mixing/rehearsal room acoustic treatment

[missmoo]

Hello great people of this great forum!

I have been working for years on my small basement studio project with this forum (the ongoing construction thread is here: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=17603). This forum is absolutely amazing. All of the required forum details are in my other thread, so I'm not sure if I am supposed to repeat them here to adhere to forum rules.

I am finally at the point where I need to figure out how to treat the room with acoustic panels, bass traps, or any other elements that will achieve my desired balance of a subtle "live" sounding environment for recording, mixing, and rehearsal (with a rock band). I know it's a small space and that presents MANY challenges/impossibilities as far as acoustics, but it's the best I could do (it took me more than a year to optimize it this much).

It's a rectangular room with the following dimensions:
-- L 10' 10"
-- W 8' 11"
-- H 7 '

The walls are drywall, with the exception of two small windows at the top of one wall (glass windows integrated into the wall) and a wood door.

The floor is concrete.

I've attached an image that shows the rough outline of the room, the location of the windows, and my proposed location for the desk. I also plan to have amplifiers and a very small drum kit in the room (I know, it will be full).

I'm hoping for advice on the following:
- Desk location (under the windows). Is this a logical spot? How far should the desk be out from the wall that's behind it?
- I'm using near-field monitors. How far should the monitors be from the side walls? How far should the monitors be from the wall behind them (the wall with the windows)?
- I was planning to leave the floor as concrete and just treat the walls and ceiling. Does this make sense?
- Considering the small size of the room, I'm hesitant to use superchunk bass traps in the corners (because they seem like they will take up 4' of space on a wall that's only 8' 10'). Should I use panel bass traps instead? If so, where should I put those panels?
- How should I treat the ceiling?
- How should I treat the walls?
- Should I use an area rug?

Any advice would be GREATLY appreciated. I'm also happy to provide any information that I may have overlooked.

Thanks!

[Soundman2020]

All of the required forum details are in my other thread, so I'm not sure if I am supposed to repeat them here to adhere to forum rules.

That's fine! No problem. Putting the link in is good enough, but it might also be better to keep all your posts about your build in one single thread.

I know it's a small space and that presents MANY challenges/impossibilities as far as acoustics, but it's the best I could do (it took me more than a year to optimize it this much). It's a rectangular room with the following dimensions: -- L 10' 10" -- W 8' 11" -- H 7 '

It actually looks pretty darn good on Bob Golds' calculator! The biggest problem is the low ceiling, of course, and there's no way around that, but the ratio is excellent. It looks like you did a good job with sizing the room.

- Desk location (under the windows). Is this a logical spot? How far should the desk be out from the wall that's behind it?

Yes, that's the best location for that room. Centered side to side, and set up so that your head is about 4'6" from the front wall.

- I'm using near-field monitors. How far should the monitors be from the side walls? How far should the monitors be from the wall behind them (the wall with the windows)?

The room is not big enough to locate the speakers far away from the walls, so they must go hard up against the front wall, with just a layer of thick absorption in between, such as 4" of OC-703. The will also need to be about 2'6" from the side walls (that refers to the acoustic center of the speaker! Not the left or right side of the box), and at a height of about 47.5" above the floor (also acoustic center, tot the top of bottom of the box). Set them up on very heavy, massive speaker stands, with Sorbathan pads underneath, to decouple, and angled at 30° inwards so they are pointing just behind where your head will be.

- I was planning to leave the floor as concrete and just treat the walls and ceiling. Does this make sense?

Yes! Perfect sense. That's the best way to do it.

- Considering the small size of the room, I'm hesitant to use superchunk bass traps in the corners

You could do them in the ceiling/wall corners on the front and rear walls, and in the vertical rear corner opposite the door, and also on the corners at the front of the room. If the "standard" size is too big, then make them a bit smaller, but don't go too small or you lose effectiveness.

Should I use panel bass traps instead?

You can use panel traps, but those are normally tuned to a specific frequency to treat a problematic mode. You can do panel traps that cover a broader range of frequencies too, but that implies angling them across the corners, which would take up the exact same space as a superchunk ...

- How should I treat the ceiling?

Cover it in absorption. You don't really have enough height for a cloud (although you might be able to fit in something), so I would start by just covering most of the ceiling with thick absorption.

- How should I treat the walls?

I would "checkerboard" some absorption panels on the sides, and do the entire rear wall with thick absorption.

- Should I use an area rug?

Probably, yes, but wait until the end for that, to see if it needs it.

HOWEVER! Before doing any treatment, I would set up your speakers, desk, chair, and do a "baseline" room test using REW software (its free), so you have a point of comparison later, to see how things are improving and what still needs to be done. Then do another REW test after you install each part of the treatment, so you can see what it did. To me, this is a very important aspect of "room tuning": you can see exactly where you are at each point in the process, you can see what is working and what isn't, and you can plan your next move intelligently, instead of just guessing. And you also have a hard record of how much you have advanced, and how the room ends up responding at the end, after you have done as much as you possibly can, so you are aware of any remaining issues and how they might affect our mixes.

- Stuart -

[missmoo]

Stuart - you absolutely rock! I am taking your suggestions!

It actually looks pretty darn good on Bob Golds' calculator! The biggest problem is the low ceiling, of course, and there's no way around that, but the ratio is excellent. It looks like you did a good job with sizing the room.

I intentionally sized it like this based on your suggestions in the other thread. Thanks

Monitors - Set them up on very heavy, massive speaker stands, with Sorbathan pads underneath

Are there any designs for very heavy, massive speaker stands on this forum? Any design you would recommend? What thickness of Sorbathane pad should I use? I see a bunch of them online that I could order, I'm just not sure what thickness/qualities to look for.

Superchunks - You could do them in the ceiling/wall corners on the front and rear walls, and in the vertical rear corner opposite the door, and also on the corners at the front of the room. If the "standard" size is too big, then make them a bit smaller, but don't go too small or you lose effectiveness.

It sounds like I should just bite the bullet and use superchunks, despite the impact on space in the room. If i just use the triangular pieces all 4 corners, stacked up to the ceiling, would that suffice? How small could I make them before I negate their purpose?

I would start by just covering most of the ceiling with thick absorption.

What material would you recommend for thick absorption? Is there anything relatively cheap I could use?

I would "checkerboard" some absorption panels on the sides

I do own a bunch of aurelex foam acoustic panels (various shapes and sizes). Would that work for the "checkerboard" absorption on the sides? How would you recommend me attaching that foam to the walls without damaging my new paint job? Is there any particular patterns or location I should focus on (maybe to cut off early reflections when I'm sitting in a listening position?

THANKS AGAIN!

[Soundman2020]

Are there any designs for very heavy, massive speaker stands on this forum?

I've seen one somewhere for a stand done with large diameter PVC pipe filled with sand (the size used for sewer drain pipes), but the easiest way to build one fast, is by stacking some concrete blocks, putting a concrete paving stone on top, then wrapping the whole thing with fabric to make it look nice.

What thickness of Sorbathane pad should I use?

That depends on a couple of factors, such as the mass (weight) of your speakers and the exact type of rubber you use. To be certain, you should calculate the size of the pads based on those.

If i just use the triangular pieces all 4 corners, stacked up to the ceiling, would that suffice? How small could I make them before I negate their purpose?

I would try to keep them to no less than 24 inches across the diagonal front face, if possible, and certainly not less than 20". But bigger is better!

What material would you recommend for thick absorption? Is there anything relatively cheap I could use?

The best is OC-703, but good alternatives are fiberglass or mineral wool insulation. "Thick" means about 4" or more, but not less than 2".

I do own a bunch of aurelex foam acoustic panels (various shapes and sizes). Would that work for the "checkerboard" absorption on the sides?

Yes, but I would double them up (thickness) in some places and leave them single thickness in others.

How would you recommend me attaching that foam to the walls without damaging my new paint job?

Make light weight metal frames or wooden frames for them, and hang those on the walls with hooks or french cleats screwed into the studs.

Is there any particular patterns or location I should focus on (maybe to cut off early reflections when I'm sitting in a listening position?

Right. first reflection points first, with at least 4" of absorption, then some more on the side walls behind that, in the checkerboard pattern. The actual pattern isn't that critical: Just try to make sure that every place there is blank wall on one side of the room, it is facing absorption on the other side. So no "blank to blank" areas.


- Stuart -

[missmoo]

I've seen one somewhere for a stand done with large diameter PVC pipe filled with sand (the size used for sewer drain pipes), but the easiest way to build one fast, is by stacking some concrete blocks, putting a concrete paving stone on top, then wrapping the whole thing with fabric to make it look nice.

I'm curious - what's the purpose of the massive speaker stands? Is it just to prevent sound from traveling into the floor? Wouldn't the neoprene do that without a massive speaker stand? I'm just curious, not doubting... and I'm wondering how important it is (particularly for my financial situation).

The best is OC-703, but good alternatives are fiberglass or mineral wool insulation. "Thick" means about 4" or more, but not less than 2".

With my ceiling being only 7' tall, is it worth it acoustically to lose 4 inches of height?

I do own a bunch of aurelex foam acoustic panels (various shapes and sizes).

Just to clarify, these are the somewhat skimpy foam panels (like these http://www.auralex.com/acoustic_foam_we ... edgies.asp). Would that be enough absoption to be worth putting checkerboard on the walls? I know they aren't the best...

first reflection points first, with at least 4" of absorption, then some more on the side walls behind that, in the checkerboard pattern. The actual pattern isn't that critical: Just try to make sure that every place there is blank wall on one side of the room, it is facing absorption on the other side. So no "blank to blank" areas.

Sorry, but how do I find the first reflection points? What's the technique? And I assume that those points are symmetrical and should be treated symmetrically with 4" of absorption, right? It's the rest of the wall that need to be "assymettrical" checkerboard, right?

Also, one more question. For the thick Oc 703 absorption on the walls and ceiling, is it ok if that absorption is flush up against the wall? I'm assuming I don't need to build a frame that is offset from the wall/ceiling, right?

Thanks again!

[Soundman2020]

I'm curious - what's the purpose of the massive speaker stands? Is it just to prevent sound from traveling into the floor? Wouldn't the neoprene do that without a massive speaker stand? I'm just curious, not doubting... and I'm wondering how important it is

Neoprene is pretty good at isolating mid and high frequency vibrations, but not so good in the low end. The heavy stand helps with that. and even though the rubber is isolating the direct flanking vibrations from the speaker, there is still airborne sound to be concerned about: that can easily make a light-weight stand vibrate.

(particularly for my financial situation).

The two options I mentioned are really cheap: stacking up half a dozen concrete blocks and wrapping them with fabric is only going to set you back a few dollars. Likewise for a 4-foot section of large diameter PVC pipe, and a bag of river sand. These are things you can find at your local Home Depot. The stand does not have to be fancy or expensive in order to work well acoustically.

With my ceiling being only 7' tall, is it worth it acoustically to lose 4 inches of height?

You really don't have a lot of choice here. The ceiling needs absorption. You could probably get away with putting just 2" or 3" of 703 on most of the ceiling, but at least at the first reflection points and around the edges, where it meets the walls, you need 4". Or even more...

J

ust to clarify, these are the somewhat skimpy foam panels (like these ...). Would that be enough absoption to be worth putting checkerboard on the walls? I know they aren't the best...

They will still help, but I would consider using them on the front of thicker panels made from fiberglass insulation (or mineral wool, or 703). For example, if make panels from 3" 703, then putting some of these foam panels on the front would help a lot.

Sorry, but how do I find the first reflection points? What's the technique?

Use the "mirror method". Set up your speakers and chair in the final positions where they will be, sit in your chair in the way you will normally be working, and get a friend to hold a small mirror up against the walls, and move it around all over. Any place you can see either of the speakers reflected in the mirror, is a first reflection point and needs treatment. Check the side walls like that AND the front walls AND ALSO the ceiling. Your friend might need need a ladder or stepping stool to hold the mirror up on the ceiling.

And I assume that those points are symmetrical and should be treated symmetrically with 4" of absorption, right? It's the rest of the wall that need to be "assymettrical" checkerboard, right?

Right.

Also, one more question. For the thick Oc 703 absorption on the walls and ceiling, is it ok if that absorption is flush up against the wall? I'm assuming I don't need to build a frame that is offset from the wall/ceiling, right?

It will work OK up against the walls, but it works even better down to lower frequencies if you can leave an air gap behind it. There are several ways of doing that. But even up against the wall, 4" 703 still works reasonably well down to lowish frequencies.

- Stuart -

[missmoo]

I edited this post to simplify and prioritize my questions, some of which were badly written.

I found 2" thick OC703 (2'x4' sheets) and I'm moving forward. A few more questions:

1. In a previous statement, you said I should put chunks in the wall/ceiling corners. Should I run the chunks from wall to wall and floor to ceiling?

2. If I run chunks from wall to wall and floor to ceiling, I foresee ending up with a gap in trapping at the wall-wall-ceiling "tri corners". As I understand it, that is the most important area to have trapping. I don't really have time or energy to build my own fancy beveled "tri-corner" traps... So I was thinking I could put a cube trap (easy to build with my horrendous carpentry skills) in each "tri corner" and have the flat triangular end of the chunks just butt up against that cube. That would avoid a gap near the problematic "tri-corner", right? Would this technique work? Any other methods I should consider?

3. For my superchunk design, can I get away with just stacking about 6'10" of OC703 in the corner, without any kind of shelf in the middle to break up the weight of the stack? Do I need to be worried about the OC703 compressing under it's own weight over time? I've spent way too many hours trying to find an answer to this by searching forums...

4.

You don't really have enough height for a cloud (although you might be able to fit in something), so I would start by just covering most of the ceiling with thick absorption.

- What qualifies as "most of the ceiling"? Should I just cover all of the ceiling?

5.

Speaker stands - stacking up half a dozen concrete blocks and wrapping them with fabric

If I do this, I assume the stands will literally be butting up against the wall that will also have the desk on it. Should I build "cutouts" in the desk that allow the heavy speaker stands "penetrate" through the desk and essentially allow the speakers to sit where they otherwise would if I were to put them on the desk? Or should the desk just sit in front of the speaker stands?

6. In your previous post, you talked about having my head 4' 6" away from the front wall. Is that 4' 6" away from the actual drywall, or 4' 6" away from the surface of the 4" bass trap that's is going to be on top of that drywall?

Thank you!

[missmoo]

Hi there - any thoughts on my last post? I certainly don't want to nag anyone, but I'm just curious.

Also, one more question - for my superchunks, should I be wary of using breathable fabric and absorbing all of the high frequencies out of the room? If I'm going to have chunks in all the vertical corners and in the wall ceiling corners, should I use a more reflective fabric so the room retains highs?

Also, just to clarify, are you recommending that I cover the front wall, rear wall, and ceiling entirely in broadband absorption? When combined with high frequency absorption in all of the corners (the chunks), would that make the room too dead? Or is checkerboard reflective drywall and a concrete floor enough for high frequencies in such a small room?

By the way, I just ordered a Dayton calibrated EMM-6 mic to do some room measurements before anything is in the room.

Thanks again,
Adam

[missmoo]

Stuart? Anyone?

Bump

[Soundman2020]

I found 2" thick OC703 (2'x4' sheets) and I'm moving forward.

Great!

1. In a previous statement, you said I should put chunks in the wall/ceiling corners. Should I run the chunks from wall to wall and floor to ceiling?

If you can, yes! The bigger the better, in general. The "tri-corners" are the most effective places in the room: those are the corners where two walls and the ceiling meet, or two walls and the floor.

I foresee ending up with a gap in trapping at the wall-wall-ceiling "tri corners".

Why? If you stack triangular shaped pieces of 703 from floor to ceiling, then you have fully covered the tri-corners. You can then start any horizontal suprechunks next to where the vertical ones end.

So I was thinking I could put a cube trap (easy to build with my horrendous carpentry skills) in each "tri corner"

I'm not sure what you mean by "cube trap". Maybe you could explain?

3. For my superchunk design, can I get away with just stacking about 6'10" of OC703 in the corner, without any kind of shelf in the middle to break up the weight of the stack?

That should be OK, yes. You'll still need some sort of frame up the edges, to keep it all in place, and also for attaching the fabric.

Do I need to be worried about the OC703 compressing under it's own weight over time?

Not a problem. It isn't that heavy anyway, and the slight deflection at the bottom doesn't make much difference to how it works.

What qualifies as "most of the ceiling"? Should I just cover all of the ceiling?

If you can do it all, then that's great.

If I do this, I assume the stands will literally be butting up against the wall that will also have the desk on it.

Correct!

Should I build "cutouts" in the desk that allow the heavy speaker stands "penetrate" through the desk and essentially allow the speakers to sit where they otherwise would if I were to put them on the desk? Or should the desk just sit in front of the speaker stands?

either way is fine. First work out where the chair needs to be, based on the "standard" geometry for speaker angles and listening position location, then set up the desk in a comfortable position for that, and see if you need to but holes for the stands, or not. Just make sure that the desk does not touch the stands, and the stands do not touch the wall: leave a small gap (1/8" or so).

6. In your previous post, you talked about having my head 4' 6" away from the front wall. Is that 4' 6" away from the actual drywall,

Right! That's the distance from the drywall, which is the solid, hard, massive room boundary. All acoustic mode calculations are done with respect to room boundaries.

Also, one more question - for my superchunks, should I be wary of using breathable fabric and absorbing all of the high frequencies out of the room? If I'm going to have chunks in all the vertical corners and in the wall ceiling corners, should I use a more reflective fabric so the room retains highs?

For anything above your head, cover it with thin plastic. Something like the typical 6mil plastic used as vapor barrier inside walls, is fine. That helps with two issues: One is, as you said, to keep the highs in the room, and the other is to prevent the insulation from "shedding" fibers into the room over time. Those can cause damage to your equipment, as the are abrasive. So you don't want those slowly filtering down all over your gear and instruments!

When combined with high frequency absorption in all of the corners (the chunks), would that make the room too dead?

Probably, yes. But then you can return the "liveliness" by strategic use of slats, panels, and possibly even some types of diffuser. The normal way of doing this is to do a test with REW at each stage of treatment, to see what effect it had and also what side-effects it had, so you can plan the next round of treatment accordingly.

By the way, I just ordered a Dayton calibrated EMM-6 mic to do some room measurements before anything is in the room.

Cool! Please post the MDAT file as soon as you have the first ("baseline") measurement done!


- Stuart -

[missmoo]

Thanks so much for your responses!

I have a bunch of new questions. I've pulled this together and consolidated a few different posts and a PM to Stuart.

The most important one is #9 below (I wrote it last).

1. I am literally in the process of cutting wood for my desk and I got paranoid and decided to double check the dimensions I'm working with.

I re-read your (Stuart's) post that says I should have my head 4'6" from the front wall and I am all of a sudden confused by how you came up with 4'6". Is that supposed to be 38% Of the room length? The room is 10'10", so 38% would be about 4'1".

Then I got paranoid that you based the 2'6" figure (for the monitors distance to side wall) off of the 4'6"
Figure.

All of this will affect the size and shape of my desk.

Would you mind confirming if 4'6" is correct? Also, could you explain how you got that measurement, as well as the 2'6" distance between the speaker and the wall?

It's a rectangular room with the following di'mensions -- L 10' 10" -- W 8' 9" -- H 7 '


2. I have some left over Roxul Safe and Sound (3" thick) and it's enough to build a single full height superchunk for one corner in my room. Is it ok if I build one vertical chunk out of that Roxul and the other 3 vertical corners are OC703? Will the asymmetry in the bass trapping matter when I'm mixing?

3. In one of your past posts, you said I should have a horizontal chunk at the top of the wall (across the wall-ceiling corner) in the front and back of the room. As it turns out, the windows in the room are aligned along the top of the wall in the front of the room, right above the desk, right under the ceiling (typical basement windows). If I put a horizontal chunk in that wall-ceiling corner in the front of the room, it will completely cover the windows. Can I get away without that horizontal chunk at the top of the front wall? Can I just have one along the top of the back wall and in all the vertical wall-wall corners? Or will that dramatically screw with the bass trapping at the front of the room, close to the spot where I'm mixing? If I need more bass trapping after doing the vertical corners and the top of the back wall, could I just run chunks horizontally across the top of the two side walls?

I'd just love to have those two windows with some light getting into the room...

4.

You'll still need some sort of frame up the edges, to keep it all in place, and also for attaching the fabric.

Great. I was thinking about just stacking the insulation in the corners and building a facade with a small wood frame and some fabric. How does that sound?

5.

I'm not sure what you mean by "cube trap". Maybe you could explain?

By "cube trap", I guess I mean a rectangular trap . Woops. I mean a trap that's, say 8" x 8" x 16" of absorption/insulation that sits directly in the corner. It seems like it would cover a similar "depth" as the triangular 24" faced trap (maybe a little less). I know it would have less surface area, but would it still function? The reason I ask is that the vertical superchunk in the left front top corner of my room would cover half of my window if I make it a triangular 24" faced trap. I'm wondering if I can get away with using a 8' rectangle there, and then below the window I could start the longer 24" face triangular trap. Sorry in advance if this is confusing. Here is a picture

question about small left window space.jpg

7.

For anything above your head, cover it with thin plastic.

So should I do that for the entire ceiling? If so, the highs would still be bouncing around... so does that mean I should have an area rug instead of the plan concrete floor? I think I know the answer, which is to use my ears and look at the change in response in REW as I incrementally add each piece

8.
Ok I just had a potentially large money and time saving idea pop into my head.

I have a TON of different foam panels lying around that I bought from someone for really cheap. Could I use that foam (aurelex stuff) to fill triangular superchunks in my corners? It would be a huge win, if so.

I also have a full bag of pink fluffy Kraft faces r13. Can I use that for a 2 ft faced superchunk (remove the paper)

I only have room for the 24 inch faced chunks. Can material with this lighter density work? Would it matter if I'm using different materials for each corner?

[missmoo]

Stuart and the forum is so generous with feedback, so I feel guilty writing "bump".

I know this is a long list of questions... But I would greatly appreciate any advice.

Thanks

[Soundman2020]

Hi missmoo. Sorry about the delay! I've been on vacation....

1. I re-read your post that says I should have my head 4'6" from the front wall and I am all of a sudden confused by how you came up with 4'6". Is that supposed to be 38% Of the room length? The room is 10'10", so 38% would be about 4'1".

That's mostly to get the speaker geometry good. 38% is not really a rule, just a starting point. 4'6" is not that much different: about 41%. The worst spots are 50% and 25%, but anywhere around 38% is fine.

Then I got paranoid that you based the 2'6" figure (for the monitors distance to side wall) off of the 4'6" Would you mind confirming if 4'6" is correct? Also, could you explain how you got that measurement, as well as the 2'6" distance between the speaker and the wall?

It's all related, and there's a bit of trade-off involved, to adjust things to fit your room dimensions reasonably. Ideally, the speakers should be at about 30% of the room width (28% - 31%, give or take), which means about 2'6". That places them about 3'9" apart, which means your head should also be about 3'9" from each speaker. Assuming about a 10" depth (speaker acoustic center to wall), that places your head about 4'6" from the front wall. It won't work out exactly like that, of course, due to the insulation behind the speakers, the actual speaker sizes, depth of the desk, etc., but it is close enough to get you in a good location. You can adjust them all a couple of inches either way and not affect things greatly. The most import thing is to keep the geometry symmetrical, so the speakers are the same distance from the walls, and you are the same distance from each speaker, and you are on the center line.

2. I have some left over Roxul Safe and Sound (3" thick) and it's enough to build a single full height superchunk for one corner in my room. Is it ok if I build one vertical chunk out of that Roxul and the other 3 vertical corners are OC703? Will the asymmetry in the bass trapping matter when I'm mixing?

No problem. Or build them all 75% with 703 and 25% with roxul...

Can I get away without that horizontal chunk at the top of the front wall? Can I just have one along the top of the back wall and in all the vertical wall-wall corners?

That's fine.

If I need more bass trapping after doing the vertical corners and the top of the back wall, could I just run chunks horizontally across the top of the two side walls?

Yep!

Great. I was thinking about just stacking the insulation in the corners and building a facade with a small wood frame and some fabric. How does that sound?

Perfect!

It seems like it would cover a similar "depth" as the triangular 24" faced trap (maybe a little less). I know it would have less surface area, but would it still function?

That's fine too. No problem.

So should I do that for the entire ceiling? If so, the highs would still be bouncing around...

Right. The entire ceiling. But the plastic won't be doing that much to the highs. The plastic is thin (maybe a couple of mil), and will only affect the very high end. But that is GOOD! Bass trapping also sucks up the highs drastically, so you do need something over the ceiling absorption to keep the highs back in the room, for better balance.

does that mean I should have an area rug instead of the plan concrete floor?

Perhaps, but an area rug won't make a huge difference either. Just a final small touch, if necessary. And based on what REW and your ears are telling you....

I think I know the answer, which is to use my ears and look at the change in response in REW as I incrementally add each piece

Yup!

Ok I just had a potentially large money and time saving idea pop into my head.

I have a TON of different foam panels lying around that I bought from someone for really cheap. Could I use that foam (aurelex stuff) to fill triangular superchunks in my corners? It would be a huge win, if so.

If you are absolutely certain that it really is proper acoustic foam, then yes, that would be fine. But do be careful: There are quite a few unscrupulous "foam by mail" places that sell you packing foam but claim it is acoustic foam: it looks very similar, but is useless, acoustically. So make sure that what you have really is proper acoustic foam, maybe by a reputable manufacturer.

I also have a full bag of pink fluffy Kraft faces r13. Can I use that for a 2 ft faced superchunk (remove the paper)

That's fine too. You could even leave the paper on, as long as it does not face the room directly...

Can material with this lighter density work?

What is the density?

Would it matter if I'm using different materials for each corner?

As I mentioned above, you could build all of the superchunks the same way, with most of it made from 703 and the rest down with other insulation. Put the 703 at the top and bottom, and the other stuff in the middle of each superchunk.


- Stuart -

Your biggest problem with that room is not so much the speaker geometry as the very low ceiling.

[missmoo]

Incredibly helpful. Thanks Stuart!

So as far as my aurelex stuff, I have a ton of this:
http://www.sweetwater.com/store/detail/RoomDST36C/

And this:
http://www.sweetwater.com/store/detail/SF2in22CHA/

Am I correct in thinking that the aurelex foam won't help much at all on my walls or ceiling as panels (because I want 4 inches of denser material like Oc703 on the front and back wall and on the ceiling). Am I correct that since it's not very dense, it won't help as much a denser material that's 4" thick? I was going to use some of the aurelex foam on the side walls for simple reflections... but I'll have a bunch left over that I could use in the super chunks.

Am I thinking about this right? Or should I consider using the aurelex, doubling it up to make it 4 inches, and just using that as my front and rear absorption on the walls?

[Soundman2020]

Am I correct in thinking that the aurelex foam won't help much at all on my walls or ceiling as panels (because I want 4 inches of denser material like Oc703 on the front and back wall and on the ceiling). Am I correct that since it's not very dense, it won't help as much a denser material that's 4" thick?

It's not so much a problem of density as thickness and absorption coefficients. Acoustic foam can be very good at absorbing some frequencies, even though it is thin: You should compare the published figures for each type of material to see which will work best for the frequency range you are targeting. So you might well be able to use that foam as part of the solution, provided that it has good characteristics for low frequencies. Auralex probably has those figures on their website some place.

- Stuart -