Breaking 90 degree corners from control room

[DharmaBum]

Hi Everyone:

I have a construction/design question.

I am renovating a small 11.6'x9.6' room as my control room. I'm having to do some soundproofing work to the room especially the ceiling. While I'm in there I'm adding an extra layer of interior wall/sound board paneling to all walls.

My question is at this point I have the option to cut all four corners of the room (I.e break the 90 degree angle by adding a section of paneling say at 120 degrees) but will this truly be beneficial/worth it? Also for that matter doing the same to all the ceiling-wall corners all the way around the room.

The thought in mind is to try and break up some of the parallel walls. I was planning originally to put straddling bass traps in each (or actually 3 as I have a door in the way) corner and one in corner 12 (from 12 dihedral room model) because of the door.

I'm still thinking even after/if breaking the corners to add the bass traps along this new wall of each corner just like the bass traps would be anyways and still with some space between the wall and the absorbers.

Do you think it is worth it to break up these corners or not? I have seen many studio designs where corners 1 & 2 are angled (wide angle) in but the rear corners are left at 90 but i'm not going that wide.

What are thoughts and advise here for me.

many thanks!
Frank

[Soundman2020]

Hi Frank. Please read the forum rules for posting (click here). You seem to be missing a couple of things!

I'm having to do some soundproofing work to the room especially the ceiling. While I'm in there I'm adding an extra layer of interior wall/sound board paneling to all walls.

If that is a typical house wall, then adding an extra layer of drywall to one side will increase your isolation by about 3 dB, with luck. That assumes that the wall is already well sealed.

The questions you should be asking are: "How much isolation do I need? (in decibels)" and "How much isolation do I have at present? (in decibels)" and "How is the existing wall built?". Only once you have the answers to those three questions, can you look at construction materials and methods that will increase the existing isolation to the level you need.

My question is at this point I have the option to cut all four corners of the room (I.e break the 90 degree angle by adding a section of paneling say at 120 degrees) but will this truly be beneficial/worth it?

No. It would do nothing at all to improve either isolation or treatment, and in fact would make the room worse overall, since it would remove the very best locations in the room for dealing with modal issues. All modes terminate in room corners, so the room corner is the best point to install the treatment to deal with that.

Also for that matter doing the same to all the ceiling-wall corners all the way around the room.

Ditto. Same as above.

The thought in mind is to try and break up some of the parallel walls.

Cutting off the corners does not change the angle of the walls. To change the angle of the walls, you would have to actually change the angle of the walls! And you don't need to do that anyway. It's a myth. A very well propagated and very well perpetuated myth! But a myth nevertheless. Everybody "knows" that you have to angle the walls of a studio to make it "sound good", ... but if you ask them what acoustic effect you get by angling the walls, you normally get a blank stare, or a "Emmm.... well.... err... I think it stops the sound from going ... errr... bouncing .... emmm.... ahhhh....".

The truth is that angling the walls can eliminate flutter echo, which is one small problem in acoustics. But in order to accomplish that, you need to angle one entire wall by at least 12°, or each of the opposite walls by 6°, or by another combination that totals 12°: Any less, and the flutter will still be there. But angling the walls reduces the available floor area and room volume, both of which are bad, and flutter echo can be dealt with in several other ways that DON'T wast space.

The only other reason you might want to validly angle your walls, is if you plan to implement a true RFZ-style control room, or a similar design (CID, NER, etc.). In that case, only part of the wall is angled, and the angle is carefully calculated to produce the desired reflections.

I have seen many studio designs where corners 1 & 2 are angled (wide angle) in but the rear corners are left at 90 but i'm not going that wide.

It sounds like you might be talking about RFZ-style design. That's a very, very good design, with excellent acoustics, and very good, valid reasons for the angles. But I'm not certain that's what you are referring to. Maybe you could post a link or photos of the type of studio you are talking about?


- Stuart -

[DharmaBum]

Stuart:

Thank you very much for your advice and help. I updated my profile to add my location and will add a few more details about the room below. It seems thought that the bottom line to my most pertinent (90 degree corners) question is "NO" which is what I was looking for (some thoughts and explanations why this would be a good or bad idea).

The room in question is built inside a concrete warehouse along the front and one side of the side walls. One exterior door in front, one leading to the rest of the warehouse, one on the back wall and a bay door. The height is 8' inside the room. The construction of this room is very basic as it was probably just intended to be an office and built some time ago. It's a simple 2"x4" framed room 24'' spaced beams for the two interior walls which have drywall and basic insulation between the beams. There's just thin (1/8") wood paneling all around (against the drywall of the two interior walls and against the other two concrete walls. I plan on removing all the 1/8" paneling. Adding soundboards all around for panels on a light steel frame. The ceiling I'm going to completely redo as right now there's just a drop ceiling and some flimsy 1"x6" joists running across. I plan on making an air tight ceiling. New frame, new support, three layers; Top layer drywall or soundboard, MLV layer, frame, sound insulation between beams, outer MLV layer, soundboard, green glue, second layer of soundboard. Also using acoustic sealant to seal up all seams etc. Also putting in a proper window to look into warehouse as there is already one there just not good with plexi. The rest of the warehouse (outside this room) is carpeted and has acoustic foam on like 85% of it (from previous band). This location has been my band(s) rehearsal space for many years. Right now I'm more interested in recording some original material properly as well as maybe taking on some side projects. I have a degree in audio engineering and production. This is the first time designing and constructing a proper (as much as can be done in this scenario) recording environment. I hope I have provided all the information needed.

I have also attached a quick illustration to help.

thanks!

[Soundman2020]

I updated my profile to add my location

Yup! That was the biggie!

11.6'x9.6' room ... height is 8' inside

Great! That gives us the basics for figuring out your modal response. Your ratio is 1 : 1.2 : 1.45, which is close to Louden's 5th best ratio, at 1 : 1.2 : 1.5. That's number 9 on a list of 25 generally accepted good ratios. It's not fantastic, but certainly not terrible.

However, the floor area is only 111 ft^2, which is only about half of the "minimum recommended" area for critical listening rooms, which is 215 ft^2. That's not so good. Your room is going to need a LOT of treatment to make it usable. The smaller a room is, then more treatment it needs.

It's a simple 2"x4" framed room 24'' spaced beams for the two interior walls which have drywall and basic insulation between the beams.

Studs. Not beams, but studs. Beams run horizontally, spanning over empty space, and support large loads. Studs are the vertical members inside walls that support the actual sheathing (drywall). Terminology is important!

So you have 2x4 stud framed walls, 24" OC, and you need better isolation and great acoustics.

There's just thin (1/8") wood paneling all around (against the drywall of the two interior walls and against the other two concrete walls. I plan on removing all the 1/8" paneling. Adding soundboards all around for panels on a light steel frame.

... which would actually decrease your isolation in the low end! Yup. Surprising as that may be, it is true nonetheless. You would be creating a 3-leaf system like that, and even worse, two of the leaves would be coupled.

Here's the issue:

All objects have a natural resonant frequency. If you bang any particular object with something hard, that's the "note" that it will produce. A wall is obviously made up of "objects" (such as studs and drywall), each of which has its own natural resonant frequency. But when you put objects together to create an air cavity in between, you also create another resonant frequency, which is not related at all to the resonant frequency of each object. Rather, it is related to only two things: the mass (surface density) of the "objects" that define the cavity (in your case: the drywall on either side of the studs), and the depth of the air cavity between them. In effect, you have a Mass-Spring-Mass system (MSM) where the air trapped in the middle is the "spring". All MSM systems resonate.

So your entire wall system will resonate at this new MSM frequency. The problem is, if the wall is resonating, then obviously it is not isolating! In fact, not only is it not isolating, it is actively amplifying that particular note. So if your music happens to contain the note that makes your wall resonate, then that note (and the ones around it) will be clearly heard outside, very loudly, since the wall itself transmits and amplifies them. Not good! So walls are designed to have a MSM resonant frequency that is lower than the notes that it has to isolate. Ordinary house walls typically have resonant frequencies in the lower mid-range portion of the musical scale, or the upper part of the low frequency portion of the scale. Which is why they are reasonably good at stopping voices, but not so good at stopping music, and lousy at stopping bass guitars and drums.

That's the situation you have now, and what you propose sounds logical and good at first glance, but is in fact a very common error.

By adding another thin frame and another layer of drywall, you change the system from being a 2-leaf MSM system, into a 3-leaf MSMSM system. You need a very different equation to calculates the resonant frequency, because there are now TWO air gaps (two springs) and THREE masses (leaves of drywall). It turns out that the resonant frequency for such a system will always be higher than for the equivalent 2-leaf system, all other factors being equal. So although the wall will isolate voices even better, it will isolate bass guitars and kick drums even WORSE than before (which it wasn't doing very well anyway!).

Resonance is a bitch: Excuse my French. Resonance will always get you when you least expect it, and this is one of those cases that gets a lot of people, because it just isn't intuitive at all! Who would expect that adding an extra layer to a wall would make it worse? Not obvious... until you understand resonance. Many people make the mistake you were about to make, and end up with walls that don't work, after they spend a lot of time and money on them.

Here's what you really need to do: You need to keep your wall as a 2-leaf system. It turns out that this is the best of all possible wall configurations for studio isolation, and is the reason why practically all pro studios are built as 2-leaf systems these days. So that's your first priority: Do whatever it takes to make your final wall into a 2-leaf system. Not 3-leaf, not 4-leaf, not one-leaf. 2-leaf only.

But you also need to "de-couple" the leaves: right now, the studs are transmitting the sound directly from the drywall on one side to the drywall on the other side, bypassing the air gap, and the drywall then acts like an enormous loudspeaker. You need to cut that path, such that the drywall on side "A" is totally independent from the drywall on side "B".

You also need more mass on your wall.

And you need a bigger air gap.

So, here's the plan: take off the paneling, and also the drywall, and also the insulation, so that you have bare studs facing the room. While you have it like that, seal that framing and drywall absolutely air-tight, all around the edges, any cracks, gaps, slits, etc. Fill any holes, too (like where nails are badly placed, leaving tiny air holes). If there are electrical boxes on the other side for switches or outlets, remove those completely and cover over the holes with drywall, carefully sealed in place. Seal the hell out of it! Then seal it all over again. Did I mention that air-tight seals are important?

Now add more mass to that "leaf" of your wall. The easiest way to do this is to put strips of drywall in between the studs, pressed up against the drywall on the far side. This is often called "beefing up the wall from the inside". Cut the strips if drywall to shape, push them in carefully, seal up the edges with caulk (did I mention that sealing is important?), and put in small cleats nailed sideways into the studs, to hold the drywall "beef" in place.

Now put insulation in there. But not just any insulation: It can be either mineral wool with a density of 50 kg/m3, or fiberglass with a density of 30 kg/m3.

Now build your new frame about an inch away from that existing wall, put more insulation in that frame, put a layer of ordinary 5/8" fire rated drywall on the frame, seal up the edges very well (I think I forget to mention that sealing is critical...), then put another layer of drywall directly on top of the first layer with Green Glue in between.

And you are done! It's that easy. That is now a fully-decoupled 2-leaf MSM isolation wall, and it will give you pretty darn good isolation across practically all of the spectrum, except for the very low lows (canon fire, earthquakes, planets colliding, etc.).

You were planning to do most of this anyway (new frame, new drywall), so it's not such a big deal. You'd' just be adding "strip old sheathing / seal / beef up outer leaf". (Oh, I nearly forget: it's important to seal everything air-tight.)

The ceiling I'm going to completely redo as right now there's just a drop ceiling and some flimsy 1"x6" joists running across. I plan on making an air tight ceiling.

Right! Pull all of that out, then take a close look at what is above that: the existing ceiling. That's the key. Your new ceiling is only half the equation: Remember MSM? Your ceiling is just one of those "M's". You need to take a look at the other "M", the existing ceiling above you, and figure out what to do about it.

Top layer drywall or soundboard, MLV layer, frame, sound insulation between beams, outer MLV layer, soundboard, green glue, second layer of soundboard.

That's one hell of a sandwich! But not a lot of use for good isolation. And rather expensive. And rather complex to build.

Once again, you would be making a two-leaf ceiling, and you would be combining it with the existing ceiling above it, thus making it into a 3-leaf system or maybe even a [GASP!] 4-leaf system! Not good at all.

What you need to do here is this:

After fixing whatever needs fixing in the existing ceiling above you, in whatever way is necessary, put new joists across your new inner-leaf walls, taking care that they don't extend too far and touch the old outer leaf. (You must avoid all connections between inner-leaf and outer-leaf.) Your new joists should be sized correctly to take the live load and dead load of the new ceiling. Stuff the same type of insulation as for the walls up there, as thick as you can get it without compressing it too much, then put one layer of 5/8" drywall, seal, and a second layer of 5/8" drywall directly on the first layer, once again with Green Glue in between. (Damn! I keep forgetting to tell you about the importance of sealing! It's important.)

And you are done!

OK, so how come I'm not suggesting exotic things like "soundboard" and "MLV", considering that they are so highly recommended? One simple reason: cost. I'm assuming you want to do this at the lowest cost possible? So here's the thing. The equations for MSM resonance consider only two main factors, and neither of those is "price". Here's the actual equation:

F=c[(m1 + m2)]^.5 / [(m1 x m2 x d)]^.5

Where:
C=43 for imperial, 1897 for metric
m1, m2 = surface density of leaf #1 and leaf #2 (pounds per square foot, or kg/m2)
d=depth of air gap


Did you notice something interesting there? There's no place to plug in the price tag! It would seem that the price you pay for the materials is irrelevant! Darn! This is bad news for the manufacturers of those expensive products. Sound waves just don't care! They can't read the price tag, and they aren't elitist at all, so they really don't care how much you paid for your mass. All they see is mass, and they react to the quantity of mass, not the cost of the mass. So it seems logical that you should use the mass that costs the least, pound for pound (or kg for kg).

It turns out that in most places on Planet Earth, the cheapest mass you can get in common building materials is found in plain old drywall. Best is fire-rated drywall, which is usually a bit heavier for not much increase in price. Yes "soundboard" is heavier still... but compare the prices! Ask yourself: "For the same money or less, could I put on another layer of ordinary drywall, or use thicker drywall?" If the answer is "yes", then your path is clear: ordinary drywall.

"But what about MLV"? you say. "That's even better," you say, "because it is limp mass. And limp mas is wonderful stuff!". Yes it is, but if you restrain it with layers of drywall, then it isn't "limp" any more: it is now just "mass"... and you are paying an awful lot for that "limp mass that isn't limp"! I know of a much cheaper option for "mass that isn't limp". Its called "drywall"...

MLV has some uses in acoustics, but adding mass to a wall isn't a good one. (Despite what the manufacturers say). It works, of course, because it IS mass, after all. But the cost... sound waves... reading skills--- price tags.... Hmmmmmm....

Also using acoustic sealant to seal up all seams etc.

Yes! Very much so! (Not sure if I already mentioned that sealing is very, very important...?)

Also putting in a proper window to look into warehouse as there is already one there just not good with plexi.

Right. You will need two panes of laminated glass for that window. One pane goes in each leaf: You calculate the thickness of the glass such that it has the same surface density as the leaf itself. So fore example, two layers of 5/8 drywall has a density of about 24 kg/m2, so you'd need each pane of glass to have at least the same density, and preferably a bit higher. The density of glass is roughly three times higher than the density of drywall, so you need about one third the thickness. Two layers of 5/8" drywall is 1-1/4" thick, so you need laminated glass that is about 7/16" thick. call it 1/2", to be safe. So you would need to order ' 1/4"+1/4" laminated glass with acoustic PVB interlayer '. It might also be listed as "6mm+6mm with acoustic PVB". You would need two of those for each window, one in the inner leaf and one in the outer leaf.

The rest of the warehouse (outside this room) is carpeted and has acoustic foam on like 85% of it (from previous band).

It must sound like crap in there! (Excuse my French again...) Let me guess: a bit "boomy", somewhat "honky", very "muddy", mostly "mushy" in the mid range, harsh in the high mids, and teeth-achingly tinder-dry in the high end. Am I close?

I imagine that after you get the CR in shape, your next project will be to fix the "other" room and make it into a usable live room / tracking room?

Anyway, that's the outline of what I'd suggest for getting the control room isolation in order. The only other things is doors: you need two doors in each doorway, not just one. They go back-to-back, one door in each leaf. And each door needs at least two full-perimeter seals (both sides, top and threshold). Because you need the doors to seal completely air tight when they are closed. I should mention that sealing things air-tight is critical to getting good isolation. I forgot to mention that before, I think...


- Stuart -

(Edited to correct some schpelink mizteaks, to clarify some not-so-clear things, and to add a bit more detail)

[DharmaBum]

WOW Stuart!!

Thank you SO much for all this wonderful and valuable information and guidance. I was never expecting this kind of help. Thank you so much!!! I would like to take some time to soak in all this information. I would like to post some more detailed information of my room as the information I supplied was off the top of my head at work. There are a couple of small details I missed and some info that I don't feel I conveyed accurately. This way you can get a really complete and accurate idea of what's going on in my room and the plans/ideas that I have to implement. I will create some cross section drawings of what is currently there and what I propose. Then maybe we can better discuss this issue and I would love to hear you're input.

thanks - Frank

[Soundman2020]

Thank you SO much for all this wonderful and valuable information and guidance. I was never expecting this kind of help. Thank you so much!!!

You are entirely welcome! That's what the forum is all about: providing info to help others.

I would like to post some more detailed information of my room

Excellent! That will help us to get a better idea of what you are facing. Take some photos too, and post those here.

I will create some cross section drawings of what is currently there and what I propose.

Perfect!

I'm looking forward to seeing that.


- Stuart -

[javamad]

I updated my profile to add my location

Yup! That was the biggie!

11.6'x9.6' room ... height is 8' inside

Great! That gives us the basics for figuring out your modal response. Your ratio is 1 : 1.2 : 1.45, which is close to Louden's 5th best ratio, at 1 : 1.2 : 1.5. That's number 9 on a list of 25 generally accepted good ratios. It's not fantastic, but certainly not terrible.

However, the floor area is only 111 ft^2, which is only about half of the "minimum recommended" area for critical listening rooms, which is 215 ft^2. That's not so good. Your room is going to need a LOT of treatment to make it usable. The smaller a room is, then more treatment it needs.

It's a simple 2"x4" framed room 24'' spaced beams for the two interior walls which have drywall and basic insulation between the beams.

Studs. Not beams, but studs. Beams run horizontally, spanning over empty space, and support large loads. Studs are the vertical members inside walls that support the actual sheathing (drywall). Terminology is important!

So you have 2x4 stud framed walls, 24" OC, and you need better isolation and great acoustics.

There's just thin (1/8") wood paneling all around (against the drywall of the two interior walls and against the other two concrete walls. I plan on removing all the 1/8" paneling. Adding soundboards all around for panels on a light steel frame.

... which would actually decrease your isolation in the low end! Yup. Surprising as that may be, it is true nonetheless. You would be creating a 3-leaf system like that, and even worse, two of the leaves would be coupled.

Here's the issue:

All objects have a natural resonant frequency. If you bang any particular object with something hard, that's the "note" that it will produce. A wall is obviously made up of "objects" (such as studs and drywall), each of which has its own natural resonant frequency. But when you put objects together to create an air cavity in between, you also create another resonant frequency, which is not related at all to the resonant frequency of each object. Rather, it is related to only two things: the mass (surface density) of the "objects" that define the cavity (in your case: the drywall on either side of the studs), and the depth of the air cavity between them. In effect, you have a Mass-Spring-Mass system (MSM) where the air trapped in the middle is the "spring". All MSM systems resonate.

So your entire wall system will resonate at this new MSM frequency. The problem is, if the wall is resonating, then obviously it is not isolating! In fact, not only is it not isolating, it is actively amplifying that particular note. So if your music happens to contain the note that makes your wall resonate, then that note (and the ones around it) will be clearly heard outside, very loudly, since the wall itself transmits and amplifies them. Not good! So walls are designed to have a MSM resonant frequency that is lower than the notes that it has to isolate. Ordinary house walls typically have resonant frequencies in the lower mid-range portion of the musical scale, or the upper part of the low frequency portion of the scale. Which is why they are reasonably good at stopping voices, but not so good at stopping music, and lousy at stopping bass guitars and drums.

That's the situation you have now, and what you propose sounds logical and good at first glance, but is in fact a very common error.

By adding another thin frame and another layer of drywall, you change the system from being a 2-leaf MSM system, into a 3-leaf MSMSM system. You need a very different equation to calculates the resonant frequency, because there are now TWO air gaps (two springs) and THREE masses (leaves of drywall). It turns out that the resonant frequency for such a system will always be higher than for the equivalent 2-leaf system, all other factors being equal. So although the wall will isolate voices even better, it will isolate bass guitars and kick drums even WORSE than before (which it wasn't doing very well anyway!).

Resonance is a bitch: Excuse my French. Resonance will always get you when you least expect it, and this is one of those cases that gets a lot of people, because it just isn't intuitive at all! Who would expect that adding an extra layer to a wall would make it worse? Not obvious... until you understand resonance. Many people make the mistake you were about to make, and end up with walls that don't work, after they spend a lot of time and money on them.

Here's what you really need to do: You need to keep your wall as a 2-leaf system. It turns out that this is the best of all possible wall configurations for studio isolation, and is the reason why practically all pro studios are built as 2-leaf systems these days. So that's your first priority: Do whatever it takes to make your final wall into a 2-leaf system. Not 3-leaf, not 4-leaf, not one-leaf. 2-leaf only.

But you also need to "de-couple" the leaves: right now, the studs are transmitting the sound directly from the drywall on one side to the drywall on the other side, bypassing the air gap, and the drywall then acts like an enormous loudspeaker. You need to cut that path, such that the drywall on side "A" is totally independent from the drywall on side "B".

You also need more mass on your wall.

And you need a bigger air gap.

So, here's the plan: take off the paneling, and also the drywall, and also the insulation, so that you have bare studs facing the room. While you have it like that, seal that framing and drywall absolutely air-tight, all around the edges, any cracks, gaps, slits, etc. Fill any holes, too (like where nails are badly placed, leaving tiny air holes). If there are electrical boxes on the other side for switches or outlets, remove those completely and cover over the holes with drywall, carefully sealed in place. Seal the hell out of it! Then seal it all over again. Did I mention that air-tight seals are important?

Now add more mass to that "leaf" of your wall. The easiest way to do this is to put strips of drywall in between the studs, pressed up against the drywall on the far side. This is often called "beefing up the wall from the inside". Cut the strips if drywall to shape, push them in carefully, seal up the edges with caulk (did I mention that sealing is important?), and put in small cleats nailed sideways into the studs, to hold the drywall "beef" in place.

Now put insulation in there. But not just any insulation: It can be either mineral wool with a density of 50 kg/m3, or fiberglass with a density of 30 kg/m3.

Now build your new frame about an inch away from that existing wall, put more insulation in that frame, put a layer of ordinary 5/8" fire rated drywall on the frame, seal up the edges very well (I think I forget to mention that sealing is critical...), then put another layer of drywall directly on top of the first layer with Green Glue in between.

And you are done! It's that easy. That is now a fully-decoupled 2-leaf MSM isolation wall, and it will give you pretty darn good isolation across practically all of the spectrum, except for the very low lows (canon fire, earthquakes, planets colliding, etc.).

You were planning to do most of this anyway (new frame, new drywall), so it's not such a big deal. You'd' just be adding "strip old sheathing / seal / beef up outer leaf". (Oh, I nearly forget: it's important to seal everything air-tight.)

The ceiling I'm going to completely redo as right now there's just a drop ceiling and some flimsy 1"x6" joists running across. I plan on making an air tight ceiling.

Right! Pull all of that out, then take a close look at what is above that: the existing ceiling. That's the key. Your new ceiling is only half the equation: Remember MSM? Your ceiling is just one of those "M's". You need to take a look at the other "M", the existing ceiling above you, and figure out what to do about it.

Top layer drywall or soundboard, MLV layer, frame, sound insulation between beams, outer MLV layer, soundboard, green glue, second layer of soundboard.

That's one hell of a sandwich! But not a lot of use for good isolation. And rather expensive. And rather complex to build.

Once again, you would be making a two-leaf ceiling, and you would be combining it with the existing ceiling above it, thus making it into a 3-leaf system or maybe even a [GASP!] 4-leaf system! Not good at all.

What you need to do here is this:

After fixing whatever needs fixing in the existing ceiling above you, in whatever way is necessary, put new joists across your new inner-leaf walls, taking care that they don't extend too far and touch the old outer leaf. (You must avoid all connections between inner-leaf and outer-leaf.) Your new joists should be sized correctly to take the live load and dead load of the new ceiling. Stuff the same type of insulation as for the walls up there, as thick as you can get it without compressing it too much, then put one layer of 5/8" drywall, seal, and a second layer of 5/8" drywall directly on the first layer, once again with Green Glue in between. (Damn! I keep forgetting to tell you about the importance of sealing! It's important.)

And you are done!

OK, so how come I'm not suggesting exotic things like "soundboard" and "MLV", considering that they are so highly recommended? One simple reason: cost. I'm assuming you want to do this at the lowest cost possible? So here's the thing. The equations for MSM resonance consider only two main factors, and neither of those is "price". Here's the actual equation:

F=c[(m1 + m2)]^.5 / [(m1 x m2 x d)]^.5

Where:
C=43 for imperial, 1897 for metric
m1, m2 = surface density of leaf #1 and leaf #2 (pounds per square foot, or kg/m2)
d=depth of air gap


Did you notice something interesting there? There's no place to plug in the price tag! It would seem that the price you pay for the materials is irrelevant! Darn! This is bad news for the manufacturers of those expensive products. Sound waves just don't care! They can't read the price tag, and they aren't elitist at all, so they really don't care how much you paid for your mass. All they see is mass, and they react to the quantity of mass, not the cost of the mass. So it seems logical that you should use the mass that costs the least, pound for pound (or kg for kg).

It turns out that in most places on Planet Earth, the cheapest mass you can get in common building materials is found in plain old drywall. Best is fire-rated drywall, which is usually a bit heavier for not much increase in price. Yes "soundboard" is heavier still... but compare the prices! Ask yourself: "For the same money or less, could I put on another layer of ordinary drywall, or use thicker drywall?" If the answer is "yes", then your path is clear: ordinary drywall.

"But what about MLV"? you say. "That's even better," you say, "because it is limp mass. And limp mas is wonderful stuff!". Yes it is, but if you restrain it with layers of drywall, then it isn't "limp" any more: it is now just "mass"... and you are paying an awful lot for that "limp mass that isn't limp"! I know of a much cheaper option for "mass that isn't limp". Its called "drywall"...

MLV has some uses in acoustics, but adding mass to a wall isn't a good one. (Despite what the manufacturers say). It works, of course, because it IS mass, after all. But the cost... sound waves... reading skills--- price tags.... Hmmmmmm....

Also using acoustic sealant to seal up all seams etc.

Yes! Very much so! (Not sure if I already mentioned that sealing is very, very important...?)

Also putting in a proper window to look into warehouse as there is already one there just not good with plexi.

Right. You will need two panes of laminated glass for that window. One pane goes in each leaf: You calculate the thickness of the glass such that it has the same surface density as the leaf itself. So fore example, two layers of 5/8 drywall has a density of about 24 kg/m2, so you'd need each pane of glass to have at least the same density, and preferably a bit higher. The density of glass is roughly three times higher than the density of drywall, so you need about one third the thickness. Two layers of 5/8" drywall is 1-1/4" thick, so you need laminated glass that is about 7/16" thick. call it 1/2", to be safe. So you would need to order ' 1/4"+1/4" laminated glass with acoustic PVB interlayer '. It might also be listed as "6mm+6mm with acoustic PVB". You would need two of those for each window, one in the inner leaf and one in the outer leaf.

The rest of the warehouse (outside this room) is carpeted and has acoustic foam on like 85% of it (from previous band).

It must sound like crap in there! (Excuse my French again...) Let me guess: a bit "boomy", somewhat "honky", very "muddy", mostly "mushy" in the mid range, harsh in the high mids, and teeth-achingly tinder-dry in the high end. Am I close?

I imagine that after you get the CR in shape, your next project will be to fix the "other" room and make it into a usable live room / tracking room?

Anyway, that's the outline of what I'd suggest for getting the control room isolation in order. The only other things is doors: you need two doors in each doorway, not just one. They go back-to-back, one door in each leaf. And each door needs at least two full-perimeter seals (both sides, top and threshold). Because you need the doors to seal completely air tight when they are closed. I should mention that sealing things air-tight is critical to getting good isolation. I forgot to mention that before, I think...


- Stuart -

(Edited to correct some schpelink mizteaks, to clarify some not-so-clear things, and to add a bit more detail)

Wow. Probably one of THE best posts I have seen in a while. You were inspired there Stuart! Clear info, using examples, great stuff. I understood everything! Pity this forum does not have a "like" option for posts.

Many thanks, I will be using these tips to get my design together before I post it.

[Soundman2020]

Wow. Probably one of THE best posts I have seen in a while. You were inspired there Stuart!

Thanks! It's comments like yours that make all the effort worthwhile.

Pity this forum does not have a "like" option ....

We do, actually! Scroll to the top of the page, and you'll see the 'like' button there, in the middle. It is yellow, and marked "Donate". You can even type in a number, to show how much you like it!


But more seriously, that's actually a good idea. I'll see if there's a way of doing that, adding a 'like' button to each post...


- Stuart -