Hi,
This is my first post to the forum though I've been a long time reader. A new addition is going to be built to our Musical Arts Center. It will include 2 large rehearsal rooms with a large recording studio/teaching space adjacent. I have been working with the acousticians on the design, while they've designed numerous educational facilities in music schools, it's pretty clear that they have limited experience designing recording studios. I thought I'd post the design here for comments. Since this is new construction we have the opportunity to design the space correctly from the beginning. Presently we are in the preliminary design phase with construction slated to start within a year. This studio will be used both for recording and teaching classes with as many as 20 students.
The space will be isolated from the rehearsal rooms by double masonry walls. Raw dimensions are about 20' high, 24' wide 27' deep so there's plenty of space to work with. The acoustician came up with a design featuring splayed walls with approximate dimensions of 16' high, 20' wide, 24' deep, very close to an ideal ratio, and it puts the room modes at about 20 - 30 hz which is very good. However he has proposed framing the room with lightweight material, basically making the entire space a large Helmholtz resonator. This strikes me as difficult to pull off correctly - I've worked in countless studios and I don't ever recall seeing this kind of design. We are not planning on soffit mounting speakers, so we will have to deal with the low frequency reflections from the front of the room. He has indicated bass trapping in the front of the room, but does not appear to be familiar with traditional studio trapping design. He plans to treat the rest of the room by hanging acoustic panels on the walls. I have explained to him that a studio is not a performance space, or even a listening space, it must be as flat and even as possible but I think that he is used to designing performance spaces where greater reverberation in the low end is desirable because it has a warm sound. Here is the acoustician's design:
And here is the architect's drawing:
I am working on my own design for the space with a slightly different side wall splay and a more traditional approach to acoustic treatment. I'll post it when finished.
New Studio - Indiana University School of Music
Originally posted at johnlsayers.com, topic 14431.
Which "ideal ratio" would that be? The dimensions you give turn out to give a ratio that is in the general ball park of Louden's 5th best ratio (which is 1:1.2:1.5, while yours is 1:1.25:1.5). But since you have splayed walls, ratios are somewhat of a moot point anyway. It also looks suspiciously like you are going to have some three-leaf walls in there.a design featuring splayed walls with approximate dimensions of 16' high, 20' wide, 24' deep, very close to an ideal ratio,
Actually it gives you 39 modes under 100 Hz, and 119 modes below 130 Hz. Only the first two are in the range you mention, at 23.5 and 28.3. But the mode spacing isn't all that great, and room modes are dominant all the way up to 73 Hz. But once again, that is theoretical for a rectangular room, and yours is going to have splayed walls, so all bets are off on what the real modes will turn out to be, other than the vertical and lengthwise axials.it puts the room modes at about 20 - 30 hz which is very good.
I'm not sure quite what he means by "making the whole room into a Helmholtz resonator"! How would that work? In order to work as a Helmholtz Resonator, it would have to have some kind of restricting neck open to something else, with a slug of air resonating in the neck! How can a sealed, isolated, airtight room also be a Helmholtz Resonator? Maybe he could explain that to you, since it's hard to picture. A room will resonate at its natural modes anyway, but that doesn't make it into a Helmholtz resonator.However he has proposed framing the room with lightweight material, basically making the entire space a large Helmholz resonator.
Any particular reason for not doing that, when you basically have a blank sheet of paper to design on, and soffit mounting is so beneficial?We are not planning on soffit mounting speakers,
What about the floor and ceiling? What plans does he have for those? If the inner leaf is basically a masonry shell with concrete floor and ceiling, with that "light weight construction" thing inside it, and the only treatment is some bass trapping at the front of the room and a few panels on the walls, it sounds to me like that room will still be rather too live, to say the least! A concrete cave with just a bit of absorption on the front wall, that isn't really an effective bass trap at all... Perhaps you should consider hiring a real studio designer, who has a proven track record in designing spaces like this, such as John. - Stuart -He has indicated bass trapping in the front of the room, but does not appear to be familiar with traditional studio trapping design. He plans to treat the rest of the room by hanging acoustic panels on the walls.
Thanks for the quick reply. As you can tell, I am out of my area of expertise here. This studio is part of a $40 million expansion, the acousticians were hired by the architects, I did not have a say in the choice. I did request using a studio designer for the control rooms, but it has been made clear to me that this is not an option.
Could you please explain this? I am not familiar with the termIt also looks suspiciously like you are going to have some three-leaf walls in there.
That was my term, I realize it's not an accurate description of a Helmholtz resonator, but the acoustician described something like this: the lightweight walls will absorb low frequency energy and even out the room's response. It seems to me that it will be difficult to predict how this will affect the frequency response of the room.How can a sealed, isolated, airtight room also be a Helmholtz Resonator? Maybe he could explain that to you, since it's hard to picture. A room will resonate at its natural modes anyway, but that doesn't make it into a Helmholtz resonator.
I am prepared to be convinced otherwise, but there are several practical reasons not to soffit mount - the ability to swap monitors, use the speakers in another venue, and a general distrust of the acoustician.Any particular reason for not doing that, when you basically have a blank sheet of paper to design on, and soffit mounting is so beneficial?We are not planning on soffit mounting speakers,
The floor will probably be glued carpet on top of concrete with tile or wood insert at the console. I asked him about the ceiling and he has not answered yet, but I would expect it will be sloped and 'lightweight' too.What about the floor and ceiling? What plans does he have for those?
Exactly my impression. My thoughts are that the room should have a greater splay in the front third and then a gentle splay to the rear. The front will need considerable bass trapping and absorption and then a combination of absorption and diffusion for side walls and ceiling, with more trapping along the rear wall.If the inner leaf is basically a masonry shell with concrete floor and ceiling, with that "light weight construction" thing inside it, and the only treatment is some bass trapping at the front of the room and a few panels on the walls, it sounds to me like that room will still be rather too live, to say the least! A concrete cave with just a bit of absorption on the front wall, that isn't really an effective bass trap at all...
Would be nice. but niot an option unfortunately. On the other hand, the guy working on the studio seems open to learning.Perhaps you should consider hiring a real studio designer, who has a proven track record in designing spaces like this, such as John.
I've been doing some research on construction techniques, this forum is really fantastic BTW. In my initial meetings with the Architects I asked for maximum isolation between the rehearsal space and control room, so we could be mixing loud rock and roll while a quiet acoustic rehearsal was taking place in the other room. They recommended masonry walls and no control room window. the drawing shows double masonry, my assumption is that this will be cinder block that is filled with concrete, I have asked for clarification but no response yet. Am I correct that this will be two single leaf walls? I asked about inner shell, the acoustician responded that this would be 1/2" Sheetrock on metal studs. This is how he describes it: "you will get moderate low frequency absorption... it's not as much as a tuned absorber or bass trap but it is more broadband and we will have a lot of it so it's impact will be significant". Here is how he described the ceiling: "the ceiling could be a lay-in grid with a combination of sound-transparent and sound absorbing tiles to conceal ductwork etc. The ceiling space should definitely have sound batts, and maybe even some tuned low frequency absorbers".It also looks suspiciously like you are going to have some three-leaf walls in there.