Hello everybody
I am just starting the build of a tiny 1 room studio at the bottom of my garden in South East London. I thought that it would be of great help if I started a thread here given the expertise herein for me and others in the UK with regard to sourcing materials and to see a humble build develop. I have Rod Gervais's book, who I note is a regular contributor here, which has helped heaps so far. It would be great if issues/flawed logic/obstacles that I might come across could be wisely addressed for myself and others by experts!
The internal dimensions are 2.8m (w) x 5m (l) x 2m (h). I realise this is far from optimal but that's the space I have.
I am interested in drums :shot: as I play a little so isolation is important and there will be a kit permanantly set up in the room that I will float on a neoprene-mounted platform - the cavity underneath the riser will be exposed to minimise resonance or should I build a clever low frequency resonator here that can benefit the whole room? I am a guitar player so there'll be some other sources of volume and I have some 3-way beefy monitors that will get turned up on occasion!
I have yet to decide on traps, helmoltz resonators and other treatments but I know that I will be prioritising the room as a listening room first and recording room 2nd. I don't mind deadish raw sounds (not that I have much choice with a room of this size). I have a pretty big house and access to other areas should I ever want to record with more natural ambience. Decisions regarding treament will be made further down the line as I am sure whatever I decide now will be wrong when I finish the proofing! I would warmly welcome some insight here if this is a flawed approach.
The basic plan for sound proofing
Floor: chipboard T&G is mounted on a metal subframe that is on concrete. I will add layers as follows: greenglue --> 6mm ply --> pine t&g floorboards.
Walls: Double frame 100% decoupled 2-leaf wall made from 1 layer of 12mm chipboard (particle board) and 1 layer of 12mm plasterboard (drywall). I am using chipboard to supply more stability so less 3x2 studding (more precisiely 89mm x 38mm) can be used which will allow for slightly thinner walls which is important given the 2.8m width of the room. I have designed the studding mechanisms so that more will be taken out of the 5m length of the room. Each leaf will be mounted on 12mm Neoprene. Great care will be taken with sealant at every surface to absolutely maximise attentuation leaving as small an overall amount of combined air gap as possible. Rockwool RWA45 will fill the air gap.
Ceiling: 2 ceilings will be mounted on the 2 wall leaves achieveing 100% decoupling from both the existing ceiling and the inner and outer ceiling leaves. Again chipboard and plasterboard will be used with insulation.
Where I am at now:
I am working on the floor tonight and tomorrow! The boards creak more than they should so I will try to add a few more judiciously placed screws. I will then use acoustic sealant to plug air gaps and allow to dry for a bit. 6mm ply will be "greenglued" and screwed to add mass, minimise creaking and placed to cover air gaps. I will add more acoustic sealant and screw the pine floorboards to the ply directly. I will glue the groove to the tongue.
My first questions is: Should I add some kind of underlay inbetween the ply and the pine? I think not but please feel free to post strong views if you have them.
I shall continue to post on a regular basis adding pictures and suppliers.
YB Studios - new build in London UK
Originally posted at johnlsayers.com, topic 14673.
Hi Tony, and Welcome! It's always great to have a newcomer who did his homework, follows all the rules, and does a great, detailed first post, with all the basic info! :)
A couple of comments:
Ouch! That's not looking very good at all. Is there any chance at all you can change some of those dimensions (especially the height), or are you absolutely stuck with them? If it's a shed type structure in your yard, then surely you can at least go a bit higher, even if you can't increase the footprint?The internal dimensions are 2.8m (w) x 5m (l) x 2m (h). I realise this is far from optimal but that's the space I have.
Personally, I'd leave it open and stuff it with rockwool or fiberglass. That will help both the cavity and the room, to a certain extent.the cavity underneath the riser will be exposed to minimise resonance or should I build a clever low frequency resonator here that can benefit the whole room?
It's a small room, so it will absolutely need large bass traps. You could probably allow for those in at least the four vertical corners now, in your early plans, since that will be the very least you will need, without any doubt. It might help you in laying out windows, doors, HAVC and electrical if you already have those accounted for, to avoid conflicts later.I have yet to decide on traps, helmoltz resonators and other treatments
Not necessarily true! You should be able to get a reasonable balance if you design and build carefully.I don't mind deadish raw sounds (not that I have much choice with a room of this size).
... except for the bass trapping: that goes without saying!whatever I decide now will be wrong when I finish the proofing!
You have extremely limited height: Is there any reason why you could not just leave plain concrete floor, and gain back those few cm from the floor? Plain concrete makes a good acsoutical floor anyway. If it is too ugly you could stain it: look around the forum to see some of the stunning effects people have done here with stained concrete floor.Floor: chipboard T&G is mounted on a metal subframe that is on concrete. I will add layers as follows: greenglue --> 6mm ply --> pine t&g floorboards.
12mm is too thin, for both of those. Resonant frequency too high, too flexible, and not enough mass. It will not isolate well. Go with 16mm, and instead of the particle board I'd go for plywood, OSB or MDF, for the extra mass and strength.Walls: Double frame 100% decoupled 2-leaf wall made from 1 layer of 12mm chipboard (particle board) and 1 layer of 12mm plasterboard (drywall).
:shock: For all that weight ???!!! :shock: I reckon I'd go with at least 2x4, and even better 2x6. 2x3 is not only questionable from the strength point of view, it is also too flexible to be much use for isolation in the low end.3x2 studding
unfortunately, you can have thin walls, or you can have good isolation. Pick only one... (Unless you want to spend a lot of money on exotic materials for your walls, like steel plate or lead sheet... )for slightly thinner walls
Why? Is that just to get a good seal against the floor, due to the concrete being uneven? If that is not the reason, then you don't need it: It won't do much for you for isolation.Each leaf will be mounted on 12mm Neoprene.
Bad idea: Reducing your air gap reduces your isolation greatly. Anything less than about 4" of air gap (10cm) is worthless, and especially if you are only going with lightweight, thin leaves. To get good isolation you need heavy, dense leaves and large air gaps.leaving as small an overall amount of combined air gap as possible.
Whoa! Either I'm totally misunderstanding what you said, or that is a four leaf ceiling you are planning! Maybe you could do a diagram in SketchUp to show what you have in mind?Ceiling: 2 ceilings will be mounted on the 2 wall leaves achieveing 100% decoupling from both the existing ceiling and the inner and outer ceiling leaves.
Once again, if you already have a concrete floor, I'd just leave it like that and forget all that stuff on top. It will give you good acoustic floor, more ceiling height, and save you money! - Stuart -My first questions is: Should I add some kind of underlay inbetween the ply and the pine? I think not but please feel free to post strong views if you have them.
Hi
You are too kind!Hi Tony, and Welcome! It's always great to have a newcomer who did his homework, follows all the rules, and does a great, detailed first post, with all the basic info!
The building has already been built!Ouch! That's not looking very good at all. Is there any chance at all you can change some of those dimensions (especially the height), or are you absolutely stuck with them? If it's a shed type structure in your yard, then surely you can at least go a bit higher, even if you can't increase the footprint?Quote: The internal dimensions are 2.8m (w) x 5m (l) x 2m (h). I realise this is far from optimal but that's the space I have.
I will certaily have corner traps and have accounted for that. Who knows what else!It's a small room, so it will absolutely need large bass traps. You could probably allow for those in at least the four vertical corners now, in your early plans, since that will be the very least you will need, without any doubt. It might help you in laying out windows, doors, HAVC and electrical if you already have those accounted for, to avoid conflicts later.Quote: I have yet to decide on traps, helmoltz resonators and other treatments
The building exists as described. I will simply be adding layers to existing T&G on the steel mounts. Otherwise I would not have bothered and worked directly on the concrete.You have extremely limited height: Is there any reason why you could not just leave plain concrete floor, and gain back those few cm from the floor? Plain concrete makes a good acsoutical floor anyway. If it is too ugly you could stain it: look around the forum to see some of the stunning effects people have done here with stained concrete floor.Quote: Floor: chipboard T&G is mounted on a metal subframe that is on concrete. I will add layers as follows: greenglue --> 6mm ply --> pine t&g floorboards.
Stuart - Do you think that adding another layer of 12mm Platerboard will achieve sufficient mass and lower resonant frequency? I have already bought some products but will buy thicker materials for the next wall! It is important to remember I only have 2.8m width to play with...Quote:12mm is too thin, for both of those. Resonant frequency too high, too flexible, and not enough mass. It will not isolate well. Go with 16mm, and instead of the particle board I'd go for plywood, OSB or MDF, for the extra mass and strength.Walls: Double frame 100% decoupled 2-leaf wall made from 1 layer of 12mm chipboard (particle board) and 1 layer of 12mm plasterboard (drywall).
Ok - that's £100 saved! I thought that some 'bounce' would deflect energy but I'll put that money into more greenglue...Why? Is that just to get a good seal against the floor, due to the concrete being uneven? If that is not the reason, then you don't need it: It won't do much for you for isolation.Quote: Each leaf will be mounted on 12mm Neoprene.
I think I wasn't clear - this was in reference to carefully caulking the room leaving as little air to escape the walls as possible. Now we are on the matter of gaps between leaves... is less than 4" really worthless? Again I only have 2.8m width and there's no way I can lose 4" in a 2m ceiling.Bad idea: Reducing your air gap reduces your isolation greatly. Anything less than about 4" of air gap (10cm) is worthless, and especially if you are only going with lightweight, thin leaves. To get good isolation you need heavy, dense leaves and large air gaps.Quote: leaving as small an overall amount of combined air gap as possible.
The ceiling will have only 2 leaves - each mounted on a wall leaf. I am aware of the 'more-than-2-leaf' issues.Whoa! Either I'm totally misunderstanding what you said, or that is a four leaf ceiling you are planning!Quote: Ceiling: 2 ceilings will be mounted on the 2 wall leaves achieveing 100% decoupling from both the existing ceiling and the inner and outer ceiling leaves.
I think you know now I don't have T&G flooring on top of steel frames on concrete. So do I use underlay between the ply and the pine flooring?Once again, if you already have a concrete floor, I'd just leave it like that and forget all that stuff on top. It will give you good acoustic floor, more ceiling height, and save you money!Quote: My first questions is: Should I add some kind of underlay inbetween the ply and the pine? I think not but please feel free to post strong views if you have them.
Huge thanks for your considered response that has got me thinking and more focussed. I am mostly worried by the 'less than 4" air gap being worthless' comment which suggests I shouldn't even bother at all! I will certainly address the wall thickness issue and use stronger carcassing. I think I have to be a realistic knowing that balancing the requirements of isolation whilst having at least some room size to actually work in is tricky. So the really big question now is: Should I just create a single leaf room with a 4" air gap to the existing structure? This is a major rethink and will save lots of money. Will this create a kind of 3-leaf system as the exising walls are 2 leaf and thermally insulated? I will certainly completely decouple the inner leaf from the existing structure so I think this would act independently of the outer walls but I am not sure... 2nd post and I think I have completely confused myself and thrown my plans in the air seeing how they land. Tony- Stuart -
What you haven't done is to explain with some detail what the building you are using is made of, how it is built, etc.
A lot of energy has already gone into explanations that don't amount to much if the building design is not taken into consideration.
I imagine a metal shed with steel members and thin exterior sheathing and what would be more useful to this would be to add mass to the structure >IF it can support it. Doing a room-in-a-room type construction, with a metal floor and plywood that already creaks, will most likely not give you the results you think it will.
Pictures, we love pictures and it is true that a picture is better than a thousand words.
There's two things going on here: One is the resonant frequency of the drywall itself, as a single independent sheet. The other is the resonant frequency of the entire MSM wall. Adding mass to the wall will, indeed, reduce the resonant frequency of the entire wall, but it won't change the resonant frequencies of the individual sheets of drywall. It also won't change the flexibility of those individual sheets. This gets a bit more complex, since various parts of the spectrum are isolated by different properties of the wall itself. At very high frequencies, coincidence / damping are what most affects isolation. From there down to about twice the MSM resonant frequency, it is the MSM resonance itself that controls the isolation, mostly. From there on down to below resonance, it is the mass of the wall that controls isolation, not the resonance (in fact, resonance is acting AGAINST isolation in this region). And below that (way down low), it is the mass and stiffness of the wall that controls isolation. But it's way more complicated than that simple outline, since there is plenty of overlap between those regions, and they all interact anyway. Theoretically, an infinitely stiff wall would be a perfect isolator, since nothing could make it vibrate, at any frequency. In reality, you can't achieve enough stiffness in any realistic wall to be useful. And on the flip side of that coin, flexibility is good to have for some regions of the spectrum! An infinitely massive wall would also be a perfect isolator, since once again nothing could make it vibrate, but once again that is rather hard to achieve in reality. An infinitely damped wall would also be a perfect isolator (once again, if it is damped perfectly, it cannot vibrate). And once again impossible to achieve. OK, so that's my long meandering rant about nothing, that merely illustrates that good isolation is really hard to achieve, since different things have a greater or lesser affect on isolation for different parts of the spectrum. The point being that adding the WRONG thing to a wall can have an effect that you didn't count on. One of those "wrong things" is thin, flexible lightweight members, such as 12mm drywall. It adds mass, yes, but it is thinner, less rigid, and has a higher resonant frequency than 15mm drywall does, so it won't act quite the same as 15mm drywall does. Even though it is only 3mm thinner. its interactions with the rest of the wall are nowhere near the same. And adding yet another layer of the same stuff, even though it sill increases the mass of the entire leaf further, still does not produce the other properties that 15mm drywall has. It's not just the total mass that you put on a leaf that matters: there are other factors that matter too. If it was just mass that mattered, then you could just stack up some really thick layers of egg crates until you get to the same mass as drywall, and you'd have a perfect studio! :) I guess that probably didn't answer your question at all, did it?Stuart - Do you think that adding another layer of 12mm Platerboard will achieve sufficient mass and lower resonant frequency?
If you really could get it to "bounce" properly, then it WOULD help! But the problem is that you have to nail/screw/bolt the framing right through that neoprene and into the subfloor. As soon as you do that, you create a flanking path that bypasses the "bounce" entirely. You "short-circuit" the rubber. But even if you could get away without attaching your walls to your floor ( :shock: ) the chances of you accidentally loading the neoprene just right, to get it to bounce, are pretty slim. As in somewhere less than zero... :) Floating a mass on a spring is not easy: you have to first know exactly how much the "spring" needs to be compressed so that it acts like a spring: compress it too much, and it flanks. Don't compress it enough and it flanks. That is stated in terms of how much deflection it needs at a certain load. In other words, you need to get xx % deflection using yy kg/m2 of load. So now you have to know the entire weight of your wall, and figure out how to distribute that and adjust the surface area of your neoprene at each point, accordingly, to get it to compress to exactly that %... Lots of math, and the chances of hitting it by luck are nil.Ok - that's £100 saved! I thought that some 'bounce' would deflect energy
Ahhh! OK, got it. Yes, caulking everything is a must. If it can possibly leak, then caulk it. Even if you know for sure that it cannot possibly leak air, then caulk it anyway, just in case... :)I think I wasn't clear - this was in reference to carefully caulking the room leaving as little air to escape the walls as possible.
Probably, but not necessarily. Two major factors set the MSM resonant frequency of your wall: Mass on each leaf, and size of the air gap between them. More mass is good, more air gap is good. So in theory, if you have to decrease your air gap, then you can compensate by increasing your mass. For large air gaps, it is roughly linear: Halve your air gap, and you can compensate by doubling the mass on both leaves. But it gets down to a point where the relationship is no longer linear, and for very small air gaps you need to add huge amounts of mass to compensate. And that brings the other issue: Mass itself takes up space! If you have to add four layers or 15mm drywall to compensate for reducing your air gap by 2” (for example) then you lost out overall because those extra four layers of drywall are thicker than 2”! So it gets down to the point where you just cannot do anything, since it ends up being counter-productive. That cross-over from “useful” to “not useful” occurs at around 4”, depending on other factors. Less than 4” of air gap means that you have to add unreasonable amounts of mass to still keep MSM resonance down where it needs to be.Now we are on the matter of gaps between leaves... is less than 4" really worthless?
You might not need to, depending on how the roof above is built.... :) That's why posting photos and diagrams of what you actually have is so important: There are techniques that might be applicable to your case, but we'll never know unless we can see what you have, in detail.Again I only have 2.8m width and there's no way I can lose 4" in a 2m ceiling.
Anything is better than nothing! But only you can decide if it is "good enough" for what you need. How much isolation do you need?I am mostly worried by the 'less than 4" air gap being worthless' comment which suggests I shouldn't even bother at all!
Bad idea. 3-leaf.So the really big question now is: Should I just create a single leaf room with a 4" air gap to the existing structure?
Yes it will create a 3-leaf system. So if you currently have a 2-leaf insulated wall, and space is at a premium, then the ideal solution is to take off the existing inner leaf from that wall, beef up the outer leaf from within the wall, between the studs, then build a new frame a couple of inches away from the now-beefed-up-single-outer-leaf, and put a couple of layers of 5/8 drywall on just ONE side of that new frame. If you do the drywall "inside out" (drywall facing the cavity, new frame facing the room) then you have a bout a 4" air gap in there, and you have the plus of the frame facing the room, where you can use it to put up your treatment without eating any more into the room. Or if you do the drywall "normally" (drywall facing the room, frame facing the cavity) then you have about an 8" air gap, which is great for isolation.Will this create a kind of 3-leaf system as the exising walls are 2 leaf and thermally insulated?
Welcome to the crazy, muddled, non-intuitive world of acoustics and studio building! :) You have now successfully passed the initiation ceremony. (Next, we'll teach you the secret handshake, and the special chant... :) ) - Stuart -2nd post and I think I have completely confused myself
Hi xSpace Let me try to address this with pictures and quotes from the manufacturers http://www.greenretreats.co.uk. The floor is "constructed from an 80mm thick composite sandwich using no less than 5 layers" I think this is ply>celotex>1 other layer?>chipboard>flooring> and is mounted on a gulvanised sub frame on top of concrete. The walls are 80mm thick all wood contruction with insulation that "sit squarely on the steel frame and are secured with high tensile plated bolts through the steel section. Once all the joints are sealed, the side sections are clad on site with superior grade 22mm thick Redwood spruce shiplap". Then there is membrane - insulation - melamine coated chipboard (yuk) which is the inside wall. The ceiling is "90mm thick self supporting metal ribbed roof. Sturdy 4" x 2" timber lintels support a 4" thick composite roof" Hopefully the attached pics will be of some help The first pic is of the actual buildingWhat you haven't done is to explain with some detail what the building you are using is made of, how it is built, etc. A lot of energy has already gone into explanations that don't amount to much if the building design is not taken into consideration. I imagine a metal shed with steel members and thin exterior sheathing and what would be more useful to this would be to add mass to the structure >IF it can support it. Doing a room-in-a-room type construction, with a metal floor and plywood that already creaks, will most likely not give you the results you think it will. Pictures, we love pictures and it is true that a picture is better than a thousand words.
Stuart said:
Oh my... that is radical and my wife will kill me if I do this. This is more than a little heart breaking I must say. I really don't want an iso booth in what is a tiny room so don't want to go that route either. My instinct tells me I have planned this quite well but clearly my instinct is way, way off. I think I might have been planning a 4 leaf system when I thought I was creating a room within a room! :oops: Is it abandon project before I even start having just spent £800 on materials that are filling my garden and house? Whoops! Insight greatly appreciated right now as I am now completely left scratching my head. Many, many thanks to you Stuart for setting me straight. I should have asked before blowing any money.So if you currently have a 2-leaf insulated wall, and space is at a premium, then the ideal solution is to take off the existing inner leaf from that wall, beef up the outer leaf from within the wall, between the studs, then build a new frame a couple of inches away from the now-beefed-up-single-outer-leaf, and put a couple of layers of 5/8 drywall on just ONE side of that new frame. If you do the drywall "inside out" (drywall facing the cavity, new frame facing the room) then you have a bout a 4" air gap in there, and you have the plus of the frame facing the room, where you can use it to put up your treatment without eating any more into the room. Or if you do the drywall "normally" (drywall facing the room, frame facing the cavity) then you have about an 8" air gap, which is great for isolation.
Not necessarily! Don't abandon hope yet... Tony, the one question you haven't answered yet, is the most basic of all: "How much isolation do you need?" In other words, what are doing inside that room, and how loud is it? Measure it with a sound level meter, C weighting, slow response. That answers "How loud am I?". Then measure the normal ambient level outside that room at the closest location where you are most likley to cause a disturbance (EG, neighbor's bedroom window, etc.), at the quietest time of day/ night, with nothing going on inside that room. That answers the question "How quite do I have to be?". Subtract B from A. That answers the question "How much isolation do I need?". Until you do that, you cannot really decide on what kind of structure you need to to reduce level "A" to level "B". You might already have more than you need (unlikely), or you might need an amazingly huge amount extra (unlikely), or most probably you need something in between. But unless you do the actual test, you cannot possibly know. I'd suggest that before you do anything else at all on the room, get out your sound level meter (or buy, beg, or borrow one), and do the test! :) - Stuart -Is it abandon project before I even start having just spent £800 on materials that are filling my garden and house?
Hi Stuart I have ordered a sound meter and will test as you say. I do know for sure I would like more isolation than the room is currently giving me. I will set up my monitors and get them working and perform measurements as you suggest. Many thanksNot necessarily! Don't abandon hope yet... Tony, the one question you haven't answered yet, is the most basic of all: "How much isolation do you need?" In other words, what are doing inside that room, and how loud is it? Measure it with a sound level meter, C weighting, slow response. That answers "How loud am I?". Then measure the normal ambient level outside that room at the closest location where you are most likley to cause a disturbance (EG, neighbor's bedroom window, etc.), at the quietest time of day/ night, with nothing going on inside that room. That answers the question "How quite do I have to be?". Subtract B from A. That answers the question "How much isolation do I need?". Until you do that, you cannot really decide on what kind of structure you need to to reduce level "A" to level "B". You might already have more than you need (unlikely), or you might need an amazingly huge amount extra (unlikely), or most probably you need something in between. But unless you do the actual test, you cannot possibly know. I'd suggest that before you do anything else at all on the room, get out your sound level meter (or buy, beg, or borrow one), and do the test! :) - Stuart -Is it abandon project before I even start having just spent £800 on materials that are filling my garden and house?
I'm looking at those photos that you posted, and in the wall one it looks like the insulation is some kind of Styrofoam and foil sandwich. Is that it? If so, it is not doing anything at all for you, acoustically. Just replacing that with ordinary fiberglass insulation would probably improve things a couple of dB.
How come you can't take the interior drywall off that structure? That's all you really need to do, to get down to one leaf, then from there you can proceed.
One more about the floor: Maybe I'm just a bot dense here, but I still don't get how that is built. Basic question: do you have a flat concrete slab under there somewhere, with everything else sitting on top of that? If not, then what is on the "bottom" of all of it?
I mean, right down at the lowest level, you have dirt: plain old planet earth. What comes next? A layer of concrete poured on top of the dirt? Or an air gap, then some wood, then all the rest shown on that photo? This floor issue is important.
- Stuart -
Hi Stuart
I just read this fascinating thread (http://www.johnlsayers.com/phpBB2/viewt ... =1&t=13629) featuring the creme de la creme of this forum (John, Rod, Andre, Eric) regarding multiple leaf designs and it reassured me that there will be a way to move forward whatever way I end up there! from what I have read a 4" gap and a dense inner leaf will certainly improve matters especially if I add mass to the centre leaf.
The inside layer is malamine coated chipboard and the wall is a prefab panel constructed offsite. I am not sure how to deconstruct it and my wife will really disapprove and most likely kill me or at the very least maim me. I'll look at it more throughly tomorrow. I read somewhere that the leaf could be negated by drilling holes and reducing the overall size of the panel. This could be a way forward as, should I have to remove the sound proofing when/if we move, I could simply cover the walls (and holes) with plasterboard.I'm looking at those photos that you posted, and in the wall one it looks like the insulation is some kind of Styrofoam and foil sandwich. Is that it? If so, it is not doing anything at all for you, acoustically. Just replacing that with ordinary fiberglass insulation would probably improve things a couple of dB. How come you can't take the interior drywall off that structure? That's all you really need to do, to get down to one leaf, then from there you can proceed.
From the bottom: Concrete > Metal subframe (and thus a 8 inch or so air gap) > ply > insulation > chipboard. I am not so worried about the floor and am just adding some mass with a greenglue layer. I really must sleep now - it is 3am and am forumed out! TonyOne more about the floor: Maybe I'm just a bot dense here, but I still don't get how that is built. Basic question: do you have a flat concrete slab under there somewhere, with everything else sitting on top of that? If not, then what is on the "bottom" of all of it?
OK, that's what I feared: I don't see how you are going to be able to do what you need to do, at a reasonable price. The problem is weight. Let me explain: Like I said before, you can compensate for the small air gap by putting more mass on the leaves, and you can compensate for your third leaf by putting more mass on the leaves, and since your existing two-leaf has low mass and no acoustic isolation, you can also compensate for that by putting more mass on your one remaining leaf. That's a lot of mass. But the problem here is that your floor will very likely not be able to support all of that extra mass that you are talking about! You might have to beef up the support structure for that floor. You say that your sub-floor is plywood, and now you are talking about putting thousands of pounds of extra weight on it, all concentrated around the edges. I don't see how that sub-floor is going to handle that load. I'd strongly suggest that you need to get a structural engineer to take a look at what you have, and tell you how much extra load you can put on it, safely. And you might have another issue, too: You say there is an underlying concrete slab, then an 8" air gap, then your sub floor which is supported on a metal frame. So basically you have something like a floated floor (but NOT floated correctly for acoustic isolation) or an MSM floor. Either way, it is a resonant cavity down there, but the floor mass isn't high enough to get the resonant frequency down where it needs to be, so I see an isolation issue in your floor, too. Once again, the solution is to add mass to the floor, and damping (insulation) in the cavity, but here too you have an issue with the load capacity of the floor, and possibly access to the cavity so that you can put the insulation in. Then there is the issue of the roof: I just don't see much mass at all on that roof. So you will have to put a lot of mass on your ceiling to compensate for the lack of roof mass. Once again, that mass has to be supported by the sub-floor... I think you really need that structural engineer to tell you how much that floor can take, and look into methods for beefing up the supporting structure so it can handle the load that you will have to place on it. - Stuart -From the bottom: Concrete > Metal subframe (and thus a 8 inch or so air gap) > ply > insulation > chipboard. I am not so worried about the floor and am just adding some mass with a greenglue layer.
Hi Stuart
I MUST send you some amazon gift(s) for your kind input!
Ok so right now would big air gaps, insulation and green glue solutions be the way to go? I Can't get too heavily invested in this financially so will take the hit in terms of physical space.I don't see how you are going to be able to do what you need to do, at a reasonable price. The problem is weight. Let me explain: Like I said before, you can compensate for the small air gap by putting more mass on the leaves, and you can compensate for your third leaf by putting more mass on the leaves, and since your existing two-leaf has low mass and no acoustic isolation, you can also compensate for that by putting more mass on your one remaining leaf. That's a lot of mass. But the problem here is that your floor will very likely not be able to support all of that extra mass that you are talking about! You might have to beef up the support structure for that floor.
Right (or should that be ouch very wrong!?!?!?)! I really can't go the route of expensive solutions so how does this sound? Non-parallel walls are ok for a listening room as long as we have symmetry so I am thinking that the 'inner room' can have angled side walls with an 8" air gap at one end and a 4" at the other and end walls with an 8" air gap. I have created a quick pic to help explain this. Can localised extra mass/extra green glue help at the point where the air gap is at its minimum (i.e. 4")? I think I have to go with the room getting smaller than I expected which isn't a problem as I will mostly be working alone or collaborating with lone musicians. I will not be playing drums everyday but there will be times when there might be extended use. The neighbours will just have to suffer. The sound meter arrives tomorrow! TonyAnd you might have another issue, too: You say there is an underlying concrete slab, then an 8" air gap, then your sub floor which is supported on a metal frame. So basically you have something like a floated floor (but NOT floated correctly for acoustic isolation) or an MSM floor. Either way, it is a resonant cavity down there, but the floor mass isn't high enough to get the resonant frequency down where it needs to be, so I see an isolation issue in your floor, too. Once again, the solution is to add mass to the floor, and damping (insulation) in the cavity, but here too you have an issue with the load capacity of the floor, and possibly access to the cavity so that you can put the insulation in. <snip> I think you really need that structural engineer to tell you how much that floor can take, and look into methods for beefing up the supporting structure so it can handle the load that you will have to place on it.
Hi
Many months later and snatched hours and weekends inbetween a full time job and the build is nearly finished. I thought I'd be able to better document the process here but that hasn't quite worked out.
Attached are images of the plans that I used for layout of the inner shell. more posts and photos to come over the next few days. I've also developed an unhealthy addiction to eBay UK and my mic, preamp and guitar list has trebled! I also spent a lot on green glue - I really hope it has helped.
The idea for the plan was to maximise airgap and introduce as many slight angles to minimise mode buildup. I know my knowledge is very limited compared to many of you here so please don't scoff too much!
Stuart's input at the beginniing was a massive help to me even though I am sure he may well be wincing at my methodologies and decison making!
Anyway I've had fun and that's part of it for sure.
Room measurement, treatment and speaker placement are next and there's much research still needing to be done!
First I wanted to add some mass and stability to the somewhat creaky floor. Ply was added to the chipboard tongue and groove with green glue.
Next up building a frame. This was tougher than a normal stud frame as it had to be independent from all but the floor surface. Additionally there were a number of angles involved so Pythagoras and more head scratching was required throughout this process. There was also heavy reliance on spirit levels.
The frame became solid once the full length ceiling beams were fully connected to the walls. It was surprisingly solid as rock and remains so.
You can also see layered insulation that I got for an incredible price from Wickes in Catford in a "3 for the price of 1" deal.
First wooden layer added further stability and helped ensure general squareness. the build actually ended up within 2 mm of the design. This is probably more down to luck then enginnering prowess I would imagine...
Crimping electrical cables. Research suggested junction boxes are illegal without access although in the end I have designed access to everthing through the inner walls. I bought a proper crimping tool that worked well with 100 percent success first time on all crimps!
A plasterboard layer has gone on top of the wooden layer with a healthy amount of green glue inbetween. Getting the ceiling up was no fun and the only part of the job that has required help from others. I got some students from my school (I am now a secondary school teacher after 22 years of self employed sound engineering [and increasing deafness]) to help on one Sunday!
I have laid a pine T&G floor on top of the ply with more green glue with a raised area for the kit with an extra 3 layers of plasterboard inbetween the ply and pine for added mass.
I assiduously sealed any possible openings on all layers using acoustic sealant as I went along ensuring the minimum of air leakage. The plasterboard layer was staggered so joins were carefully covered. I am now sealing the plaster board layer using jointing compound and am about half way through this process. I also built a heavy door which is about 80mm thick which hung perfectly first time. I have yet to place the door stops and double (or even triple) seals that I have been thinking through.
Once the seals are done it's time for my drum kit to get set up and my hefty 3 way monitors to pump some air. This will inform treatment and I have already bought Knauff Rocksilk 60 (equivalent to Rockwool RW3) wth the view to putting in superchunks for starters and then other treatment. It is taking up half the kitchen and my poor long suffering wife has been most patient throughout!
God bless patient wives (or other spousal units) everywhere!
Come on, Tony! No fair! How can you START posting a series of build photos, then stop half way through, just as it is getting interesting!!!???
Where's da PICS??? :)
- Stuart -