I thought maybe I'd sit with him with the requisite sections of the Rod Gervais book to instruct him specifically on how to isolate the slab. Per someone's suggestion on this forum, I ran out and bought that book and read it cover to cover before posting here. It's really helpful!
You should probably get "Master Handbook of Acoustics" as well (by F. Alton Everest), affectionately reffered to as "MHoA". That gives you the acoustic background behind what Rod does in his book. It's always better to understand WHY you are doing something, rather than just do it blindly. If you understand the acoustic theory behind decoupled walls, then you can apply that to your own walls, and make adjustments as needed by your specific situation, rather than just do things "cookie cutter" style from Rod's book.
That part I'd love some guidance on - I imagine there's a best practice for connecting a hallway to a structure in such a way wherein the studs aren't actually touching the new structure; I seem to recall some of that from the Gervais book.
That's what I figured with my comment about your contractor not having thought it through. If he hasn't done that, which is rather basic, I'd be concerned that there are many, many other aspects of isolation and acoustics that he hasn't thought through either, any one of which could have serious repercussions for your studio. I'd suggest that you might want to hire someone like John to design your place for you, then just give the plans to the contractor so he can build it. It's far better to let an expert designer do what he does best, rather than someone whose field of expertise is entirely different, and his only connection with acoustic design is a book that you bought him, which doesn't even deal with acoustic design theory!
Again hoping the book will be helpful in instructing him on what to do.
See comment above!
I did a search and couldn't find the ITU BS.1116-2 document you reference. Can you point me in the right direction?
Did you google it? It's not hard to find...
https://www.itu.int/dms_pubrec/itu-r/re ... !PDF-E.pdf
It turns out there's an updated version, ITU BS.1116-3. Only minor differences, though, but here it is if you want it:
http://www.itu.int/dms_pubrec/itu-r/rec ... !PDF-E.pdf
Yes! Due to the scope of this project (we're essentially knocking down our house and building from scratch in addition to adding the barn studio), we'll have a bunch of appliances from the old kitchen that we intend to add to the barn loft
Great! But that implies plumbing, and plumbing implies water noise, which you will need to account for in your isolation design. You don't want to be recording a beautiful soft, perfect vocal for some classic ballad, then have the wound of the toilet flushing and tank refilling get into your mic... There are ways of dealing with that, but you do have to be aware of it from the start, and that's probably something else your contractor has not considered. He would likely just install the sinks, toilets, pipes, drains, and vents the same way he always does, and you'd end up recording: "Oh Danny boy, the pipes, the pipes are calling... FLUSSSHHHHH GURRGLLLEEE SLOOOOSH GLONK GLONK GLONK!!!"
That just blew my mind. Literally every drawing I've seen in my research has some version of splayed walls, and I always just assumed it's a huge requirement. Why do they all do it? Because of that same myth?
Glad that got your attention! There are numerous studios out there with pure rectangular shapes. Many people consider Abbey Road to be one of the best studios on the planet, yet every single room in Abbey Road is rectangular...
Here's the thing: There are valid reasons why a design might want to splay walls, but if you dont' know what the reasons are, or how much to splay them, then you are wasting your time, your money, and your studio space! You are paying a LOT of money to build this barn/studio, without any doubt. Each square foot of floor area is costing you $$$$$ So why would you put a whole bunch of those $$$$$ inside a wall, where they are no use to you, unless you really need to do that?
The only valid reasons for splaying your walls, are:
1) If you are using a design concept that requires it, such as RFZ, NER, CID, or one of the derivatives. It that's the case, then your speakers will very, very probably be flush-mounted (a.k.a. "soffit mounted"), and parts of the side walls and front wall will be splayed carefully at precisely set angles that accomplish the purpose of the design.
2) To deal with flutter echo. In which case you need to angle your walls by a total of at least 12°, since that's the smallest angle that deals with it effectively. However, there are other methods for dealing with flutter echo that do not involve wasting so much space.
3) If there is some structural impediment or other layout issue that forces you to do so.
4) If it is needed in order to provide more space in an adjacent room (eg, to make a vocal booth, iso booth, machine room, bathroom, office, etc. big enough to be practical, where it would have been too small without that.
5) Purely for aesthetic reasons: ("Because it looks cool")
I can't think of any other valid reason. And certainly, the reason "Because everybody does it that way", is not valid! Once again, it comes back to understanding the acoustic principles behind the design, so that you can make intelligent decisions, rather than just doing a "cookie cutter and resize" or "cut and paste" approach.
In fact, Rod is a big proponent of rectangular studios. If you read his book, be mentions that in a couple of places. He normally does rectangular rooms, unless he has a good reason not to.
Yes, a lot of modern rooms do have splayed wall, but that's because the predominant design concept today is RFZ, or variations of that, which requires that the walls be splayed by specific angles. But there's no such thing as "one angle fits all". Each room is different, and will need a different splay angle in order to work. You cannot just copy the floor plane for a room you saw that you liked, and scale it up or down to fit your space: angles do not scale. Neither do ratios. Neither does acoustic treatment. If you want to take a design and scale it, then you need to recalculate the angles, and re-design the treatment.
I am interested in the RFZ style room, and I think I know how to get the angles right? If there's a resource you know of, however, that is a good primer on this I'd love to read up on it.
Wow! Ummm... that's sort of like saying "I think I understand the basis of playing the guitar. If there's any resource that you know of to make me play like Peter Frampton in a few minutes, then I'd love to read up on that!"
I think you get my point. Designing an RFZ room is quite an undertaking! It's not something you can learn to do in a brief time. First, you need a decent background in the basics of acoustic theory ("MHoA"), then you need a decent background in construction design (with some basis in structural design), then you need to learn a good 3D modelling tool, such as SketchUp. Then you put all those three together, to come up with the basic layout, and you adjust the angles and dimensions and layout and geometry as needed, until you arrive at the optimum compromise.
You can learn how to do it yourself, for sure: It takes time, but it certainly is possible. When people ask me about that, I estimate about 3 to 6 months to learn what you need to know, then another three or four months to actually do the design. That's realistic. I don't know of anyone who has done it faster than that: Like most skills, it takes about 2,000 hours of study and practice to get to the point where you are able to do basic things well, and about 10,000 hours to get to the point where you really dominate the skill and can use it well, in most situations.
In other words, it takes about as long to learn to design great studios, as it does to learn to play the guitar like Peter Frampton, or the drums like Phil Collins.
Interesting. Do you still recommend using them as a good starting point for room dimensions? For instance, if I'm doing a RFZ, are the dimensions I've chosen for my room kind of irrelevant now?
Room ratios are a starting point, not an end point, and there's no need to go crazy about trying to find "the perfect ratio", because no such thing exists. Small rooms will ALWAYS have lousy modal behavior, no matter how hard you try to finesse your ratio, for a very simple reason: There are not enough modes to go around. In order to get smooth modal response, the room needs to be large enough that there are at least three or four modes for every note on the musical scale, all the way down to the bottom end. In other words, your Schroeder frequency needs to be around 20 Hz, or lower. That's physically impossible in a small room. So the best you can do is to choose a ratio that is not terrible (no two dimensions related mathematically, nor within 5% of being related, plus the others listed in BS.1116-3), and that is reasonably close to one of the known good ratios. Hopefully inside the Bolt area, but even that is not an absolute requirement: there are a few good rations that are outside that area...
In other words, there's no point in spending hours and hours trying to make your ratio "perfect", simply because that is not physically possible. There's no such thing as a "golden ratio" that makes your room sound spectacular. There are no magic cuboids, or esoteric incantations that will make the modes go way. So just start with a reasonable ratio, and work from there.
OK, that does not really answer your actual question! So here goes with that: For non rectangular rooms that still have some parallel surfaces, the axial modes associated with those will still be as predicted, and so will the tangential modes that ONLY involve the surfaces that are parallel and perpendicular. So in your case, if the the ceiling and floor are parallel, then the axial modes shown by a calculator for the vertical direction will be valid (all of the 0,0,x modes). Since part of the front wall is parallel to the rear wall, there will be some modal activity in that direction too, so the front-back axials will also be valid, to a certain extent (all of the x,0,0 modes), as will any modes that involve both of those (all of the x,x,0 ) modes. But the horizontal axials will not be valid, since the side walls are splayed, so none of the tangentials that involve the side walls wil be valid either, and all of the obliques will also be invalid.. However, you
can do one test with a calculator using the largest width, and another with the smallest width, and another with the average width, to get a rough idea of how those will play out. If all three of those give promising results, then you are probably OK. However, your front wall is also partially splayed, to you will need to do the same for that one, and then you'll need to do series of nine more that are the combinations of the largest, smallest and average width, with the largest, smallest and average length, the work through all that to make sure there is nothing terrible.
So yes, sort of, kinda, somewhat, a little bit, to a certain extent, you can still use a modal calculator to get an idea of how your room will perform, if you understand what you are doing, and what you are looking at with all that data you will produce. It does give you a pretty good impression of the final behavior, but it won't be accurate for the obliques, or the tangentials that involve splayed or partially splayed walls.
And once again, there's no need to go nuts over a perfect ratio. It's far more important to correctly predict SBIR artifacts from the walls (especially the back wall) and set up the room geometry to minimize that.
This I'm learning...yikes.
Yup. And that's just the "V" part of HVAC. When it comes to the "H" and "AC", you need to start figuring out the latent heat load, and the sensible heat load for full occupancy and minimum occupancy, to make sure that your AHU can keep the relative humidity constant at around 40% all the time, in addition to keeping the temperature around 22°C all the time, so that your instruments don't need constant returning as the humidity and temperature change, and that your condenser mics don't suffer tonal changes for the same reason...
HVAC is fun!
This part confused me. Since the posts are every 12 feet, there's really no way to make an 18x14x9.5 room without at least one of them in the room itself.
Yes there is! You put them inside the wall cavity! Or rather, you design your walls around them, such that the posts end up in the cavity between the walls. You are not yet showing your Live Room inner-leaf walls, but as soon as you put those in place, you'll see what I mean. You CANNOT have any posts inside the rooms themselves: They would be flanking paths, conducting sound in and out of the room. The inner-leaf is sacrosanct: Nothing can violate it. No mechanical penetrations, and no mechanical contact. Not even a single nail or screw can connect the outer leaf to any part of any of your inner-leaves.
As far as having the post removed, I'm sure I could do it but of course everything comes at a cost.
I don't think it is necessary to do that in your case. You picked a decent basic layout concept where the only problematic posts can easily be positioned inside wall cavities. Or rather, where the walls can be designed such that the posts are in the cavities.
A machine room under the stairs is a great idea. I also need somewhere to put the furnace, other guts of the HVAC...
All of that can go in your machine room. But you do need to have an access door to get to it! And since the machine room does not need to be inside the isolation shell, you could put it anywhere. Of course, you could put it inside the shell if yo u wanted to. For example, if you have rack gear in there that you need access to all the time, then you might want to have it next to the CR, with a direct door into it. But that's an operational, or functional, decision, not so much an acoustic one.
- Stuart -
