# Hope to incorporate treatment into walls. What do you think?



## JCOA (Dec 18, 2007)

First time to post here. I have done quite a lot of research here and have come up with a plan of sorts and wondering what the people here thought. 

I am in the design phase and the wife has pretty much given me the green light on anything I want. Aesthetics are important to me though, so with that in mind, I plan to build some of the acoustic treatments into the front and back walls and also into the rafters. It is a basement room (8.5' x 14.5' x 19.25') with a walkout on long 1/2 of the room and cement to the ceiling on the other half. I plan to build a false wall about 3' out from the front wall (19.25'), making that dimension 16', but acoustically remaining at 19'. I plan to fill that wall with 2-4" Corning 703 or 705, but not putting any drywall on either side. There will be a 100" projection screen made of either laminate or the latest paint on technique, so there will be some reflection. The space behind the will have equipment and additional bass traps or sound treatments. The false wall will be covered in some kind of acoustically transparent cloth. In the rafters I have taken a sandwich of 2 5/8" drywall layers and generic Home Depot sound deadening board in between and screwed that up against the highest "I" in the joist, leaving a 1.5" airspace between the floor and the 1st layer of drywall. I plan on filling the rest of the rafters with Rockwool, Corning or just plain fiberglass insulation, depending on the consensus here. It will probably have a facing on it or sealed in plastic, since I don't want the fibers in the room. Will most likely do a mild draping of fabric to cover. Some of the ceiling in front will be covered in drywall to cover HVAC and stuff that hangs lower than the joists. The back wall, which is common with other house space, is still up in the air. I thought about doing the drywall sandwich on the outside wall at a minimum, then waiting to see what the room sounded like and then go from there. Bass traps of the triangular kind can be incorporated at the rear of the room if needed. First reflection points have not been addressed yet, and I figure something will have to be done since these wall will be covered in drywall. I think it will be fine to have something hanging here in the form of absorption/dispersion as long as it doesn't cover the whole wall. The floor will be carpet, with the thickest pad I can get. 

This room will be used for music as a first priority and Home Theater 2nd. I really would like this room to sound very good, because this is the main reason for building it. I have some latitude on room dimensions on the long side and the ceiling can be as low as 7.5'. I ran the dimensions above (14.5 x 19 x 8.5) through various room mode calculators and these seem like pretty good numbers, but nothing is set in stone yet and I will take any suggestions I can get. I was kind of concerned about having all that sound deadening in the rafters, because I don't want the room to be too dead or certain frequencies to be over damped. The general consensus here seems to be the more dampening the better, within reason, I just want to make sure I am within reason going in the right direction. So, am I all whacked in my thinking. Thanks, and sorry for the long post.

Jay

Jay


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## bpape (Sep 14, 2006)

Sorry - I'm buried with work right now - just taking a small break. Will try to respond more later.

I'd recommend that you stop. Some of the things you're doing are counter to what you're trying to achieve. A ton of mass up high but only 1" of airspace will do little to nothing and cause more issues than it will solve. The depth of the gap is 'bigger is better'.

Also, a completely dead ceiling is not desirable in a 2 channel environment, not to mention cutting off any more options for places that NEED to be deadened without overkilling things (reflections, etc.)

Bryan


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## JCOA (Dec 18, 2007)

Thanks. Not in a terrible hurry. Will wait until I hear back.


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## JCOA (Dec 18, 2007)

I have had a chance to rethink this with Bryan's input. From what I could read into his comments, it is that I don't want a totally absorbing ceiling, especially with 2 channel sound. So, I thought about doing a drop ceiling instead and stuffing the cavity above. I am really trying to avoid doing a drywall ceiling, because this will drop my ceiling height to 7' 5", which is pretty close to half the dimension of my 14' 6" room width. With the drop ceiling the height will look more like 8' 5" to the bass region, because the drop ceiling isn't really reflecting the bass like the floor above. Is this thinking correct or am I just messing everything up. The added bonus is that I have access to the ceiling down the road.


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## bpape (Sep 14, 2006)

Sorry - didn't get back. 

I'm confused how you're going to lose an extra foot of ceiling height with drywall vs drop ceiling. You should be able to lose LESS with drywall.

Bryan


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## JCOA (Dec 18, 2007)

The bottom of the joist is 7' 6", the top of the joist, which the upstairs floor sits on is a foot higher. This is why I wanted to put drywall up against the top part of the joist, to help absorb some of the sound going upstairs. Also, I figured the drop ceiling isn't like dry wall when it comes to reflecting the bass region and will be more or less invisible to the bass. Wrong??? 

Really I was just trying to avoid the 7' 5" room height from interacting with the 14' 6" room width and still provide some kind of isolation from upstairs. Looks like I need to start sitting at the front of the class.


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## bpape (Sep 14, 2006)

You're in a catch 22. Drywall up against the floor above will do little to nothing. Drop ceiling won't stop anything either. If you want any isolation, you need to fill the joist cavities with insulation and put up a real drywall ceiling on the underside of the joists and deal with the close dimensions.

Bryan


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## JCOA (Dec 18, 2007)

Thanks Bryan. 

If sound quality is the ultimate goal and isolation takes a back seat, can I get as good a sound (or close to) with a rock ceiling (@ 7' 5") and room treatments, or do I need to make the ceiling height higher. I would like minimal treatments on the side walls (but realize they are needed), but the front and back walls are fairly open to treatment. The front wall is 3 feet from the foundation and can be acoustically open or dampen some or all dampened, or rocked and most anything behind the wall is open to treatment, as long as I can walk back there (I'm small). 2-channel is is the priority, but not to the extent of bad home theater. Am I asking to much? Thanks.


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## bpape (Sep 14, 2006)

Can you post a sketch? Not sure what you mean about the front wall. People have excellent sound with less than ideal ratios all the time - you just need to be willing to do what's required to deal with it. Much can be helped purely by careful placement.

Isolation is still an important part of sound quality to allow for the best dynamic range and resolution so don't minimize it's part in the solution

Bryan


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## JCOA (Dec 18, 2007)

Thanks Bryan. I will see what I can do about a sketch.

Thanks again

Jay


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## JCOA (Dec 18, 2007)

Here's a sketch. The space behind the wall will house electronics. It's about 3 feet in width inside to inside. This space can also be used for bass traps or whatever additional acoustic treatments. The front wall will probably have fabric on it and can have whatever acoustic treatment in it. I am trying to avoid having too much acoustic stuff hanging on the walls or in the room, especially up front. The front wall will have a door or moveable bookshelf in the opening. I don't have a problem with corner traps on the rear wall, in fact I kind of planned on it. Hopefully this will give you an idea what I am trying to do.

Jay


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## bpape (Sep 14, 2006)

Is the stairwell open or walled off? If it's walled off, you'll have a better shot at good imaging and proper symmetry by rotating the room 180 degrees.

Side walls need to be treated for reflections but that can be minimal as required. If 2 channel is the priority, then we don't want to overdo the deadening. We do still need broadband bass control. There are a few tricks to get both depending on how the room layout ends up.

Bryan


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## JCOA (Dec 18, 2007)

Thanks for the fast reply. 

The stairway is not open to any part of the room. I thought about rotating the room at one point, but the entrance to the room is on that wall. The big screen would have to be quite a bit smaller to maintain symmetry and/or keep the speaker(s) from being up against the walls or in front of the screen (speakers are 3' 3" tall). The room is about 11' 3" at that end. I just figured it would end up being the same on both sides of the room in the end, with more area to work with at the other end. I can rethink this, because I wouldn't mind having larger space for seating and openness, but I think the screen will end up being too small. 

Jay


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## k730292 (Feb 25, 2008)

JCOA said:


> Thanks for the fast reply.
> 
> The stairway is not open to any part of the room. I thought about rotating the room at one point, but the entrance to the room is on that wall. The big screen would have to be quite a bit smaller to maintain symmetry and/or keep the speaker(s) from being up against the walls or in front of the screen (speakers are 3' 3" tall). The room is about 11' 3" at that end. I just figured it would end up being the same on both sides of the room in the end, with more area to work with at the other end. I can rethink this, because I wouldn't mind having larger space for seating and openness, but I think the screen will end up being too small.
> 
> Jay


Greetings. Something to consider if you want quality sound and wish to "incorporate sound treatment into walls" is ASC "Iso Wall" construction. This is a somewhat complex (and pricey) commercial system that creates a resilient wall that flexes with bass energy. I'm primarily a 2 channel guy and will probably finish my dedicated sound room using this method. I've heard rooms that incorporate the IsoWall system and the results were quite good. The method also reduces sound transmission to the rest of the house. Check out http://www.asc-soundproof.com/ for info.

Bryan, I'm interested in your experience with this (or similar) produts.


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## bpape (Sep 14, 2006)

Gotcha. I was thinking the stairs came down the other way and dumped out into the left side of your drawing. If the door is on that other end, you'll have to leave it where it is.

The iso-wall, as you said, is for isolation purposes. It will do very little to change the interior sound of the room. I personally don't care for resiliant channel. It's too unpredictable as to what it WILL do to interior sound and I personally don't care for the idea of pads with 90% of the wall leaving an air-space. 

RSIC-1 and hat channel is much more predictable but does take up more spaced. Instead of the pads, I prefer Green Glue as it provides 100% coverage, and acts as a visco-elastic damping layer that's very effective.

If you're very careful when you build and you isolate the tops of the walls with DC-04 clips, you can skip the RSIC on the walls and only do it on the ceiling and still have excellent isolation.

Bryan


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## gullfo (Nov 25, 2006)

some of ASC products lend themselves to common tactics such as constraint damping on the studs in lieu of RSIC or RC, but some of their other products are less well understood as to their benefit. It may be that a combination of wall damp (or even felt strips) on the studs and RSIC EXT-04 on the ceiling could give you the desired isolation - keeping in mind the isolation walls are your boundaries and you will have to manage the contained sound - room modes are important, as well as the usual host of suspects - early reflections, flutter echoes, reverberation (or something like it), etc. so plan on incorporating room in the design for absorption, panels, etc needed to balance the space.


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## JCOA (Dec 18, 2007)

I thought I had a plan, but now it seems hopeless with this space. I have no idea what you guys are talking about in the last three posts. Well, I kind of do. You are trying to isolate the room as much as possible, it seems. How important is this. There is only two of us, and we will most likely be in this room at the same time, just not always. I also want good, if not great theater sound, but 2-channel is the priority, but not at the expense of horrible home theater. Are they mutually exclusive? Should I just build it, and not worry about room modes. Try to make up for it with acoustic treatments. With a hard ceiling, I will run into room modes, unless I build out the width dimension, which will be difficult, due to all the drain pipes above.

Jay


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## bpape (Sep 14, 2006)

Isolation is not just about sound getting out - from a performance standpoint, it's about sound getting IN and raising the ambient noise floor of the room and killing your dynamic range. It's all a matter of how far you want to go with it.

There are many things that can be done to help an existing space. If you can start from scratch, it can be just as effective for less money or WAY more effective for about the same or a bit more money.

Good 2 channel and HT are not mutually exclusive by any means - I do it in mine with 2 channel as a priority - they're just different design goals. Some is the same, some is different, but they can coexist peacefully.

Bryan


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## gullfo (Nov 25, 2006)

with the pipes - build out soffits to enclose them, as Bryan points out, isolation (and other noise reduction) is important to the HT experience. as far as isolation outbound, if there's no one else to disturb, then lower isolation can be good from the standpoint of needing less bass trapping as it can escape through the walls. best bet is to build enough isolation to get the noise levels down (taking care to consider HVAC noises such as forced air ducts carrying fan noise) to 50db or less.


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