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PostPosted: Thu Aug 02, 2012 1:22 pm 
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Joined: Sun Jun 24, 2012 4:05 pm
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Location: Bloomington, IN, USA
Hello People of John Sayers' Forum!
First of all, thank you for taking your time to read this, and I hope to receive your constructive criticism and advice as I progress along this thread!

Now, to the point.
Fairly simple story: I’m a teenager in high school, I’m in a band, I enjoy music and technology, and I would like a recording studio/practice space in my backyard. Hooray!

When I decided I was going to save my money for recording gear, I told my dad about my wish. Fortunately, he has a local friend building a house out of earthbags (exactly what they sound like: bags filled with earth of some type) filled with a crushed rock/lime mixture. That’s when the light bulb dinged. So, after talking about it with Dad, we decided to try the same idea for our backyard recording studio! :mrgreen:

A few links to info on earthbag construction:
http://en.wikipedia.org/wiki/Earthbag_construction
http://home.howstuffworks.com/earthbag-home.htm
http://www.earthbagbuilding.com/

Recently, after discussing our plan of action, we concluded that it would be best to construct a smaller building, such as a “jam-shack”, and using that as a practice space until we better understand the acoustical and isolative properties that these earthbags have to offer. After completion of that build, we plan to make additional extensions to the preexisting building.

The reasons that we decided to use an earthbag approach to building a studio are: 1) earthbags are a very inexpensive alternative for building a home, 2) they are known for being quite energy-efficient and having good insulation values, 3) using crushed rock is forgiving, whereas concrete is not (you would need many tools to take concrete out), so if we mess up, it’s easy to reverse, and 4) the workforce required is very minimal, since all you really need is a shovel. Essentially, the process of earthbag building is to obtain the bags, get your earth, fill the bags, tamp the bags, and to stack the bags. That’s about it!

NOTE: We have a few restrictions to our construction, including the fact that there is an inactive gas line below most of the backyard, which prevents us from digging very far down. Next, there are electric cables that run along the canopy of the area, so we can’t build too high. Also, we want enough space in the rearmost area of the yard to fit a dump truck, in case we need another load of crushed rock, which is probable. Lastly, Indiana law states that a building must be at least 5 feet away from the property boundary.

As for current progress, Dad ordered twenty tons of crushed rock some time ago, and we have mostly been experimenting with it thus far.
The first thing we did with it was to make a “platform” out of it to see what structural capabilities it has. After, shoveling, leveling, dampening, and tamping, we left it to the elements to see how it fared in weather. We observed that it kept well in rain, despite some erosion on the edges. Since then, it has been about three weeks, and using the tamper on it gives a reassuring “thud”. However, sharp edges will still tear it up.

On to earthbags; we got a smaller length of polypropylene tube from the friend I mentioned earlier, and to experiment, we made four out of five sides of a pentagon out of it. We now have an idea of the work it takes with two people to make a small course of an earthbag building. After tamping the filled bags, they are seemingly very sturdy and do not move at all. We will now either finish the pentagon to get an idea of the acoustic characteristics it has, or take it out, order more bags, and start the jam-shack.

What I hope to have is: 1) a comfortably sized live room able to fit a drum set and an amp or two, 2) a good-sounding control room that fits a workstation desk, monitor stands and a couch, 3) a vocal booth able to fit a person with a guitar, and possibly 4) an additional isolation booth.

For electricity, we may just have an extension cord running from the house to the studio. Nonetheless, if we ever get the chance to install an electrical system in the studio, we may set up electrical outlets in each room.

Next, I understand I do not have the money for professional acoustic treatment, so I will try taking the DIY route, and making my own panels/diffusers/deflectors and see what kind of sound quality that gives me. This will be primarily in the live room and the control room. However, it is possible that I will use brand acoustic foam in a vocal/iso booth. For windows and doors, it may just be better for us to build our own. (What do you think of using two 0.5" thick acrylic panes for the control room window?)

As a last question, I was wondering if curving corners where walls meet would be better for acoustics than if they met at a sharper point. Like if you took a thin sheet of plywood and flexed it into an angular curve, versus joining two straight pieces together at an angle. Also, how would curved walls themselves do?

Thanks for reading! I will try my best to keep this thread current as much as possible. If you can, I would appreciate as much help/opinions as I can get. I'm considering also asking Gearslutz, but I thought this would be a more appropriate first forum. Will post pictures, measurements and construction updates as they become available. Building this studio is definitely going to be experimental! And hopefully, I'm going about it in the right direction!

(Terribly sorry if this is in the wrong place on the site. Please correct me if possible!)
-Joseph


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PostPosted: Sat Sep 29, 2012 2:09 pm 
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Joined: Thu Aug 21, 2008 10:17 am
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Location: Santiago, Chile
Hi Joseph, and Welcome! :)

I have never even heard of "earthbag" construction until now! So, a few comments:

While that might be fine for walls, I'd still suggest at least having a proper concrete slab and foundation. You mentioned a weight of 20 tons initially, plus probably more later, so there's going to be a huge amount of mass in that. You don't want it sitting on something unstable. Plus there's the issue moisture and possibly gasses rising from the earth, so I'd really suggest that at the very least you lay a proper slab. I most certainly would not want to have my equipment and instruments in an environment that is basically just a bare ground floor.

Also, while that seems like it should be great for acoustic isolation (lots of mass, well damped), I don't see that it can possibly have any use as a structure around your studio to which you can nail/screw/bolt treatment and equipment. And it also brings up the point of the ceiling and roof: How do you plan to do those?
Quote:
For electricity, we may just have an extension cord running from the house to the studio
:shock: :!: Apart from being dangerous, that's probably illegal. I very much doubt that your local building code will allow that! I'd suggest that you get an electrician to run a proper branch circuit.

Quote:
and making my own panels/diffusers/deflectors and see what kind of sound quality that gives me.
Trying things at random to "see what that will give you" isn't a good way of building a studio. You should start with a set of clearly stated goals that you want to meet, then plan each room accordingly, by incorporating the acoustics into the design itself: ie, not using bad ratios, splaying walls if/where needed, having enough room volume, having your ceilings high enough in each room for the purpose, angling ceilings if/where needed, avoiding acoustically bad angles, laying out the rooms with correct geometry, etc. There are also general rules of thumb for placement of initial room treatment, and methods for measuring the resulting acoustic response, then adding additional treatment as indicated by the results of the analysis, etc. So there is a basic method that you should follow if you hope to have a usable studio, regardless of the materials that you use to build it.

One word of caution, though: You'd be entirely on your own as far as "earthbag acoustics" is concerned. I have never seem any research at all on how "earthbag" wall react to sound waves, so you will be your own guinea pig and acoustic test facility, all rolled into one. Nobody will be able to help you with information on what to expect.

Quote:
What do you think of using two 0.5" thick acrylic panes for the control room window?
Bad idea. Not enough mass to be of much use for isolation. Just go with normal laminated glass.

Quote:
I was wondering if curving corners where walls meet would be better for acoustics than if they met at a sharper point.
Probably also a bad idea: Concave curves tend to focus sound at a point.

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Also, how would curved walls themselves do?
Even worse! I have actually been in studio in Argentina where they "designed" it to look really cool, with lots of curved walls... it sounded terrible and was basically unusable as a studio. They wasted a huge amount of money building something that looked great but absolutely could not be used for the purpose for which it was designed. The architect understood aesthetics very well, but didn't have a clue about acoustics. Disaster.

Hope that helps!


- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.


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