Sound Isolation with Sloped Ceiling - AVS Forum
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Old 03-24-2014, 09:02 PM - Thread Starter
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I have a bonus room above my garage that I am beginning to think about converting into my home theater.  There are a few issues that I am currently struggling with during these early planning stages.

 

THE SETUP:

 

There are two short doors on either side of the room toward the rear.  These doors open into attic space on each side.

 

Facing the back wall there is an unknown enclosure (HVAC related?).  On the back right is a closet.  Both of these structures need to stay in place. 

 

 

 

I would like to build a room within a room, but I am not sure how this would tie into the back of the theater (unknown enclosure + door to hallway + closet).  My questions are:

 

1. I think I can build a room-within-a-room, but I am not sure what to do with the entire back wall.  Would I want to build a room-within-a-room on the front and side walls, and then remove the drywall from the back walls in order to stagger studs (should I mix techniques like this)?

 

2.  I will still need to have access to the side attic space.  What is the best way to continue to allow this access, while at the same time preventing sound from entering/escaping the room?

 

3.  Since this room is on the second/top floor do I need to add sound isolation to the ceiling (e.g. channel + DD)?

 

4. What is the best way to treat the floor?  I will be removing the existing carpet.  I believe I have seen a rubber mat-type material laid down on the subfloor underneath carpet.  What is the best way to go here?

 

NOTE: My renderings show the ceiling line coming to a point, which was a mistake I made while hastily putting together the renderings.  The ceiling actually slopes in a few feet and then is flat for about a six foot portion at the top.

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Old 07-10-2014, 05:48 PM - Thread Starter
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Anyone want to weigh in?
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Old 07-10-2014, 06:10 PM
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Originally Posted by Robert Jones II View Post
Anyone want to weigh in?
You can get about 90% of the soundproofing with whisper clips, furring channel and DD+GG (Double-Drywall with Green Glue). Maybe a floating floor -- Serenity Mat with one or two layers of OSB on top. But if you are trying to soundproof, you need to do all the walls and the floor.
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Old 07-10-2014, 10:10 PM - Thread Starter
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Originally Posted by LeBon View Post
You can get about 90% of the soundproofing with whisper clips, furring channel and DD+GG (Double-Drywall with Green Glue). Maybe a floating floor -- Serenity Mat with one or two layers of OSB on top. But if you are trying to soundproof, you need to do all the walls and the floor.
Thanks for your response LeBon. It's been a while since I read your thread, so I'll have to go back through and read it again.

My big concern at this point is that back wall where the closet is. This wall connects with the rest of the house. The other three walls are exterior and underneath is the garage. Between the closet and "unknown" enclosure I am not exactly sure how to treat this wall. Would I DD+GG the inside back wall of the closet and leave the door side of the framing as is?
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Old 07-11-2014, 09:12 AM
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Thanks for your response LeBon. It's been a while since I read your thread, so I'll have to go back through and read it again.

My big concern at this point is that back wall where the closet is. This wall connects with the rest of the house. The other three walls are exterior and underneath is the garage. Between the closet and "unknown" enclosure I am not exactly sure how to treat this wall. Would I DD+GG the inside back wall of the closet and leave the door side of the framing as is?
If you are really wanting to soundproof, I would tear out the closet, and treat the wall behind and the "unknown" chase with Clips, DD+GG. It is relatively easy to then replace the closet inside the soundproof shell, if you really need the closet space. Just my 2 cents...
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Old 07-11-2014, 10:48 AM - Thread Starter
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Yeah, ultimately I think you are right. The more thought I have put into the room the more that I am realizing that all roads lead to removing the closet. In addition to allowing me to better isolate the room, the extra feet will also come in handy in several other ways.

Any thoughts on how to keep access to the two side doors, while still maintaining the sound bunker?
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Old 07-17-2014, 04:56 AM
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Quote:
Originally Posted by Robert Jones II View Post
<p>I have a bonus room above my garage that I am beginning to think about converting into my home theater.  There are a few issues that I am currently struggling with during these early planning stages.</p>
<p> </p>
<p>THE SETUP:</p>
<p> </p>
<p>There are two short doors on either side of the room toward the rear.  These doors open into attic space on each side.</p>
<p> </p>
<p>Facing the back wall there is an unknown enclosure (HVAC related?).  On the back right is a closet.  Both of these structures need to stay in place. </p>
<p> </p>
<p><a class="H-lightbox-open" href="http://www.avsforum.com/content/type/61/id/399962/"><img alt="" class="lightbox-enabled" data-id="399962" data-type="61" src="http://www.avsforum.com/content/type/61/id/399962/width/500/height/700/flags/LL" style="; width: 500px; height: 448px"></a></p>
<p> </p>
<p><a class="H-lightbox-open" href="http://www.avsforum.com/content/type/61/id/399963/"><img alt="" class="lightbox-enabled" data-id="399963" data-type="61" src="http://www.avsforum.com/content/type/61/id/399963/width/500/height/700/flags/LL" style="; width: 500px; height: 425px"></a></p>
<p> </p>
<p>I would like to build a room within a room, but I am not sure how this would tie into the back of the theater (unknown enclosure + door to hallway + closet).  My questions are:</p>
<p> </p>
<p>1. I think I can build a room-within-a-room, but I am not sure what to do with the entire back wall.  Would I want to build a room-within-a-room on the front and side walls, and then remove the drywall from the back walls in order to stagger studs (should I mix techniques like this)?</p>
<p> </p>
<p>2.  I will still need to have access to the side attic space.  What is the best way to continue to allow this access, while at the same time preventing sound from entering/escaping the room?</p>
<p> </p>
<p>3.  Since this room is on the second/top floor do I need to add sound isolation to the ceiling (e.g. channel + DD)?</p>
<p> </p>
<p>4. What is the best way to treat the floor?  I will be removing the existing carpet.  I believe I have seen a rubber mat-type material laid down on the subfloor underneath carpet.  What is the best way to go here?</p>
<p> </p>
<p>NOTE: My renderings show the ceiling line coming to a point, which was a mistake I made while hastily putting together the renderings.  The ceiling actually slopes in a few feet and then is flat for about a six foot portion at the top.</p>
Hi Robert

I had my colleague ask me this question on a Google Hangout we recorded yesterday so that I could respond in full as typing takes me too long (I type like I have hooves for hands!). You can see the video here on YouTube.com:

At 1.30 minute in I begin my response to my colleague as he completes reading out your question.

So I hope it helps and please let me know if you need any further advice.

Thanks
Dennis
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Old 07-17-2014, 06:40 AM
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You could either tear out closet and do room inside room, then rebuild closet inside sound proof shell ... Or ... You could cut the room short and do a wall 6" or so from the closet inside the room all the way across and just have a small hall to enter room or the closet. The new wall would server to further increase sound proofing in that direction, but treat the original areas just the same. It would make your back wall more square and easier to design the interior.

I don't see where the attic entrance is, but could it be on the other side of the wall in the hall or in the closet ? That helps things since you get an extra wall to diminish the sound before the attic hatch, which should help sound leakage into attic and vice versa.

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Old 07-17-2014, 09:02 AM - Thread Starter
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Thanks Dennis and MFusick.

Quote:
Originally Posted by dennisfoley View Post
At 1.30 minute in I begin my response to my colleague as he completes reading out your question.
Dennis: To summarize my understanding of what you said: (1) The room dimensions are difficult and too small (under ~14ft) (2) If I want to continue doing the work myself I should hire an expert to at least draw the room up.... and you could be that person. Sound right? I definitely understand that my room dimensions are not ideal and maybe on the small side, but those are the cards I was dealt, so that's what I am working with.

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Originally Posted by Mfusick View Post
You could either tear out closet and do room inside room, then rebuild closet inside sound proof shell ... Or ... You could cut the room short and do a wall 6" or so from the closet inside the room all the way across and just have a small hall to enter room or the closet.
That's an interesting idea. For a short time this was a consideration, but I would imagine that this would become problematic with surround speaker placement. I will probably create a false wall plus acoustically transparent screen up front, so that reduces the length of the room considerably as is.

Quote:
Originally Posted by Mfusick View Post
I don't see where the attic entrance is, but could it be on the other side of the wall in the hall or in the closet ? That helps things since you get an extra wall to diminish the sound before the attic hatch, which should help sound leakage into attic and vice versa.
I am probably using the wrong terminology when I talk about attic space. I am not referring to a normal hatch that goes into attic space above, but rather the two small doors on either side of the room that enter the side "attic" space. You can kind of make this out in the pictures from my first post. I did not show the walls for the outside attic space, but I did put in the 2x4s to show the attic space structure.
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Old 07-17-2014, 09:23 AM
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Originally Posted by Robert Jones II View Post
Thanks Dennis and MFusick.



Dennis: To summarize my understanding of what you said: (1) The room dimensions are difficult and too small (under ~14ft) (2) If I want to continue doing the work myself I should hire an expert to at least draw the room up.... and you could be that person. Sound right? I definitely understand that my room dimensions are not ideal and maybe on the small side, but those are the cards I was dealt, so that's what I am working with.



That's an interesting idea. For a short time this was a consideration, but I would imagine that this would become problematic with surround speaker placement. I will probably create a false wall plus acoustically transparent screen up front, so that reduces the length of the room considerably as is.



I am probably using the wrong terminology when I talk about attic space. I am not referring to a normal hatch that goes into attic space above, but rather the two small doors on either side of the room that enter the side "attic" space. You can kind of make this out in the pictures from my first post. I did not show the walls for the outside attic space, but I did put in the 2x4s to show the attic space structure.
Hi Robert,

No one likes hearing that their room is too small, believe me I get that. I have to tell people all the time, from an acoustical standpoint, and they are often offended or hurt and ignore my advice. But I tell it like it is and won't put square pegs in round holes just to sell a product or service.

I was offering you my opinion gained from years of experience. If you don't want to take that advice then that's OK. And no not advocating me as the professional to do it. I was simply stating that if I was in your shoes I would seek the advice of a professional because it is a big job.

I wish you good luck with your project.
Dennis
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Old 07-18-2014, 01:46 PM
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Quote:
Originally Posted by Robert Jones II View Post
Thanks Dennis and MFusick.



That's an interesting idea. For a short time this was a consideration, but I would imagine that this would become problematic with surround speaker placement. I will probably create a false wall plus acoustically transparent screen up front, so that reduces the length of the room considerably as is.



I am probably using the wrong terminology when I talk about attic space. I am not referring to a normal hatch that goes into attic space above, but rather the two small doors on either side of the room that enter the side "attic" space. You can kind of make this out in the pictures from my first post. I did not show the walls for the outside attic space, but I did put in the 2x4s to show the attic space structure.
From your pics it looks like your second "back" wall could be only a few inches from the existing closet wall now. You might only lose 10" of total length if you do it right. worth it.

Put the door to the attic space in the closet. Have two doors to enter the closet from the back wall, one in the new rear wall and one existing. Put weatherproofing seals on the bottoms. That should aid in the sound proofing, doors generally suck at that. Having double doors with small gap hall between should be more effective than a single door. Even if the second door is a cheap one.

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Old 07-18-2014, 02:09 PM - Thread Starter
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Mfusick, do I understand you correctly that you are suggesting removing the closet, moving the attic door further back towards the back wall (where the closet would have been) then adding the second interior stud wall with a second interior door that, when opened, would lead to the newly moved "outside" door (the one that actually access the attic space)? I like that idea. Perhaps if the interior-side attic door were heavy and sealed enough it might work okay. In the design of the room I could probably even cover the attic doors in a way that makes them disappear into the room. Thanks for the suggestion!
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Old 07-18-2014, 11:19 PM - Thread Starter
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Dennis (or anyone else): since you did indicate that my space was more narrow than you normally like to see could you explain why the width is a problem? You indicate in one of your other video responses that a room that is around 15ft wide is fine, so I'm curious why that 1.5ft makes a difference. I'm assuming something to do with room modes, but I haven't gotten very far into my research on that topic yet. What possible options exist for dealing with the width restriction here? Currently the room is 13'11" wide, but it will likely be even less once I start construction on the room. Thank you for your input.
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Old 07-24-2014, 07:39 AM
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Quote:
Originally Posted by Robert Jones II View Post
Dennis (or anyone else): since you did indicate that my space was more narrow than you normally like to see could you explain why the width is a problem? You indicate in one of your other video responses that a room that is around 15ft wide is fine, so I'm curious why that 1.5ft makes a difference. I'm assuming something to do with room modes, but I haven't gotten very far into my research on that topic yet. What possible options exist for dealing with the width restriction here? Currently the room is 13'11" wide, but it will likely be even less once I start construction on the room. Thank you for your input.
Hi Robert,

I'll get my colleague to put this on the reply list for next Tuesday so I can answer in full in a video. So look out for a full reply next Tues/Weds.

Thanks
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Old 07-24-2014, 07:16 PM - Thread Starter
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Hi Robert,

I'll get my colleague to put this on the reply list for next Tuesday so I can answer in full in a video. So look out for a full reply next Tues/Weds.

Thanks
Fantastic Dennis. Thank you.
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Old 07-26-2014, 08:56 PM
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How's the project? Tearing anything down, building anything up?

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Old 07-26-2014, 11:50 PM - Thread Starter
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I wish! Currently I am still in the early days of planning; I am jealous that you are nearing the end of your build. In the next week or two I am hoping to start building a couple of DIY speaker projects: 1099's from DiySoundGroup.com for LCR duty and two-martycubes with Stereo Integrity HT 18" drivers.

All of that is good and well, but it would be fun to just start ripping drywall down for the fun of seeing what's behind the curtain, so to speak.
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Old 07-27-2014, 08:47 AM
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I wish! Currently I am still in the early days of planning
Plan and plan some more. I spent roughly 4 months planning and I am happy that I that did but there were some thing that I still had not thought about or knew until I got to them in the build stage.
One thing that I did was keep a notebook, which I sectioned off, and as I would read through the posts I would make a note of who's site it was and the page/post# it was. It was a quick reference to go to if I had questions on how someone else did what I was working on at the time.

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Old 07-27-2014, 11:07 AM - Thread Starter
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.
One thing that I did was keep a notebook, which I sectioned off, and as I would read through the posts I would make a note of who's site it was and the page/post# it was. It was a quick reference to go to if I had questions on how someone else did what I was working on at the time.
Absolute gospel. I now use Microsoft Onenote which is brilliant for this type of notetaking. It allows for easy organization. I wish I had started taking better notes from the beginning. some of these threads get into the hundreds of pages and I did not always reference the post number. Now what I do is right click the post number and copy the link, which makes it easy to jump right to the post.
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Old 07-29-2014, 12:51 PM
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Quote:
Originally Posted by Robert Jones II View Post
Dennis (or anyone else): since you did indicate that my space was more narrow than you normally like to see could you explain why the width is a problem? You indicate in one of your other video responses that a room that is around 15ft wide is fine, so I'm curious why that 1.5ft makes a difference. I'm assuming something to do with room modes, but I haven't gotten very far into my research on that topic yet. What possible options exist for dealing with the width restriction here? Currently the room is 13'11" wide, but it will likely be even less once I start construction on the room. Thank you for your input.
Hi Robert,

Here's my reply. I hope the explanation helps.

Let me know if you have follow up questions. Sorry if I'm ever negative but I try to just be honest and present the information I would want to know.

Thanks
Dennis
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Old 07-29-2014, 06:00 PM - Thread Starter
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Dennis, thanks again for taking the time to create a video response. The videos are a nice change of pace.

Attached is a diagram showing the width of my space. The green area represents the current boundaries (knee walls = ~7' 1" tall, height at middle of room = 10' height, width=13'11"). The gray area represents the side attic space, each side representing about 3' 3" of additional space (6' 6" total).

Based on your explanation it sounds like even though I have sloped ceilings, there still might be a large performance gain if I am able to move the knee walls further out. I am pretty sure the knee walls are purely decorative, so doing something along these lines might actually be an option.


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Old 07-30-2014, 04:38 AM
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Dennis, thanks again for taking the time to create a video response. The videos are a nice change of pace.

Attached is a diagram showing the width of my space. The green area represents the current boundaries (knee walls = ~7' 1" tall, height at middle of room = 10' height, width=13'11"). The gray area represents the side attic space, each side representing about 3' 3" of additional space (6' 6" total).

Based on your explanation it sounds like even though I have sloped ceilings, there still might be a large performance gain if I am able to move the knee walls further out. I am pretty sure the knee walls are purely decorative, so doing something along these lines might actually be an option.


Thanks Robert,

I hope the videos help. I would never be able to respond if I was typing so glad they are helpful.

I made this response to another question in this forum during yesterdays hangout. This goes someway to answering your follow up question.

Thanks
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Old 07-30-2014, 07:54 AM
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I'm going to disagree with the notion that the room has to be expanded unless there is a significant budget to start changing roof lines. In rooms that I have done in the past of this type, I have often shortened the width of rooms not elongated them. If you try to expand, you run into roofline issues where you frankly bang your head. Further, you also run into issues of where to put surround speakers. I would elongate the room, but the width is just fine.

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Old 07-30-2014, 08:25 AM - Thread Starter
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I believe the knee walls in my case are purely decorative, so moving them out may not be a structural issue.

I would like to try to isolate the room as much as possible from the rest of the house. If I were to go the room-within-a-room route then I would lose up to a foot in width (1" air gap plus 3-1/2" stud plus (2) 3/4" sheets of drywall = 6" on either side). So that's 167" (13' 11") - 12" = 155" remaining. Put four seats at around 126" [ (5) 6" armrests + (4) 24" seats ] and I am left with 29". If I centered the chairs in the room that would leave me 14.5" inches of isle space on either side of the chairs - obviously not an option. So, in addition to any acoustical advantages that might have been gained per Dennis Foley's video response, I was also considering expanding the width for layout reasons. I do not think it would make sense to go the full width of the available attic space for fear of banging my head on the new ceiling height, but maybe an extra 6-12" on either side would be nice - at the very least to compensate for the new false walls.

Shawn: is it your opinion that by extending the room width I might create more acoustical issues than I would solve?
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Old 07-30-2014, 09:18 AM
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Depends how you go about dealing with the sloped ceiling. There are two ways to approach it, either by stepping the ceiling or directly treating it. I prefer the stepped approach. Allows for a few things and breaks the ceiling up nicely.

My question is, why do you want to do room within room? You would lose less spacing by using other methods. Also, expanding it out further for walkways with a shorter ceiling height, you're running further into the territory of banging skulls. You still have the issue of speaker heights. If you push the room wider, you may run into an issue where the surround speakers aren't high enough. If you are going to expand the room, I would do it just enough to keep the current dimensions of the room. The more you expand, the greater that roof line is going to become a serious problem. This has nothing to deal with structural issues, but it does become an acoustical and ergonomic issue. One suggestion I have is eliminating the closet. That creates a lot of headaches.

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Last edited by SierraMikeBravo; 07-30-2014 at 09:28 AM.
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Old 07-30-2014, 12:00 PM - Thread Starter
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Depends how you go about dealing with the sloped ceiling. There are two ways to approach it, either by stepping the ceiling or directly treating it. I prefer the stepped approach. Allows for a few things and breaks the ceiling up nicely.
I have not reached any sort of conclusion on the sloped ceilings yet. I love the stepped look in sloped ceilings - especially since the ceiling is flat at the top already The problem that I have with this idea at this point is that I am currently leaning towards building a riser that matches the height of the entry step (12" total height). That reduces the room height at the rear from ~7' 1" to 6' 1". Adding a stepped-style soffit potentially reduces that even further, and that doesn't include any ceiling treatment. Now we're back to square one: the ceiling guillotine.

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My question is, why do you want to do room within room? You would lose less spacing by using other methods. Also, expanding it out further for walkways with a shorter ceiling height, you're running further into the territory of banging skulls.
My understanding about room-within-room is that it has the highest STC rating. I am completely green on most of these topics, so please correct me as necessary. This will likely be one of the many areas that I have to make comprises from what I would like to do. I could just as easily go staggered studs (or clips/channel).

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You still have the issue of speaker heights. If you push the room wider, you may run into an issue where the surround speakers aren't high enough. If you are going to expand the room, I would do it just enough to keep the current dimensions of the room.
I do not think I need a lot of extra width for walkways, so if I moved the walls solely for that purpose I would probably do as you are suggesting: move them out to compensate for a new internal wall. Of course if I go with one of the other methods I may be able to leave the existing walls as they stand (preferred).

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The more you expand, the greater that roof line is going to become a serious problem. This has nothing to deal with structural issues, but it does become an acoustical and ergonomic issue. One suggestion I have is eliminating the closet. That creates a lot of headaches.
I am pretty confident that the closet is going to be removed. The front wall to the closet is ~17' and removing the closet adds an extra 3' to length.

Here's are three-quarter views to show how I currently envision the riser filling the back of the room after removing the closet.



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Old 07-30-2014, 12:19 PM
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What's most important. A riser with a step, even entry way or acoustically dealt with ceiling? I would step down 6 inches to accommodate the ceiling. You won't need to treat it if you step it. That's the point of the stepping. Oh, and the stepping doesn't have to go around the circumference of the room.

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Old 07-30-2014, 01:41 PM
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Why would you not need to treat it if you step it ? Doesn't it still reflect?

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Old 07-30-2014, 01:59 PM - Thread Starter
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This is probably something better answered by the experts, but presumably the soffit/steps would still be treated with insulation. It would just be that the reflections would be more predictable, i.e. you would have top/bottom, side/side, front/back, as opposed to the weird angles imposed by the angled ceilings.
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Old 07-30-2014, 03:01 PM
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Why would you not need to treat it if you step it ? Doesn't it still reflect?
Not unless the steps are quite large. If you keep them a foot or less in height, it offers a small area for reflective surfaces. Far better than leaving the ceiling as is. Treating the angled ceiling, or rather over treating it, will have the effect of over dampening a room, and make it sound dead. Stepping the ceiling will keep things a bit more lively. The steps also don't HAVE to be square. They can be curved. Square is just easier to build. The stepping acts like a first order diffusor. Further, if you use speakers with waveguides as THX specifies, it will limit the dispersion of the sound field in the vertical. But, the only way to truly know for sure is to perform an energy time analysis once the room is done.

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