Hi all,
I am about to embark on designing a new studio that is on the cusp of not needing U.K planning permission for an outbuilding. In essence a glorified shed – man cave.
I have a moderate knowledge of acoustics and i am hoping you guys can help me out, or spot a massive oversight in my design... :)
I will be updating as the project moves along, and posting the odd question that arises.
The limitations are as follows:
• The structure must not exceed 30 square metres
• Eaves must not be higher than 2.5m
• The highest point of a double pitched roof must not exceed 4m
• Any other roof must not exceed 3metres
• Single storey
The structure must be at least 2metres from a boundary and at least 5m from the main house.
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'THE SHED' will be constructed of pressure treated Timber and wall stud configurations, the room will be used predominately for mixing and mastering, and occasionally as a secret hideout.
To get necessary isolation, the 'room within a room' concept will be used
Concrete base 5 x 6m (30 sqaure metres)
100 x 100mm pressure treated skids
100 x 50mm pressure treat floor joists
Floor 30mm OSB
50 x 100mm x 2.2m wall studs
After laying necessary structural foundations the only room height left to play with is 2.2metres
The dimensions of the studio (inner room) are:
L = 4.65m
W = 3.875m
Z = 2.2m
The outer room will be lined with insulation whilst being spaced 100mm away from the edge of the inner rooms wall studs, the inner room will
also be lined with insulation (100mm rock wool). + hardboard and cladding.
The inner and outer rooms are coupled by the floor, only the floor. The ceiling is supported by the inner room and the roof by the outer wall.
This is okay right? i didn't see another option.
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I plan to soffit mount the speakers and angle the walls to create a reflection free zone (See figure C), after drawing the room I am concerned
the room is too small for the RFZ design?
or too small for diffusion at least? (See figure B)
maybe the rear wall should be made highly absorptive instead?
The front ceiling will also be splayed (See figure E), more to come on that another time.
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Regarding soffit mounting the speakers:
The speakers should be decoupled from the front wall right? my research leads me to believe the speakers should be mounted in solid concrete, however; the speakers i plan to use are quite small (focal CMS 65 near fields, and a subwoofer btw), so i thought, they won't cause significant vibration (just the stereo L+R that is) and therefore i could save costs and difficulty by just coupling the speaker stands to the floor and that would be sufficient?
The infinite baffle that is the front wall, should be how thick? to be effective, say 20mm MDF/PLYWOOD/OSB?
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So much care has been taken to direct reflections away from the listening position, but what about the floor? i should go with carpet surely?
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Ow, and a quick question about splaying walls; is it a case of trial and error when drawing ray reflections? or is there a better method/preferred angles etc
Let me know if anything was unclear, I look forward to hearing from you.
Many Thanks,
Gareth
THE SHED: A project within U.K planning permissions RFZ?
Originally posted at johnlsayers.com, topic 19447.
Hi Gareth, and Welcome! :)
How much is that, in decibels? "Necessary" is a subjective term, that can't be measured. "47 dB TL" is an objective term that can be measured, and therefore you can design the structure to get there. It is important to have objective goals when designing a studio: if not, then there is nothing to base the design on! :)To get necessary isolation,
"Skids"? I'm not familiar with that term in construction. Is that the UK equivalent of a sole plate? Or maybe a joist?100 x 100mm pressure treated skids
Whoa! You said you had a concrete slab for your floor, so why do you need another floor on top of that? Floating a studio floor is almost always unnecessarily, and will almost always turn out to be a total failure if not done correctly. Where "correctly" implies extensive engineer calculations of masses and displacements and spring compressibility, resilience, compliance, resonance, and numerous other things, and also implies deep pockets. You can't float a floor with a bit of MDF on top of some 2x4's. Here's a thread that you absolutely must read before you decide on how to build your studio: viewtopic.php?f=2&t=8173 In other words, your concrete slab is the perfect, best, most amazing studio floor you could possibly have. About the only thing you might want to do to make it look prettier, is to lay tiles, laminate flooring, or linoleum on top. But trying to float it would be a baaaad idea.100 x 50mm pressure treat floor joists
Why? Your regulations say how far you can go UP: they do not say how far you can go DOWN first... :) I'm designing a studio right now for someone in London, and he went down a meter before going up. So even though his eves will come in at 2.3m above GROUND level, he'll still have more than 3m room height inside... :)After laying necessary structural foundations the only room height left to play with is 2.2metres
Without knowing what your isolation goal is (decibels) then it is impossible to say if that 100mm is way too much, nowhere near enough, or just right. My guess would be "too much". You only need a small gap between the outer-leaf framing and the inner-leaf framing, usually. What matters for calculating the isolation (MSM resonant frequency) is the total air gap between the leaves, not the gap between the frames. Since the studs on the outer leaf are at least 2x4s, that implies at least 90mm of air gap right there. So even if you do an inside-out wall, you'd only need another 10mm or so to the inner-leaf, unless you need unusually high levels of isolation.The outer room will be lined with insulation whilst being spaced 100mm away from the edge of the inner rooms wall studs,
Why not plasterboard? What type of "cladding"? Hardboard is usually pretty thin and light weight, and won't do much with isolation. Plasterboard (drywall, gypsum board, etc) is thick and massive: just what you need.the inner room will also be lined with insulation (100mm rock wool). + hardboard and cladding.
Right! That is, indeed, the correct way to do it.The ceiling is supported by the inner room and the roof by the outer wall. This is okay right? i didn't see another option.
Soffit mounting is highly recommended, but you seem to be over-thinking the design, using all those different angled sections to attain RFZ. I normally only use two sections: the soffit itself (which needs to be as wide as possible), and an angled section to blend that into the side wall. Same for the ceiling: usually, a single angle for the entire front section of the ceiling is fine, or maybe a cloud at a single angle. You don't normally need multiple angles.I plan to soffit mount the speakers and angle the walls to create a reflection free zone (See figure C), after drawing the room I am concerned the room is too small for the RFZ design?
The vast majority of home studios are too small for diffusion, so I wouldn't worry about that. And they don't need it either! :)or too small for diffusion at least?
Absolutely, yes! For a small RFZ design, that is normally the best way to achieve it.maybe the rear wall should be made highly absorptive instead?
Not necessarily. There are two basic ways to build a soffit: what I call the "John Sayers" method, which means mounting the speakers and baffles extremely rigidly, so that they cannot move at all, and the "Barefeoot" method, which still implies mounting the baffles very rigidly, but involves decoupling the speaker from the soffit. With this method, the speaker "floats" freely, and does not touch the baffle. with the John Sayers method, the speaker is firmly coupled to the baffle. Both methods work, if done right.Regarding soffit mounting the speakers: The speakers should be decoupled from the front wall right?
I normally use at least a couple of layers of 19mm plywood/OSB/MDF. And I have been known to design baffles in concrete, too... :) They have to be massive, and rigid. So make it as thick as you can, and as dense as you can, and provide as much bracing as you can.The infinite baffle that is the front wall, should be how thick? to be effective, say 20mm MDF/PLYWOOD/OSB?
you are very unlikely to have any reflections coming off your floor: the problematic reflections will be coming off your console and desk, not the floor. The desk will be "shadowing" you from the floor reflections, but creating reflections of its own... And no, carpet has no place in a studio. Or very little place: you might want to have a throw-rug of some type under your chair, but the floor itself should be hard, solid, rigid and reflective: Such as concrete, for example... :)So much care has been taken to direct reflections away from the listening position, but what about the floor? i should go with carpet surely?
That's the way to do it, yes, but you need to go out BOTH ways from EACH speaker: both left and right, not just one way... - Stuart -Ow, and a quick question about splaying walls; is it a case of trial and error when drawing ray reflections?
Thankyou! this place is awesome...
Well, lets say I'm typically monitoring at 90dB and occasionally crank it up, i would like to be able to work at night without causing a nuisance, I believe the design i have discussed is in a sense the maximum isolation i can get on my budget, which is around £2000-3000 btw. Wall configurations adhering to STC 63 The garden in which the shed will be, backs on to a few neighbouring gardens, but not particularly close to anyone's actual house. We haven't moved there yet (in july), so pictures and distances will come then. ___________________________________________________________________How much is that, in decibels? "Necessary" is a subjective term, that can't be measured
Skids is something I have come across when researching shed design, i am no expert with building construction and am purely copying from youtube 'build a shed videos' - seems legit :roll: __________________________________________________________________Skids"?
It is more of a weather proofing technique, again something i have gathered from 'building sheds' videos :lol: .. It is not an attempt to isolate the floor, although it appears as exactly that I have thought about placing the walls on just the concrete slab, but my problem there is: a) the weather: what if the garden floods / rain /snow, it will just get under the walls and into my studio? b) Another thing is; what's stopping a would be thief sticking a car jack under a wall and winning the lottery? I wanted it to be a single sealed unit for security, maybe i have missed something regarding mounting the wall studs to concrete.. Still a bad idea? So, i have since researched mounting the stud walls directly to a concrete base, looks good - and it will save on materials! _________________________________________________________________Whoa! You said you had a concrete slab for your floor, so why do you need another floor on top of that?
That sounds like a possibility, you really don't need planning permission to dig down? but i would imagine it would increase costs considerably, and i presume i would have to consult a structural engineer regarding stopping the earth coming back in? but maybe though, i will look into going down. _________________________________________________________________Why? Your regulations say how far you can go UP: they do not say how far you can go DOWN first..
Essentially i don't know how much isolation i need :( , until i have decided the exact location and the distances to anyone else's property (in a few months). My thoughts here were to keep the outer room within regulations (30 square metres) and the inner room to a good modal ratio that fits inside... Lets hypothesise for now, and say i will be typically monitoring at 90 dB whilst occasionally cracking it it up to 100dB, i don't want any neighbours to hear a thing from their houses.. so providing their house gives 30dB attenuation from my noise, and THE SHED attenuates 60 dB, all is well..? Could you link me some literature on calculating the resonant frequency and transmission loss of stud walls? __________________________________________________________________Without knowing what your isolation goal is (decibels) then it is impossible to say if that 100mm is way too much, nowhere near enough, or just right. My guess would be "too much"
Sorry, i should have been clearer - i haven't confirmed all of the construction materials as yet, but i will be using plasterboard __________________________________________________________________Why not plasterboard? What type of "cladding"?
Yayyy, i got something right :yahoo: ___________________________________________________________________Right! That is, indeed, the correct way to do it
It wasn't particularly clear in the last post, the way i had drawn the baffle around the speaker made it look like there are more splayed walls Is this still too complex? with 3 splayed side walls.. Does the speaker need to be placed symmetrically in the first baffle face? (in the centre) and i have seen a lot of soffit design with tilted speakers, i don't plan to do this... just speakers at ear level. Lots more questions about soffits will be posted later ______________________________________________________________________Soffit mounting is highly recommended, but you seem to be over-thinking the design, using all those different angled sections to attain RFZ.
Sorry figure D from the last post is reflections from the left speaker (only) to the right wall, which will just be mirrored for the right speaker on to the left wall, what your saying is i should also draw reflections from the right speaker onto the right wall as well? I think if i have splayed the walls correctly, the latter will be fine. _______________________________________________________________________ Granted, figure E (The vertical reflections) will make the splaying of the ceiling quite complicated, but then if you only use one tilted edge, then surely you are in fact not creating a reflection free zone? I have noted all of the information i didn't need to reply to, Thanks for your help Stuart!That's the way to do it, yes, but you need to go out BOTH ways from EACH speaker: both left and right, not just one way...
Careful with STC ratings... STC is no use for measuring studio isolation: It was originally meant for putting a single number to isolation in typical house/office/shop/school walls, where the "noise" is moistly voices, telephones, HVAC air noise, typewriters, office equipment, and suchlike. Not meant for music. STC does not even consider the bottom two and a half octaves of the music spectrum at all! Drums, bass, the low end of keyboards and electric guitars, etc. just aren't taken into account when calculating the STC rating for a structure. so you can quite easily have a wall rated at STC-60 that does a really lousy job of isolating a studio, and another wall rated at STC-50 does an amazing job. When talking about studio isolation you should be talking what is knows as "Transmission Loss" or "TL", which is basically a graph that shows isolation across the entire spectrum, and can be summed up reasonably accurately by measuring the "inside" and "outside" levels with a decent sound level meter set to "C" weighting and "slow" response. "STC-60" does not mean that the wall provides 60 dB of transmission loss...Wall configurations adhering to STC 63
Great! So we have one of the two numbers you need! We have the "how loud" number: now you just need the "how quiet" number. That one, you can get from your local municipality. Ask for a copy of the noise regulations that govern your area, and that will tell you how quite you have to be, legally, so as to "not cause a nuisance".Well, lets say I'm typically monitoring at 90dB and occasionally crank it up, i would like to be able to work at night without causing a nuisance,
Yeah, lots of stuff on YouTube "seems legit"!!! :shock: :!: But that certainly isn't where I'd be looking for info on building anything more than a dog kennel! And even then, I'd think twice... :) Seriously, do not trust YouTube for anything about building a studio: any idiot with a camera and an internet connection can now be an acoustical expert, and post his "wonderful" solutions.... :cop: If I had a dollar for every YouTube video that shows a total load of garbage about acoustics and sound, I'd be a very rich man indeed...Skids is something I have come across when researching shed design, i am no expert with building construction and am purely copying from youtube 'build a shed videos' - seems legit
Build it the same way your house is built: Build the slab so it sticks up above the surface of the ground by several cm, then overlap the siding down the sides of the slab, with suitable DPC (waterproofing) in between. Or if you go the "dig a big hole" route, then you'd use concrete blocks for your foundation walls, sitting on the edge of the slab, and you'd water proof that on the outside with suitable products, and a good drainage system around the perimeter, next to the slab.It is more of a weather proofing technique, again something i have gathered from 'building sheds' videos ... I have thought about placing the walls on just the concrete slab, but my problem there is: a) the weather: what if the garden floods / rain /snow, it will just get under the walls and into my studio?
With the way you have it now? Nothing at all! If he has a big enough truck, he can take your entire studio with him, wholesale. But if you build it right, with the framing bolted to the slab, and the siding overlapping, that makes his task a lot more complicated....b) Another thing is; what's stopping a would be thief sticking a car jack under a wall and winning the lottery?
You just bolt them down. Use pressure-treated wood for the sole plates if you are worried about damp, and use the normal building techniques for water-proofing that. No problem.I wanted it to be a single sealed unit for security, maybe i have missed something regarding mounting the wall studs to concrete..
And give you much better headroom inside! :)So, i have since researched mounting the stud walls directly to a concrete base, looks good - and it will save on materials!
Better check with your local municipality to find out for sure, but likely you don't need that.That sounds like a possibility, you really don't need planning permission to dig down?
You'll need a structural engineer anyway: Isolating a studio implies lots of mass, with a large proportion of that hanging over your head! You really do need to check that your roof and ceiling designs are sound, in that sense. As I mentioned above, if you dig down, you'd dig a hole bigger than the slab, pour the slab, then lay concrete blocks to build back up to ground level, or a bit above ground level. You would then add the drainage around the slab, the waterproofing on the foundation walls, etc., then back-fill with some of the the dirt you dug out, until you get level with the ground again, up to the foundation walls. You could then either carry on with concrete blocks up to the roof, or switch to stud framing from that point up. Your call!but i would imagine it would increase costs considerably, and i presume i would have to consult a structural engineer regarding stopping the earth coming back in?
Not really: There are legal requirements you have to meet, so you don't have the cops knocking on your "shed" door with a noise violation ticket for you... And the amount of isolation provided by the neighbors house does not come into the picture at all! Noise regulations these days pretty much always specify how loud you can be AT YOUR PROPERTY BOUNDARY, regardless of whether your neighbors live in a concrete bunker or a tent. So you need to design our isolation such that the level measured at your property line is less than the legal limit, while you are playing your 90 dB heavy trash metal inside the studio.Lets hypothesise for now, and say i will be typically monitoring at 90 dB whilst occasionally cracking it it up to 100dB, i don't want any neighbours to hear a thing from their houses.. so providing their house gives 30dB attenuation from my noise, and THE SHED attenuates 60 dB, all is well..?
Sure! :) ( you HAD to ask.... :) ). First, the famous "Wyle Report", which dates back to 1973 but laid the foundations for understanding how isolation works. It's rather technical, but if you browse through it you'll get the idea, and you'll find the equations. Then for a set of detailed laboratory tests on hundreds of different ways of building walls, and how much isolation each one provides, IR761 is the single best study out there: http://archive.nrc-cnrc.gc.ca/obj/irc/d ... /ir761.pdf Then I'd also suggest two books: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais. Between those, you have more than enough to figure out how to design and build your studio.Could you link me some literature on calculating the resonant frequency and transmission loss of stud walls?
You could do it like that, but that's more of a CID design than RFZ. It will work, but is probably unnecessarily complex, and will increase your construction difficulty and cost. Normally two sections is enough, if you angle them right...Is this still too complex? with 3 splayed side walls..
No. You got that right too! :) In fact, it should NOT be centered: if it is centered, then it creates a sort of "focusing" or "lensing" of the pressure waves, which isn't good. So the distance from the acoustic center of the speaker to EACH of the edges should be different: A good rule of thumb (but not written in stone!) is to set the speaker at about 2/5 of the baffle width, and about 1/5 of the baffle height.Does the speaker need to be placed symmetrically in the first baffle face? (in the centre)
Smart move! Tilting the soffits creates more new problems than it solves, if you aren't careful...and i have seen a lot of soffit design with tilted speakers, i don't plan to do this... just speakers at ear level.
Sort of: I'm saying that you shows reflections from the left speaker on the right wall, and also the left speaker on the left wall, and also the right speaker on the left wall, and the right speaker on the right wall, and both speakers on the ceiling.... Yes, you can do just one speaker in SketchUp ray-tracing both left and right, and up, then mirror that about the room center-line to get the other speaker. But the important point I was trying to make is that you need to look both ways form each speaker, not just one way.Sorry figure D from the last post is reflections from the left speaker (only) to the right wall, which will just be mirrored for the right speaker on to the left wall, what your saying is i should also draw reflections from the right speaker onto the right wall as well?
It will only be fine if you test and confirm that it is fine! :) Don't assume anything about studios: it's the little details that you "assumed" would be fine, that always get you in the end. Murphy was an optimist... :)I think if i have splayed the walls correctly, the latter will be fine.
You sure can do it with just one surface, if you angle it enough! :) - Stuart -Granted, figure E (The vertical reflections) will make the splaying of the ceiling quite complicated, but then if you only use one tilted edge, then surely you are in fact not creating a reflection free zone?
What's funny is I thought I had a handle on this, but you've gotta love a challenge.
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So the permitted noise level according to Defra is:
34 dBA if the underlying level of noise is no more than 24 dBa, or 10 dBA above the underlying level of noise where this exceeds 24 dBA.
Does this sound like the right limitations? my local council literally did not know anything about permitted decibel level...
But the defra document "provides guidance to local authorities in England on the powers available to them to deal with night noise emanating from dwellings and licensed premises which exceeds the “permitted level” of noise prescribed under the Noise Act 1996".
I will be emitting 100dB of noise, so my studio needs 66dBA TL
So from that document you linked, I will be using STC 65:
single layer of 13 mm gypsum board
single layer of 13 mm gypsum board
90 mm wood studs at 610 mm on centre
90 mm of glass fibre insulation in cavity
25 mm gap filled with air
90 mm wood studs at 610 mm on centre
90 mm of glass fibre insulation in cavity
single layer of 13 mm gypsum board
single layer of 13 mm gypsum board
Based on the availability and cost of 13mm plasterboard in local hardware stores
But this will never get the TL required below 400Hz, but then none of the wall configurations do...?
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Hahaha, yeah i won't be doing that again. __________________________________________________Yeah, lots of stuff on YouTube "seems legit"
As much as i want to dig a big bunker and gain some extra headroom (no pun intended), i just can't justify it - afford it - or get away with it. So I am going to go with: the wall stud-to-concrete base option.Build it the same way your house is built: Build the slab so it sticks up above the surface of the ground by several cm, then overlap the siding down the sides of the slab, with suitable DPC (waterproofing) in between. Or if you go the "dig a big hole" route
Hahaha you raise a good point! but mine is a completely rational fear; bolted down it is. :lol: _____________________________________________________With the way you have it now? Nothing at all! If he has a big enough truck, he can take your entire studio with him
Duly noted'. _____________________________________________________You'll need a structural engineer anyway
Ahaaha Lucky i have them right here :wink: ___________________________________________________________Then I'd also suggest two books: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais.
Wow, i didn't even know such a thing existed, cue - google search, cue - looks of reading I like my reflection design though, it has a large RFZ and i am willing to put in the the work constructing the sidewalls. The ceiling splay however will undoubtedly need simplifying.You could do it like that, but that's more of a CID design than RFZ
you say if you angle them right, then what would you suggest?Normally two sections is enough, if you angle them right...
It would be a very steep ceiling though? _____________________________________________________You sure can do it with just one surface, if you angle it enough!
I plan to place each speaker at ear level 30 degrees off centre to the listeners axis, surely the baffle simplictically goes around this position? _____________________________________________________No. You got that right too! In fact, it should NOT be centered: if it is centered, then it creates a sort of "focusing" or "lensing" of the pressure waves, which isn't good. So the distance from the acoustic center of the speaker to EACH of the edges should be different: A good rule of thumb (but not written in stone!) is to set the speaker at about 2/5 of the baffle width, and about 1/5 of the baffle height.
Attention to detail is important... got it! Cheers Stuart, very useful info! Lots to doIt will only be fine if you test and confirm that it is fine! Don't assume anything about studios: it's the little details that you "assumed" would be fine, that always get you in the end. Murphy was an optimist...
That sounds very much on the low side! 34 dBA is about as quite as you can possibly find in the real world: such as if you go stand in the middle of the Sahara desert, late at night on a windless day, with nothing that makes any noise at all around you for several kilometers in each direction! :shock: Most sound level meters aren't even able to measure such quiet situations. They might get down to about 35 or so, but 25 is off the bottom end of the scale, for everything but the highest quality meters. So it certainly sounds pretty darn unrealistically quiet! You'd be in violation of that regulation just for whispering to someone standing next to you.... As a point of reference, normal conversation between two people is around 70 dB....34 dBA if the underlying level of noise is no more than 24 dBa, or 10 dBA above the underlying level of noise where this exceeds 24 dBA. Does this sound like the right limitations?
I guess that's a good sign! It suggests that they don't get too many noise complaints, or if they do, then they don't go out to actually measure it...my local council literally did not know anything about permitted decibel level...
66 dB is do-able. However, TL is normally measured dBC, not dBA. C weighting is more appropriate for high levels of full-spectrum music. The good news is that dBA is far less sensitive to low frequencies than dBC, so if you you are well isolated as measure by dBC, then you are even better isolated as measured by dBA.I will be emitting 100dB of noise, so my studio needs 66dBA TL
Careful! STC is not a good method for measuring studio isolation.... It does not consider lows of highs at all: only mid range: (voice range).So from that document you linked, I will be using STC 65:
That's a good plan, but I would switch to 16mm drywall, or even 15mm if you can't find 16mm, since it is much better overall than 13mm.single layer of 13 mm gypsum board single layer of 13 mm gypsum board 90 mm wood studs at 610 mm on centre 90 mm of glass fibre insulation in cavity 25 mm gap filled with air 90 mm wood studs at 610 mm on centre 90 mm of glass fibre insulation in cavity single layer of 13 mm gypsum board single layer of 13 mm gypsum board
Don't get hung up on individual frequency bands! What matter is the OVERALL transmission loss, across the entire spectrum. Since our ears are less sensitive to low frequencies than to mids and highs, that's where it maters most.But this will never get the TL required below 400Hz, but then none of the wall configurations do...?
You could go with a flat ceiling and just hang an angled cloud under it (hard-backed, of course): That does the job too.The ceiling splay however will undoubtedly need simplifying.
Only for the part that matters... :) The rest can be flat.It would be a very steep ceiling though?
Yes, but not equally in all directions. If each speaker is perfectly centered in its baffle (eg. exactly 40cm from the acoustic center of the speaker to each edge of the baffle) then you are creating a sort of "lens" that tends to focus lobes of sound in certain directions. On the other hand, if you have a different distance to each edge, then you avoid that. - Stuart -I plan to place each speaker at ear level 30 degrees off centre to the listeners axis, surely the baffle simplictically goes around this position?