John Sayers' Recording Studio Design Forum

Hi Everyone,

Firstly just like to say that this site is an incredible resource!

I was hoping for some design help on a basic small studio for voiceovers and basic foley for the production of a radio show.....

I have a concrete room in an office building 6 x 3 x 3 metres, which I know is not ideal, but was hoping I could make work somehow..
I hope to split into CR, and voiceover/foley room but was wondering on where to split the rooms to make this work the best it can.
I know two rooms of rougly 3 x 3 x 3m would create all sorts of bad room modes, would i be better off making the VO room acoustically dead like a boothe, and keeping the control room slightly larger say roughly 4 x 3 x 3 for the control room and 2 x 3 x 3 for the VO room ?

The best popular room ratio seems to be 1:1.14:1.39 , but this is difficult to make work because the width and height are very similar.

The other problem is the materials for buidling are very limited, as far as I know I cannot get any rigid fiberglass or rockwool, and will probly have to use rolls of roofing insulation or mattress foam from a company called Vita foam. The most dense foam they do is advertised at a density of 32-40 kg/m3, is this of any use acoustically ? I can also get rubber matting I think but that is about it !

I have yet to build the two outer walls in the picture aswell, would offsetting the angle a few degrees improve the acoutics ?

I could possibly install a drop ceiling aswell although the tiles would probably be the normal type rather than acoustically rated.

Thanks

I may only have 5x3x3m is this too small for a CR and overdub/foley booth ?

That's a nice size for a control room... by itself! If you had another similar size space you could put the Foley booth in there.

But, if that's the space you have, then that's what it will have to be. I'm skeptical that you'd be able to split it successfully (it's just too small), so maybe one option is to build it as a single-room studio. However, that has drawbacks for Foley work. One of the basic requirements for Foley is silence. Absolute silence. You sometimes need to record some pretty quite things, then crank that up to very high levels, so any background noise gets cranked along with it, including HVAC noise, distant traffic rumble, and the sound of the equipment in the room (hard disks, cooling fans, etc.). So doing Foley work inside the control rooms means that your control room needs to have disk-less and fan-less equipment, or you need to put all the equipment outside the room, or otherwise isolate it.

That also implies a high level of isolation for the room itself, which takes up space.

Have you taken any sound level measurements in that room as it is right now, to see what kind of ambient levels you might be dealing with? You say this is inside an office building, so I imagine there will be structure-borne noises that you'll have to deal with: elevators, doors opening and closing, people walking, plumbing, pumps, motors, maybe traffic sounds if you are on a busy street, etc. There might also be airborne sounds, such as phones, talking, music, etc. The first thing I'd do is do some tests in the room as it is currently, hopefully with a spectrum analyzer or RTA to get an idea of not just the levels, but also the frequencies: it's one thing to isolate a 70 dB peak from a hissing compressed air line, and quite another thing to isolate a 70 dB low frequency peak from an elevator rumbling past your room...


You didn't mention: is this room on the lowest level (basement, parking level, etc.) of the building, or is it up high somewhere?


You MIGHT be able to split it like that, using the basic concepts of John's small 3D studio design, but what John doesn't show on there is the isolation that you'd need for a decent Foley studio.

There's a reason for that: When all 3 dimensions are very close to each other, then you don't have a usable ratio, period! The entire point of looking at ratios is to ensure that your room modes are spread out evenly. If all 3 dimensions are similar, then by definition your room modes are NOT spread out evenly! They are all clumped close together, with big gaps in between. There ARE no ratios better than Louden's for rooms with similar dimensions: That's the best there is. There are other plenty of other ratios for rooms with very different dimensions, but the one you mention is as good as it gets for rooms with similar dimensions. Any closer than that, and the modal spread just gets to be very problematic.

Depends on what you want to achieve! If your reason for splaying the walls is to control flutter echo, then yes, that's one way of doing it, provided that you there is a difference of at least 12° total between opposite surfaces (6° on each side, or example). But if your plan is to design an RFZ based control room, then you'll need much larger angles for a small space like that. If you are trying to deal with the modal issues by splaying the walls, that might help too, but predicting the outcome is beyond the realm of spreadsheets and simple equations: As soon as the room becomes non-rectangular, all those normal mode calculators go out the window, and it's time to call in the FEM/FEA expert, with some powerful software, if you want accurate predictions. On the other hand, if your reason for angling the walls is just to try to make good use of space, by making one room wider where the other can be narrow, then you can do that too, and there might or might not be acoustic benefits to that. It all depends on so many factors.... Hard to say, without seeing the actual plan of what you have in mind.

Drop ceilings are not much use in studios, for either isolation or for treatment. Actually, they are no use at all for isolation, and very limited use for acoustic treatment. Most types of acoustic ceiling tiles are designed for typical office applications, which is moderate levels of mid range sounds (people talking, phones ringing, HVAC air movement, computer fans, photocopiers, etc). Studios don't have moderate levels of mid range: They have very loud levels of ALL ranges, and especially in the low end. Ordinary acoustic tiles don't have much effect on that.

So, I guess the real question is: How good does this studio have to be? If this is just a hobby studio, fooling around with Foley to get the hang of it, then you are probably just fine with doing a single large room (or even two very, very small rooms). Ditto if the building you are in is very quite already and doesn't need much additional isolation. But if this is meant to be a professional Foley studio for high-end film work, then I'm not so convinced that it would work out.

Maybe you can explain a bit more about your goals for this room, and also what budget you have in mind.


- Stuart -

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

Thanks a lot stuart for the very detailed reply, fantastic!

Does it matter that the inner leafs are not de-coupled from the thick concrete walls?

If I built all inner leafs using the inside out wall method would that give me enough isolation (there will be an office on other side of double framed wall) ?

Thanks !!!!

Really need some help on this one! I don't want to add an inner leaf around the concrete wall because it will decrease the width of the room which is already very narrow (2.7m).
thanks

Define "enough"!

What I mean by that is that before you can do anything, you MUST do some real-world testing with a sound level meter, speakers, instruments, implements, and ears. You need to answer the single, basic, most important of all questions: How much isolation do you need, in terms of decibels of transmission loss? (dB of TL).

You do that by answering two other questions: 1) How loud are you? (measure decibels with meter). 2) How quiet do you need to be? (measure decibels with meter). The difference between those two numbers is how much isolation you need, in objective, scientific, physical, real-world terms.

With that number in hand ONLY THEN can you look at construction methods, materials, methods, techniques, spaces, etc. There are several publications that you can look at with literally hundreds o different ways of building walls, floors, ceilings, windows, doors and HVAC systems, so you can page through those until you see something that provides the level of isolation you need, and that also fits your space, and that also fits your budget. That's the logical way of going about things. If you don't know how much isolation you need, then nobody ca tell you if what you propose is "good enough" to attain it!

You mention that you want to do Foley work, and that it will be for professional broadcast (albeit on radio), so that implies that you need QUIET in there. The issue with Foley is that you often need to record very quiet things, then amplify that to make it sound really loud. So if, for example, you have a pit set up with gravel in it, and you are walking on that to simulate the sound of someone walking outdoors on rough ground, then you need to make that much louder to get it convincing for your radio show. If you push up the gain, you amplify the soft crunchy, gravelly sounds, but you also amplify the distant background sound of the toilet flushing in another room, and the dog barking next door, and the ambulance going past six blocks away! If you were recording drums or electric guitar, that stuff most likely wouldn't matter, since it would be totally drowned out by the instruments themselves. But for Foley it is critical: Broadcasting the sound of the neighbors dogs and your toilet, along with the gravel, is probably not what you wanted!

So for Foley work, really good isolation is important. You need your structure to isolate well enough that your mics will never pick up even faint sounds from outside the room, as those could end up audible in the final product.

OK, so getting back to your proposed incomplete isolation shell. Here's the question: Are there any noises at all going on in the building, that you do not want to record? You say this is an office building, so my guess is that there are doors opening and closing, people walking around, water running, phones ringing, pumps and fans running, traffic arriving and leaving, elevators rising and descending, and any other number of sounds that are very likely not just airborne, but also structure-borne. Meaning that they are causing the structure of the building itself to vibrate. Once the vibration is in the building structure, then you have a problem: Solid things transmit sound very well, and the harder they are, the better they transmit sound. Much, much better than air. Ever see the old cliche of someone putting their ear to a train track, to hear if train is coming? That works because the vibration in the track can travel MILES through the solid steel, but no more than a few hundred yards through air. You can hear the train on the tracks LONG before you hear it through the air. Sound also travels much faster through solids than trough air.

So look at it this way: with your plan, you have bare concrete building wall fully exposed on each of your rooms. Any sounds that are present in the building structure, will be present in those walls, and particularly low-frequency sounds (traffic rumble, machinery, pumps, a helicopter flying overhead, etc.) and impact sounds (footsteps on floors, doors slamming, things dropped, water hammer in pipes, etc.) will be clearly audible in those walls.

Personally, I very much doubt that you could build a Foley studio like that. There's just too much chance for those sounds to be picked up.

If this were just a rehearsal room for a band, or a hobby studio for playing around, then you might be fine like that (although then outgoing sound might be an issue!) but for a professional Foley studio, I don't see that happening successfully in an office building where the building walls are directly exposed to the room.

If space is the issue, then use the techniques for increasing isolation without losing so much space! Use higher density materials, use inside-out construction, use more layers of mass, etc.

- Stuart -

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

Great stuff, thanks!

Unfortunately I cannot take any dB measurements (I'm in the UK!) and I'm just working with what my friend in Kenya has told me....
By the time I get out there in two weeks wall constructions will be completed... We are having to work quickly with limited planning, the studio will record mainly dialogue for radio drama, isolation does not need to be perfect. Also the broadcasting standards over there are lower than the US or UK.

I have 3 options when it comes to constructing the isolation shell
1. Build a partial shell as in the picture from last post.
2. Build a fully isolated frame that will deduct 200mm from width of control room (2.5m resulting width), and 200mm from width of live room (2.5m resulting width). This is still a partial shell because there is no floated floor or ceiling.
3. Same as 2, but build inner shell inside out to save a little space.

Good acoustics are generally more important than isolation given that we will be recording groups of voice actors mainly, and given that these are very small rooms anyway, I'm leaning towards option 1.

Would option 2 really give me a lot more isolation than 1 considering that there will be no floating floor or ceiling (will not be a full isolation shell anyway)?

I have attached a plan showing the proposed room dimensions. The Live room must be big enough for a few actors to work in so we have had to cut down the size of the CR. Dimensions are 3.5Lx2.7Wx3H LR, and 2.5Lx2.7Wx3H CR. The grouping on these room modes seems to be the best I can get for the overall dimensions and practical considerations.

I have also though about splaying the partition wall 10-15 degrees for practical and acoustic reasons, although I understand there is a lot of differing opinion about the acoustic advantages on here. The one main disadvantage seems to be the unpredictability of the room modes. For this reason I'm leaning towards a perpendicular wall which will also be easier to construct. I have attached a straight wall design and a 10 degree splayed wall design. The splayed wall seems to work better practically making better use of the space but I am worried because the room modes are unpredictable…

Any input on the design greatly appreciated!

Hi mate,

Sorry for barging into your thread, but I am somewhat in a similar situation, except my space might be even smaller than yours.

If you already have the space constructed and fully functional, could you please let us (me) know how it turn out?

What is your final dimension for your control room and iso booths, and will you be kind enough to show us (me) some photos (of your studios) for inspiration?

Thanks so much!

Regards,
[Charles]

Thanks a lot to stuart for helping me with this project which is now finished! There were a lot of problems along the way but we got there in the end...
Acoustic treatment was done with hanging broadband panels and clouds- nothing too complex!

Charles- the final dimensions were not ideal at all. the control room turned out to be 2.7x3m, and the live room about 5x2.7m. We went with a perpendicular wall in the end seperating the two room as with the angled wall room modes are obviously unpredicatable. We were more concerned with making the live room sound good because when recording dialogue for radio, the mixing process is not as important obviously as with music... Using small speakers the Control room actually sounds not bad at all (maybe becaues of the high ceiling height). Good luck with your project