Question regarding Mineral Wool and Broadband Absorber

Hello, first post and hopefully I am following the rules! I am in the process of treating my control room as well as renovating a separate room for re-amping and tracking/isolation. As soon as I learn sketchup and get all my information in order, I will have a much longer post detailing all of my goals. In the meantime I had a quick question about mineral wool. I found a lot of Thermafiber SAFB for very cheap from a supplier. I was looking for OC 703 or equivalent but not having much luck. I have included pictures of the product here So to my questions: Q1: Are the Thermafiber Panels I purchased ok to use for broadband absorbtion if I stack them to create 4" thickness inside of a 16" x 48" frame? Q2: I know that typical panels are 2' x 4', but I need to build custom panels along one wall that has existing picture mouldings on it. And placing two 16" panels next to each other on this wall in between each moulding frame works perfectly. They have less than a 1/2" reveal between them. Is there any reason that multiple 16" wide panels in sequence would be bad ? Q3: Can anyone tell me from the pictures I have posted if they know the pcf density of this particular product (I have searched quite a bit and I believe its 2.5 but am still not completely sure) ? Q4: I searched and read just about everything referencing Thermafiber on this site, but didnt see anything with direct questions or answers regarding using it in panels. From what I gather in the http://www.bobgolds.com/AbsorptionCoefficients.htm, it seems that if I stack 2 of these thermafiber blankets inside a panel frame, it should give me close to the same absorbtion properties as 4" 703 or similar. I am just taking the absorbtion percentage of 4" thermafiber at 2.5pcf density and assuming that doubling my 2" thickness will yield the same results. Is this correct ? Here are some photos of the material Thanks in advance! Patrick

epilogstudio wrote:

Hello, first post and hopefully I am following the rules!

welcome, looks like a good start!

Q1: Are the Thermafiber Panels I purchased ok to use for broadband absorbtion if I stack them to create 4" thickness inside of a 16" x 48" frame?

By the looks of it, yeah they will work. If they don't have a "hard" surface (a screen) then it's more than okay to stack'm. sure, no problem!

[color=#0040FF]Q2: I know that typical panels are 2' x 4', but I need to build custom panels along one wall that has existing picture mouldings on it. And placing two 16" panels next to each other on this wall in between each moulding frame works perfectly. They have less than a 1/2" reveal between them. Is there any reason that multiple 16" wide panels in sequence would be bad ?

16" diagonal? If that's what will fit your plan perfectly then, yes! it will work. 2x4 is just a "convenient" size (since most wool slabs are pre-cut at that size). There's no hard rule. The total coverage and depth is what counts. Preferable plan to place absorbers opposite of a hard surface.

Q3: Can anyone tell me from the pictures I have posted if they know the pcf density of this particular product (I have searched quite a bit and I believe its 2.5 but am still not completely sure) ?

sorry, I have to look it up too. But by the looks of it, it'll do. Remember the density doens't play an important role in choosing the right absorber. It's, again, the total amount of coverage and depth. tho 48kg/m3 is the most suited density (again, no hard rules)

Q4: I searched and read just about everything referencing Thermafiber on this site, but didnt see anything with direct questions or answers regarding using it in panels. From what I gather in the http://www.bobgolds.com/AbsorptionCoefficients.htm, it seems that if I stack 2 of these thermafiber blankets inside a panel frame, it should give me close to the same absorption properties as 4" 703 or similar. I am just taking the absorption percentage of 4" thermafiber at 2.5pcf density and assuming that doubling my 2" thickness will yield the same results. Is this correct ?

euhmm... dunno exactly what ye mean... my guts says "yes" tho :) You can stack wool as much as you want to get more depth and thus better low-end absorption.

Thanks Ro! I have had a very productive weekend with Google Sketchup. I have my control room drawn in 2d with measurements as well as a 3d look at the inside of the room with my idea for finished acoustic treatment . Since the goal of this room is acoustic treatment, should I just continue in this Acoustic forum? Or should I post in Studio Design? Thanks again, excited to start building all my panels today :) Patrick

It's up to you, but stuffing your design, questions and pix in this topic will do fine. (If any MOD things otherwise, he/she can move the topic for ya.) keep your plans comming :)

Hi epilog, I'll be interested in your results using that material (if you build yours before I get to mine), because I have the same stuff and am planning on doing my chunks and panels with it. As I remember it (but can't point you in the right direction now as I forget where it was), I think the density was in the "good" range . . . not that that is very specific or scientific :roll: Good luck with your build!

Yeah from what I researched it had good acoustic properties. I already built my superchunks in the back corners. I framed with 2x4's filled the corner with the mineral wool, then stacked 2 panels back to back and then worked my way up securing with string so they didnt flop forward on me. Its a bit messy comparing to working with rigid material, just wear a mask and glasses if you can, your bound to get lots of breakup/dust working with the superchunks. So far just adding these two superchunks really cleaned up a lot of resonant buildup in the room. I have a pretty light aurelex kit spread out over the rest of the walls, but its not doing that much. I am excited to get the panels made and installed, and the cloud. But I will post my full design here soon so I can see what you all think. Here are some photos of the superchunks, I just need to frame out the fabric borders where I cut it with some basic moulding, and add baseboard so it looks like its built in.

I have found in the few pieces I have cut so far it isn't the easiest stuff to work for for sure. I think the rigid would be a lot easier to fabricate.

Ok so here are my plans to start with. I have other rooms sketched here, I will end up focusing on the tracking/isolation room after I dial in the control room. There is a bit more construction work/modifying that will be happening in there, so I want to give it a lot of attention. In my control room I cannot do any modification to the room other than adding acoustic treatment/panels. The only thing missing in this drawing is a futon that sits directly behind mix position, with its back even with the start of the hallway opening and a double sized rack unit to the right of my chair/desk. My control room is a bit tricky. From what I gathered its actually an optimal size, but because of the opening to the house, rear opening to hallway, and pocket door with louvres to kitchen, I get a lot of scatter. The floors are tile in here as well, but I will either be putting in carpet or wood, or a combination of both. I am not allowed to build a wall or door at the opening to house, which is why I am thinking about the moveable panel. Not the most ideal but seems to be a decent solution? Because of this, I cannot put superchunks in these front wall corners, well I could on the right side, but not where this opening is. Does this seem like a good solution? Any suggestions? The cloud system can be extended back into the room, but I am wondering about possibly putting some diffusion clouds/skylines towards the back of the room. Would this be wise to do if I want to record some acoustic instruments in this room? Should my cloud panels be a different thickness from the other broadband panels? I am thinking of hanging the cloud panels from adjustable hooks, so I can tweak the height overall, and drop front or back lower or higher etc.....not sure if this will work out, but its an idea. My monitoring system is a pair of Focal CMS50 (5.5" woofers) with a KRK 10s Subwoofer that is positioned behind the middle of the desk. (sorry should have added that subwoofer note in the drawing). Also would the gobo idea behind the monitors be beneficial? Or is that just overboard Hope I am not forgetting anything, I will update as I progress with drawings, if anyone would like any more specific information or photos/files...let me know :) Any input/advice criticism is greatly appreciated patrick

Also here is the sketchup file in case anyone wanted to poke around

mshetler.design wrote:

I have found in the few pieces I have cut so far it isn't the easiest stuff to work for for sure. I think the rigid would be a lot easier to fabricate.

Yeah most definitely rigid would be easier. The thermafiber is just so flimsy to work with. I have to build my panels at 47" to fit within existing picture moulding, and I just ripped the bottom of the SAFB off, it took literally no effort, just fell apart. Stuffing the superchunks was awful, had to wear glasses and long sleeves/mask etc.... Messy business! But it works and its cheap :) So far it sounds good, I am sure if I treat the room as planned, it will be a significant improvement. I just need to figure out how to use room eq and Ill try to do some before and after waterfall plots. I typically am not too concerned with that stuff, I am really just trusting my ears, but I am curious now what that plot will look like :)

Ok so I am starting on my ISO room today. I have attached a plan view of this room, I have resized it, and will attach the sketchup file in case anyone has trouble reading dimensions. As of right now the room is at rough state, exposed studs. We are about to fill between studs with thermafiber mineral wool blankets. Then do z channel, then double 5/8" drywall, then treatment. I also plan on doing the same with a dropped ceiling, right now its about 8.5' so I have a bit of room to bring it down to 8' or lower. THE ROOM IS 7' X 9' WITH 8' CEILING PERGO WOOD FLOORING ON FOAM LAYER OVER CONCRETE Budget is about $300 Here are my goals and questions: Goals: I am planning on using this room MAINLY for recording guitars. I mainly do hard rock/metal so will be using a variety of guitar heads ranging from 20 watts to 100 watts for the most part. All run through a 4x12 cab. I would also like to be able to record vocals in here, but the main concern is guitar tone and if there is too heavy of a compromise to be able to do both, I am fine with just focusing on the guitars. My worry of course is the size of the room. I have read people stating that they have only gotten good results with guitar cabs in large rooms, but I have also seen and read of people using very small rooms like this and being able to get good results. In my case it is all I have! So I have to try and make it work. I need the room to be pretty soundproof, so I do not get a lot of interference in the control room as well as preventing sound from reaching neighbors. There is a niche in the corner, I plan on turning this into a closet or built in shelving unit of sorts, for mics and accessories. Figure this will work decent for diffusion, could hang a curtain in front if I am not wanting as much diffusion. Questions: and please forgive if a lot of these are pretty ignorant, because well I am pretty ignorant to acoustic knowledge! Starting with rough buildout, as I said I planned on doing mineral wool between studs, z-channel, double 5/8" dywall, then acoustic treatment. Is this adequate? I was thinking of attaching soundboard to the studs, then doing z-channel and drywall, but my friend who is helping me said that in the high rises he has soundproofed, they just do the double 5/8" and that should be fine. I know how loud a 100 watt tube head through a 4x12 is though and I am thinking I might need more than this! Would I benefit acoustically by lowering the ceiling in this room to compensate for the lack of length? Would I benefit more from diffusion (I was thinking of doing a massive amount of various QRD Diffusion on walls and ceilings) or a lot of absorbtion ? What kind of floor, wall and ceiling surfaces would be ideal, pre- diffusion/absorbtion? Any help is greatly appreciated. Thanks, and apologies if I am forgetting anything, please let me know I am happy to post any additional info, or do more elaborate sketchup work.... Patrick

We are about to fill between studs with thermafiber mineral wool blankets. Then do z channel, then double 5/8" drywall, then treatment.

Is that "Z-Channel" proper resilient channel? If not, then you should re-think that. If you want good isolation, you need to decouple the drywall form the studs. Only proper resilient channel will do that, or alternatively RSIC clips plus ordinary hat channel.

I was thinking of attaching soundboard to the studs, then doing z-channel and drywall,

Bad idea. That would make a 3-leaf system with a very thin air gap. You would lose a lot of low frequency isolation like that.

but my friend who is helping me said that in the high rises he has soundproofed, they just do the double 5/8" and that should be fine

Your friend is more correct, but you still need the resilient channel between the studs and the drywall.

Would I benefit acoustically by lowering the ceiling in this room to compensate for the lack of length?

On the contrary, I would try to get the ceiling as high as possible. Volume is your friend. If you reduce the volume of the room, it sounds worse. Lowering the ceiling reduces the volume.

Would I benefit more from diffusion (I was thinking of doing a massive amount of various QRD Diffusion on walls and ceilings) or a lot of absorbtion ?

QRDs in a small room like that would also be a bad idea: lobing. You might want to consider making at least one of the walls a slot wall, perhaps two of them, and checkerboarding thick absorption on the other two plus the ceiling, and maybe lay laminate flooring. That should keep the booth sounding decently live. - Stuart -

Thanks Stuart! I believe it is in fact proper resilient channel. My buddy calls it z-channel, but when I called Home Depot they referred to it as resilient channel. I will be sure to verify this before I purchase. I do remember that the intent was for decoupling.... About the slotted walls. So the cabinet will be facing the length of the room.....which walls should be slotted in this case, the sides or front and rear (either can be front and rear) ? Should I build these slotted walls after the drywall buildout or instead? (I really should understand this concept first I guess, Ill start some research unless you have any links handy as reference?) thanks again :)

So the cabinet will be facing the length of the room.....which walls should be slotted in this case, the sides or front and rear (either can be front and rear) ?

I reckon I'd do two adjacent walls, and angle both of them a bit to get broader coverage. For example, do the rear wall (behind the cab) and one of the side walls as slot walls, but keep the end wall and the other side wall absorptive. If you did the right side wall as a clot wall, it's long enough that you could do two or even three shorter slot walls and different angles. That would be my suggestion: others might have better ideas.

Should I build these slotted walls after the drywall buildout or instead? (I really should understand this concept first I guess, Ill start some research unless you have any links handy as reference?)

You say that you need lots isolation, so you'll have to do the drywall first, then build the slot walls in front the drywall. The drywall is the second leaf of your 2-leaf MSM isolation, so you must have that. Then the slot walls go directly in front of that, on their own frames. So in effect, the drywall becomes the back of the slot wall device. Of course, you need to take care to seal the slot wall structure to the drywall, all around. The rear of the slot wall must be sealed airtight on order for it to work. If you don't want to get all muddled in the math of calculating the slot widths, and the slat depths and widths, then just go with John's design: he already figure that out for you, and his dimensions will work fine for most rooms. - Stuart -

Is this the detail you are referencing Stuart? Some more questions: I was not planning on doing any serious drywall finishing, just basic taping, the doing treatment directly to that, or should I maybe do a thin layer of neoprene or something, then treatment? Also if that is the slot wall detail you are talking about, are you saying to basically just build a large frame applied to the wall, slats running horizontally between and attached inside the frame? caulk/seal the outside of the frame and all edges of slats to wall? Just trying to be sure I understand, I will do some more detailed drawings with my intended application and acoustic materials and update here... Thanks again Patrick

That's the general idea, yes. Here's an idea of how it could look, with several angles in it: viewtopic.php?f=1&t=226&p=1259&hilit=+slot+wall+#p1259 And here are some more details on how to do the math, if you feel so inclined! :) http://johnlsayers.com/Recmanual/Titles/Acoustics2.htm

I was not planning on doing any serious drywall finishing, just basic taping,

That's fine, but don't mud and tape. Since you will be doing two layers of drywall, use backer rod and caulk in the joints on the first layer, and you can probably do the same on second layer too, since most of it will be hidden by the treatment (either slot walls or absorption panels). - Stuart -

oh man I am horrible with math!! haha I just read that about the formula for calculating the helmholtz resonant frequency....I am assuming that is what you are talking about? I am not sure where to even start there. Would I need to do measurement in the room first with room eq wizard ? to know what frequencies need the most taming? and then do the formula for those frequencies? If it seems pretty safe and effective overall to use johns design I may be more inclined to do that. I will start on some more detailed drawings and see what you think about the angles and attachment etc.... Or will the angles need to be determined by the math/measuring?

If it seems pretty safe and effective overall to use johns design I may be more inclined to do that.

Yeah, I'd do that too! John knows what he's doing better than any of us, that's for sure! And his designs are tried and tested. Just go with his dimensions for the slats/slots, and put a slight angle on them. - Stuart -

I had one more question about adding an angle to the walls. Should this be done with the drywall.....or with the wood slats. I ask because you had mentioned making sure the slats are sealed tight to the drywall....so I am wondering how this angle attachment is done without an air gap.

Should this be done with the drywall.....or with the wood slats. I ask because you had mentioned making sure the slats are sealed tight to the drywall....so I am wondering how this angle attachment is done without an air gap.

Well, you still need a gap behind the slats! They must be on some type of frame that angles away from the wall a bit, to create the depth behind them. It's the FRAME that has to be sealed to the wall. A slot wall is basically just a large Helmholtz resonator: A restricted gap over an airtight cavity. In this case, the restricted gap is the slot between the slats. There is a "slug" of air stuck in that gap, that vibrates in and out in sympathy with a certain frequency that is set by the dimensions of the slot and the depth of the cavity behind. One common way of describing how it works is blowing across the top of a Coke bottle, to make the bottle hum. That's the perfect example of a Helmholtz resonator. The "slug" of air trapped in the neck of the bottle vibrates up and down the neck, and the frequency is set by the dimensions of the neck and the depth of the cavity inside the bottle. Put water in the bottle and the note changed, because the depth changed. But if the cavity is not sealed, then it won't work. If you cut the neck off a Coke bottle and blow over it, it won't hum, since there is no cavity, even though the neck is identical. Same if you just cut a hole in the bottom of the bottle. The cavity has to be sealed. So your slats have to be mounted on the front of some kind of box, or at least on a frame that is sealed to the wall, and is itself sealed all around. That's what I meant when I said that the slot wall must be sealed to the underlying drywall, if it is just a frame with slats on it. But if it is a complete box that already has a back on it, then of course it is the box that must be sealed, and it doesn't matter if you also seal it to the wall or not. The reason why you might want to just build a frame with no back on it and seal it to the wall, is money! The back needs to be a thick, heavy, rigid piece of wood, and that costs $, so if you already have a good isolation wall there with two or more layers of 5/8 drywall on it, then you can skip the back on the box, and use the drywall instead. - Stuart -

perfect.....now I totally understand it :) just finished demo'ing the room, going to put in mineral wool today, hang resilient channel and drywall tomorrow... then I will get on some drawings and post some ideas for the finishing (treatment and slot wall) thanks again!

Ok so trying to pick out some acoustic foam for 2 of the walls and ceiling. I had purchased some of this stuff for an isolation box and I have a decent amount left over.... http://www.foambymail.com/EC2-5-F-CH/2-5-eggcrate-foam.html But wondering if I would be better off using something like this for the walls http://www.musiciansfriend.com/accessories/auralex-studiofoam-designer-kit/422602000001000?src=3WFRWXX&ZYXSEM=0&CAWELAID=872249099 and these for ceiling http://www.foambymail.com/DCT/drop-ceiling-tiles.html we should be done with drywall today, also one more question about the floor The floor right now is concrete with a thin foam underlayer, and some cheap wood laminate flooring. I have much nicer red oak flooring that I only have enough to do a room this size. Would real wood be ok for the floor? I would imagine it would be similar acoustically? Maybe better? Also if I did use the real wood should I just put it over the laminate with another underlayer? Or do a floating floor?

I had purchased some of this stuff .... http://www.foambymail.com/

I have rather bad news for you: You wasted some money! There's a reason why proper acoustic foam made by reputable companies such as Auralex and others, costs a lot more than the stuff of totally unknown origin and even less known acoustical properties: it is because the foam made by the reputable companies, actually does work as advertised... :) Personally, I would never use any acoustic material for which there is no published test results, by an independent acoustic lab. Reputable companies do publish such data. The others don't. On the other hand, there is also a huge amount of published literature on the acoustic properties of common building materials, with testing done in reputable independent acoustic laboratories all over the world. All of that mountain of research shows that plain old mineral wool and plain old fiberglass, of the type commonly used in building houses, has excellent acoustic properties, and is less expensive than commercially manufactured foams. So yes, Auralex foam will most likely work as advertised, but so will plain old mineral wool. The question is, how much you want to pay for the materials that you use. The sound waves cannot read price tags, and really don't care how much you paid for it: they only care about the actual acoustic properties of the materials. :)

Would real wood be ok for the floor? I would imagine it would be similar acoustically? Maybe better?

Real wood would be just fine. Nice aesthetically, and nice acoustically.

Or do a floating floor?

:shock: :!: :!: :!: Before you even THINK about floating your floor, please read both of these, very carefully: viewtopic.php?f=2&t=8173 http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir802.pdf

Also if I did use the real wood should I just put it over the laminate with another underlayer?

Take out the laminate and the underlay, and use whatever method is normally recommended for that wood, that also gives you the firmest attachment to the underlying concrete, with no air gaps. - stuart -

Thanks Stuart, I actually just bought that foam for a isolation box, so not really that big of a deal, I am selling the isolation box and making a little more money back than the cost to make it. And the foam that is left is just about 60"x60" square piece. So not too much left over when I went and checked it out. I have some auralex left over too, but its not as thick. Im going to just go with a bunch of auralex squares in here because I think building more panels for this room will be a bit of a pain and the auralex will look nice. k sounds good, my buddy is asking me if there was a specific method for using the backing rod with the drywall, do we leave a gap between the drywall sheets for the foam rod etc.. Im going to search here and see if I come up with any photos/details I can show him. have only been able to get a few hours in each night and lots of running for materials so been going slowly...should be done by weekend though :)

so from what ive read, I just leave a gap (slightly smaller than the rod) , push the rod in between, then caulk, then do the next layer of drywall and rod/caulk like you mentioned earlier?