Trying to Finish a Basement for Mixing, Recording, and Living

[Celestial]

Hello, I just found this forum while googling around for the term "inside out wall," which I found is the name for what I was planning to build in my basement.

Basically I'm trying to turn my partially-unfinished basement into a finished space that's decent for mixing, listening to music, and recording.

Originally, the basement was finished and my plan was to simply build acoustic panels to treat the space, but I ended up having to install an interior french drain, and as a result, most of the drywall has been torn off, leaving the foundation walls exposed. I viewed this as an opportunity to leave the framing/studs open, with insulation stuffed between, and covered in fabric. This would cover more surface area and safe physical space. I've since learned this idea isn't new and is called an inside out wall.

I need some advice on actually building it, though, or deciding if it would be best to go the more traditional route of drywall plus panels.

The foundation is poured concrete and there is currently a vapor barrier installed against it. For an inside out wall, do I just build 2x6 framing with a small gap between the foundation and the studs?

I've attached pictures to help show the room.

One potential problem is that the ceiling is only 7'. It also has a couple of bump outs for some HVAC venting. I cannot remove the venting, but I can remove the drywall surrounding the venting and creating the bump out. I'm not sureif there is a good solution here for treatment.

I've also attached a rough mockup of the floor plan and general setup. The orange lines represent the bump outs on the ceiling. Blue is speakers. Green is desk. (Nothing to exact scale). The laundry room door can be moved as indicated with the red arrow so that I can treat the side wall.

The Rec Room area would probably house a couch and TV and be the general tracking area (when necessary). Most of the year would just be me working at my desk alone. Only infrequently would there be a full band or some sort of vocal or acoustic guitar tracking.

Similar to the walls, I’m considering removing the drywall from the ceiling, stuffing the joists with insulation, and covering it with fabric. This will negate the need for a cloud and maintain the 7’ ceilings. That said, I don’t know how much of the ceiling to do or if I will unintentionally create a space that’s too dead.

I've also attached some REW measurements I took from before the drain install with no treatment. My desk was set up in the Rec Room area, but the side walls are not symmetrical. I've decided setting up in the small portion of the room will be better in terms of functionality of the room, but the ceiling bump outs may pose a challenge.

Thanks for any help!

[Soundman2020]

Hi Celestial, and Welcome to the Forum!

Hello, I just found this forum while googling around for the term "inside out wall," which I found is the name for what I was planning to build in my basement.

As far as I know, the term (and concept) were invented by the late John Sayers, who passed away last year and is very well regarded in the studio and music industries. There are other terms used for the same concept, but "inside-out" describes it best.

Originally, the basement was finished and my plan was to simply build acoustic panels to treat the space, but I ended up having to install an interior french drain, and as a result, most of the drywall has been torn off, leaving the foundation walls exposed. I viewed this as an opportunity to leave the framing/studs open, with insulation stuffed between, and covered in fabric. This would cover more surface area and safe physical space. I've since learned this idea isn't new and is called an inside out wall.

Great! The concept of the "inside out" wall is mostly used for studios that need good isolation (sometimes called "soundproofing"), where the existing outer-wall (in your case, that would be the existing bare basement wall) forms the "outer-leaf" of something called a "2-leaf system". That's the most efficient method for isolating a room, as it uses the least amount of materials (and therefore lowest cost!), when you need high isolation. The "inner-leaf" is then built as a separate stud-framed wall, just a few inches away from the original outer wall, and with drywall on only ONE side of the studs (not both sides).

There are two ways of doing that: one is the "traditional" way, where you put drywall on the side facing the room (the side you would see when standing in the finished room), and the other way is the "inside-out" method, where the drywall goes on the "far" side of the studs, facing the cavity between the two leaves. Both systems work, and each has its pros and cons. The main advantage of the inside-out wall, is saving space. As you noted, you can use the space between the studs for acoustic treatment, as well as other things, and simply cover it with fabric, and perhaps wood slats in some places (you can size and space those slats carefully to "tune" them, to deal with specific acoustic problems in the room).

From the photos, it doesn't look like you are building a true "inside out" wall. Rather. Your studs are attached directly to the outer leaf wall. If you wanted a true inside-out wall, the stud framing would be built as a totally separate thing, a short distance away from that wall, and not touching it at any point. If you are interested in all the techinal details of how that "2 leaf" system works, then here's a couple of articles I wrote about that, a while back.
- What is "room-in-a-room" construction?

- What is MSM? How does it work?

That said, I'm not sure if you need isolation for your room, or not! Do you have any issues with noise getting into your studio from outside, or noise getting out and annoying other people in the house, or even worse, annoying your neighbors? If you haven't already done so, then you might want to do some testing to find out if you have an isolation problem. If you do, then "room in a room" construction, with inside out walls and ceiling, might be the way to go, as described in those article. But if you already have enough isolation (nobody else in the house, or outside, bothered by your studio noise), then you probably don't need that.

So what you are proposing is possible solution: What you have at present isn't a "real" inside out wall, but you could easily take off that framing and make one. If you have the studs there already, then you can certainly use them!

However, just filling all those existing bays with insulation and putting fabric on top, would also not be a good solution. That would mean that all of the absorption would be concentrated in a certain frequency range, mostly in the mids and highs, so the room would sound very "dry" and "dead", yet also "boomy" because the low end would not be absorbed. So you would need to deal with that issue, by adding bass traps where needed to deal with the low end, and adding wood slats over some of the insulation bays, to prevent it from absorbing too much of the mids and highs. In other words, you want to "balance" the treatment across the musical spectrum, so you are giving each frequency range just the right amount of treatment.

I need some advice on actually building it, though, or deciding if it would be best to go the more traditional route of drywall plus panels.

Definitely better to carry on with your current plan! It would not be good to just nail up drywall onto those studs again, as that would create a strongly resonant wall! Any time you have a flexible panel (such as drywall) over a sealed air cavity, you create a resonant system that will resonate at just a few very specific frequencies, governed mostly by the density of the panel and the depth of the cavity. Not a good idea! The room would end up sounding pretty bad if you did that. It would not be a proper inside-out wall. In fact, it would act very much like an acoustic device called a "panel resonator" also sometimes called a "membrane trap".

The foundation is poured concrete and there is currently a vapor barrier installed against it. For an inside out wall, do I just build 2x6 framing with a small gap between the foundation and the studs?

Basically, yes! It's that simple. 2x4 framing would be better, as it would save you the extra couple of inches on each side of the room, which might be important.

One potential problem is that the ceiling is only 7'.

Ouch! Not very high. Is that ceiling also concrete, or is it drywall attached to joists above? If you have joists up there, then you might have more options. If it is concrete, then you are stuck with that... so you'll just have to deal with what you have. It's not ideal, but also not the end of the world!

I cannot remove the venting, but I can remove the drywall surrounding the venting and creating the bump out. I'm not sure if there is a good solution here for treatment.

That would end up going across the control room, a bit behind where the mix position will be. Also not ideal, but there might be some work-around there. Have you looked inside those HVAC soffits, to see what is in there? At least they are not directly overhead the mix position, so you do have some options there.

The laundry room door can be moved as indicated with the red arrow so that I can treat the side wall.

Is there any chance you could move that door to the other wall, where the washer and dryer are, leaving the wall where it currently is completely unbroken? That would be ideal, but might not be possible, I guess.

Also, do you plan on extending that side wall back further into the "Rec Room" area, so you can make the control room bigger? At the current 11x10, it isn't very big at all. If you can do that, I would strong recommend it.

Also, how are you planning to close off the back end of the control room? Right now, the entire back end opens completely into the "rec room", and that's an issue. Possibly! For two reasons. 1) Control rooms need to be symmetrical, and the Rec Room area would make the rear end very non-symmetric. That said, symmetry is far more critical in front of the mix position, and not so critical behind it. 2) In any control rooms, the most important wall (the one that needs a ton of treatment), is always the back wall: the one behind you as you sit at the mix position. If you don't close off the rear of the room, then your "back wall" is actually the other side of the Rec Room! That's not going to be easy to treat...

Similar to the walls, I’m considering removing the drywall from the ceiling,

Ahhh! That answers my question above. So it is just drywall on joists up there. Good! So your potential ceiling height is actually, maybe, possibly a bit higher than 7'. But there are LOTS of caveats here! What is up above? Right now, you are getting at least some attenuation from that drywall, so whoever is up above is not getting the full force of your instruments/speakers. Removing that drywall would, indeed, increase your acoustic ceiling height by however big the joists are (I'm guessing 10"?), which would be great! But that will also reduce the isolation to upstairs. There are ways of dealing with that issue too, but first it would be good to better understand what the repercussions might be.

...stuffing the joists with insulation, and covering it with fabric. This will negate the need for a cloud and maintain the 7’ ceilings. That said, I don’t know how much of the ceiling to do or if I will unintentionally create a space that’s too dead.

Actually, it would increase the height of the acosutic ceiling by however deep the joists are! The visual height would go back to 7', yes, but the acosutic height would increase. Low frequency sound waves (the roughest ones to deal with) won't "see" the fabric or insulation: the only "see" the solid, hard room boundary, which would be the floor above you. That extra height is a very good thing! If you can use it...

I've also attached some REW measurements I took from before the drain install with no treatment.

Great! It would be excellent if you could post the actual MDAT file here on the forum, so we can examine it in more detail. There's not enough visible in your images to judge accurately. What I can say is that the decay times are far too long to be useful for a control room. Right now, they seem to be around 400 to 500 ms (some go up to nearly 700 ms). That needs to come down to around 200 ms, give or take a bit, and it needs to be even across the entire spectrum (right now, you have large variations between adjacent bands). The actual MDAT files will allow us to focus in on the details, and give you better advice.

I seem to be asking more questions than I'm answering! But its easier to answer questions intelligently, based on better information!

- Stuart -

[Celestial]

Hi Stuart, thank you so much for the reply!

Regarding isolation needs, I'm much more concerned with having a tighter sounding, balanced room. Street noise isn't excessive in this area and I'm not too worried about my speakers carrying upwards into the floor above. Drums will be tracked only rarely. Of course, isolation would be great, but if it significantly reduces the space available in the room or increases expense, I'd have to sacrifice it some.

I was thinking of the "inside out" wall as simply 2"x6" studs, with a small 2" air gap against the foundation walls. The joists would be stuffed with 6" of rockwool (or similar). You mentioned that 2x4 would be better for space savings, but my thought is that 2x6 would allow for thicker insulation, which will treat the low end more effectively. I think 6" and a 2" gap would theoretically treat the frequency range relatively evenly, but I could always add some binary diffusion slats if it sounds too dry or dark. I could also add additional corner traps if necessary.

One annoyance is that the left wall would be drywall with panels while the right wall would be "inside out" with a concrete foundation.

If I were to put up drywall again to improve material symmetry, I'd rebuild the framing, insert insulation, then cover with drywall as it was before. Then I could build acoustic panels and hang them at first reflection points, corners, and ceiling, but I'd lose a fair amount of space with 6" thick panels.

I wasn't planning to close off the back of the control room, although I suppose I could put up some sort of curtain to at least cut down on high-frequency echo or flutter. I realize there are symmetry issues with the back of the room, but I don't think it will cause a big problem for me.

The main reason I'd move the laundry room door is to be able to treat the left side reflection point with a hanging panel. However, I could theoretically move the door to the Rec Room side.

Regarding the ceiling, yes the joists are roughly 8" or 9" deep. There are some pipes and vents, but I'd be able to stuff most joists with insulation I imagine. I had thought about installing a layer of mass-loaded vinyl to improve isolation a bit, but I don't think it wuld be worth the investment. Theoretically there is no insulation in the joists currently, so perhaps adding insulation would offset the drywall removal in terms of sound transmission.

Source of the post It would be excellent if you could post the actual MDAT file here on the forum, so we can examine it in more detail. There's not enough visible in your images to judge accurately. What I can say is that the decay times are far too long to be useful for a control room. Right now, they seem to be around 400 to 500 ms (some go up to nearly 700 ms). That needs to come down to around 200 ms, give or take a bit, and it needs to be even across the entire spectrum (right now, you have large variations between adjacent bands).

Yes, its far too reverberant, which is my main issue with the room as is. At the time, I simply selected a mix position that was the most balanced frequency response-wise, but I knew I would need treatment to tighten up the decay at the very least. Regardless, I don't plan on sitting at that location in the "final" version of the room, so those graphs were just for fun.

[Soundman2020]

Source of the post Regarding isolation needs, I'm much more concerned with having a tighter sounding, balanced room. Street noise isn't excessive in this area and I'm not too worried about my speakers carrying upwards into the floor above. Drums will be tracked only rarely. Of course, isolation would be great, but if it significantly reduces the space available in the room or increases expense, I'd have to sacrifice it some.

That's good! If you don't need extra isolation, then that saves you a lot of money. Isolating an existing room is usually not cheap.

Source of the post I was thinking of the "inside out" wall as simply 2"x6" studs, with a small 2" air gap against the foundation walls.

As long as there's nothing solid behind the studs, that is a possibility. In other words, just air between the outer wall and the insulation. I fact, it would be better to have no air in there at all: just out the insulation up against the outer wall itself, and make it as thick as possible.

I think 6" and a 2" gap would theoretically treat the frequency range relatively evenly, but I could always add some binary diffusion slats if it sounds too dry or dark. I could also add additional corner traps if necessary.

If you treat the entire room (or a large part of it) with exactly the same method, then that will be affecting one part of the spectrum way too much, while not affecting other parts. With a 2" air gap and 6" of insulation, that will absorb quite well from about 200 Hz upwards, but very little below 100 Hz, and practically nothing at all below 50 Hz. That would make the room sound very "dull" and "lifeless" but also a but "muddy" and "boomy", since it would be absorbing high frequencies that don't really need absorbing, while not absorbing the very low frequencies that do.

So, if you did that (2" air, 6" insulation) all around the room, then you would need to add a lot of hard surfaces over that (eg, plastic sheeting, wood slats, etc), to help keep the highs in the room, and you would also need some much thicker insulation in a few key parts of the room, to deal with the low frequencies.

So it is an option, yes.

One annoyance is that the left wall would be drywall with panels while the right wall would be "inside out" with a concrete foundation.

That would definitely be a problem for the "control room" part of the studio, where you have your speakers and mix position. For accurate mixing, you need to have your left ear and right ear listening to roughly the same acoustic response. If your left ear is facing a hard surface and your right ear is facing absorption, that messes with the ability of your ears and brains to correctly figure out what you are listening to! In other words, that part of the room needs to be acoustically symmetrical, so your left and right ears are hearing the same acoustics "signature". This is a very important aspect of room design. It's not really a problem at all for a live room, tracking room, rehearsal room, isolation booth, bit it is a big thing for the control room.

Source of the post If I were to put up drywall again to improve material symmetry, I'd rebuild the framing, insert insulation, then cover with drywall as it was before. Then I could build acoustic panels and hang them at first reflection points, corners, and ceiling, but I'd lose a fair amount of space with 6" thick panels.

Or you could do it the other way around! Put insulation on the "hard" wall, to match what you have on the other side. You might then need to put up wood slats over that on both sides of the room, in some places so as to not lose too much of the high frequencies, but that would be up near the ceiling and down near the floor so as not to create reflections at head height.

Source of the post I wasn't planning to close off the back of the control room, although I suppose I could put up some sort of curtain to at least cut down on high-frequency echo or flutter. I realize there are symmetry issues with the back of the room, but I don't think it will cause a big problem for me.

A curtain isn't going do do much at all. Pretty much the entire audio spectrum can easily get through a thin curtain. It would have to be very thick to make a useful difference.
Symmetry is far more important at the front of the room (roughly speaking, in the region between your ears and the speakers). It isn't so important at the back of the room, especially if you make the back mostly absorbent and the front a bit more reflective.

Source of the post Regarding the ceiling, yes the joists are roughly 8" or 9" deep. There are some pipes and vents, but I'd be able to stuff most joists with insulation I imagine.

That would be a smart move! Put as much insulation as you can up there, then put fabric up there too, so that any loos fibers from the insulation don't fall down on you and your equipment, over time.

Source of the post I had thought about installing a layer of mass-loaded vinyl to improve isolation a bit, but I don't think it wuld be worth the investment.

Right. Not worth the cost and difficulty of getting up there. It would have to go right up against the floor above you to be effective, and that would probably be difficult to do, with all the pipes, wires, and joists up there. If you don't need isolation to the room above you, then it isn't necessary to do that.

Source of the post Yes, its far too reverberant, which is my main issue with the room as is. At the time, I simply selected a mix position that was the most balanced frequency response-wise, but I knew I would need treatment to tighten up the decay at the very least. Regardless, I don't plan on sitting at that location in the "final" version of the room, so those graphs were just for fun

In the article on how to use REW to measure your room, there's also a link to another article on the "Walking Mic Test" that gives you a procedure you can use to help you find the best spot for the ix position. Since your room is a complex shape, that would be the best way to do it. For a simple rectangular room, it's reasonably easy to predict that, but for non-rectangular rooms, it's better to actually measure it, using that procedure.

- Stuart -