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Jcoop Basement Build - Questions
Old 31st July 2019
  #1
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Jcoop Basement Build - Questions

Hey Guys,

Endgame here is to build a suite in the unfinished basement of my new (not newly built) home.

For now I'm still planning the build so, I'll keep it simple for now...

The basement is a concrete foundation that goes right up the the ceiling. It's already framed in and insulated around the perimeter. I'm looking at doing MSM/double wall construction for the suite. 2 walls will need to be built from scratch so, I'll do drywall, insulation, gap, insulation, drywall for those.

But, my main question here is, can the concrete foundation act as the first layer of mass on the 2 other walls or do I need to use drywall? I know that sounds like a silly question but in Gervais' book, it sounds like having the same material is important to create that "spring" effect that effectively bounces the sound around inside the gap/insulation to effectively neutralize it.

Thanks for any feedback.

Joe
Old 31st July 2019
  #2
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Quote:
But, my main question here is, can the concrete foundation act as the first layer of mass on the 2 other walls or do I need to use drywall?
The concrete foundation wall IS your outer leaf. It is massive (very!), rigid (very!) and solid (very!). So you would only need one other leaf to complete your two-leaf MSM system. However, you say that you already have framing over that: " It's already framed in and insulated around the perimeter", so there's the basis for your second leaf... Asuming that the framing does not touch the concrete foundation wall, nor the ceiling above, you could just put drywall on that, and you'd be done. But if the framing DOES touch the outer walls and/or the ceiling, then you won't be able to uses that for your inner-leaf framing, so just leave it as it is, and put up a second frame next to it, a short distance away (not touching the outer wall or ceiling), and put your drywall on that.

Quote:
I know that sounds like a silly question but in Gervais' book, it sounds like having the same material is important to create that "spring" effect that effectively bounces the sound around inside the gap/insulation to effectively neutralize it.
The air gap between the two leaves is the "spring", not the leaves themselves. The leaves are mass. That's why it is called "MSM", for "Mass - Spring - Mass". You have one bunch of mass on the outside (the foundation wall in your case), another bunch of mass on the inside (the new drywall in your case), and the air trapped between them is the spring. That "MSM" is a resonant system, much like a weight suspended on a rubber band bouncing up and down, or the suspension system in your car. It is tuned to a specific fundamental frequency, and that frequency is governed by the amount of mass on each side, and the depth of the cavity (which basically controls the "springiness" of the air spring). You also need suitable insulation in the gap, to act as a damper on the resonance.

- Stuart -
Old 31st July 2019
  #3
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Thanks for the clarification, Stuart.

I'm fairly handy and have read through "Build it like the Pros," and "Master Handbook of Acoustics." But, I'm a big "Why" asker. I like to know why I'm doing what I'm doing because inevitably (especially in a project like this) things come up and you have to rethink or improvise. I don't want to ruin the blank slate that is my unfinished basement with a bad move or missed opportunity.
Old 31st July 2019
  #4
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Asking "why?" is always a good idea! People tend to design better and build better when they fully understand what they are doing and the reasons why they are doing it. Helps to avoid mistakes, too! So don't be afraid to ask "why" all the time!

- Stuart -
Old 2nd August 2019
  #5
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Hey Guys,

Next question...

I have a gas-line junction I need to figure out. I'm not interested in moving/re-running it. Though, I know I can't cover it up because the shut-off valve for the gas fireplace needs to remain accessible. I'm thinking I need to fashion some sort of access port in the area. My fear, though, is spending all the time and money building a solid room only to have it ruined by stupid little hole... lol

Am I worrying too much about this? Should a small hatch framed into the area with a firm "lock" and proper gasket keep me in the game?

I've attached a few pictures of the problem area. There's also an outlet that the fireplace is plugged into. I think that's easier to deal with, though.

Sorry for the upside-down duplicates...
Attached Thumbnails
Jcoop Basement Build - Questions-20190801_204018.jpg   Jcoop Basement Build - Questions-20190801_204026.jpg   Jcoop Basement Build - Questions-20190801_204036.jpg   Jcoop Basement Build - Questions-area.jpg   Jcoop Basement Build - Questions-gas-valve.jpg  

Jcoop Basement Build - Questions-outlet.jpg  

Last edited by Jcoop; 2nd August 2019 at 01:51 AM.. Reason: Duplicate pics
Old 2nd August 2019
  #6
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As long as the access door is airtight and matches the mass of your inner leaf, its not an issue acoustically. Up to code could be a different story. Check local building codes.
Old 2nd August 2019
  #7
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Roger that, Jason. Thanks.

So, I'm looking at doors... Seems like, unless you want to pay an arm and a leg for a prefab studio door, there isn't much in the way of high-mass/density doors you can buy from home depot, lowes, etc...

If I glue and/or screw 2 of the heaviest wood slabs together, is there anything wrong with that? It'll end up being about a 3.5" thick door.
Old 2nd August 2019
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If you are not a master carpenter one practical option is to buy a pair of solid doors from your local DIY centre and add (ie. screw or glue) mass (often MDF) to them. That way you can rest assured that the hinges and handles have been correctly and neatly installed. Just check that the hinges will be sufficient to carry the extra weight.
Old 2nd August 2019
  #9
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Great! Thanks, Starlight.
Old 2nd August 2019
  #10
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Quote:
Originally Posted by Starlight View Post
If you are not a master carpenter one practical option is to buy a pair of solid doors from your local DIY centre and add (ie. screw or glue) mass (often MDF) to them. That way you can rest assured that the hinges and handles have been correctly and neatly installed. Just check that the hinges will be sufficient to carry the extra weight.
+1 ! And to add extra hinges. Use heavy-duty hinges, for sure, but add a couple of extra ones. I normally have two close to the top, two close to the bottom, and one in the middle.

Also, make the MDF panel a bit smaller than the original door slab, so you can have two separate full-perimeter seals on the door, and use an automatic door closer, both to control the closing rate and also to apply pressure to the seals when the door is closed.

- Stuart -
Old 2nd August 2019
  #11
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Yea I've seen/read about a slightly smaller size to be able to create 2 seals for the door. To be honest, properly sealing 1 edge already scares the crap out of me. Sealing 2? I don't know... What I do know is the limits of my handiness. If all that stuff doesn't line up nice and snug, it is all for nothing.
Old 2nd August 2019
  #12
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Quote:
Originally Posted by Jcoop View Post
What I do know is the limits of my handiness.
Be wise and know when to call in a carpenter.
Old 2nd August 2019
  #13
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I guess my fear with that is a professional may do a great job but, will they understand the gravity of having an absolutely perfect seal? I don't know about you but, where I live it can be a bit of a mascarade. So, my trust in "professionals" is low.

I cut my own hair.
Old 2nd August 2019
  #14
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https://www.bobgolds.com/PaulsDoor/home.htm

This is helpful for doors
Old 3rd August 2019
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This is great, Jason! Thanks!
Old 8th August 2019
  #16
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Quote:
Originally Posted by Jason Foi View Post
As long as the access door is airtight and matches the mass of your inner leaf, its not an issue acoustically. Up to code could be a different story. Check local building codes.
Back to the hatch!

I found some hardcore acoustically sealed hatches - designed for studio use - but they're likely expensive and I think overkill for my application (https://hushcitysp.com/product/acoustic-access-panels/). I don't intend on opening the access door. Ever, really. It's just a matter of having access to the gas shut-off valve in an emergency.

So, I came across an ABS drain cleanout fitting. It's 4" (small hole but big enough to squeeze my hand through), it's deep (I can pack it with material to bring the cavity back up to some kind of isolating "par"), and it's airtight.
Attached Thumbnails
Jcoop Basement Build - Questions-abs-cleanout-fitting-lowes.jpg  
Old 9th August 2019
  #17
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Quote:
Originally Posted by Jcoop View Post
Back to the hatch!

I found some hardcore acoustically sealed hatches - designed for studio use - but they're likely expensive and I think overkill for my application (https://hushcitysp.com/product/acoustic-access-panels/). I don't intend on opening the access door. Ever, really. It's just a matter of having access to the gas shut-off valve in an emergency.

So, I came across an ABS drain cleanout fitting. It's 4" (small hole but big enough to squeeze my hand through), it's deep (I can pack it with material to bring the cavity back up to some kind of isolating "par"), and it's airtight.
If you can get the mass right, the cleanout would work. I would think a diy door would be easy and cheap, but whatever youre comfortable with.
Old 9th August 2019
  #18
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I guess I just figured the smallest possible hole would be best and easiest to make air tight. I'm not necessarily confident in constructing an access hatch from scratch that will be air tight. If I just glue the circle of drywall - I'll need to remove from the wall to insert the fitting - into the lid of the fitting, mass should match up pretty well, right? I can even back that with a circle of roxul. It'll match the layering of the wall almost perfectly.
Old 10th August 2019
  #19
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Quote:
Originally Posted by Jcoop View Post
I guess I just figured the smallest possible hole would be best and easiest to make air tight. I'm not necessarily confident in constructing an access hatch from scratch that will be air tight. If I just glue the circle of drywall - I'll need to remove from the wall to insert the fitting - into the lid of the fitting, mass should match up pretty well, right? I can even back that with a circle of roxul. It'll match the layering of the wall almost perfectly.
Yes, sounds like a plan to me.
Old 15th August 2019
  #20
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Ok so I have 2-3 questions about doors...

I won't pretend to know the physics behind this but, it is my understanding that, considering mass law, a door needs to (at minimum) have the same mass as the wall it's being built into.

First off, in a mass spring/air mass wall - or double wall - system, will a single door negate the isolation effect of the room in a room? Presumably the frame will span both walls? Unless you're supposed to build the door into only one of the walls, frame the other wall opening and leave a gap (cover with fabric, rubber, cork strips?)?

Do you need to have double doors?

Either way, when calculating the required mass of the door(s), do you consider both walls or just 1? I.e. The mass of 2 sheets of 5/8 or 4 sheets of 5/8?

Thanks.
Old 15th August 2019
  #21
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Quote:
Originally Posted by Jcoop View Post
Ok so I have 2-3 questions about doors...

I won't pretend to know the physics behind this but, it is my understanding that, considering mass law, a door needs to (at minimum) have the same mass as the wall it's being built into.

First off, in a mass spring/air mass wall - or double wall - system, will a single door negate the isolation effect of the room in a room? Presumably the frame will span both walls? Unless you're supposed to build the door into only one of the walls, frame the other wall opening and leave a gap (cover with fabric, rubber, cork strips?)?

Do you need to have double doors?

Either way, when calculating the required mass of the door(s), do you consider both walls or just 1? I.e. The mass of 2 sheets of 5/8 or 4 sheets of 5/8?

Thanks.
In a decouled double wall you need two decoupled doors each of the same mass as the individual leaf it is in and with the same gap as the leafs.
Seal like your life depends on it (the seal dictates the isolation prestation).
And put absorption on the inside door leaf(s).
Old 15th August 2019
  #22
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Everything you want to know (and more) about isolation...

https://www.google.com/url?q=http://...aPPDL6Pu_fGepT
Old 15th August 2019
  #23
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Quote:
Originally Posted by Jason Foi View Post
Everything you want to know (and more) about isolation...

https://www.google.com/url?q=http://...aPPDL6Pu_fGepT
This is an excellent resource. Thanks, Jason!
Old 18th August 2019
  #24
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If you plan to have clients in here, it may worth it to check your local home-occupation ordinances before you get too far into it. Obviously it's your decision to make on what you ultimately want to do, and every area has different rules. But it's worth considering because building a proper home studio is expensive and it would be shame to do all that and then now be able to use it as you hoped.

Of course if this is just for personal use then there should be no issues. And a lot of people do have commercial studios in the house with no problems, but certainly some don't.
Old 9 hours ago
  #25
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So I have a question about how to terminate an air gap...

I'm going to have a double door entryway into the "studio" right of and perpendicular to these sil-plates (about where the lally column is). My exterior wall running against the column (of the double wall construction) in this case is also going to be the wall of a basement bathroom. It is going to extend further than the end of the studio's interior wall. How do I close this gap without coupling the walls together?

There's a 1 inch gap between the walls. Would a backer-rod or 1x2 wrapped in sil gasket and secured to 1 of the walls work? Then just do the "fabric over the gap" thing like between the doors...?

I thought I had it all worked out then I got to this point and I'm stumped...
Attached Thumbnails
Jcoop Basement Build - Questions-20191016_230109.jpg  
Old 6 hours ago
  #26
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I don't understand. The outter leaf should be completely sealed perimiter. The inner leaf should be an independent completely sealed perimeter. Are you saying it goes down to a single leaf at that wall? Not a MSM system? Can you draw a labeled picture of the scenario? I think i might just be misunderstanding.
Old 5 hours ago
  #27
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Quote:
Originally Posted by Jason Foi View Post
I don't understand. The outter leaf should be completely sealed perimiter. The inner leaf should be an independent completely sealed perimeter. Are you saying it goes down to a single leaf at that wall? Not a MSM system? Can you draw a labeled picture of the scenario? I think i might just be misunderstanding.
As soon as I started drawing it, I realized how dumb that question was... Sorry. I was mistaken. Not you... I was up late last night working on the framing and was obviously tired when I reached that point...

Anyway, I'm well underway so I think I'll start a build diary and keep going from there.
Old 5 hours ago
  #28
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Quote:
Originally Posted by Jcoop View Post
As soon as I started drawing it, I realized how dumb that question was... Sorry. I was mistaken. Not you... I was up late last night working on the framing and was obviously tired when I reached that point...

Anyway, I'm well underway so I think I'll start a build diary and keep going from there.
All good, glad you got it sorted. I look forward to following your progress. Good luck.
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