room design and alternative solutions

Hi there. im new at this forum and I wish I had found it sooner, but better late than never. Great forum. thanks for the effort John sayers. Its great :yahoo: 1 year ago i started to build a studio for film mastering and recording. My daugter and i have a small company. She´s doing film editing, and im one of these soundaholic´s. i love gear, plays guitar and other instruments...a musician, editor and work as sound engineer and producer at a local TV station here in denmark. The Facelity is built into a wooden barn of approximately 140 sqm divided into 2 compartments. one room will become an optimally regulated acoustic listening room with 7.1 surround installed. The other room for different purposes with movable walls for recording and all kind of activities.. gallery and a medium size foto studio for eksample! I been working in several control rooms with lousy acoustic control, so i decided to perform as perfect a space as possible. Heading for HTX´s standards, as HTX hysterical specs sets milestones in what to achieve. I do not want to be HTX qualified, but the specs is nice to aim for. When it about post production its interesting, but music production is another story. therefore the room should be changeable. with sliding walls that change the damping. for surround you need highly damped acoustic, for music you need a more live space with some reverb in the high end. I have had many thoughts about the ordinary version of a recording studio, and came to the decision that space and air, to feel comfortable in the room meant just as much as the requirement for vocal boot's and isolated small chambers that would be filled with rubbish or other storage. space is essential. which is also the basis for being able to make a proper acoustic control. I decided to isolate the building with straw bales. with plasterboard to the outside and clay plaster on the inside. The building is located far from neighbors as a real external noise problem does not arise, and straw structure allows the low frequency pass out of the building, with the expectation that I can achieve a nice frequency response in the low range. The sound isolation isn´t that bad. with 90db inside i measured 30-35 db outside at the nearest point to the sound source.. (The other side of the wall) When the plaster is sprayed on the wall it can be at variated thickness. between 1-3 inches depending on the purpose. the surface can be strait or dented. Again depending on the purpose. A diffuser kan be sprayed and the surface of the diffuser will act like a fractal diffuser because of the material is a mix of different materials. I use cutted straw,gravel and paper wool for arming and reinforcement of the clay. Furthermore the clay plaster does make a perfect climate inside the building with a stabil humidity that is important too. I have attaced som pictures of the control room and the work we have done. The question i have is about an idea that i want some opinion about. A middle wall?. instead of turning the face to the lower end of the room i would turn the direction against the high end. The cieling is constructed with 18 degrees rising and then stops and fall down to create a sort af shelf where the machine room should be placed under. I will then place a wall in line with this cieling but with no corners I will leave a passage. i will able to enter the back of this wall that.. is made of strawbales. Again. Im a strawman :lol: So, this wall is not massive, but hard near the speakerplacement (thick plaster) graduated in the stiffnes so the area between the speakers is changing to thin plaster. The strawbales can be covered with concrete wood thet meet the requirements for fire protection. This wall can by a trap, with the right covering. Main monitor system is Genelec 8250, left center and right, and 8240 as surround speakers. I do have other speakersystems but these will be the main set. Placed in front of the wall. I consider flushing the genelec´s but they are not that easy to build into a wall. I hope to get some feedback on the issue of orientation and this wall..see (Studie nordorient) as I think of doing. Maybe just to see how it behaves. One of my concerns is to me that i avoid the the pressure build-up in the corners and will have free passage to the back where the equipment will stay. all the best Lasse Luffe

While hay bales do have good acoustic properties, I think my big concern with building a studio like that would be the large fire hazard. How do you fireproof so much hay?

When it about post production its interesting, but music production is another story. therefore the room should be changeable. with sliding walls that change the damping. for surround you need highly damped acoustic, for music you need a more live space with some reverb in the high end.

You are talking about the live room there, not the control room, right? Control rooms should not have variable acoustics: they should have neutral acoustics that conform to ITU, AES and EBU specs.

The sound isolation isn´t that bad. with 90db inside i measured 30-35 db outside at the nearest point to the sound source.. (The other side of the wall)

60 dB of isolation is pretty good for a studio, so the hay is clearly not "allowing low frequency to pass out of the building".

A diffuser kan be sprayed and the surface of the diffuser will act like a fractal diffuser because of the material is a mix of different materials.

The surface would have to have have vary large variations to provide diffusion at useful frequencies. Small variations (less than 5 cm or so) would have little effect on the important frequencies that actually need diffusion.

The question i have is about an idea that i want some opinion about. A middle wall?. instead of turning the face to the lower end of the room i would turn the direction against the high end.

I'm not sure I understand what you mean by the "middle wall". Maybe you could explain that in more detail?

The cieling is constructed with 18 degrees rising and then stops and fall down

Then it is sloping the wrong way! The room dimensions should increase as you go back in the room, not decrease. The narrowest point/lowest ceiling should be at the front, over the speakers, and the widest point / highest ceiling should be at the back.

Main monitor system is Genelec 8250, left center and right, and 8240 as surround speakers. I do have other speakersystems but these will be the main set. Placed in front of the wall. I consider flushing the genelec´s but they are not that easy to build into a wall.

Soffit mounting (flush mounting) is always advisable, but the issue I see in trying to do that inside bales of hay is the cooling: You need to have good ventilation past the rear of the speaker, to provide enough cooling so that the speaker does not overheat. Doing that inside hay bales might not be easy.

I hope to get some feedback on the issue of orientation and this wall..see (Studie nordorient) as I think of doing. Maybe just to see how it behaves.

Well, you should still follow the general guidelines for soffits and for speaker / mix position geometry. Using bales of hay or any other materials does not change the basic layout. So you should still set up the geometry according to ITU-R BS.775-1, EBU 3276, or AESTD1001. Hi Lasse, and welcome to the forum! :)

One of my concerns is to me that i avoid the the pressure build-up in the corners and will have free passage to the back where the equipment will stay.

Well, you cannot avoid that. Modes are a consequence of the dimensions of the room, ONLY, and there is no way to get rid of them. Building a partial wall does not get rid of the corners: it just moves them to a different place. You can only control modes by choosing a suitable ratio for your room, and by damping them with suitable treatment in the corners, or in extreme cases by using resonant devices. Building your soffit wall only part way across the room does NOT eliminate the corners: the corners are still there, just in another place, and you have now also added back the problem that soffits are supposed to prevent: edge diffraction around the sides of the speaker baffle. In this case, your "partial wall" is the speaker baffle, and since it is not sealed to the side walls, low frequency waves will wrap around the ends of that wall, get in behind it, and cause some of the the same problems that the soffit was trying to prevent. You can calculate the frequency at which this problem will start occurring by using the normal baffle-step response equations. - Stuart -