HI there "nicklear", and Welcome!
I am not aiming for a professional studio, nor do I have that kind of budget (have ~$3000 for sound isolation and treatment).
OK; so isolation is out of the question, and you are basically talking about treatment only on that budget.
solid brick external walls.
That will give you reasonably decent isolation.
- room measures mid 50's on my phone SPL app and mid 60's in the attic
Measuring what and measuring how? There's a big difference between A and C, fast and slow, and also between rock music and general residential ambient noise levels. Please be more specific about what you measured, and how you measured it.
I'm afraid i don't have budget for an omni mic to do REW properly
So how are you going to treat and tune your room? If you really do want to prove the ""nothing good comes from Manenberg" myth wrong, instead of just perpetuating it, then you'll need to put a bit more effort into it!
A decent acoustic measurement mic costs around $ 100, or even less. It also makes for a great overhead mic on drums, and doesn't do half bad as an ambient mic on many other instruments. As a room mic on electric guitar, for example, it does a pretty acceptable job. I even used one once to record an entire university choir... it's a useful addition to your mic collection, as well as being the only possible way of getting accurate readings from your room, so you can treat it.
Challenges of sound isolation:
You don't have the budget to isolate. Sorry.
... layers of drywall with green glue there to isolate.
A single crate of Green Glue will eat up 10% of your entire budget, and you would need several crates. That's not a good way of spending it. Green Glue is great stuff, but only if you have the budget for it. I don't normally use it for low-budget studios. Only high-budget.
Then I would build a false ceiling with fluffy fibreglass across it for treatment.
The entire ceiling? All tuned to the same frequency?
114mm x 38mm timber (4”x1.6”)
Technically, that's a 2x5, which is an unusual size. Mote common is 2x6, which is 140 x 38 mm. Perhaps yours were trimmed down for some reason?
I haven't found resilient channels anywhere.
I'm pretty sure you can get normal hat channel in the RSA, so have you looked into RSIC clips or something similar?
So either a DIY plug which I have a thread on or seal it with another layer. I don't tend to open the window anyway.
On a tight budget like that, I would go with a removable plug.
- the bass that comes through the floor I think i will live with. (there is some blanket thing under the laminate floor)
That's the underlay, and it does nothing to stop sound. It's only useful for a bit of thermal insulation, and reducing impact noise to a certain extent.
Two questions: Why do you have "bass coming through the floor"? And: What is the floor made of?
- I realise I haven't addressed ventilation, but HVAC isn't used around here and I have been through winter and summer here and had no problems with heat or cold,
You need to re-think that. Fast. Deep. Building a studio automatically implies that it will be sealed air-tight, twice over, then wrapped in thick insulation. In other words, it will be like working inside a sealed plastic bag, inside a sleeping bag...
People need to breath. If the studio has no ventilation, it will become unpleasant to work in there, very fast.
Also, many musical instruments and some mics are affected by changes in humidity and temperature. The tone changes as the conditions change. If you hope to produce music that is better than "nothing good", then you want to be sure that the instruments and mics sound the same at the end of the session as they did at the beginning... You will need HVAC. You might think you don't, but you do. This is a discussion I have rather often with studio builders, and once they think it through and do the math, the realize that it's a major issue. For a serious recording studio, HVAC is not a luxury: it is a must. It is every bit as necessary as having speakers and a DAW.
I really lose confidence in the whole project when I try to get my head around ventilation.
And that should be a major big whopping glaring frantically waving bright red flag! Any time you get to the point in a studio build where you don't understand something, and decide to sweep it under the carpet to forget about it, that's a MAJOR sign that you should stop right there, and not advance even one step further until you figure it out. Ignoring such blatant warning signs can only lead back to "nothing good" coming out of this...
My plan is to open the door sometimes
Think this through: How would opening a door help, if the room is sealed air tight? There is no place for the air to go! If you want air to move, you have to create a pressure difference between two points, but opening the door only provides one point.... How would you create a difference in pressure between one point and itself?
Watch this brief you-tube video to understand the problem:
https://www.youtube.com/watch?v=ah5Rm-1bS3U The glass is your studio. The water inside the glass is the air inside your studio. The reason the water does not run out of the glass is the same reason the air will not run out of your studio: it is held in place by air pressure. Think about it...
1) Any reason not to go for the idea of moving ceiling up to the rafters, e.g. unsafe or waste of money?
Insufficient budget. You need to save every penny you can, in every possible way.
2) Do I need additional batons to hold the weight / will the rafters take the weight?
The only person who can tell you that is a qualified and certified structural engineer. It will cost you money to hire one.
After a visit from a couple of architect friends, they completely ripped my idea of moving the ceiling up to the roof, pointing out that it would be difficult to isolate the beams as well as the roof tiles.
They are right!
In fact, looking at it again, I think my drywall ceiling is coupled via numbers 1-6 in the diagram to the roof?
And also through the walls! The roof rests on the walls. The ceiling rests on the walls. Flanking! No isolation.
As I understand it, with brick walls surrounding the space, I only need one double layer of sheetrock (with green glue) inside in order to create a M-A-M.
Correct, but skip the Green Glue. You don't have enough budget for that. You will also need to seal the brick walls, with some type of masonry sealant. Brick is porous, and you need to seal the pores so that the brick surface is fully hermetic.
small air gap
Fluffy fibreglass
Why do you want a small air gap? Is that something that is required by local building code? If there is no legal reason why you need the gap, then get rid of it and fill the entire cavity with insulation. Leaving empty space in the cavity robs you of isolation.
Fluffy fibreglass
...
Denser 703 equivalent fibreglass
703 is not that dense. It is light. It is 3 PCF, roughly 48 kg/m3. But it is semi.rigid panels, which is not the same acoustically as equivalent ordinary fiberglass. So when you say "703 equivalent", what exactly are you talking about? It would only be equivalent if it really is semi-rigid panels with a density of around 48 kg/m3 and a GFR of around 15,000 rayls and similar surface impedance.
Cloth
Some covered with slats
I would do this for all 4 walls and
Slats on the ceiling? Why? Also, it's not usually a good idea to have tuned devices at the front of the room, as they can potentially "color" the sound before it gets to your ears.
But not do a floating floor as I'm on ground level concrete slab
Excellent!
!!! But if you are on a slab-on-grade floor then I don't understand the earlier comment: "- the bass that comes through the floor I think i will live with.". What "bass" is "coming up through the floor", if you have a slab on grade?
And I will try to get over my fear & ignorance of ventilation to get that sorted
YES!!! Smart move! Very smart.
(one reference attached in pics) ... Does this look good?
Ummmm... Nope! Whoever built that "snake in a blanket" box does not have a clue about how to isolate HVAC. All that would accomplish is to greatly increase the static pressure but with no useful insertion loss at all! It would actually make the air flow noisier, not quieter. I'm not sure where you found that monstrosity, but you ca safely ignore whatever other advice they give you...
Here is what proper silencers look like:
http://www.johnlsayers.com/phpBB2/viewt ... 0&start=45
http://www.johnlsayers.com/phpBB2/viewt ... 9&start=74
http://www.johnlsayers.com/phpBB2/viewt ... 25&start=2
http://www.johnlsayers.com/phpBB2/viewt ... 42&start=5
http://www.johnlsayers.com/phpBB2/viewt ... 61&start=0
http://www.johnlsayers.com/phpBB2/viewt ... 5&start=98
http://www.johnlsayers.com/phpBB2/viewt ... &start=157
http://www.johnlsayers.com/phpBB2/viewt ... =2&t=13821
http://www.johnlsayers.com/phpBB2/viewt ... 8&start=44
http://www.johnlsayers.com/phpBB2/viewt ... 2&start=16
- With just one single wall layer for the inner room, do I then still need to improve TL on all windows and doors in outer room?
Absolutely! Isolation is not walls. It is not floors. It is not ceilings. It is not windows. It is not doors. It is not HVAC. It is not electrical. It IS all of those! Isolation is the entire complete system of the entire complete studio. Isolation is only as good as the weakest point. If you isolate your walls really well but don't bother about isolating the ceiling to the same level, then you wasted a stack of money on isolating your walls, because the sound will simply get out / in through the ceiling. If you really did do the walls and ceiling well, but didn't do anything about the doors, then you wasted even more money, since the sound will ignore the wonderful ceiling and walls and will enter/exit through the door. If you did the walls, ceiling and door to the same level but forgot the windows, then ditto: you wasted even more money than before and still got the same result, because sound will always take the easiest path in/out: through the windows. And if you did the windows too, but forget to isolate the HVAC ducts, then ditto. And if you did the HVAC ducts along with everything else but forgot to isolate the electrical system, then one again: Ditto! Lots of money wasted, as sound will take the easy path in and out: through the electrical system.
Isolation is the entire studio, not just one part of it. Isolating walls, doors, HVAC and electrical is just as important as isolating walls. And far more complicated. And far more expensive. Doors have to open and close, but they have to be massively heavy, and they also have to seal air-tight. Not easy to do. Expensive. HVAC ducts are basically huge holes in your wall or ceiling: they have to let large volumes of air pass through but somehow prevent the sound from getting through. Complicated. Expensive. Windows have to let light through, but block sound. Obviously, you cannot put insulation in the gap between the two window panes! You would not be able to see if you did that! Yet they have to isolate to the same level as the walls, ceiling, etc. Complicated. Expensive. The electrical system has to allow the wiring to come in through the wall while stopping the sound from coming in. So you cannot do the normal thing of chopping holes in your walls and ceiling to put the electrical boxes and conduit through.... complicated. Expensive.
That's why I said up front that your budget is insufficient to isolate your room. Yes, you might have enough to frame the walls and ceiling, and hang some drywall on it, but I don't see that you'll have enough to also isolate the doors, windows, HVAC system and electrical system, which are more complicated and more expensive. It's been a long time since I last lived in the RSA (30 years or so), so I'm not very up to date on building material costs, but I suspect that they won't be much different from what they are anywhere else in the world. I do not see that your budget is enough to do everything that really needs doing. Note that I said "everything that really
needs doing". Not just the things that you have thought of so far, but also the things you thought of then discarded (such as HVAC), and also the things you didn't think of yet, .... such as full perimeter door seals, surface-mount handles, heavy-duty hinges, automatic door closers, mini-split system, structured raceway surface mount electrical system, thick laminated glass with acoustic PCB interlayer, duct liner, HVAC silencer boxes, fans, ducts, registers, crate loads of caulk.... etc. All of that adds up, fast. Those are the unexpected costs that kill underfunded and under-planned projects part way through. Your budget probably does cover the very basic structure itself, but there's no way it can cover all the other stuff, and also your equipment. And we have not even started talking about the cost of the acoustic treatment yet....
So my number one suggestion would be to increase your budget to something more realistic, or scale down the plans to fit the budget. If that budget is as far as you can possibly go, then it is only good for the HVAC system and the basic equipment, nothing else. No isolation, and no treatment.
Would it be better to still have an extra stud wall at the entrance end?
If you forgot to include that one as part of your "room-in-a-room" isolation system for the complete studio, then yes!
- Could I still let in daylight via a double glass panel in the inner room?
Yes you can, and it's always great to have daylight in a studio! But it costs money to do that. Thick laminated glass with acoustic PVB is not cheap.
- With the inner room ceiling under the current ceiling plus the roof above - is this 3 leafs and therefore a problem?
YEs it is 3-leaf, but no it is not a problem. The "air gap" distance to the roof is very large, so the MSM resonant frequency will be very low, and therefore not a problem.
- Is it worth angling the side walls 6 degrees at the front to help with reflections
To "help" in what way?
Angling your walls is another one of those acoustic myths that refuses to die... you do not need to do that to "help with reflections"! The only time that is needed is to deal with flutter echo.... but flutter echo can be dealt with in other ways. The only other time you would need to angle walls (or rather, parts of walls) is if you are doing a true RFZ design concept, or any of its variations, such as CID or NER. And if that's the case, then 6° is way to little. You will need a much larger angle for those.
Some people still think that angling walls somehow helps with modes, standing waves, reflections, SBIR, or just "to make it sound good". All of that is pure garbage. Angled walls do not eliminate modes (standing waves), reflections, nor SBIR, and won't make a room sound better. The ONLY valid reason is for RFZ or derivatives. Or maybe "because it looks cool"! On the own side, it increases costs, wastes space, complicates construction, and makes it much harder to predict the acoustic response.
- Should I soffit mount my active Tannoy 501A's
I would, yes. In which case I would also suggest that you do an RFZ-type design for your room.
- Roughly what % to cover with slats and spread over the room or more in the mixing end or the tracking end?
You cannot have one single room that is excellent for both tracking and mixing. The two phases require different acoustics. Control rooms for mixing and mastering must be neutral, symmetrical, even, non-specular, etc. Tracking rooms should NOT be symmetrical, nor neutral, nor even, etc. Tracking rooms are supposed to have "character". Control rooms are supposed to NOT have "character". Clearly, you cannot have one room that does both. Either it will be a great control room but lousy for tracking, or a great tracking room that is lousy for mixing.... or you could try to make it both at once and end up with a room that is pretty bad for mixing and also pretty bad for tracking. The only way you can make that work, is by making the acoustics variable. You can design devices that allow you to change the acoustic "signature" of the room, by opening, closing, sliding, flipping, rotating, etc. parts of the device. That is possible, and I have done a few rooms like that, but not on your budget. It's expensive to design, expensive to build, and expensive to test such devices.
Anyway, overall it looks like your biggest problem is budget. You have good plans for the room, but no way to implement them on the budget you mentioned. Raising your budget or lowering your goals are the only two options, realistically.
- Stuart -