetically fully hard. In your case they are not. Also the treatment will change the acoustic dimensions.
DD
So unless the roomwalls are made out of concrete the ratios doesn´t really matter? I was under the impression that the room ratio matters even with a room that has double studwalls and double drywall/sheetrock as "boundaries" of the room. Seems to be the way a lot of studiorooms are built.

Any suggestions as how to approach this project?
I could go with building the walls out of concrete but would it be an overkill for a project this size?

I know the easiest way for me is to give up trying to learn this stuff and just split the space to make the studio room with a doublestud wall, leave the angled wall as it is, make 1stud walls with 10cm insulation around the room with double drywalls. An then just measure it and hope its ok and then just trap it according to the measurements and add absorption and diffusion to make the best of it.

hmm.
Old 9th March 2014
  #9
Gear Guru
Purpose

I would start from basics. What is this room intended to do? At what level of professionally? How much sound isolation is needed? How is the room performing right now? Budget? and so on.
Be aware that stud mounted drywall has significant LF absorption.

DD
Old 9th March 2014
  #10
Gear Head
 

Level is professional songwriting, recording of vocals and some instruments in the room as well as mixing. These are things that i do for living. I´ve been able to get professional results even in my previous room which was troubled in the low end. That room was pretty much fixed with good basstrapping, absorption and diffusion.

Idea is to build a good basis on which to improve.

Have a good ratio with sheetrock as calculated boundaries and then treat the lowend according to the cutoff that the gypsum has. So that the room has a good ratio in the upper spectrum and then treat the bass according to the fact that there is a cut off in the boundaries. The LF will pass the sheetrockwall boundaries and bounce off the boundaries/structures behind the studiowall and of course take into account the LF absorption that happens on the way.

Does this make any sense? :D

There is need for some degree of sound isolation. Especially to the direction of the narrow end of the space where there will be a small lounge and thena songwritingroom behind a wall that probably will be a double stud wall.
Old 9th March 2014
  #11
Gear Head
 

So the LF absorption of a stud mounted drywall will cause problems in the low end and the room ratio is useless in the LF modes are created from outside of the room boundaries?

So i could calculate the approximated room ratio having the angled wall as it is and just building one wall to make the room.

If i make this one wall (next to the "lounge") triple sheet rock then 2"x4" studs with rockwool then 2,5" airgap, another 2"x4" studs plus rockwool and then double sheetrock could i use this heavy wall as a basis for the calculations? Then i´d have 3 walls as boundaries that are brickwalls and one boundary that is triplesheetrock heavy insulating wall that will lets some LF through but can be used as a hypothetical boundary fo calculations.
Old 9th March 2014
  #12
Gear Guru
Nope

Sorry it is just not like that. We would have a much more productive discussion on how to get the best from this room, if ratios were omitted from the agenda.
You have a fine big space (by Irish standards at least) Plenty of room to install simple guaranteed to work deep fibre trapping. Nice slats on the surface, done. Take a look at boggy's My Room Acoustics over on FaceBook.
Again, I recommend measuring the room acoustically so we can have some facts to work with.
Measuring Room Acoustics

DD
Old 9th March 2014
  #13
Gear Head
 

Quote:
Originally Posted by DanDan View Post
Sorry it is just not like that. We would have a much more productive discussion on how to get the best from this room, if ratios were omitted from the agenda.
You have a fine big space (by Irish standards at least) Plenty of room to install simple guaranteed to work deep fibre trapping. Nice slats on the surface, done. Take a look at boggy's My Room Acoustics over on FaceBook.
Again, I recommend measure the room acoustically and let's work with the facts.

DD
Got it! :D

Let´s forget the room ratios.

Heres the situation.

Room height 3m
Upperwall in the picture 6.60m
Left wall 11.61m
Narrow end wall 4.70m

My room is to be built in the upper end of the space and that room should be isolated from the "hallway" and the second smaller room to make my room as good as possible. Should i just choose where to cut the space in half and build a wall there and then measure it and then start a treatment accordingly?

Old 12th March 2014
  #14
Gear Guru
Yes

Logic seems to suggest exactly that Al. If you want really good soundproofing between the two rooms you would build a wall at both sides of the 'hallway'.
The quality of the doors used and in particular the seals around them will be a big factor. Your dividing wall(s) could be angled to prevent flutter echo if you wish, although this will probably be killed by treatment in any case.
Look out for a Sound Path from room to room, overhead.
I should probably have started with this. In the past I designed a room, concrete walls. I used ModeWiz to optimise within the planning permission limits. I got it within centimetres, and pass all 4 criteria at once. When built the room was nothing like the predictions.
Also, modes are most likely not the biggest player on the field at all. http://realtraps.com/art_modes.htm
DD
Old 15th March 2014
  #15
Gear Head
 

Apparently i also have to have some soundproofing on the side brickwalls. Would building a single 2"x4" stud wall with double gypsum layers, 2"x4" studs and fill with 10cm (4") rockwool leaving a 5cm (2") airgap before the Brickwall suffice?

I will of course separate the wall from other surfaces using neoprene and make sure the gypsum layers won´t touch the floor, ceiling or the other walls, then seal properly.
Old 15th March 2014
  #16
Lives for gear
 
jhbrandt's Avatar
Al,

Good points by Dan above...

Sound-proofing: How much attenuation do you require? in Decibels.
For some help here, go to my publications page and download the two papers entitled, "Sound-Proofing: The Quest" and "How to find out how much Isolation you need".

1. You don't want to use Rock wool in the wall cavity.. use the cheaper light-weight fiberglass building insulation. Save the Rock Wool for your acoustic treatment.

2. If you are on the ground floor, you don't need to decouple the wall from the floor. BUT if you are only adding another wall, without building the rest of the isolated box - this means you need an isolated ceiling as well, then you could have a problem. Soundproofing is only as good as it's weakest link.

3. A heavy brick wall can approach STC 48 on it's own. Of course, for a music studio you are going to want a minimum STL of about 55 dB. - Depends on what THEY are doing on the other side of said wall.

4. Don't throw out good room ratios. We use everything that is proven to help when we build studios. It's important to test your room dimensions with a good mode calculator, get the best possible without reducing the size of the room, and then treat it properly.

Control Rooms are treated very differently from Tracking rooms. "Room Acoustics Design and the Frequency-Power Spectrum" is another of my papers that you might find useful.

Good luck!

Cheers,
John
Old 15th March 2014
  #17
Gear Guru
Soundproofing

Soundproofing can be difficult to succeed at. I have two clients at the moment who both employed companies to 'soundproof' party walls between houses. Both failed entirely.
Yours plan is pretty common, but success or failure will depend on the details.
Overlapping the sheetrock gaps. Filling them. Green Glue perhaps.

As John said, how much soundproofing, in particular at what sort of level, and in particular what frequencies? LF is very difficult to contain. You can test all of that with some loud gear, e.g. a small PA, Pink Noise, and an SLM.
Listen for 'Flanking transmission' That is bypass paths around and above the wall.

Here's a pandora's box. http://archive.nrc-cnrc.gc.ca/obj/ir...r761/ir761.pdf

It cannot be helpful for professionals to disagree publicly, so I am prepared to EDIT email anyone interested the comparison between an idyllic predicted room, concrete boundaries, and the resulting totally different modal pattern. It is from this evidence that I am firmly in favour of more space and more treatment rather than prediction. This is compounded when the boundaries have complex partly absorbent and partly resonant behaviour, as studded walls do. They are reactive. Furthermore the thick layers of fibre which I would envisage will slow down the sound waves, effectively changing the acoustic dimensions. The fibre will be 1.2 -1.4 times sonically deeper than visibly. Obviously it would be wise to avoid daft ratios such as 2:1 etc. but in the context of the above I wouldn't go fine tuning in inches.

If the brickwork is exposed, a layer of cement render will help significantly.
I would fully fill the gap between stud wall and brick wall, with the usual insulation 'blankets' used for this purpose. Fully fill but do not compress which would cause some LF transmission between the leaves. Support the fibre from sagging.

DD
Old 15th March 2014
  #18
Lives for gear
 
John White's Avatar
 

Quote:
Originally Posted by DanDan View Post
send you the comparison between an idyllic predicted room, concrete boundaries, and the resulting totally different modal pattern. It is from this evidence that I am firmly in favour of more space and more treatment rather than prediction.
Dan,

It's always helpful to present data as long as it's supported. Please do.

Thanks,
Old 15th March 2014
  #19
Gear Guru
OT

The usefulness or not of Modal prediction, or indeed the often assumed but often nonexistent dominance of modes are worthy of other threads perhaps, but I reckon it best to stay close the the OP's topic here. Albeit now changed from treatment to soundproofing. That's fine though, quite often just redefining the question results in the best answer. If anyone really wants or needs to see the data behind my reference to a spectacular failure, PM me your real email and I will oblige.

DD
Old 16th March 2014
  #20
Gear Head
 

Thank you all for the input!

The space I have is in the first floor of a three story building. My ceiling is a concrete slab about 20-25 cm thick (have to confirm the exact thickness) separating the room from an office above. I probably have to visit them and test how much sound gets through the ceiling and possibly other flanking pathways. Haven´t really heard any noise coming from upstairs though so I probably don´t have to worry about the ceiling, unless the concrete slab happens to be a flanking pathway when dividing the room into smaller rooms. Then of course I will consider lowering the ceiling.

The question remains where to have the speakers and the listening position and should I go with the 3m x 4.8m x 5.5m inner shell ratio? I am aware that because there is a window in the wide end of the room and there is the angled wall to the side behind the proposed wall, the ratio doesn´t really work with LF.

As for treatment I guess is should get the walls done and then measure and treat accordingly with bass trapping, broadband absorption and diffusion. I intend to have a laminate floor without any matress and have the needed amount or absorption in the ceiling instead.

The ventilation still has to be thought out. I´ll probably have to make a couple of sound isolation boxes (the labyrith type) for the air ducts coming from the smaller room through the hallway and of course for my room ventilation as well. Luckily the airvent in the room leads straight to the roof through a stairwell.

I am kind of a perfectionist when it comes to any type of construction or finishing a mix so I think I will be able to get the soundproof part done really well :D

Any how, below are the intended structural choices I have been thinking about with some pondering in between.


The wall dividing my room from the lounge:

according to National Research Council Canada linked by DanDan
http://archive.nrc-cnrc.gc.ca/obj/ir...r761/ir761.pdf

STC 66 Page 345

1 single layer of 13 mm type X gypsum board
2 single layer of 13 mm type X gypsum board
3 90 mm wood studs at 406 mm on centre
4 90 mm of glass fibre insulation in cavity
5 25 mm gap filled with air
6 90 mm wood studs at 406 mm on centre
7 90 mm of glass fibre insulation in cavity
8 single layer of 13 mm type X gypsum board
9 single layer of 13 mm type X gypsum board

or

STC 64 Page 346

1 single layer of 13 mm gypsum board
2 single layer of 13 mm gypsum board
3 90 mm wood studs at 406 mm on centre
4 90 mm of glass fibre insulation in cavity
5 25 mm gap filled with air
6 90 mm wood studs at 406 mm on centre
7 90 mm of glass fibre insulation in cavity
8 single layer of 13 mm gypsum board
9 single layer of 13 mm gypsum board

I will probably go with the STC 64 structure because of the current budget as I can add another gypsum board layer(s) later if needed.

There will be a double soundproofing (38db or 30db) doors in this double stud wall. I have been considering building a window as well but I have pressure to have as little downtime as possible so maybe I will just skip the trouble.


Side walls of my room (on the right and left side of the picture) next to the brickwalls:

1 single layer of 13 mm gypsum board
2 single layer of 13 mm gypsum board
3 90 mm wood studs
4 90 mm of glass fibre insulation in cavity
5 25 mm gap filled with air
6 100mm Brickwall already on place

I am considering the extra hard gypsum board at least for the layers inside the room so that I´ll be able to hang some heavy treatment on the wall. I have four pieces of heavy pine 60cm x 60cm BBC skyline diffusers that I built a few years ago etc.

If I straighten the angled wall with a double layer gypsum and a single stud wall with insulation (presuming this is enough to stop me from terrorizing the office behind the brickwall) I will fill the empty space from floor to ceiling with insulation blankets as Dan suggested.


Another space dividing wall between the small hallway / lounge and the smaller room at the narrow end:

according to National Research Council Canada

STC 56 Page 290

1 single layer of 13 mm type X gypsum board
2 single layer of 13 mm type X gypsum board
3 90 mm wood studs at 406 mm on centre
4 130 mm of glass fibre insulation in cavity
5 single layer of 13 mm type X gypsum board
6 single layer of 13 mm type X gypsum board

or

STC 54 Page 292

1 single layer of 13 mm gypsum board
2 single layer of 13 mm gypsum board
3 90 mm wood studs at 406 mm on centre
4 90 mm of glass fibre insulation in cavity
5 single layer of 13 mm gypsum board
6 single layer of 13 mm gypsum board

The Idea is that the bigger room will be a well treated room that has a good RFZ for mixing and mastering as well as have the room live enough soundwise (done with diffusion i presume) to be able to also record vocals and live instruments when needed. The smaller room at the narrow end will be mainly a songwriting/mixing room for my brother, but in case there is a need for a bigger recording session with a band, theres always the possibility to have the monitoring in the smaller room.

I´ll add some pictures later today so you get to see how the space looks before any construction.
Old 17th March 2014
  #21
Gear Guru
Plan

Glad to hear of the concrete ceiling.
I don't know if the heavier plasterboard is capable of hanging loads, I would attach to the studs if possible.
I would be inclined to keep the angled wall, as it has the advantage of preventing flutter echo. I think windows, if the idea is to provide visual contact, are a waste of time. In my experience Inter Muso visual comms only really occur when in the same room and or with a great headphone system.

DD
Old 18th March 2014
  #22
Gear Head
 

Thank you for the insight DanDan!
I´ll keep the angled wall as you suggested and build one stud wall (with double gypsum, 100mm studs plus 100mm insulation and an airgap) next to it for soundproofing.

I am wondering where should I place the listening now that I keep the angled wall? Should i make symmetry with treatment to the angled side and still put the listening there like this?



If I place the listenin postition to the oppisite side of the room, obviously there will be windows just to the right and then I´d have to block the window side with some broadband absorbtion panels (Of course it could be that i eventually have to do that anyway). Maybe place it in front of the window instead, speakers shooting to the narrow end of the room (where the door to the hallway is) and then trying to make symmetry with some treatment?

Any insight very much appreciated at this stage!
Old 18th March 2014
  #23
Gear Guru
Mystic

I am afraid the response of the room is not exactly predictable. Acoustic symmetry will not be the same as visual. With treatment such acoustic symmetry is easily done at HF, and it is debatable as to how valid the notion of symmetry is at LF. What with subs and so on. If all boundaries are made of the same material, it is usually best to fire into the long dimension of the room. In this case, the boundaries are dissimilar, so measurement is really the only way to choose amongst the placement options.
DD
Old 18th March 2014
  #24
Here for the gear
 

Hello,

I see that jhbrandt and DanDan have given good pointers here. Dan do you mean that Al should build the soundproofing wall (bottom wall in the picture) and do measurements after that? Can he get some useful insight by doing some testing in the large room? He is practically missing one wall from his future room then.

-R
Old 18th March 2014
  #25
Gear Guru
Interesting

Testing is nearly always interesting at least, often useful.
Irrespective of the lack of the dividing wall the other two main modes might be very visible, or not. Testing really is just a bunch of answers sitting there waiting to pop out.
DD
Old 19th March 2014
  #26
Lives for gear
 
jhbrandt's Avatar
Al,

Unless the room is a rectangular cuboid, a mode calculator will be a random guess. BUT if the room is a rectangular cuboid of concrete, the calculator on my site will be extremely accurate.

I'd recommend keeping as much space in the tracking room/area that you can, including the angled walls. But the control room is best built in a pre-calculated, rectangular cuboid enclosure (for best results).

Also note that IF the existing noise of the area of the building is not high and you mix at normal mix levels... The existing concrete structure walls might provide enough isolation without the necessity of building a 'room-in-a-room' for the CR.

This is something to think about and I'd recommend a site-survey / noise testings be done. - For a commercial studio, you may very well need that isolation level since you may not always be the one in control of the volume knob.

Just remember that when you do layouts, Form Follows Function... and things should 'flow'. Keep sight-lines open and work areas connected without compromising the acoustics or isolation.

Good luck

Cheers,
John
Old 22nd March 2014
  #27
Gear Head
 

I measured the room with REW using an se2200a. The speakers (Dynaudio BM6as) were positioned as in this picture. The walls are yet to be built.


Heres left speaker (red) and right speaker (green) with 1/24 smoothing


Heres both speakers from the middle (light blue) and a generated A + B from left + right (dark blue)



Heres both speakers at the same time with the mic in the middle of the listening spot. First pic without smoothing and then with 1/24 smoothing.





The nulls and boosts seem to coincide with the calculations I made with Bob Golds roommodes calculator with the room dimensions. I averaged the length (or was it width) against the angled side and it seems to work as someone suggested. Some modes and nulls were a bit higher in the measurements but the shift was maybe a hz or two max. Maybe the windows and beams and other features of the room had something to do with?

Lets see what happens after the walls are built. Hopefully theres an improvement :D
Old 22nd March 2014
  #28
Gear Guru
Modes

If you want to view the modes vividly, place the speaker(s) on the floor in a corner. Mic up at the ceiling, opposite corner. Then view them in the Waterfall window.
All modes end up in the corners and the directionality of the mic will be overwhelmed in there.
They will be quite spectacular.
Then there is the real world where modes will likely not be a dominant factor at all. Do room modes even matter? | RECORDING.ORG
Location of the speakers and listener is the single biggest and free tool we have.
The best way to find the best spot for both is for a start keep an open mind.
e.g. In the real world speakers very often deliver best response when placed extremely close to the Front Wall, rather than the urban myth of keeping them away from walls. I would try all viable options before building anything. https://www.gearslutz.com/board/9038508-post24.html
Again if the walls are build parallel they will need extensive coverage to stop the resulting flutter. Angled, large areas can be left bare.


DD
Old 22nd March 2014
  #29
Gear Head
 

Thank you for the advise DanDan! Ill do those measurements tomorrow.

How much should I angle the dividing wall opposite of the windowed wall to remove flutter?
Would 6 degrees suffice? or even less?
Old 23rd March 2014
  #30
Gear Head
 

John, thanks for the input! You´ve been very encouraging!

I unfortunately have to build the soundproofing walls because there are two other rooms to the left (in the pictures) behind a brickwall and on the right side theres an office. I tested the current sound transmission through the walls. The brickwall indeed cuts about 48db:s so I think the double layer gypsum 100mm studwalls with an air 50mm gap next to the brickwalls should work.

Both the rooms me and my brother are building are probably used for songwriting, mixing and vocaltracking and theres the possibility to use the other for tracking and other as a CR when needed. The angled wall and dimensions probably aren´t the best in terms of acoustics and positioning the listening and since I probably can´t built the boundarywalls using concrete of brick Ill have to do with soundproofing and then treating after measuring the rooms.

My biggest problem seems to be the angled wall since I need to have some kind of an idea of where to place listening before installing the door.

Do you have any suggestions prior to building the walls if theres a way to treat/build the angled side so that the listening could be on that side of the room?

Hope my plans are going in the right direction :D
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