# Misc. Design advice



## memarcus (Jan 28, 2010)

So I'm beginning to frame my dedicated theater with the attached layout and seek opinions on the following subjects. The finished room will be roughly 14.5x20.5x7.5'. The low ceiling height is due to a poorly planned chase in the original construction (runs east west about 1/3 way up from south wall). couldn't find an aesthetically pleasing way to do a tray so I'm lowering the whole ceiling for uniformity and sound isolation. Interior walls to be spaced a 1/2" from existing walls, double drywalled with green glue, and R-13 insulated. Ceiling is completely free of above structure (2x6 16OC) for isolation and insulated. the small columns around the room are for aesthetics only and will be double drywalled and insulated. All columns will have low wattage wall sconces and spaces between will have 4" cans aimed at artwork in between the columns. these two sets of lights will be on individual circuits with remote dimmers, etc. The vertical line shows a small riser (5") from the back (West wall) out to about 7' for the second row to be pulled of the wall. Front row distance is about 12 feet with some wiggle room. Plan on 3 seats up front and 4 in the back.

1. How far back to place the projector outlet and conduit opening for signal from the East wall? IIRC the projector calculated to be mouned about 13' fromt the screen. Is that about right? I had my eye set on the Panny 4000 but now that the 7000 is coming out soon may go with that one. I am concerned with screen brightness and would like to go with as large a screen as possible. Any suggestions? 

2. With the low ceiling, should I cover the ceiling up front with black velvet to reduce reflection? Plan on painting it flat black but still have worries. Also what height from the floor should the screen be mounted? I assume with the low ceiling height and size desired this will put it close to the ceiling.

3. Room acoustics, plan on 2 sonotubes in the rear corners or ~30ft sized dual driver LLT up front and center, which would be best with the probable room modes? I have read other suggestions that multiple subs are a good thing and then other schools recommend up front. Could use the front sub as a stand for the CC.
I plan on lining all the artwork pockets between columns and front wall with 2 foam and a fabric cover/drapes behind all of the posters. Will this make the room too dead or is that not enough? Room will also be carpeted.

4. Ambient light. Will be none but had planned on adding 7w step lights in the riser to prevent tripping. should these be dimmable with remote like the other lights or just ommitted? Kinda feel dumb adding a separate circuit for 14watts worth of lights. Suppose I could throw them on one of the other circuits for simplicity and cost but which one? How are others handling their step lights? Are they used often? The other light could be brought up to leave but I kinda thought these might be handly to let burn all the time when the room is in use and control on/off with a normal switch. Is that a bad idea?

5. AT screen, what spacing is needed between the CC and screen? I think I might run out of room to do an AT screen proper. Those that have them say they area must, but plenty seem to be happy without them. Currently I'm planning on a fixed screen on the east wall but I suppose I' might be convinced....

I have played with the calculators and tools available to get me to this point but need feedback. Want to be sure I'm not missing something big, as I'm about to start down the road described very soon, possibly next weekend. also equipment rack is in closet on the north wall.


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## sga2 (Nov 14, 2009)

memarcus said:


> 1. How far back to place the projector outlet and conduit opening for signal from the East wall? IIRC the projector calculated to be mouned about 13' fromt the screen. Is that about right? I had my eye set on the Panny 4000 but now that the 7000 is coming out soon may go with that one. I am concerned with screen brightness and would like to go with as large a screen as possible. Any suggestions?


I have a Panny 4k mounted at 14ft (from lens to screen) throwing 130" 2:35 image onto a light grey screen. I think the image brightness is very good for movies with total light control. We had a Super Bowl party and it did very well with that (though I set the picture mode to "Dynamic" and turned off the Eco Mode to boost brightness). If you have complete light control I think you will have no problem with a 10-11ft screen. In which case 13ft throw should work but you should check the manual to be sure based on your actual screen size.



memarcus said:


> 2. With the low ceiling, should I cover the ceiling up front with black velvet to reduce reflection? Plan on painting it flat black but still have worries. Also what height from the floor should the screen be mounted? I assume with the low ceiling height and size desired this will put it close to the ceiling.?


You'd like to have the screen about a foot below the ceiling if possible, but the actual height will depend on the screen size and viewing sightlines (can't be too low that 2nd row can't see it). If your ceiling is flat black I do not think reflections will be an issue. I have black ceiling tiles with top of screen about 8" below the ceiling and no problems.



memarcus said:


> 3. Room acoustics, plan on 2 sonotubes in the rear corners or ~30ft sized dual driver LLT up front and center, which would be best with the probable room modes? I have read other suggestions that multiple subs are a good thing and then other schools recommend up front. Could use the front sub as a stand for the CC.


As you probably know, optimal sub placement is unique to every room. However, I think corner loaded subs are a bad idea unless you have low powered subs and are just trying to maximize boom. I have two SVS PC12+s that were in the corners at first just due to convenience (still working on the screen and other things in middle of front wall at the time). Once I finished setup I moved them in to just left and right of center channel and that has made a huge difference to the performance for the entire room. It is so much smoother. Again, your results may vary, but I think two on front wall between center and front L & R is a good place to start.



memarcus said:


> I plan on lining all the artwork pockets between columns and front wall with 2 foam and a fabric cover/drapes behind all of the posters. Will this make the room too dead or is that not enough? Room will also be carpeted.


I think this would be OK but there are many others here that are very qualified to answer this one...



memarcus said:


> 4. Ambient light. Will be none but had planned on adding 7w step lights in the riser to prevent tripping. should these be dimmable with remote like the other lights or just ommitted? Kinda feel dumb adding a separate circuit for 14watts worth of lights. Suppose I could throw them on one of the other circuits for simplicity and cost but which one? How are others handling their step lights? Are they used often? The other light could be brought up to leave but I kinda thought these might be handly to let burn all the time when the room is in use and control on/off with a normal switch. Is that a bad idea?


I'd just feed from another lighting circuit upstream of the dimmer and put on a separate switch/dimmer. Not sure how bright these are but I think at least you want to be able to control independently of the other lights. And running a dedicated circuit to these is definitely not warranted.

Have fun. This will be a very rewarding project!

Regards,
sga2


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## memarcus (Jan 28, 2010)

I know subs in a corner are a bad idea unless you need the bottom end. The reason I lept to that possibility is that that's the only realistic option I've got for doing multiple subs and spacing them apart. I was thinking I might lose the benefit of an upfront sub since they'd have to be side by side and act as a point source. I'm probably going to wire for these locations anyway just in case. I have a small 10" powered sub I can use for crawl testing though. Mostly I was just wanting to make sure I had a signal outlet in the vicinity of the likely spot, that's what I was really concerned with. 

What are your thoughts about the sub being placed behind the front row? My slab doesn't contain any conduit but I could wire to the center of the riser really easy. 

what is the gain on your screen?

Thanks for the advice.


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## memarcus (Jan 28, 2010)

also does anyone think the ceiling height will be an issue? How tight can a PJ realistically be held to the ceiling? 

I don't think it will be a problem seated but standing in the back, I'm sure it will be in the way if it hangs very far from the ceiling. anyone out there got a really high and tight install and tips to acheive it?


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## SAC (Dec 3, 2009)

A few questions...
You have posited wall construction and various systems but you fail to define the design goals and issues you are addressing.

If your goal is to isolate the room, I would further ask a few questions. 
First, do you have any adjacent spaces/rooms that are not critical? Meaning, are there possibly, say, garage, hallway, bathroom, spare bedroom, or workshop, or other 'non-critical' spaces adjacent to the space?

Aside from the need to determine exactly how must isolation you need, and then analyzing existing wall systems in order to design the proper addition proven to accomplish said additional isolation - in addition to addressing ALL flanking vectors...a common mistake is to build a monolithic rectangular room.

Let me explain.

Modes see the massive boundaries as determinant in establishing the modal distribution - which, amazingly enough, in a symmetrical room places the null right in the center. And hen we get to come along after and fret and fume as to how to solve it...when a little forethought could have mitigated it. And a problem avoided is a much more elegant solution to fixing problems afterward.

So, how does all of this relate?

What we very commonly do in studio design (as one very seldom sees much bass trapping INSIDE a studio proper) is to have a massive outer shell, and then to design an asymmetrically placed reflective inner shell for the actual 'room'. This reflective inner shell provides the symmetrical boundary for the specular reflections, while allowing the high energy low frequencies to travel through the low mass inner walls and to encounter the massive external boundaries. 

Now, we then have a well behaved inner room where we can address early reflections and establish a well-behaved later laterally arriving exponentially decaying diffuse soundfield.

Meanwhile, as we have placed the inner 'room' (asymmetrically) off center of the massive exterior boundaries, the modal distribution avoids placing the null in the enter of the room. We are able to move much of the LF bass trapping out of the primary space, as well as using the spatial distribution to avoid detrimental distribution of nulls in the listening space. thus we let the geometry of the space, solve many of what would otherwise be substantial problems.

This can easily be done in most installations by simply making use of the adjacent unused 'neutral' spaces and including their volume in the massive exterior boundaries.

So, that is just one idea, but may I suggest that before you start building, that you define your necessary objectively verifiable performance parameters a bit more rigorously. 

And PLEASE review you proposed 'isolation system! Simply filling voids with insulation may help keep the area warm or cool, but it is not going to achieve the isolation you desire!

Check out the isolation docs listed* here*.

And PLEASE do not rely on modal calculators as if they actually model real spaces! If you have a real existing space, MEASURE it and determine the REAL behavior. And don't stop with modal measurements! You have a real space, determine what is actually happening in it NOW! And THEN determine what must be modified based upon a comparison with the desired acoustical response model which will allow you to define exactly what must be accomplished - and build to solve those issues, rather than simply building and then wondering what you must do to solve all of the 'relocated' performance issues.


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## memarcus (Jan 28, 2010)

Goals are to have an isolated theatre in which I can listen at a fairly decent level without disturbing the rest of the house at reasonable cost. Just beyond the north wall is spare bedroom. I have built a walkin closet along this wall to go between the theater wall and the sleeping space. West and south walls are 10" concrete. On the east wall there is a bathroom and a mech/utility room. Directly above is the baby's bedroom which is why I opted for the floated ceiling.

Just looking for decently dead room and as much isolation as I can afford. I believe the wall construction will give me an STC rating of around 60 although I'm little skeptical fo the green glue. The architects at work suggested resilient channel as it's used all time and they've never heard of the glue but it seems like the glue would be easier to use. From what I've read the resilient channel works just as well if done right. I'm still not sure which route I'll take.

The only problems is that the wife thinks a double/airlock door is ridiculous, so for now I just have a gasketed/sealed solid door planned with the likelihood I'll add a second of the same later on the inside. So that'll prolly ruin all of my effort.

Also looking to create a space for the kids to play their drums, trumpet, etc later on if they get into to that sort of thing.


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## mnhokie (Dec 2, 2008)

The Panny has a lens shift feature as well, so you can mount the unit pretty tight to the ceiling and still adjust the lens down on the wall. I was projecting a 128" 2.35 image with my AE-3000 from about 16 feet back, and brightness was never an issue. Assuming you have total light control in the room, I think you'll be fine.


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## bpape (Sep 14, 2006)

Do not under any circumstances use RC. It's great for dialog isolation but will do very little at subwoofer frequencies and high levels. Firring channel and RSIC-1 or RSIC-V clips will do a MUCH better job. In addition, it's pretty much impossible to mess up that install. People mess up RC all the time. All it takes is a couple of screws driven just a little too deep and you've recoupled everything.

The Green Glue is an excellent product. I've used it dozens of times. Just look at their test results. 

Also, It's not a matter of channel or green glue - it's both. You use the channel to isolate physically then the green glue to dynamically couple the 2 layers of mass.

If you leave the inner walls 1/2" shorter than the distance from floor to joist, and then connect using DC-04 isolation clips, you can save yourself the cost of clips and channel on the side walls since they're already now decoupled. You'll still want the double drywall and green glue to provide the mass. 

You'd only then need to address how to decouple the ceiling from the joists above.

Bryan


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## Prof. (Oct 20, 2006)

memarcus said:


> also does anyone think the ceiling height will be an issue? How tight can a PJ realistically be held to the ceiling?


Generally speaking, you should have the projector no closer than about 2" from the ceiling..to allow for good air circulation..


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## memarcus (Jan 28, 2010)

Thanks for all of the great replies.

Bpape,

I'm not sure I understand the point about leaving the 1/2" from floor to joist (decouple ceiling from floor above?) I started framing this weekend and have left a half inch gap between theatre walls and anything external. The wall should be able to vibrate freely without touching the outer walls. They will get double DW and insulation with the green glue.

Also for the ceiling I have a fully detached/floating joist system. The basement was originally framed to 9' and due to soffits and plumbing the finished ceiling height will be about 7.5'. The ceiling joists have a space of at least 1 foot to the first floor structure. I'm plan on using R-19 in the ceiling as the joists are 2x6 and possibly filling the remaining void with blown in on top of that.


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