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Post by lathqe on Jul 18, 2016 9:52:27 GMT
Hello all you smart people. I am a long-term forum-lurker/diy-er/part-time-recording-engineer. I have the good fortune of being able to move my recording out of my bedroom into the basement of a non-profit organization I help out. They want to have a recording space and are happy for me to use it if I help them design it. The best part is that I get play with the acoustics, and for this I need advice. I have read the acoustics faq and other such resources, but since I'm basically starting from scratch with a concrete room I thought I would ask for advice. The space is divided into 2 rooms with a staircase between them. The staircase is next to a full-height, load-bearing concrete wall which has a door going to the right. The left side is to be used as a small conference room (meetings, trainings, etc) as well as a tracking/recording space. So I need to make a nice-sounding tracking room which still is useable by non-musicians for non-music events. The right side space will be the mixing room. There will be full-length storage along two of the walls. These can be whatever I deem acoustically tolerable, so I assume that means closed-door cabinets with some kind of bass trap on the doors... (right?) One hurdle is that there isn't a window between the rooms, and the stairs get in the way of having a decent one. There is actually enough room for a small window, but it wouldn't be all that useful, and it wouldn't be anywhere close to centered on a mixing desk. The staircase could be rotated 90deg. to come down the top wall, and that would provide ample space for a window (unless the wall turns out to be too thick to cut through). This would make the tracking room more long-and-skinny than it is now, and I don't know if that's a useful tradeoff. What do you think? notes: - units on the drawings are in meters - ceilings are about 2.3m (7.5') - (I still need to measure them). - Walls, floors, and ceiling are all concrete, so they'll need a lot of help - I am located in Central Asia which doesn't have easy access to most of the nice, professional products like Mr. Winer's. I can get compressed fiberglass, rockwool, and batt insulation rolls. The compressed fiberglass is quite expensive, though, and I don't know acoustic specifications for it. I've made some bass traps from it before, and they were helpful, so it can't be all bad... So, the primary questions: 1)In the mix room, do I build cabinets into the back-and-side walls or into the 2 parallel sides? 2)Given the above parameters (especially the fact that all 6 surfaces are concrete), what is the best approach to treating the acoustics of these rooms? I can put as thick of traps on the walls as I like. The tracking room has to be pretty, but the mix room can look like whatever I want if the acoustics work. 3)Do I rotate the stairs to give me a window between the rooms (if possible)? Tips? Advice? How thick/what kind of acoustic walls should I make? How short (thick) should the ceiling become? Thank you in advance!
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Post by Ethan Winer on Jul 19, 2016 20:12:16 GMT
1) I wouldn't build cabinets into the walls. I'd get free standing shelves that can be moved if needed. And don't have them cover entire walls. Leave the corners free for bass traps, and the loudspeaker reflection points free for absorbers.
2. Concrete isn't that much different from drywall, it just reflects a little more at the lowest frequencies. So the treatment strategy is exactly the same as for any other room.
3. I'd leave the stairs as they are, then get a camera and video monitor so you can see into the live room. These can be had for a very reasonable cost, surely much less than the cost of cutting a hole in the wall and adding a reasonably sized window. In fact, you can probably get two sets, so they can see you too, for less than the cost of a window.
--Ethan
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Post by lathqe on Jul 24, 2016 19:19:42 GMT
It's been a week, but I finally got to go look at the space again, and I have an update which leads to a different set of questions. It turns out we won't be able to move the stairs after all, so we'll work around the window question. Water under the bridge. - The ceiling is 2.65m (8.5ft), a little bit taller than I said previously. I doubt this changes the overall approach at all, just the math.
@mr. Winer, Thank you for your advice! It is sensible as always. I am worried about the shelving, though. Wouldn't open shelves be an acoustic nightmare since the stuff sitting on them would be changing from week to week (and rattling/resonating)?
Today's two big questions are as follows: 1)What's the basic approach to a room like this? Is it advisable to cover the whole walls/ceiling with insulation? Do I make a false wall (behind which the insulation is stuffed)? What material would that be made from? 2)How do I determine the acoustic properties of the insulation? How do I know the thickness of stuff to use? I can't exactly get a hold of spec sheets here - I'll be buying from an open-air bazaar. Is there some kind of test I can run on it? Or, does all compressed fiberglass and/or rockwoll (both of which I can get here) have acoustic absorption within predictable ranges?
I'm sorry to be asking such noob questions, but the reading I've done always has so many possible approaches and variables I can't figure out what is best in my situation. I have one shot to do this, so I'm trying to get it right. Thank you!
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Post by Ethan Winer on Jul 25, 2016 20:31:20 GMT
I doubt most "things" on a shelf will rattle audibly. You can sweep a low frequency sine wave loudly starting at 20 Hz up to 200 Hz to see what buzzes and fix it or more stuff. The basic approach to your room is the same as for all other similar size rooms: Acoustic BasicsMost compressed insulation is more similar than not. So get what you can find locally, and can afford. Note that some materials are easier to work with than others. I prefer Owens-Corning 703 and 705 because they hold their shape and shed less, but those cost a lot more than mineral wool and are often harder to get. No need to worry about making mistakes. You can start small with, say, 4-8 bass traps in corners plus left and right side reflection absorbers, then add more as you go. --Ethan
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Post by rock on Jul 25, 2016 21:24:49 GMT
I doubt most "things" on a shelf will rattle audibly. You can sweep a low frequency sine wave loudly starting at 20 Hz up to 200 Hz to see what buzzes and fix it or more stuff. --Ethan To add anecdotally the that: My band practice/recording space is shared with other family members so there's all kinds of decorations and doo-dads in the room. Every once in a while, I'll hear some "distortion" in a certain range. I usually end up walking/crawling around the room listening for the source while the offending note on my Hammond Clone is held down with a matchbook or the like. One time it was the latch on a humpback chest (you know, the kind a pirate sits on with his Doubloons inside) another time it was Tibetan temple bells. I have found that blue painters masking tape will stop most sympathetic resonances. Cheers, Rock
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Post by lathqe on Jul 26, 2016 12:04:40 GMT
Thank you again. As I've been dialoguing with the owner it's clear that he wants a locked closet rather than shelves. So I'll partition off one side of the room and put in a door for that. I've attached an updated png. (He also doesn't like the camera idea because of upkeep/breaking/hassle. Oh well. There is room for a small window.) My current approach for the mix room is: 1)stuff the ceiling as full as I can with rockwool (probably 12" or so) 2)bass trap the corners as much as possible 3)build a QRD diffuser for the back wall 4)do... um... *something* to the walls... This leads to my final question: It seems that you recommend killing the ceiling (as close to 100% absorption as possible) but not the walls. Have I understood that correctly? Why is this? How much of the walls would you recommend covering with absorbers/traps? I'm not limited for materials and labor (my own), so I could theoretically build as many traps and diffusers as I need. What would be "ideal" for this space? Or is that a question that can only be answered after measuring? Am I missing anything? After I finish this (in a month) I'll look at the tracking space. Attachments:
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Post by Ethan Winer on Jul 26, 2016 18:05:08 GMT
For a mix room the goals are plenty of bass trapping, plus absorption at all the reflection points including the rear wall behind you. That's explained in the Acoustic Basics article I linked above.
For a recording room you want to spread absorption more or less evenly around a room. It's not that walls or ceilings need less or more absorption. It's mostly about how far away those surfaces are from sound sources and microphones. In a small room all the surfaces are close by, so all should be treated. If you can stand anywhere in the room and clap your hands, and not hear that "boing" sound of flutter echo, then the main problem is solved.
--Ethan
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Post by lathqe on Dec 19, 2016 16:39:29 GMT
I want to give an update and ask another question. I'm focusing solely on the smaller, "control room." I'll finish that one completely before looking to the other. 3 months late... We finally got to clear out the room - there was approximately 5 tons of bricks and other rubble in it (literally). We then discovered it needed a new floor, which we have now finished (concrete). Finally I know what I am dealing with. It's an 18' 6" (5.7m) square concrete basement room with a concrete ceiling barely over 8'. For isolation I will be building 4 stud/drywall walls and a ceiling stuffed with rockwool. These will be free-standing, not touching the concrete. Still one big question is nagging me and I need some smart-people's opinions: Please help me understand stereo a little better. One requirement is to have one whole wall of the room be a storage closet (mostly for books, but also audio gear). I'll do that with large sliding doors made of plywood on casters. These can be constructed in just about any fashion, and I'll be putting some acoustic treatment on them. After making my "brilliant" plan, I realized that I would then have a closet on one side of me and not the other. hmmm What does that do to my stereo imaging? Should I put less-deep, identical closets on both side walls? Should I put the closet at the back wall, thus forcing myself to be oriented with the room in the "wide" way? And where did I read that I'm supposed to "shoot the length of the room"? How important are these questions? This is out of my depth since I've only ever used really bad-sounding spaces to record in. I really want to do this "right" the first time. Which of these room configurations do you recommend? Option 1 is much simpler to make but has an "off-balance" room. How important is this? Option 2 seems to solve this problem, but will be annoying to make. I just want to be sure it's worth the effort. Option 3 is to make the 1-closet version but orient the desk facing the long wall Thank you for all your advice. I really do read a lot of these threads, and I think I've read just about every tutorial I've found here (and of course Rod Gervais' book!)
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Post by starandchlorisse on Dec 19, 2016 19:14:55 GMT
Just a thought on the closets.
Option 2
1 Symmetry is good to avoid unwanted resonances in one side only
2. It provides more length - it makes the room less of a cube.
I was thinking in the past if closets with sliding doors can be also used as big bass traps by adding sliding doors which are build similar to bass traps panels .
If they are moving all the time then you might want to enclose the insulation material in plastic besides the first reflections panels which additionally they would have cotton panels on the plastic,
I m not sure if this is practical and/ or correct though. And I would like to know.
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Post by Ethan Winer on Dec 20, 2016 20:50:10 GMT
Book shelves and other "stuff" are best placed along the side walls in the rear half of the room. Behind where you listen, but not so far back it blocks the corners where bass traps need to go. If you really need so many shelves that they extend on both sides from front to back, then get some absorber panels on stands you can place correctly while mixing.
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Post by lathqe on Dec 22, 2016 5:57:37 GMT
So, am I understanding that you would recommend a room with this sort of shape: I was assuming that a bump-out like that would be a problem. The doors will not be preventing me from bass trapping - I will be putting limp-mass membrane traps on the sliding doors in the corners, and broad-band absorption on the doors that are further from the corners. Additionally, Mr. Winer, I would love some advice on the ceiling. I am trying to do what you guys did to Mr. Ferrara's room and have close to 100% absorption on the ceiling. My ceiling will be sitting on my walls (detached from the current concrete ceiling), so I can build it however I need to. You mention having "a foot" of insulation. Is that just the pink fluffy? I am planning on compressed rock wool, but pink is available here as well. More importantly, how did you keep it up there and not dropping microscopic pieces of glass dust on your heads over time? If I sheath it in plastic or paper I'll be reflecting higher frequencies... but maybe that's good? I would love to know this one. Here is a rough sketch of how I understand the construction: I would love any corrections, and I'm very curious about the use of plastic or paper. Thank you again!
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Post by Ethan Winer on Dec 22, 2016 18:30:50 GMT
Yes, low density fluffy type insulation is fine when it's 12 inches thick. In Doug's case he stapled felt fabric to the bottoms of the ceiling joists to keep the fibers out of the room. You can use paper facing around the perimeter, but leave the insulation fully absorbing (no paper) at the reflection points (area, really) between you and the speakers.
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Post by lathqe on Jan 24, 2017 15:34:31 GMT
Yes, low density fluffy type insulation is fine when it's 12 inches thick. In Doug's case he stapled felt fabric to the bottoms of the ceiling joists to keep the fibers out of the room. You can use paper facing around the perimeter, but leave the insulation fully absorbing (no paper) at the reflection points (area, really) between you and the speakers. Thank you for the input. I have the framing in place now (yippie!) - 5-sided box which sits on the floor and doesn't touch the outside walls or ceiling. I'm ready to start with wiring and insulation. Still scratching my head about a couple things: 1) With this type of ceiling construction, how does it relate to isolation? Normally I see the "mass-air-mass" mantra for isolation. In this case, though, it will be, from the top down: upstairs 10" concrete floor -> air gap -> 12" insulation -> thin cloth -> me. no mass in this construction. Is mass not necessary because of the insulation thickness? 2) Similarly, I am framing up 4 walls. These will not touch the outside walls, 3 of which are just external foundation walls. What is my best practice here? From the inside-out, it will be: drywall -> batt insulation -> air gap -> foundation wall. This leaves a 2" air channel going up to the concrete ceiling above. Do I need to change this? (fwiw, it is 2x6" studs because I have them already) Thank you all again for helping us first-timers!
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Post by Ethan Winer on Jan 25, 2017 18:53:24 GMT
1) Yes, there's no real isolation from putting insulation in the joists. Isolation requires isolated (not touching) structures. 2) Yes, put insulation against the rear side of the new inner wall. But understand that to fully isolate walls you also have to isolate them at the floor and ceiling. Do you have Rod Gervais's book? It explains all of this in more detail than I can do in a forum post: Home Recording Studio: Build it Like the Pros
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Post by lathqe on Jan 27, 2017 2:50:33 GMT
1) Yes, there's no real isolation from putting insulation in the joists. Isolation requires isolated (not touching) structures. 2) Yes, put insulation against the rear side of the new inner wall. But understand that to fully isolate walls you also have to isolate them at the floor and ceiling. Do you have Rod Gervais's book? It explains all of this in more detail than I can do in a forum post: Home Recording Studio: Build it Like the ProsYes, I' read Gervais a few times to get my head around this stuff (I also worked a few years in construction in a former life, so I know what I don't know). So, I do have a non-touching structure. I so far have build 4 walls and a ceiling - just the framing built from 2x6's. It's a free-standing structure inside of the concrete walls/ceiling, not touching any of them. (And yes, it wobbles just a little bit, but not enough to be a problem in the future). The original ceiling is a 10" concrete slab above the structure I built. So my question is whether to put some mass (plywood or drywall or osb or whatever's cheap) on the top side of my structure (4" below the original ceiling), which will mean that my ceiling insulation will be 6" thick or to leave the top side open and be able to put 12" in. I'm happy to use compressed rockwool instead of fluffy, if it would be an improvement. I can get that stuff here.
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