12 Degrees of Separation: More Questions

[Jack Russell]

I'm back with more questions about angled walls, and I see that others are also as confused as I am. My first question is this:

1) Is 12 degrees the ideal angle for opposite walls in a control room, between the left and right sides? John Sayer mentioned earlier that that is the minimum. So now I'm confused. Is it better to increase this number, if you can?

2) Another question: If 12 degrees is the total, then each wall should be angled 6 degrees, am I correct?

3) Someone also mentioned that there was a way to lay this out on a floor with a tape measure. Is there a formula I could use to find the correct measurements for a 6-degree angle? [I failed calculus in college, but I'll give it a try!!]
Thanks,
Jack R.

 

[Jack Russell]

...or would that be trig? I failed that too!
-J.R.

 

[c7sus]

a x squared + b x squared = c x squared

Use the scientific functions of the calculator in windows.

sine, cosine, tangent.

Remember "Oh Hell Another Hour Of Henry."

Or Soh Cah Toa???

Sine=opposite divided by hypoteneus

Cos=adjacent divided by hypoteneus

Tan=opposite divided by adjacent

 

[RICK FITZPATRICK]

Here is a 12 degree triangle. Lay it out on cardboard or ply or something and use it to lay your walls out. Long side=60", short side = 12 3/4"
fitZ

 

[Jack Russell]

Thanks for the info. Yeah, right: I understand the a2 + b2 = c2 formula.

Well that is the math, but still, you havent' answered my second question: would you angle each side wall 6 degrees to give you 12? The diagram you showed shows only the angle for one wall at 12 degrees. But, I suppose even a math moron like me could deduce that I would just cut the number in half to get 6: That is, 60" on one side, then one half of 12 3/4" on the other; am I right?

Or, for that matter, I still don't know if 12 degrees (total) is the best desirable angle, or if I should go for a larger angle.

 

[RICK FITZPATRICK]

But, I suppose even a math moron like me could deduce that I would just cut the number in half to get 6

That was a trick question in school. Actually, no, the degrees are cut in half, but the distance on the short leg would be 6 5/16". IF the short side were an arc instead, then the length of the arc would be half. As to the 12 degrees or 6 degree per wall, it is 12 degrees TOTAL between the two splayed walls. Sorry, I wasn't awake when I drew that. It should be 6 degrees per wall, or more. At least from my understanding, this is a minimum.
Like I said earlier Jack, the angled walls are mainly to direct the early reflections to a rear wall where they can be absorbed, diffused, diffracted or what ever you would like to do with them. Ha! just kidding. The main thing is to keep early reflections from the mixing position. Here is why.
The distance from the monitor to your ears is always shorter than the distance a reflection must travel. Therefore, the reflection arrives AFTER the direct sound. This is called a time delay gap. This TDG creates comb filtering which in essence, masks the TDG of the studio, which is exactly what the engineer is trying to hear, as early reflections at the microphone are what gives the recording its room characteristics. However, there are many other things that must be considered to achieve this correct TDG in the control room.
For one, the monitors must be soffet mounted, as near fields diffract sound back to the front wall where they create an early reflection. So does the surface of your console. In rooms where near fields are used, it is necessary to use absorption as a means to eliminate early reflections from the front wall.
Sound travels at approx 1 ft per millisecond. Since the brain will integrate all sounds that arrive at the ears within 25 ms of the direct sound, to create a TDG longer than the studio, sound wave must travel a round trip distance of at least 25 feet , plus the TDG of the studio. For normal rooms, this TDG is created by reflections from the ceiling, as it is usually the closest to the mic, which in normal 8 ft ceilings, and a mic height of 5.5 feet, means a singer would have a TDG of about 5 ms. It is this TDG of the studio that the engineer can hear comb filtering effects and the reflections itself. I'm sure you have heard recordings that illustrate this perfectly. You hear the sound of the room as SIZE, by virtue of these reflections. That is the point of having TALL ceilings in the studio, and keeping the mic away from adjacent walls as far as possible. And how do you tell what it sounds like over the monitors? Exactly. By not masking it with control room early reflections. Hence haveing side walls splayed, and a rear wall at least 25+ feet ROUND TRIP for these reflections. That translates into a rear wall approx 13 to 18 feet from the engineering position.
But let me add something here. Although it is desirable to have an RFZ. attaining it at the engeenering position in small control rooms is dubious, considering the paths for early relection control must be calculated as IMAGE POINTS to establish its boundarys. And early reflections are only part of the overall room acoustics that must be considered.
I've barely scratched the surface of this subject, so please don't consider this a concise explanation. There are volumes written on these subjects and it is difficult at best, especially for someone like me, with no education in acoustics to explain them in a few short paragraphs. And I have probably oversimplified them too. Comb filtering deserves a book chapter in itself.
Well Jack, I hope this helps. I'm certainly no expert, but this is what I've gleened from reading, although I have condensed it. Other more expert people may dispute this with more current knowlege or better understanding.
fitZ

 

[Jack Russell]

Hey, thanks a lot, Rick, for taking the time to go into detail.

The studio I'm planning will be both a rehearsal/recording and control room. The length of my space from the back wall to the front wall will be 18.5 ft, so, based on what you've explained, it looks like I'll have a hard time achieving ideal acoustics, even if I splay my walls, and that the angle of splay may be a moot point. Yes? The position of my head when I mix will end up being about 12-13 ft from the back wall. [I have a normal sized head.]

I was going to attempt to fit in a studio design like that on Ethan Winer's page, which was 15 ft by 21 ft, but it wouldn't fit.

So, tell me if I'm wrong: my dilemma now is to go ahead and splay the walls, and attempt to eventually build in sound diffusers/absorbers at the back wall to get the best results I can with the space available, or just punt and go for square walls all around and try to manage with treatments? What would you do?

 

[RICK FITZPATRICK]

I can with the space available, or just punt and go for square walls all around and try to manage with treatments? What would you do?

Hello Jack. Well, it would depend on the width of the room. At least as far as I'm concerned. And you are right about the length. By the time you put in a console and speakers(depending on where you locate them in relationship to the conslole) you will use up at least 4 feet of length. Tell you what. Tell me your rooms dimensions and I will do a quick layout in Autocad. This will tell ME what I would do. Then I'll post it. For the most part, I had a problem with the width of my room. Lenth was ok. But I really couldn't afford to splay my walls. So the next best thing is to soffet mount my speakers, use 703 absorbers on the side walls and ceiling to just past my console. Then I planed on using what John Sayers designed as angled panels to breakup standing waves(I think ). I have a deep closet at the rear that centers on the width, and that will be a hanger bass trap or a Slat absorber, with corner bass traps. Here is a plan of my space so you can see. I'll post a pic of your plan tonight if you can get the dim's to me in time.

 

[RICK FITZPATRICK]

Here is a side elevation.

 

[DDev]

Jack,

The critical place for the splayed walls is from the location of the monitor speakers to just behind the mix position where you will be sitting. If you can fit the splay into that area then the walls behind you can be minimally treated to reduce parallel reflections for the rest of the room. The design on Ethan's site uses the 6 degrees from each side (for your room length that would put the inset at the front wall at about 22 inches per side to do a whole room length splay; if you only go to your mix position, though, the inset will only be 6-8 inches per side).

You mentioned that the length of the room is 18.5 ft, what is the width? I'm assuming it must be fairly narrow if you threw out Ethan's design.

Darryl.....

 

[DDev]

Looks like Rick beat me to the question on the width.

Nice detailed drawing, there, Rick. I can't quite read what the width of your space is, though. It almost looks like 46' but I know that can't be right since it doesn't scale with your length (and I KNOW you don't do any drawings out of proportion ).

Darryl.....

 

[Jack Russell]

Wow, your plan is excellent.

Very cool, that you can do a CAD of my plan! I downloaded a CAD program yesterday, but I haven't had time to learn how to use it. So, sorry to say I can't supply a draft plan to look at. However, I'll attempt to descibe:

the space I have to build in is a corner of a basement with 9 ft ceilings (actually 8 ft 9"). I have 15 ft of width to work with along the back wall, which will end up being a little over 14 ft after the walls are up. At 133 inches from the back wall on the right side I have an obstruction: a water heater/ water treatment/furnace installation. Ugh!! This encroaches inward by about 24 inches, beginning at 133 inches, and continues for about 9 feet. So, the right side of the space goes from 14 ft down to 12 ft, at 133 inches. Thus, I'm planning on angling the wall starting at the point where the mechanical stuff gets in the way, to the front wall, which will give me 18.5 ft of space from the back wall. Although, I could stretch this wall a bit farther (forward), perhaps up to 20 ft, without messing up the rest of the plan for the basement. The room planned to be opposite the forward wall of the studio will only be a utility room, so there is some flexibility. My thinking is that I'll need to make the left side of the space have the same shape as the right, for symmetry. So, it would then also have a 2 ft wall sticking into the space at 133 inches, on the left side (as you look from the back wall).

I hope this is reasonably clear!

I'll attach a photo at least. It shows the view looking straight at the back wall. On the right is a space in which I'll be putting in an adjacent vocal isolation room (5 x 7 x9).

 

[Jack Russell]

You mentioned that the length of the room is 18.5 ft, what is the width? I'm assuming it must be fairly narrow if you threw out Ethan's design.

Darryl.....

Thanks for the insight. Width is 14 ft, but the deciding factor was the HVAC/water treatment stuff, which would have jutted into Ethan's layout. So it will be 12 ft after the point of encroachment. And it's also going to need some major soundproofing anyway. I'll have to build a double wall, with staggered studs.
JR

 

[RICK FITZPATRICK]

Hello Jack and Darryl. Guys, as you can see in my plan, I have splayed a short section, but it is a quasi splay. I couldn't even get 6 degrees, at it encroachs on the distance I need from speaker center to the splay, which SHOULD be 4 or 5 speaker diameters on the baffle to the splay. Oh well, nothing is perfect in my space anyway. I'm just sort of doing what I can. I don't even have any isolation stuff. Of course, its quiet as hell up here on the hill. Except for an occasional train horn, or ship horn. Ha! Man, you should hear it. The valley has an RT-60 of 15 seconds!!! Hahahahahaha! Talk about reverb. Sounds beautiful.
Anyway, got to go fix a water heater. I'll be back later to address your dim's Jack. later
fitZ

 

[punkin]

Some great stuff here guys and leave it to me to interject some useless information and pointless questions but, what if; you were to build a completely round room? Would it work for listening or tracking or would it be a complete mess?

 

[RICK FITZPATRICK]

what if; you were to build a completely round room? Would it work for listening or tracking or would it be a complete mess?

Well, I don't know about a mess, but I don't think you would like the sound. I believe it would completely destroy any sense of stereo image. I bet there would be serious nulls and peaks at every point in the room, as a concave surface focus's sound to the center point. What happens there is anyones guess, but I know for a fact, all reflections would still be focused there. Convex surfaces on the other hand, diffuse sound. Hence convex diffuser panels. If you had a flat ceiling parallel to the floor, the modal response for that dimension would probably dominante the room acoustics. Thats just a guess though. Who knows? But then, you would end up with flat panels at doors and the window, which would probably also cause predominate reflections. Ever tried to build a door jamb for a curved wall? I have. NO fun, especilally when it comes to the header jamb and trim. Baseboard isn't to bad, if you use veneered MDF. But the real test is curving and fastening drywall. Its a BITCH!! I don't think you would like that either Believe me, I"VE done it. ARRRRRGGGGGGGGGGGGGGGRRRR!!!!

fitZ

 

[RICK FITZPATRICK]

Ok, I think I figured out your intent. The emphasis is on "think" Anyway, here is a quicky basic layout just to check if we are on the same page . If this works, let me know. Couple of things though, I drew soffets AND near fields not knowing what your situation is. Also, doors.....where? A dimension of the right existing wall to the corner of where it makes a right angle turn? Access to the water heater and stuff? Any window at the front(are you going to use this room opposite the front wall for a studio or just a ?room. Anyway, lots of stuff to consider to layout a complete plan. We'll get there.
fitZ

 

[Jack Russell]

That is fantastic, Rick! Thanks a ton for taking the time to make the layout. You have nailed it. Yep, I plan on having soffit-mounted speakers in addition to near-fields. The distance from the rear existing wall along the existing wall on the right, to where the wall turns is 138" (as I look at your plan with the mixing end at the bottom). As for doors, there will be a 32-inch door on the 133' wall on the left. There will also need to be access in to the vocal room, which will be on the right (with a small window for the performer/singer to look in to the mixing area). This door, I hope to sqeeze into the 24" space where the wall jogs out on the right. This might be an issue for code, because the size of a door might require 22" for egress, which would be impossible in a 24" wall. That cold a problem to build in, although I might just make it a simple removable wall or something. Or I could plan an egress door going out at the back of the vox room to the bottom.

I don't plan on having a window at the front of the control area, since the room opposite the wall to the bottom will be a utility room. the recording/rehearsal space is behind the seat of the recording engineer (at the top of your plan).

Access to the water heater and HVAC: I will have to build in an access panel at the point on the left where the wall jogs out 24" (on the 24" wall itself), to get into the water treatment settings panel. Also, I'll need access at the bottom left corner into the HVAC space. This can be done with a door adjacent to the bottom left corner of your plan.

One thing that might be a problem is getting access to the back of the recording gear. There isn't much room left between the sides of the console and the angled walls. Thus, I'd have to climb over or under the console to get to the backs of the racks. (No, I have no patch bay, yet. hahaha.) So, perhaps I could builid in an access panel/door at the front end, when I need to get into that space? I use Adats and a rack of gear, but plan on moving into the DAW realm in the future. So then the front of the studio will have a 60-inch plasma mixing screen. HAHAHA! Just kidding!!

One other minor problem. If you look at the photo, you'll notice that there are some ducts on the ceiling, at the upper left of your plan. These will have to be soffited in, and that will drop the ceiling there from 8' 9" to 8' 0". I suppose that will mess up the 'symmetry' a bit, huh? Would you build the same soffit on the right then, just to maintain symmetry? or wing it?

A question: The soffitted monitors appear to be set into the angled walls. Is this possible?

One last thing. I figured I would angle the back wall just a bit to avoid standing waves from the front to the back. I was thinking of moving in the center of the back wall, perhaps by 3 inchs, so that it tapers back into the rear corners. Some of the reflections off the back wall could then be captured in the two 24" walls, with treatments, yes?

Thanks again for your help, Rick!
Jack

 

[Jack Russell]

Some great stuff here guys and leave it to me to interject some useless information and pointless questions but, what if; you were to build a completely round room? Would it work for listening or tracking or would it be a complete mess?

Howdy, Punkin. Neat idea. But yeah, the curved walls would kill my budget. Actually, this is in a basement of a custom house we built recently. At one point we were planning on builiding a half circle curved wall in the foyer, just to be cool. However, we began looking at the costs for labor and materials for that, and it was one of the first cost-cutting measures we took to reduce the $$$ for the whole house. Also, the curved wall took up space, over that of a wall with three angles. So, we went with a wall with three angles instead of a half circle.
-Jack

 

[Jack Russell]

Just another point about the dimensions: you have 24" on the far right, for the length of the entire space. It is actually 20 feet (133 + 108 inches).

Thanks,
Jack