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In reality:
No, you don't! It is not necessary to angle (or "splay") your studio walls. It's a myth.
There are many reasons often given by people, about why walls supposedly must be angled or "splayed" in a recording studio, among them:
- 1. "To get rid of standing waves"
- 2. "It will sound better"
- 3. "Gets rid of flutter echo"
- 4. "Makes the room sound bigger"
- 5. "Because everyone does that"
- 6. "Makes the room sound wider"
- 7. "To reflect sound away from the mix position"
- 8. "To stop the bass building up in the corners"
Except that in reality they do NOT need to be angled. Of that list above, only #3 and #7 on that list have any truth to them: Let's look at all of them in order:
#1. "Angled walls get rid of standing waves". Ummm... no, they don't. I'll deal with that one right at the end of this article, as it needs a bit of space to explain.
#2. "Angled walls will make it sound better". Ummm... no, it won't. There's nothing special about angling a wall that will make the room "sound better". In fact, control rooms should not "sound better", or even "sound good" at all! The purpose of a control room is that is has no sound of it's own... it must be totally neutral, natural, transparent... it must sound as though it is not even there. It must not add anything to the sound coming from the speakers, and it must not take anything away. Thus, doing something to the control room to make it "sound good", is actually a bad idea. Even if splaying the walls could do this, it would be incorrect to do it.
#3. "Angled walls kill Flutter echo". Yes, this one is true. Angled walls can, indeed, eliminate "flutter echo". That's the sort of rapidly repeating "zingy" sound that you sometimes hear if you clap your hands sharply in an empty room with parallel walls. It happens because the sound zips back and forth across the room, bouncing between the side walls, as a repeating series of echos, and each time the "package" of sound waves rushes past your head, you hear it. But it happens so fast, that it sounds like a slightly reverberant hollow "buzz" or "zing". If you angle the walls, that can eliminate flutter. True.
However... In order to prevent flutter, the total angle has to be about 10° to 15°. The suggested number often mentioned is 12°. So you could angle one wall at 3° and the other at 9°, or both at 6°, or one at 12°, or whatever, as long as the total difference is 12° or more. In some rooms, you might be able to get away with 10°, but 12° works pretty much always. In extreme case, you might need as much as 15° total.
OK, so let's say you do angle your walls at 12° in your room: What did you accomplish? Well firstly, you wasted a hell of a lot of space!
Let's assume that your room measures 5m long by 4m wide (about 16' 5" long x 13' 2" wide): So your left side wall is 5m long, and you angle it 12°... well, that means you have lost nearly 2.7 m2 from the room (about 29 square feet)! It also means that one end of the room is now more than one meter (3 feet) narrower than the other end. Can you afford to waste that much space? Here's a diagram that demonstrates this issue clearly: As you can see, that's a LOT of wasted space! You have lost more than thirteen percent of your entire floor area! (For clarity, the diagram shows just one wall angled at 12°, but it's the same if you angle two walls each at 6°).
Second, angling your walls makes construction more complicated: try to get a typical house framer to build a wall at 12°, instead of 0° or 90°, and see how that works out...
Third, it isn't even necessary! There are several other ways of dealing with flutter echo that do not require complicated construction and wasted space. Flutter echo isn't hard to treat with simple acosutic absorption or diffusion panels on the walls and ceiling. In fact, you will need to put acoustic treatment on the side walls and ceiling of the room in any case, for other reasons, and those will also kill the flutter quite effectively. So there's no need to angle the walls for flutter echo.
#4. "Angled walls will make it sound bigger". Ummm... Actually, no. The opposite is true. Since angling the walls makes the room smaller, that also means that it sounds smaller! A small room can never sound like a bigger one. Simple physics.
#5. "Walls must be angled because everyone does it". Ummm... no. Not true. Those who insist that studios must always have angled walls to be any good, and that all the big studios do it, should probably take a look at places like Abbey Road, Galaxy, and Blackbird.... those are often considered among the best in the world, yet their main tracking and mixing rooms are pure rectangular boxes, with parallel walls, floor, and ceiling...
#6. "Angled walls will make it sound wider, more spacious". Ummm... Actually, no. Just like with #4, if you angle the side walls, then part of the room gets narrower, not wider! And the angle might even create additional psycho-acoustic issues that make it sound narrower still, or mess up your perception of where the sound is coming from... Not good, for a control room.
#7. "Angled walls reflect sound away from the mix position". This is also true... sort of! Some control room design concepts do, indeed, require angled wall surfaces, for this very reason: to reflect unwanted sound away from the mix engineer at the console, so that he does not hear it. The RFZ, NER and CID room design concepts call for this, and it is also often used in other design concepts, such as the now-obsolete LEDE concept. If you look at photos of such rooms (for example, this one, which is an RFZ style design:
... Except that the actual walls of that room are NOT angled! In fact, the room is rectangular, and the surfaces you see there were built inside the room. Here's a view of some of the framing behind that front section.
Thus, even for these control room design concepts that require angled reflection surfaces, the room itself is almost always rectangular, and then additional surfaces are added into the room at strategic locations, to provide the necessary reflections. So even in those cases where angled walls are part of the design, the walls are not actually angled! Other things are, but the walls aren't.
#8. "Angled walls prevent the bass building up in the room corners". Ummm.., no, they don't. All room modes terminate in corners (or against walls, which happen to end in corners), so the bass will ALWAYS be loudest in the corners. There's nothing you can do to prevent that... except build a spherical room, with no corners! Which would sound really awful, for other reasons.
OK, so let's look at the other valid reasons on the list... Oh but wait! There are no other valid reasons on the list! ... Oooops!... Therefore: Angling your walls does not make the room sound bigger, better or wider, it does not eliminate standing waves (which would be a bad idea, even if it did work), it does not "stop the bass building up in the corners" (whatever that means!), and no, not "everybody" does it. In fact, people who understand acoustics well do NOT do it.
So no, it is a myth that you need to angle your room walls.
Let's look at it from the opposite side: Here's what happens if you do angle your walls:
1. You waste a lot of space (as you can see from the top diagram above). Between 10% and maybe 20% of your entire floor area is wasted for nothing. And with the cost of building or renting being so high, that is rather silly. Why would you want to pay rent for or building costs for floor area that you can never use?
2. You make it more complicated to build: Framing carpenters are really good at making 90° corners in rooms. They can probably also do 60°, 45° and 30° corners reasonably well, if they have to... but try getting one to do a pair of 6° angled walls on opposite sides of the room, keeping them precise, accurate, and symmetrical! Good luck with that. Even if you can find a master framer that can do that well, the cost will be higher, and it will take longer to do.
3. You make it harder to predict the modal response of the room. MUCH harder. There are a number of "room ratio calculators" and "room mode calculators" on the internet, that you can use to predict various things about your room, based on the dimensions. However, they ONLY work for purely rectangular rooms, with six sides (4 walls, 1 ceiling, 1 floor). As soon as you angle one wall, or add an extra wall in somewhere, those calculators are no longer valid. So you cannot predict what the modal response will be. Thus, you cannot choose a good room ratio.
4. You make it harder to fit in furniture. Control rooms very often have a "client couch" at the rear, and if the room is wide enough, there might be small coffee tables on each side of that.... Have you ever found a nice sofa or coffee table that has the sides angled at 6°? Have you ever tried to fit a normal sofa or coffee table into a corner that is angled? Good luck with that! And if you wanted to put a rack of gear back there... Hmmm.... I've never seen a rack with a 12° angle on one side... And even if there was, I think you'd have a hard time finding angled gear to fit in your angled rack!
So there you have four very weighty reasons why it is a BAD idea to angle the walls of your control room, or even of your live room. There is no need to do that.
To finish, let's take a closer look at that stubbornly persistent #1 "reason" on that list: "Angling your walls gets rid of standing waves (room modes)". Here's a long and very detailed article about room modes, standing waves, room ratios, and dimensions, with more info about that: "I have too many room modes" ), but for our purposes here, I'll keep it simple: Firstly, "room modes" and "standing waves" are the exact same thing. Both terms refer to the way a sound wave can bounce back and forth between walls, if it is exactly synchronized with itself, quickly building up strength into a form of resonance. This happens in ALL rooms, regardless of shape or size, and occurs at certain very specific frequencies that exactly match the distance between the boundaries of the room (walls, floor, ceiling). If the distance between two of those boundaries is exactly half the wavelength of any given tone, then you get a "standing wave" at that frequency. That's a confusing term, actually, because it makes you think that the wave is not moving: it is just "standing still" in the room, motionless, but that's not true, of course: the wave is still rushing back an forth across the room at the speed of sound, which is 343 meters per second (1,125 feet per second), so the wave is not standing still at all! It is moving really fast... The reason it is called a "standing wave" is because, each time the wave rushes across the room, its pressure peak occurs at the exact same spot in the room: So the pressure peak "stands still" from that point of view, even though the wave is still moving like any other wave.
In fact, if you play a tone that coincides with a room mode (standing wave), you can then walk around the room and hear the difference: at some points in the room your ears will be in the pressure peak, and you'll hear the tone loudly, while at other points your ears will not be in the peak, and you won't hear it at all, or it will be very soft. That's why it is called a "standing wave": because it appears to be stationary in the room, even though it isn't.
Here's an animated diagram that shows where the pressure peaks and nulls will occur in an arbitrary room for one specific type of room mode. Red indicates pressure peak (node), blue indicates pressure null (anti.node).
- room-mode-animated.gif (948.76 KiB) Viewed 26402 times
- room-mode-animated.gif (948.76 KiB) Viewed 26402 times
It's actually not too hard to calculate exactly what the full set of room modes will be for your room: here's the equation, if you want to do it by hand:
- Room-mode-equation--MHoA P327.GIF (3.45 KiB) Viewed 26402 times
- Room-mode-equation--MHoA P327.GIF (3.45 KiB) Viewed 26402 times
)Or you could just use one of the many on-line calculators that does all that hard work for you. Here are two that I use:
Bob Golds Room Mode Calculator
Andy Mel's Room Mode Calculator
OK, if you think about it, standing waves (room modes) like this are not good! If there are some spots in the room where you can hardly hear a B# played on the bass guitar, and other spots where the same note is very loud, then that's clearly not a good thing! As you play a song, what you hear would depend on where you are standing or sitting! You would hear different "versions" of the song as you move around the room... so how could you ever mix it, if you don't even know which of those versions you can hear is the right one? Is there even a right one? Big problem...
Even worse: once you stop playing that B# on the bass (or any other note that happens to coincide with a room mode), the room will carry on playing it for a while (maybe up to a second or so, in some cases), because the standing wave has "stored the energy" of that tone, and it continues to release that energy again is the wave bounces around the room, back and forth, following the same fixed path each time, until it eventually dies away. That is VERY clearly not good for a control room! You don't want the music to carry on playing after the musician or the speaker stops making it! This is why some people think that it would be good to "get rid of the modes".... but that's not true.
Thus, "room modes" seem to be really bad (that's not true either... modes are good, not bad... more on that in the article on modes and what to do about them). Those people who think it would be good to make all modes "go away" sort of remember that standing waves only form between opposite surfaces in a room, bouncing back and forth... so they figure that if you could just ANGLE one of those surfaces, then that would upset the "bounce": the wave would bounce at a different angle, going off to one side, and the mode would go away! Except that it does not work like that (and even if it did, it would not be a good idea to get rid of a mode: they are good, not bad).
The problem is that people often think of modes and sound waves sort of like rubber balls bouncing around a room, and they are sometimes even shown that way in diagrams and books. But that's not correct. Modes are not at all like bouncing rubber balls! Rather, they are like water sloshing back and forth in your bath tub or swimming pool. Sort of like this:
- water-sloshing-swimming-pool-animated.gif (1.11 MiB) Viewed 26402 times
- water-sloshing-swimming-pool-animated.gif (1.11 MiB) Viewed 26402 times
Now, imagine if you put a sheet of plywood across part of that swimming pool, so that it blocks off part of the water, making the pool not round any more, but flat in one area. Do you think that would somehow stop the effect you see there? Make it go away completely? Clearly, it would not. It would just move the peak of that wave around a bit, to a new location, that's all. Placing that angled surface in the pool, would not make the mode go away.
Getting back on track: Those people who insist that angling walls is good because it "gets rid of modes", are forgetting a minor detail: Wavelength. The frequencies where room modes are problematic, are at the very low end of the musical scale, where the wavelengths are very long: many meters (dozens of feet). The wavelength at 20 Hz, for example, is about seventeen meters.... and if you were to angle your walls at 6° in a room that is 5m long, then you have only moved the far end by half a meter... a wave that is 17 meters long does not even notice that! Hlaf a meter vs. 17 meters.... That's only 2.9% of the wavelength... not significant at all! So the mode still "sees" the wall in the exact same manner as before, and is NOT moved, killed, destroyed, attenuated, or modified at all. At best, the peak might be slightly displaced in the room, and the frequency might be slightly different, but the overall effect is ... nothing! The mode is still there.
So, to finally hammer the last nail into the coffin of the "angled wall" myth: Angling your walls does nothing useful to the room modes. It hardly even budges them, and certainly does not "get rid" of them.
Here's a diagram that shows the actual pressure gradients for one specific mode in a rectangular room (left side of diagram), as compared to another room that has the exact same floor area, but with very drastically angled walls (right side of diagram): As you can see, the mode is still there, even when TWO of the walls have major angles on them. The pressure gradient pattern is shifted, and the frequency of that mode changes a bit (from 81.1 Hz to 85.5 Hz in this case), but the mode is still there.... it did not disappear.... And those are HUGE angles on the walls!
So: Nope! Angling the walls does not make modes "go away".
Conclusion: For a control room, do not angle your walls. Rather, keep the room rectangular, which is cheaper, faster to build, maximizes floor area, maximizes room volume (very important), and makes it possible to predict acoustic response easily. For a live room, you can angle one or more walls if you want to, for other reasons, but it won't get rid of modes there either.
The only other reason you might validly want to angle your walls, is: Because it looks cool!
If you don't mind wasting the space and the money and the time and the effort, and can make sure that angling the walls won't mess up the acoustic response of your room, and you think it looks cool to do that, then... Fine! I guess.... 
- Stuart -
Thanks, Andre! While I was writing that article, I was thinking of including the "cars don't have modes" myth, but then it slipped my mind in the end. Thanks for adding that! Very pertinent.