Hi there "TPSP", and welcome to the forum!
First post, lets make it a big one i hope its not too big
No problem! Big is good: providing a lot of information helps us understand your situation better.
This is my first studio build. I have been reading the 'Rec Manual' for a couple of months now, pretty sure i understand most things
Good! I'd suggest two other books: "Master Handbook of Acoustics" by F. Alton Everest, and "Home Recording Studio: Build it Like the Pros", by Rod Gervais.
Space: Volcanic rock cave.
That's interesting! I think this is only the second time that someone on the forum has had access to a cave for building their studio.
it has a natural front-to-back slope(approx. 1m) and a right-to-left slope(approx. 1ft).
The ceiling slope is very useful. The wall slope: not so much.
When you knock on the walls of the cave there are many spots/patches of various sizes(ranging from 6cm-60cm diameter approx. guess) which are hollow. Almost like little hemholtz resonators...
Helmholtz resonators don't usually ring when you knock on them... What you are hearing is simply cavity resonance, which isn't the same as Helmholtz resonance.
Naturaly the cave has alot of absorption and diffussion(affecting/treating HI,MID & LO freq.).
Well, that's the cave itself, but none of that will be involved in the final acoustics of your room, since you are proposing to build a proper "room-in-room". The acoustics of the outer-leaf (the cave) have very little to do with the final interior acoustics of the inner-leaf.
I think once the room is plastered the sound would bounce around more before being absorbed(what i want). is my thinking right here?
Sort of. Partially. Kind of. But not really. Your inner-leaf will create a totally different acoustics environment, with practically no relationship to what you have now. The dimensions of the new walls will define the modal spread as well as the overall decay time, and the construction materials will have an effect on that too. The acoustic treatment will have to be designed specifically for the inner-leaf room, and not at all for the existing cave, since that doesn't even come into the equation.
Right now when listening to a piece of music the LO's and MID's could have a little more punch. More fat push. The sound needs to be bigger overall. The HI's are dry. It really sounds like theres nothing i could take from the HI frequencies. The sound right now seems somewhat tubby. But never the less the sound is above average. tight sound all accross. The HI's need raising. or maybe to put it a different way, the HI's need to bounce around a little more before being absorbed
OK, but none of that matters, since you will be defining a new acoustic space with your new walls and ceiling.
Im actually thinking to build a drum room in the right corner
The drum booth should go wherever the ceiling is highest. Drums need a lot of space around them to sound good, and they also need high ceilings. If not, then you get reflections, comb filtering, LBIR and other artifacts on the overhead mics, due to the sound bouncing back from the ceiling and interfering with itself at the mic position.
Im thinking to construct the skeleton from steel studs(the thinner ones), insert some lite insulation and cover with 1 ply of plasterboard/sheetrock.
That would, indeed, be a good plan. That's the correct way of doing it. However, 1 layer of drywall (plasterboard) might not be enough to get you good isolation between the CR and the drum booth. You might need two layers.
I dont think bass_traps are necessary, right? Wrong?
Wrong! Bass traps are ALWAYS necessary in small rooms. The smaller the room, the bigger the bass traps.
Im thinking just to build a simple room with no treatment, let the sound escape. What would people say to that?
What I would say, is that this would be a terrible idea! Control rooms need very tightly controlled acoustics, not random guesses. There are several specifications that must be met in order for a control room to be usable, and they all define similar characteristics, such as the minimum and maximum size, the frequency response, the time-domain response, the layout and positioning of the speakers and listening position, etc. If you do not follow those guidelines and get your room as close as possible to those specs, then it will not be usable as a control room. It is that simple. You need to look at documents such as ITU BS.1116-2, EBU Tech-3276, AES-111 MÄKIVIRTA ET AL, Genelec OY-2003, and several others. Those all show you exactly how the acoustic response of your control must be if you want to use it for serious work.
Q: Should i use all the height of the cave? Would an arched ceiling be better than a triangular one?
If you can figure out how to gable your inner-leaf ceiling to roughly follow the existing cave rough, then that would be great. It is always better to maximize the interior volume of the room, if you can. However, do not arch the inner-leaf ceiling, as that would focus sound where you do not want it. Curved concave surfaces should be avoided in studios. It would also be very difficult to build and treat such a surface.
Q: Ive been told by a friend to use a piece of pressure treated wood between the concrete and the stud for moisture.
You say this is a cave. In my experiences, caves are often damp. You MUST deal with that issue first, before you can build anything in there. My guess is that you will need to spray the entire save surface with shotcrete that has a waterproofing compound added, and even then all of your lumber that is exposed to the cave side will need to be pressure-treated, and you will not be able to use normal interior grade drywall (plasterboard) for your sheathing, since it absorbs moisture and will soon fall apart. You would need to use something like OSB or marine grade plywood instead, and even then you should paint it with something to seal the surface even better, and/or use Tyvek or some similar moisture barrier.
its like a floating floor
Ummm... no, it isn't. That is nothing at all like a floating floor.
i would obviously take the chance and put some neoprene strips before the wood
That would be a waste of money, and time, and is not necessary at all. Floating a wall is a lot more complex than just putting any old piece of rubber under it. There's a whole set of equations that you need to calculate to make sure you order the right correct rubber, with the correct resilience, and load it with the correct load, to get the correct deflection so that it really does float.
If i build with a floating floor(and the rest of the structure on top) in the end once plasterboard is up, would it give me more reverb inside the room VS. non-floating floor.?
You seem to be completely misunderstanding the purpose of a floating floor, and also how to build one. A floating floor is ONLY needed in situations where you already have a serious vibration or structure-borne sound problem in the existing structure, before you start building the room, and you need to isolate the room from that, or where you expect that your floor will pick up enough impact noise or air-borne sound that will be transmitted into the existing structure, and would annoy others. You do not have either of those situations, so you do NOT need a floating floor! You also do not have enough budget to build a floating floor: they are expensive to do properly. Floated floors have nothing to do with increasing reverb within the room. In fact, the exact opposite is true: floating floors must be tuned such that the fundamental natural resonant frequency (MSM) is tuned to at least one octave below the lowest frequency that needs to be isolated. Therefore, a properly designed and built floating floor will NOT produce any reverberation at all in the room. It's very purpose is to isolate the room and prevent any such reverberation.
You probably should read through this thread, carefully:
http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173
Theres a possibility of inserting the monitors into the volcanic rock, i imagine it would eat up the frequencies very well.
No, it would not "eat up the frequencies". It would do what all flush-mounts do: it would eliminate SBIR artifacts, edge diffraction artifacts, some types of comb filtering artifacts, as well several early reflection issues, and it would also eliminate the need for the inherent power imbalance that is built into all small speakers, so you would need to roll off the lows by 6dB using a gentle shelving filter with the center point set at the baffle step response frequency for the speakers you will be using.
However, since you will be building a room-in-a-room, then it will not be possible to flush-mount the speakers in the rock. And the rock is not angled correctly anyway. If you do want to flush-mount your speakers to get all those benefits, then I'd suggest doing in the conventional way.
What would people say to me leaving 1 wall as it is and just adjoining the walls,floor,ceiling,plasterboard structure to the rock?
There would be no logical or acoustical reason to do that, that I can see. Why would you want to do that?
I would have to make sure its not touching the rock and then fill the air gap (between the rock and woodwork/plaster)with silicon right?
Once again, why? What is your reasoning for doing that? Is the rock vibrating, and you need to isolate the walls from the rock?
would i do something else? Can anyone recommend anything?
I would suggest building two conventional "room in a room" concept spaces here, one designed as a conventional control room, perhaps following the RFZ concept if you wanted to do that, and the other as a drum booth. Both of them would be done as four single-leaf walls and a single-leaf ceiling, using conventional framing techniques, but with treated lumber for the framing, and non-hygroscopic sheathing. I would also suggest using conventional treatment for both rooms, but specifically in the case of the control room I would suggest using large, deep bass traps in as many corners as possible, plus the usual treatment at the SBIR points and first reflection points, deep absorption on the rear wall, and whatever else is needed to get it within ITU specs for a room that size, in order that it really can function as a control room.
- Stuart -