Stockport Sound Studio Build

Continuing on from my previous threads and various studio plans that came to nothing, I have finally started construction. The basic building is a 12 metre by 8 metre steel shed, wall height is 3 metres and the roof peaks at 3.6 metres. At this stage I am lining the walls and ceiling with Soundscreen, then a layer of gyprock to keep it in place. This will be completely sealed and form the outer wall. I then plan to construct the studio, control room, drum room, vocal booth and office each as a stand alone room within a room. The control room, studio, vocal booth and drum room will use the inside out wall technique. The ceiling in the control room will slope from 2.4 metres at the front to 3 metres at the rear. The ceiling in the vocal booth will be flat at 3 metres. The ceiling in the studio will slope up for 3 metres from each side, from 3 metres to 3.3 meters with a 2 metre, flat centre section at 3.3 metres high. The drum room ceiling will be flat at 3 metres high. I have attached a floor plan, which at this stage can easily be varied if anyone can see any potential disasters. I have also attached a 'skeleton' view of the shed frame. I have found the diaries of the various studio builds to be of enormous value and have given me the impetus to build my own, and to keep a diary on the build here. I have been particularly encouraged by the success of the Lilith_Envy thread, which began as a similar shed to mine.

How do I get the pics to display in the post rather than just the links?

You didn't post any pics! You just posted SketchUp files, which are 3D model data, not pics. If you want to post pics of your model, you have to export them from SketchUp, then post them here. When you do that, please make sure that you make them no more than 700 pixels wide, since that is one of the rules of this forum. Also, please post some actual photographs of your space: it helps so folks here can better understand what you are dealing with. - Stuart -

Thanks Stuart. Here are some pics: And a picture of the floor plan.............

yer building already? Your CR isn't symmetrical, to start with.

The only building I'm doing at this stage is the outer shell, putting a layer of Soundscreen and a layer of gyprock on the walls and ceiling and sealing it to form the outer wall. I have not started on any of the inner rooms as yet. I looked at the symetry issue and since the walls will be inside out and the CR is symetrical forward of the mixing position I considered that any issues would be minimal. I have been in a number of CRs over the years that weren't symetrical, Trafalgar/Electric Avenue, for one, and it was not an issue.

and the CR is symetrical forward of the mixing position

Actually, it isn't. Not even close. The left side wall is at an angle of roughly 120 degrees to the front wall, while the right one is at an angle of only about 105. That's a 15° difference! The chair is about 3.3m from the left wall, while only 2.9 cm from the right wall. I don't think I'd call that symmetrical! The speakers are also not equidistant from the chair (although the difference is minimal there, about 4 or 5cm), and the speakers are at the wrong angle, and aimed at the wrong location: they are aimed at a point about 1.9 meters behind the engineers head, and about 80 cm in front of the couch, so nobody is going to be in the sweet spot. There will be first reflections off the glass to the vocal booth on the left, as well as the main door on the right, but at different angles and different distances, yet there is no treatment shown for that. I would pity the poor producer sitting on that couch at the back, trying to make sense of the different path lengths and crossed reflections arriving at his ears, not to mention the rather different response he's be hearing from each ear. The soffits won't work too well as shown either. But I agree with Ro: the basic issue here is symmetry, followed closely in second place by speaker geometry.

since the walls will be inside out and the CR is symetrical forward of the mixing position I considered that any issues would be minimal.

Why would building the walls inside-out make any difference to room symmetry or acoustic treatment? Sorry, I don't understand your reasoning there. Could you explain that please?

The only building I'm doing at this stage is the outer shell, putting a layer of Soundscreen and a layer of gyprock on the walls and ceiling and sealing it to form the outer wall.

I'm wondering if you might be building a 3-leaf system there? Maybe you could describe how that outer wall is built, listing all the materials form the extreme outside, to the extreme inside. - Stuart -

It isn't a 3 leaf per se, but it is a coupled exterior assembly. You are going to want more distance (air) between the exterior and the start of framing on the interior unless degraded low end performance is your goal ;).

Thanks for the replies Stuart. Regarding symetry, I will have another look at the layout and see if I can achieve a symetrical design. Re the walls. The outer skin is steel, then a layer of thermal insulation, then the Soundscreen then the gyprock. This is then sealed and forms the outer wall of the building. There is then an air space followed by gyprock on a timber frame, filled with Soundscreen then cloth and timber, spaced slats. I have discussed this at length in a previous thread and that construction was at thge advice of John Sayers. The ceiling will be similar except that the cloth and timber slats will be replaced with perforated gyprock.

"I have discussed this at length in a previous thread and that construction was at thge advice of John Sayers. " That is all good, but there is an air space requirement for this type construction or you will produce a low frequency acoustic hole. If you could point out the thread that you refer to, we might be able to get the measurement that Mr. Sayers would have recommended.

The previous thread was at viewtopic.php?f=2&t=15594&start=15 Floorplan 2.0

Regarding air space, the light blue in the floor plan is the air space and there are three large areas around the control room, but I guess you are saying that the space between the outer wall and the inner walls, where it is closest, is too narrow. I have allowed a minimum space of 10 cms and I cannot find a reference to how to calculate the correct amount of space. Can anyone point me to it? Regarding the soffited speakers, they are essentially for listeners at the couch, I will be mixing mainly with the near fields on the desk. They are placed so that the centre lines meet at the couch, is that correct? I could change the angle of the walls so the soffit centre lines meet at the mix position, but I thought that this would not be good for sound at the couch? My reference to having inside out walls was that it is my understanding that these will reduce reflections in the control room. I will also add absorbent panels to the doors, if necessary, and a diffusser behind the couch. I'm not sure how I can prevent reflections from the vocal booth glass, other than having it angled from top to bottom. Any advice would be gratefully received.

I wonder if the "dead air" at the rear of your control (behind couch) couldn't become a large bass trap? Not sure if that will affect the symmetry. But at least you have some great storage space. Have you looked at most of johns designs where the live room is to the left or right of the sitted mix position? That would give you less waste and more floor space. I built in a shed kit and know the cost involved so every sq/cm you get out of it is gold. Lil

Something like this?

Now that layout makes a LOT of sense, Lilith. Much better symmetry, much better use of space. - Stuart -

Thanks for your replies Lil, your studio and the way you built it have been an inspiration to me. The reason for the orientation of the control room is that I really want to have the desk facing out into the main studio. The spaces at the sides will probably be used for storage, if I put a door in, or bass traps if I need them. My plan was to put diffusers behind the couch though. Do you have any information/expeience with regards to how wide the air gap has to be between the outer and inner walls?

My plan was to put diffusers behind the couch though.

The room is too small for diffusers to be advisable.

Do you have any information/expeience with regards to how wide the air gap has to be between the outer and inner walls?

That information is available in numerous places all over this forum, if you search for it! :) The question is not "how big does the air gap have to be", but rather "What MSM resonant frequency do you want your wall tuned to?", and you can only answer that question once you calculate how much isolation you need for each part of the audio spectrum, which in turn you figure out by measuring how loud things will be in those rooms, and how quite they have to be in the surroundings. In other words, your studio plan should start out by actually measuring real-world levels with a real sound level meter. This will lead you to define the NC curve that you want for your studio, and the TL that you need to attain in your walls in order to achieve that specific curve. That will lead you to determine the MSM resonance for your walls, which is what determines the size of the air gap and the amount of mass on each leaf. This is a process, not a guess. Asking "how big should the gap be?" is like asking "how long should my rope be?": the answer in both cases depends on what you are trying to do. To answer your question more scientifically, the way you calculate (not guess, but calculate) the correct air gap size is as follows: Fmsm=c[(m1 + m2)]^.5 / [(m1 x m2 x d)]^.5 where: Fmsm is the MSM resonant frequency of the wall (determined by the spectrum that you need to isolate) C=43 for imperial measurements, 1897 for metric. m1, m2 = surface density of leaf #1, leaf #2 (pounds per square foot, or kg/m2) d=depth of air gap (inches or mm)

The spaces at the sides will probably be used for storage, if I put a door in, or bass traps if I need them.

It's not a question of "if" you will need them, but rather of "how big" you will need them. It is a small room, so it WILL need bass trapping, and lots of it. That goes without saying. The questions you need to ask are "How much?" "What dimensions?" and "Where in the room?". That can only be answered fully by calculating the modal response of the room, which is relatively easy to do for a rectangular room but extremely hard to do for any other shape. I hope that helps you to get a better handle on how to go about designing your room. It isn't a matter of guesswork, or trying to incorporate things that you might have seen in other rooms: every room is different, acoustically. You cannot just add something to your room because it looks cool or because you believed some acoustic myth that you found on the internet. You only add something to your room if you understand WHY you are adding it to the room and WHAT it will accomplish in YOUR specific room. Treatment inside a room has to be designed for that specific room, not for any other room. The same goes for isolation: you design YOUR isolation for YOUR room, based on YOUR needs, using the correct equations, not guesswork. This is all about following the procedure, doing the math, and coming up with a design that makes sense, from the point of view of the science of acoustics and the commonly used equations. - Stuart -

Thanks for your reply, Stuart.

In other words, your studio plan should start out by actually measuring real-world levels with a real sound level meter.

How can I do that before the studio is built? BTW I do have a sound level meter and sound sources. With regard to isolation from the outside world, this is not too big an issue as my studio is on my property in the country and I don't have any close neighbours to upset, I do, however, need to keep out the usual country noises, birds, wind, rain, etc. Maybe I need to do some more reading and investigation because I don't understand a lot of what you talk about, above.

That can only be answered fully by calculating the modal response of the room, which is relatively easy to do for a rectangular room but extremely hard to do for any other shape.

Since it is pretty well established that a rectangular room is not suitable for recording, there must be a process that others have used to solve these issues? I get the feeling that in essence you are saying that this is too hard for me to do, so I shouldn't even try.

The same goes for isolation: you design YOUR isolation for YOUR room, based on YOUR needs, using the correct equations, not guesswork.

I was trying not to use guesswork, but to find out how to go about doing the design using the equations, I just need to find out where they can be found. That was the whole point of posting here, if I wanted to guess I wouldn't need any help from the good folks on this site. Are you suggesting that until I have completed a degree in acoustics I shouldn't build a home studio?

Since it is pretty well established that a rectangular room is not suitable for recording,

It is??? Really? Wow! that's going to be news to a lot of the professional designers who hang out here! I bet they have no idea that most of their designs are "not suitable for recording"... :) John himself is going to be pretty disappointed, since some of his best work on really small studios has been based on rectangles, and he thought they turned out just fine. This is going to be very sad news for him... :) Seriously, why do you think that rectangular rooms are no good for recording? Where did you get that myth from? - Stuart -

How can I do that before the studio is built? BTW I do have a sound level meter and sound sources.

Great! Then set up your full-range system to play sine sweeps, pink noise and music that covers the full spectrum, with emphasis on the low end. Set it up to play whatever level you normally get in tracking sessions (that would be about 115 dB or more, if we are talking average rock band genre). Measure the levels in a bunch of locations in and around the building, and note them down carefully. Now get someone to slowly turn down the system while you carry on walking around those same locations, until you can no longer hear anything from the system (just ambient sounds), or alternatively, the level that you and your neighbors judge to be acceptable, and note down the levels in all those locations again, as well as in the room. Subtract "A" from "B" and you have the level of isolation you need to design for. Now you know the level of TL that you need for your build. Look in the NRC documents to find some form of construction that you like and that will give you that level of isolation. It will undoubtedly be an MSM structure, and the materials and dimensions will be given. Alternatively, work backwards from the TL that you need and the lowest frequency that you need to isolate, and use the MSM equations to find the mass and air gap that gives you a sufficiently low MSM resonance (no greater than half of the lowest frequency that you need to isolate, and preferably no greater than one third of that frequency). It isn't hard to do, when you understand the basics.

I do, however, need to keep out the usual country noises, birds, wind, rain, etc.

OK, so reverse the above process! Measure what the loudest sounds are in the area (cars/trucks/tractors, aircraft,, rain/thunder/wind/animals, etc), and decide what NC curve you want for your studio. Once again, subtract "A" from "B" and you have the TL level that you need for your walls. Then proceed as above.

Maybe I need to do some more reading and investigation because I don't understand a lot of what you talk about, above.

You might want to consider buying "Master Handbook of Acoustics" by F. Alton Everest, which explains things very clearly, starting out from the assumption that the reader knows nothing about acoustics, and proceeding clearly with only a minimum of math. Also buy "Home Recording Studio: build it like the pros", by Rod Gervais, which teaches you the basic techniques for actually designing and building.

there must be a process that others have used to solve these issues?

Like I said, for rectangular rooms the process is relative easy: there are many calculators available on-line, and many examples of good room ratios (Louden, Sepmeyer, etc.). Plug in the dimensions for a room that is close to what you need, run the analysis to see how it works out, and adjust the dimensions as necessary to get away from known "bad" ratios and close to one of the "good" ratios. It doesn't really matter which "good" ratio you choose: there isn't much difference between them, if you stick to the top dozen or so. Whatever makes sense for your existing space is fine. You also don't need to get crazy about hitting a ration perfectly: ballpark is fine. And if your room is NOT rectangular, then you CANNOT use those simple modal calculations, because they are no longer valid. In that case you need to learn how to do finite element modeling and finite element analysis on arbitrarily shaped objects, and you need the software to do that. Not for the feint of heart! Or you can follow some general rules of thumb, build the basic room shell, and measure the actual response with something like REW (which is free, and easy to use), then design treatment to deal with the problems in the room, then measure again, and repeat as many times as necessary until either you are satisfied with the outcome or you hit the law of diminishing returns.

I get the feeling that in essence you are saying that this is too hard for me to do, so I shouldn't even try.

No, on the contrary, I'm saying that it ISN'T hard, and that you SHOULD try, but that you need to learn the basics first, before you try. If someone told me they had never ridden a motorbike before but planned to ride one at 75 MPH on the freeway next week, I'd tell them the same: don't, until you learn how. Is it possible for someone to ride a bike at 75 MPH on the freeway? Sure! People do it every day, and it isn't hard. Should you do that the first time you get on a bike, without even understanding where the clutch brake and gear shift are? Ummmm... Nope! first you have to learn the basics, then you have to practice a bit, and only then should you get on the freeway.

I just need to find out where they can be found.

Master Handbook of Acoustics covers that pretty well, as do a number of other books and publications. You can also find all of that information here on the forum, if you look around a bit. This place is actually an unbelievably rich goldmine of solid, valid, acoustical information (unlike so many places on the internet, that are filled with either marketing hype or acoustic myths and legends).

Are you suggesting that until I have completed a degree in acoustics I shouldn't build a home studio?

Nope! I'm suggesting that you at least read the owner's manual before you try to ride the bike on the freeway! :) Really, learning the basics of isolation and acoustic treatment isn't that hard. The toughest thing about it is to first unlearn the myths and legends that we all "assume" are true, but actually have no basis in acoustic reality. There's a lot of things that about acoustics that don't seen intuitive, until you first let go of concepts that you thought were right, but actually aren't (such as a 3-leaf wall being providing worse isolation than a 2-leaf wall, for example). But once you get your head around the basics, it all starts to make sense, and it really isn't rocket science to do that. - Stuart -

Stuart, thanks for a great and detailed reply, I feel that I am now getting somewhere. With regard to the initial measurements, I assume (dangerous, I know) that I should complete the outer wall as suggested by John Sayers, then do the measurements you recomend to find out what I need by way of the MSM for the inner wall. BTW John recommended that I put the layer of Soundscreen and then gyprock on the outer wall and seal it as the original steel shell does not count as a layer since it offers no sound insulation and it is not sealed.

Seriously, why do you think that rectangular rooms are no good for recording? Where did you get that myth from?

All my reading has led me to believe that parallel walls are a problem due to standing waves, surely a rectangular room has two sets of parallel walls plus a parallel ceiling and floor. All of John's designs seem to have non-parallel walls and sloped ceilings, I can't remember seeing one that was a rectangular room, but maybe I'm wrong again. I will certainly see if I can get the books you mentioned, especially the one that assumes no prior knowledge. I did use a progamme called ModeCalc, but as you suggest, it only has the ability to use the dimensions of a rectangular room, so what I did was to take the average dimensions of my proposed room to create a rectangular room for the model. Whilst I realise that it won't be perfect, it did indicate that the ratio was 1 : 1.82 : 2.01 and that I have issues at 208 - 209 Hz and at 416 - 418 Hz. This appeared to give at least as good a result as some of the recommended ratios. The thought of finite analysis worries me a bit, I have used it before in other types of modelling, RF antennas, and whilst I could use it I would prefer not to. I think your other suggestion of building a room that 'should' be OK then adjusting for the problems is more likely the way I will go. I like your comment about other sources on the internet, disinformation abounds.

But once you get your head around the basics, it all starts to make sense, and it really isn't rocket science to do that.

I have the feeling that I may have just begun to scratch the surface of the basics, thanks to your advice. ........................................... PS I got a copy of The Master Handbook of Acoustics, today and I have ordered Rod Gervais book, of which a lot of shops are out of stock. I started reading a the area on diffusers, Chapter 21, which has made me question the comment above that my room is too small for a diffuser. The MHOA shows a number of designs and photos of quite small control rooms that use diffusers extensively on the rear wall with absorbers on the front.

I have now got a copy of Rod Gervais book and have started to read it, but I'm still struggling to get a grasp on the layout. I am stuck with the actual building, which is 12 metres x8 metres with 3 metre walls and a 3.6 metre peak. Once I have completed the first layer, as suggested by John Sayers, with a layer of Soundscreen and a layer of gyprock to form the first mass, I will have an internal area of 11.8 x 7.8 x 3 metres. What I would like to achieve is a Control Room, as described by Rod Gervais, of, as close as I can get to, 70 cubic metres, Floorplan 3.0 gives 66 cubic metres, with no parallel walls, to reduce flutter echo, a sloped ceiling from 3 to 3.3 metres and bass traps. It is important for my work that I am facing out into the tracking room. Am I getting any closer to a realistic layout?

Things have been quiet around here for a while, I've been busy with other things and vigorously studying the two texts above. I am now wondering if the following is still a two leaf wall, for the control room? The outside layers remain the same, steel sheet outer on a steel frame, a layer of Soundscreen batts between the frames then two layers of gyprock, caulked and sealed. This I understand to be one leaf since the steel sheet does not offer any mass or sound insulation. Then an airspace, to be determined by measurements as detailed above, then an inside out wall, as follows, from the outside to the inside: two layers of gyprock on a timber framework filled with Soundcreen batts, then a layer of cotton drill cloth and finally timber slats. Any comments would be appreciated.

You are missing insulation in the air space between your two inner leaves! Very important. If you leave that out, it will cost you many dB of isolation.

This I understand to be one leaf since the steel sheet does not offer any mass or sound insulation.

It is still three leaf, just with a low mass third leaf. So you should leave larger air gaps and put more mass on the other leaves (especially the middle one) if you can. How much isolation do you need, and what type of music are you isolating? How big are you planning to make those air gaps? All of your gyprock should be 5/8" at least, of course. And adding Green Glue between layers would also help. - Stuart -

You see, this is where I get confused. This is a quote from John Sayers, himself, about my construction:

Bob - don't treat the outer steel as a leaf as it's not airtight and really offers no sound isolation. Your plaster layer should be treated as your outer skin, seal it totally all round including the ceiling - then build the inner walls inside out with pink batts type insulation or dacron rolls on the back. No green glue is required.

Maybe I am misinterpreting what you or John are saying, but it seems to me to contradict.