John Sayers' Recording Studio Design Forum

Hello All,

I have spent the past weeks reading over this and other forums trying to decide to decide on details of my studio build. I still have some general questions to ask but I have done my best to compile the information that is necessary to request input on this site. I will do my best below.

I have a two car garage that is 24' wide, 23' deep and 8'4" high. There are a few structural challenges. First, there are the two bay doors, each 9' wide on the 24' wall. (These will be walled up before other construction.) The other 24' wall has two doors on it. One is situated 7'9" from the right wall and is 3' wide and 6' 6" tall. The second is 5' from the left wall and is 2' wide 6'6" tall. Behind these doors are the laundry room and the AC room respectively.

From that back wall with the two doors there is a three foot span forward then a 3" ledge down in the concrete floor. From there forward there is a gradual 6" drop to the bay doors. (I could not get that into sketch up. I am just learning to use the program.)

Finally, from that same back wall 7'9" forward on the ceiling there is a beam that runs across the length of the ceiling. This beam is 24' x 5" x 11".

The floors are a concrete slab shared with the main house. The walls are wood beam and drywall of the standard width (6"). The ceiling is also drywall hung on wood beam supports. Out the front is the driveway (obviously) one wall is backed by a red brick face that heads out to a quiet street. As said before the back wall leads to the laundry room and the AC/Waterheater room. The final wall is backed by the dining room (used as a video game den for my 4 boys).

I don't know much about measuring sound... I have a meter that came as a "gift" with some equipment purchased a few years back. I played my guitar at the loudest levels I ever had and it reached 111 db with me in the room. I think I will want about 40-50db of transmission loss (if possible).

I was thinking of a control room plus a single studio room.

I record most types of pop music. Mostly singer songwriter type stuff and pop rock. I will use the main studio area as a place to play with friends (me + 3) and write.

I am open to ideas... but attached is what I was thinking up to this point.

My questions:
1. When talking of floating a floor I have read a lot about neoprene feet, but have not found a place to purchase them. Any ideas?

2. When reading of leaf wall construction, I understand that double leaf is better than more. Where I am fuzzy is, is this true in all circumstances or only when an equal number of drywall layers are concerned? i.e. four layers... one on each side of two separate walls v.s. four layers two on one side of one wall and two on one side of the other of the second wall.

What if there was one existing wall (drywall on both sides) and then another framed wall with three layers of drywall on one side? (so a total of 5 layers of drywall but with 2 air gaps.) Would four layers with one air gap be better than 5 layers with two?

Thanks for any and all input!

Hi "LilJimyG", and Welcome!


Why do you need a floating floor? You said that you already have a concrete slab-on-grade floor, and that you only need about 40 to 50 dB of isolation, so why do you think that you need to float your floor? You didn't mention your budget, but floating your floor properly is a rather major expense... You also have a limit on your ceiling height already, with that low beam running across the entire space, so losing all that additional height for a floated floor doesn't seem like a good idea to me.

Set the meter to "C" weighting and slow response, and hold it out in front of you when you measure, angled upwards at maybe 30 to 45°. If you are measuring a speaker or instrument, then take the reading with the sound level meter at least one meter (3 feet) away from the sound source. That's about all you need to do to get reasonable readings.

What type of instruments? Acoustic drums, for example? Bass with good amp and speaker? Percussion? Keyboards?

It is true always. Two-leaf fully decoupled MSM is the easiest and least expensive way of getting good isolation across most of the spectrum. It's not the ONLY way, but it certainly is the easiest, most practical, and least expensive. Wrapping a single layer of 1/2" sheet lead around your room will give you excellent soundproofing, for example, but you'd probably have to sell the house, the car and all your gear to be able to buy that much lead...

An MSM wall is a tuned system. The mass on each side is the two "M"s, and the air in the middle is the "S" for "spring". It isolates because it is a tuned band-pass filter. It allows sound through at a certain frequency (the one it is tuned to) and blocks sound progressively better at all frequencies above 1.4 times the tuning. So you tune it such that the the resonant frequency is at least 1.4 times lower than the lowest frequency you need to isolate.

You get optimum results when the mass on the two leaves is equal (for example, 3 layers of drywall on each of the two leaves, for a total of six layers. If you were to make that 1 layer on one side and 5 layers on the other side, then it is no longer isolating optimally, even though the total mass and air depth are the same.

And if you move some of those layers to create a third leaf in then middle (for example, "2 - gap -1 - gap - 3", then you mess up the tuning: You now have two resonant frequencies, f+ and f-, and they are BOTH higher than the frequency of the original wall, so it isolates WORSE at low frequencies: Hard to get your head around, but true nevertheless.

So a two leaf wall with equal distribution of mass will always give you better results than any other arrangement.

That would be a three leaf system: "MSMSM". To fix that, take the drywall off one side of the first wall, and move it to the other side of the first wall. That would make a big difference in isolation.

Yes, under practically all realistic circumstances. If you are talking about the same total thickness of the wall, then having "2 - gap - 2" would be better than "2 - gap - 1 - gap - 2", especially in the low frequencies.

Take a look at the following, to see how this works:



What you describe is roughly the same as going from the 4th to 5th case in that diagram (three-leaf to two-leaf). OK, so the diagram is about STC, which isn't a good measure for studios anyway, so the actual TL numbers would be even better than shown there (ie, the difference between the two scenarios would be even greater), but it still give you an idea.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Wow, thank you!

I am glad to hear your input on the floating floor. I was looking at it because I read in an article that because the foundation is shared with the home that the vibrations would be an issue. I would rather not loose the space or money doing it.

As for budget I am working with $4000 now and I will have another $5000 in October. All is for the room and treatment. I have the equipment I need for now.

Instruments

I have a Roland TD-12 Digital drum kit for drums
I have a 800 watt Workingman bass amp though when I record I route it via a direct box. (not mic'd)
I play my electric guitars through either my Line 6 Pod XT, my Spider amp, or my Mesa Boogie 5/25
I have a digital stage piano, again through a direct box
I also will amp the drums and piano through a 500 watt PA when playing aloud.

I am not fond of playing at loud volume.

Along with that I have a range of acoustic instruments, hand percussion, guitars, bass, double bass (though I have never recorded this), mandolin, ukelele... act.

Of course vocals.

Thanks for the info on the walls...

I feel I can move forward with my planning now.

Any further input of course would be greatly appreciated.

Thanks again!

More input on floated floors, for example?

This is why you probably don't need one:

viewtopic.php?f=2&t=8173

And of you want to really get into the theory of how a floating floor works, and how to do it right, and how bad it is if you do it wrong, then this one might help:

http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir802.pdf


I'm looking forward to seeing your design and your build!


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

The problem, you may experience, is not so much your music propagating into the rest of the house - the which sound is predominantely airborne, and percussion can usually be adequately tamed using vinyl or rubber mats (e.g. stall-matts) or even a section of carpet, but rather mechanical vibrations coming into the studio wrecking a recording session. Modern construction in view of energy/heat conservation no longer pur the slab onto earth but often have a layer of insulation -which although good for heat conservation is bad for structure born vibration. I've seen people recommend cutting the slab thereby decoupling from the rest of the house - but you'd have to judge how severe a problem this would be for you.

_________________
Brian
As you slide down the bannister of life, may the splinters never point the wrong way...

Not to much of an update but here goes...

I got the garrage cleaned out!

I know, I know... it shouldn't be that big of a step but it took a lot more effort than it should have.

I will be walling in the bay doors this weekend. Ideally I would do that last but as the cost of this project is considerably more than I expected I will have to do it in stages as the money permits. In the meantime I want a place to play... Perhaps I will make one of them modular so I can pull it off when the construction begins.

The next phase will be to pull all the drywall off the garrage side of the existing walls and trim it so I can seat it between the studs right against the the outter layer and seal that up good and tight.

Then seal the cieling up. That is about all I have the budget for for the next couple months. As I am doing all the work by myself that should be plenty.

I have a few different general plans floating around in my head but have some basic questions on them and would love some input.

The first would be two similarly sized rooms, one for the control room and the other for the tracking. These rooms would each be 10' x 18' with 8'ish ceilings (The floor slopes towards the front of the rooms from about 8' to 8'9") I will taper the walls so that they are not parallel but still keep symmetry. This idea is a little more expensive but also easier to break up into managable stages...

The second option will be a 14' x 22' x 8'ish (this time sloping to the right) contol/tracking room with a 6' x 6' x 8' vocal booth. This option will be cheaper, give me more volume for my control room and be the easier build. However unless I create a subfloor to level the drop in the concrete ($$) it will not be exactly symmetrical because of the sloping floor. Nor, will it be as ideal of a ratio as far as room modes are concerened.

All of these measurments are without any treatment in the room as well. Also I have wiggle room to change any of the demensions except the height by up to 8".

My questions being:

1) Is the extra volume worth the less ideal symmetry and ratio?
2) If I were to do the smaller control room, would it be better to have the "higher ceiling" (really lower floor) at the desk or in the back of the room?
3) Being that all and all I think I would perfer the larger control room (As this is a hobby and not a proffesion I don't NEED an seperate tracking room.) is the room shape of the larger room 14' x 22' bad? How much should I concern myself with these ratios and the floor breaking the exact symetry?

Thanks for all the input guys. I really appresiate it.

Splaying walls has its benefits, and symmetry is important for control rooms, so that's a good idea. However, the amount of splay depends on what you are trying to accomplish: is this just for flutter echo, or are you aiming for an RFZ design? Or some other reason?

I'd go with symmetry and ratio over volume, in this case. ITU and EBU recommendations for critical listening rooms is 1500 ft3. You are pretty much there with your first option ("10' x 18' with 8'ish"), plenty close enough. Symmetry is critical, at least for the front half of the room, and ratios are somewhat important, so I reckon the first option is better, especially if it allows you to splay your inner-leaf walls easily and still get close to the recommended volume.

The room should be smallest where the speakers are, and biggest at the back: Think of it like a funnel. so your desk should go where the ceiling height is lowest and the side walls are closest together, expanding to larger dimensions the further you go back.

That's not a very good ratio. The Bonello graph looks like the mountains of the moon! Up and down, all over the place. It probably could be improved with adjustments to the walls, but if that's all you can get for the final dimensions of the inner leaf, then it's not a pretty picture!


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Thanks again for the input.

The only real reason for splaying the walls is because, from what reading I have done, parallel walls in a control room = bad. Seemed the easiest way to make sure they were not parallel. Most of what I read had to due with flutter echo. I will have to read on RFZ design because I am not sure what that is.

As the learning curve is steep here for me. I have to admit, some of what I am trying to do is based off of general recommendations in reading... I am trying to wrap my head around all of this but, for fear of missing something, am trying to incorporate as much "conventional wisdom" as I can. (sometimes it seems going back to sitting in my bedroom with a tape recorder and my accoustic is more my speed )

The good news is, I still have time! I will keep my nose to the grindstone and keep learning.

Thanks for all the help!

Yeah, the learning curve for this whole "acoustics" thing sure is steep! It does take quite a while. At least, for me it does. I first had to "unlearn" all the stuff that I just "knew" was right but turned out to be oh-so-wrong, then start re-learning how sound really works. So I fully, totally sympathize with you! But don't worry: after a while, it all starts coming together and making more sense.

"RFZ" means "Reflection Free Zone" and is a design concept where the idea is that the room is arranged to keep early reflections totally away from the mix position (you, sitting in your chair). <the original goal was that you'd only hear direct sound form the speakers, nothing else, and that no reflections would get back to your ears until at least 20ms after the direct sound, and even then they had to be 20 dB quieter. That is sometimes called the "20/20" criteria. It turns out that it's pretty hard to do that in small studios, and the "15/15" criteria makes more sense: no reflections for 15 ms, and even then 15 dB lower. And for really small rooms, probably the best is to aim for "10/10": No reflections for 10 ms, and 10 dB down. Even 10/10 will still give you reasonable clarity, and is worth aiming for.

So how do you do that? One of the key things is to angle the side walls and the ceiling so that the first reflections from the speakers cannot even get to the mix position: the angles are chosen so that the first reflections completely bypass your head, and go off only towards the side walls or the rear wall. So the next part is to then treat the side walls and rear wall heavily, to ensure the 10 dB (or 15dB or 20 dB) reduction in level. That is normally done with absorption and more angles, and maybe with some form of diffusion (if the room is big enough for diffusion to work). So that's the basic idea: keep the reflections away, and attenuate them. Of course, doing that ain't so easy! In a large room the walls don't need to be angled much in order to meet the goal, but in a small room, the side walls are really close to the speakers and to your head, so you need large angles to attain a true RFZ. So there's no rule there about how much to angle the walls: You have to "ray trace" imaginary lines coming out from your speakers, and see where they go, figure out the bounce angle, and so on. You need to do that with a "cone" of rays, in all 3 dimensions, to make sure that you really do have an RFZ. The angle you end up with will be different for every room.

But if RFZ is not your goal, and you are only going after flutter echo, then the general rule is that you need an angle of 12° or more. That means that, for the walls, you can splay them 6° on each side (total of 12), and for the ceiling, well, that has to be 12° or more all by itself, since "splaying" the floor is rather problematic!

The good news is that if you splay enough for a true RFZ design, then you automatically have also splayed enough for flutter echo!

And if you are going after modal behavior, splaying the walls will certainly change that, but it's a two-edged sword: As soon as you angle your walls and/or ceiling, you can no longer use the many "room mode calculators" that are floating around, since they are only valid for totally rectangular rooms. When you boil it down to basics, this whole "room modes" and "ratios" and "spread" thing is just about paths around the room. Any time that there is a path around the room for a particular frequency (=note, =tone) where the sound wave gets back to its starting point in phase with itself, then you have a "mode". The room itself will vibrate naturally at that frequency. The sound wave that follows that path around the room for a few trips is said to set up a "standing wave", where the pressure dips and peaks always fall at the same points in the room on each trip around. The room sort of "stores energy" in that standing wave, and when the note cuts off, the energy still carries on around a few more times. So the room "rings" at those specific frequencies where these paths can occur. Obviously, there are an infinite number of such paths around the room! For high frequencies, practically any imaginable path is a "mode", and in reality, that doesn't matter. If there were a mode for every single frequency from 20 Hz to 20,000 Hz, that would be great, since the room would react the same to all frequencies. And for really large rooms, that works. But for small rooms, it doesn't. The smaller the room, the fewer "modes" there are at low frequencies, since there are fewer paths that you can find around a room that exactly fit a certain wavelength. For average "home studio" type rooms, the problems are always below about 300 Hz, and more sever the lower you go. Small rooms just cannot support low frequencies. For example, a room that is 17 m long can support a 20 Hz mode, since that's how long the wave is. But a room only 4 m long simply has no modes where a 20 Hz wave will fit, so there are no modes for it. There is no path that a 20 Hz wave can take around that room and still get back to its starting point in phase with itself. So it is said that the room cannot "support" a 20 Hz tone. And that's the problem: It tuns out that small rooms can only support a very small number of modes, which is bad because whenever one of those few tones is played, the room sing along with it, amplifying it, while it does nothing to all the other tones. So the room itself enhances certain notes, favoring them over others. The idea, then, is to choose your room dimensions so that the modes are spread around evenly across the spectrum, and not all clumped together. If you were to build a cube, with all sides measuring 2.5 m, then you would have a terrible situation, since the axial modes for all three directions will line up perfectly: the room will REALLY sing for notes that fit, and will do noting for others. That's what "room ratios" are all about: finding a set of relationships between length, width and height that spreads the modes around as evenly as possible. There are numerous spread sheets and calculators on-line that you can use to see how well your ratio is working out. It turns out there is no such thing as a "perfect" ratio, or "golden" ratio, despite what you read on some audiophile web sites and in magazines. There are good ratios and there are bad ratios, and you don't need to go crazy hunting for something that does not exist. The idea is to stay away from the bad ones, and get close to one of the good ones. Done!

But if you SPLAY a wall, then obviously things change: The sound waves now take different paths, and are reflected at different angles around the room. The modes are still there, but a bit different. If you angle one wall, then any mode associated with that wall now takes a different path: For some modes the path might be longer, and for other modes it might be shorter. so angling a wall changes the modal behavior of the room, moving the modes to different frequencies: That might be good, and it might be bad: But the problem here is that the calculators only work for rectangular rooms with parallel walls. As soon as one wall is not parallel, then the calculators are no longer accurate. You can't even put the numbers in! If your wall is splayed, then it is no longer 3 m from the other wall: it is a bit closer at one end, and a it further away at the other, so which distance do you put in the calculator? See the problem?

But it's not a huge issue: for small splay angles, then you can just use the average distance, and the results won't be too far off. And in any case, modes are not that big an issue: as long as your room is not a cube, and not close to square in any cross section, and the dimensions are not close to each other or related to each other, that's probably god enough. So the rule is aim to stay away from bad ratios, try to get close to one of the known "good" ratios, and that's all you need to do. There are other important things to consider, and hunting for the Holy Grail of the "perfect" ratio (like some home theater folks and audiophile nuts try to do) is pointless: there is no such thing.



I'm not sure if these two books are on your reading list, but they are kind of "sacred" around here:

"Master Handbook of Acoustics", by F. Alton Everest
"Home Recording Studio: Build it Like the Pros", by Rod Gervais

Read those two, and you'll have a really, really good basis for getting your head around this stuff. "MHoA" (the first one) gives you the basis for how sound works and how to design rooms and treatment, while "Rod's Book" (the second one) is more about the practical "buts and bolts" side of how to actually build the place. Between them, you get a really solid basis: and the good thing is that Rod is a member here, and occasionally posts on the forum, so you might be able to get his comments too.

And the forum itself is a true treasure trove of great information on studios. There is a huge amount of information here, most of it backed up by solid science, which is very different from some other forums on the internet, which seem to be powered by snake oil. If you spend some time just poking around, and using the search feature, you'll come up with more data than you ever wanted on pretty much any aspect of studio design and construction.

And of course, feel free to post updates to your design, and all the questions you want! That's what this place is all about: home studio people learning about building home studios, and helping out others who are doing the same. The only dumb question here, is the one you didn't ask!


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.