15'x9' Songwriting and recording room

[Poor Alice Music]

Hello all,
Thanks for providing such a great forum online for helping one another. I have been reading post and lurking on here for quite a while and have just recently become a member now that I have a project.
Let me start of by saying my plan for this build is to use the room as I have used several different rooms (extra bedrooms) in the past to record and mix my own songs. All my recordings of instruments are almost all direct with the only microphones being used to record vocals. Although in the past I have learned to" keep my volume low to keep my ears fresh" and the neighbors happy ( No complaints in the last 30 years) I have recently had one child and another on the way so there are now no extra rooms! As anyone knows with small children there is no sound low enough that they will sleep through if you enjoy what you are doing to make that sound. So I have been sent to the shed in the backyard! So when all is said and done I would like this to retain the sound level outside of the shed at same level as when in the bedroom of my 50 year old un- insulated house. I will break out the old sound meter here shortly and see exactly what that level will be. But I am sure it won’t take much to achieve better results than a wall with one sheet of ½” drywall on one side and cedar shingles on the other and nothing in between. And yes when the wind blows there are drafts through the walls.

Here is what I am starting with. These are the inside dimensions of the walls L 15’5” x W 9’5” x H 7’3”
It is an all wood structure set on a raised pier and beam foundation with ¾” plywood siding and floor with a pitched roof with asphalt shingles. 3 windows and 1 door.
It sets 25’ from the closest neighbor and 25’ from my house.

Here is what I have completed so far.
Replaced roof decking, Asphalt shingles and fascia boards
Gutted the entire building to check the framing, floor joist, electrics and level building.
Added additional 4”x4” sill beams and piers for additional weight considerations.

Here is my plan from this point.
Remove windows discard and fill voids.
Wrap building with vapor barrier/house wrap
Install Hardie siding
Beef up existing outer leaf with 5/8” drywall in-between the stud frame cavities
Install non faced insolation in stud cavities
Rewire entire buildings electrics with proper grounding and surface mounting

Replace door with solid core door and proper seal
Chalk everything with acoustical chalk
Install Mini-Split system
Install ventilation system with proper fan and damper boxes
Build room with in a room inside out to gain valuable space (per Rod’s book) using 2 layers of 5/8” drywall and green glue with 2x4 framing.
Analyze room and decide what acoustic treatments it will need. eg. Bass Traps, diffuser etc., etc.

Now, I am taking this one step at time and doing all the work myself and the budget will be whatever it cost to get it done. As the building is in the dry I can take my time and build as money allows.

Here are my questions for the group.

1. Since I will be using the inside out method to build my interior room and in an effort to use the room modes calculator to determine what the best size to make it, do I use the distance to the back of the drywall or the distance to the edge of the open wall frame. I know we are only talking a 7” difference but in this small of a room every inch seems to count in the mode calculator?

2. When using the room modes calculator to determine what size of room to build, In what order of importance are the results? Which holds the most weight for a room so small? Passing the BBC tests, The Room Ratio or the Bonello? I realize the ideal would be all three. But just playing around with some small numbers I see I can get second best choice for ratio and pass BBC test But the Bonello curve is bad and vice versa.


Thanks for taking the time to look at my post. I hope I have fulfilled all the requirements to post here. If not please let me know.
Larry

[Poor Alice Music]

So I found the answer to one of my question in another post this morning. from Soundman2020 "That would gain you many benefits, starting with a room that is about 6 inches wider than it was, better isolated, better damped, etc." So now I know what measurement to use for the room size of an "inside out room" So now I am off to the room modes calculator again to figure out which size room will work best. However I am still seeking and answer to the other question.

[Soundman2020]

Hi Larry, and Welcome!

I have recently had one child and another on the way so there are now no extra rooms!

Congratulations on the new additions to your family!

I will break out the old sound meter here shortly and see exactly what that level will be.

When you do that, make sure you are playing loud music that is typical of the type you normal record and mix, using full-range speakers that cover the entire spectrum. Play that at around 110 dB, and measure it inside your house, especially in the rooms where your kids will be sleeping. Then get someone to slowly turn down that music in the shed while you carry on listening in the bedrooms, until the point where you can no longer hear the music at all, and your meter is showing only ambient level. They should stop turning down when you reach that point. Then go back in the shed and measure that level. With that, you have the information you require to objectively calculate how much isolation you need. Guessing here is not a good idea!

I am sure it won’t take much to achieve better results than a wall with one sheet of ½” drywall on one side and cedar shingles on the other and nothing in between.

That will be in the range of 20-something decibels of isolation. So a level of 110 dB inside would be reduced to about 90 dB outside. If that were an industrial workplace, anyone standing outside would be required to hear hearing protection...

It sets 25’ from the closest neighbor and 25’ from my house.

Assuming a level of 90 dB outside your walls, that would drop off to about 72 dB at the house, which is roughly the level of a rather loud conversation between two people, or the sound of a typical vacuum cleaner, the sound of a busy freeway heard about 50 feet away, or the typical level that you'd play your radio at home.

And yes when the wind blows there are drafts through the walls.

OK, let's adjust all those isolation numbers downwards, and the sound levels upwards: if air can get through, then so can sound. That 20-soemthing number is only valid for a sealed wall: if there are cracks in it like that, then all bets are off: probably more like the mid teens, if you are lucky. You can't be getting very much isolation at all right now!

Replaced roof decking, Asphalt shingles and fascia boards

What type of decking did you use, how thick is it, and did you seal the gaps air-tight? Hopefully you did that with 3/4" plywood, and used backer rod and acoustic caulk to seal all the joints? Did you also lay tar paper or something similar under the shingles?

Remove windows discard and fill voids.

Excellent! What's the plan for closing up those gaps?

Wrap building with vapor barrier/house wrap

House wrap and vapor barrier are two entirely different things, for two entirely different purposes, and cannot go together on the same surface: The house wrap goes on the outside, between the sheathing and the siding, and allows the building to breathe while still preventing liquid water from penetrating. Vapor barrier goes inside the wall cavity, tight up against the surface that is warmest in winter, which is generally the inner-leaf wall surface. Vapor barrier greatly retards the flow of air (and therefor moisture) through the walls. If you put vapor barrier in the wrong place (such as on the outside wall surface) then you will end up with mold and mildew problems, and they will very likely occur inside your wall, where you won't even know about it until it is too late. If you put the vapor barrier in teh wrong place inside your wall, such as up against the coldest surface, then you will have problems with condensation forming and running, with similar unpleasant results. Check your local building code to find out what type of house wrap is approved, what type of vapor barrier you need, and where it must go in the wall system.

Beef up existing outer leaf with 5/8” drywall in-between the stud frame cavities

It would be an awful lot easier to just add that mass on the outside, before wrapping the building! For example, a layer of 3/4" OSB or plywood, or perhaps 1/2" of fiber-cement board... It's a lot less work to put it on the outside, rather than the very time consuming and mind-numbingly boring task of cutting dozens of pieces of drywall to the exact right shape and size, then caulking each piece individually, then adding the cleats...

Here is my plan from this point.
Remove windows discard and fill voids.
Wrap building with vapor barrier/house wrap
Install Hardie siding
Beef up existing outer leaf with 5/8” drywall in-between the stud frame cavities
Install non faced insolation in stud cavities
Rewire entire buildings electrics with proper grounding and surface mounting

Whoa! You can't put your electrical system inside the wall cavity! How will you get to the plugs ans switches, once you put the inner leaf wall in place? That item needs to move way down the list, practically to the end...

Install ventilation system with proper fan and damper boxes

You might find that the silencer boxes will be too big to fit inside the wall cavity, unless you are planning a really deep air gap. It might be necessary to put the silencer boxes inside and/or outside.

Chalk everything with acoustical chalk

I think you mean "caulk" not "chalk"! Those are two rather different things...

Build room with in a room inside out to gain valuable space (per Rod’s book) using 2 layers of 5/8” drywall and green glue with 2x4 framing.

Excellent, but what size air gap are you going to leave inside the wall? That is very important for calculating your isolation.

1. Since I will be using the inside out method to build my interior room and in an effort to use the room modes calculator to determine what the best size to make it, do I use the distance to the back of the drywall or the distance to the edge of the open wall frame.

All room ratio measurements are to the hard, solid, rigid interior boundary of the room, meaning the surface of the drywall (or OSB or whatever) that you would see when standing inside the room after you hammer the last nail in place, but before you put any furniture, equipment or treatment in there. So it is the actual wall surfaces that you use, regardless of where the studs are. The effect of the studs is negligible, so just pretend they are not even there: it's the inner surface of the wall that matters, since that is what the sound waves "see" as being their limit.

I know we are only talking a 7” difference but in this small of a room every inch seems to count in the mode calculator?

7" is a huge, major, big-time difference! Even a difference of 1" is important for room ratios....

When using the room modes calculator to determine what size of room to build, In what order of importance are the results? Which holds the most weight for a room so small?

First, the BBC tests, then the axial modes, then the tangential and oblique modes, then the Bonello chart, then the total room volume. That said, do be careful with those "pass/fail" things, such as the BBC equations and the Bonello chart: since they are based on simple "yes/no" mathematics, you can find a point where changing the dimensions of the room by even 1/64" flips you over from "all pass" to "all fail", or takes the Bonello chart from "great" to "lousy". So you need to use a little discernment and intelligence in interpreting the results: If you find that small changes in your dimensions are flipping those things from good to bad, then in reality you are probably still OK.

I can get second best choice for ratio and pass BBC test But the Bonello curve is bad and vice versa

That would be a good one! All that the Bonello curve tells you is how many modes are found in each thid-octave band in the low end, and at some point a mode that was figured to be in one band will now "suddenly" jump to another band, making the graph look ugly. In reality, the mode probably only changed frequency very slightly, imperceptibly, but because there is a fixed mathematical cut-off point where each octave boundary falls, the mode seems to "jump": i real life, it barely moved. So don't put too much faith in curves and pass/fails PROVIDED THAT nudging the dimensions a bit up and down DOES cause the graph to shift, or the "pass/fail" to flip.

But also use your eyes: Just look a where the modes are falling, how they are spread out or bunched up, and what musical notes they are falling on or close to.

And finally, there is no need to go nuts here! It makes no sense at all to spend hours tweaking your dimensions down to last tiny fraction of an inch, chasing after the impossibly illusive "perfect" ratio. In reality, as long as your ratio is pretty far away from the really bad ones, and reasonably to close to a couple of good ones, you are absolutely fine! There is no need at all to bother further with that: There are far more important issues where it would be much better spending your time, such as getting the HVAC calculations done correctly, or confirming that your room is symmetrical, or getting your speaker geometry right, or making sure that the wall, ceiling, door and window surface densities are all consistent with each other, or that the 2-leaf system is a complete and hermetic envelope, or that.... There are aplenty more important issue to take care of, not just room ratios.

Here is my plan from this point.

This might seem a little harsh, but it is meant in the spirit of constructive criticism: That's the wrong plan. Before you can consider starting with any of the items on that list, or even consider doing some of the things you already did, the very first thing you should do is to PLAN the design, completely, in every last little detail. That means either with pencil and paper, or much better, with SketchUp. Do the full, entire design of all aspects, including the exact location of every wall, stud, and sheet of drywall, based on the correct room geometry, location of speakers and listening position, HVAC calculations, electrical system, first reflection points, bass trapping, acoustic treatment, door seals, hinges, automatic closers, etc.

Yes, room ratios is part of that, but just a small part. There are many, many other issues that you need to take into account, and design fully, before you can even think of lifting a hammer or saw.

So before doing anything else on your list, your top priority should be to design the entire studio in finest detail, and that in turn should be based on your measurements of the amount of isolation you need, and your careful definition of the goals for the entire build.


- Stuart -

[Poor Alice Music]

Wow thanks Stuart! So I will dig out my sound meter and do the testing you recommend and see where I am at.After that I will be off to sketch up world and get the basic dimensions in.

I think you mean "caulk" not "chalk"! Those are two rather different things...

you mean I cant just crush up a bunch chalk and pour it in there? He he Yes I meant caulk

What type of decking did you use, how thick is it, and did you seal the gaps air-tight? Hopefully you did that with 3/4" plywood, and used backer rod and acoustic caulk to seal all the joints? Did you also lay tar paper or something similar under the shingles?

Yes 3/4" plywood,backer rod,caulk,30lbs tar paper under the shingles

All your other points are excellent! and I will address these later as they need to be addressed, for now I'm putting down the hammer and picking up the sound meter and the computer. I will post the results when I have them. Thanks so much for your help.

[Poor Alice Music]

OK I got the sound meter out set some speakers up and was already to start my test and had to go to the hospital the new baby was ready to be delivered! So that being said I will not be doing any work for the next week or two as my wife recovers from the delivery. Stay tuned will be back at it as soon as I can.

[Soundman2020]

Wow! Congrats on the new member of the family!

Now go take care of your wife and baby, and forget about the studio for a while!!!! We'll still be here when you are ready to carry on... probably around the time your baby finished college... Naah, just kidding: I sure hope it's a lot sooner than that!


- Stuart -

[Poor Alice Music]

Well it's been almost three years since I put this project on hold so 3 years and 3 babies later and I was able to get a little work done this week to the foundation of the building as I have found some termite damage that needed to be dealt with so the repairs are underway !

[Soundman2020]

Hey there, Larry: Welcome back!

3 years and 3 babies later and I was able to get a little work done

Wow! You've been a busy fellow, it seems!

Maybe you could post your updated design, and a few photos of where you are right now?

- Stuart -

[Poor Alice Music]

More termite work on the floor

[Soundman2020]

More termite work on the floor

Oh wow! What a bummer! I guess all your new lumber will be pressure treated?

- Stuart -

[Poor Alice Music]

Yes $4 a stick and $30 a sheet for the plywood and the front sill was damaged as well. So all that gets replaced too! Maybe I should have just knocked it down and started from scratch

[Poor Alice Music]

And the wall is back!

[Soundman2020]

Finally!


- Stuart -

[Poor Alice Music]

A fun filled day of pushing backer rod into seams today the case of acoustic caulk is on its way should be here next week