Small Mix Theater

[jacobfarron]

I'm converting a former RacquetBall Court into a mix theater at our video production company. This is the 5th revision to the design, so I thought it's about time to let you all tear it apart and give me some feedback.

Room dimensions are 40ft long by 20ft wide.
Metal roof at 30ft, 1" MDF framed ceiling at 20ft, we're adding acoustic tile ceiling at 9ft R30batt insulation on top.

Floor is 3/4" wood (tongue and groove) on 1" thick wood runners - resting on concrete slab. Will remain as is.

Walls are framed with 2x6s, blown in insulation, 1" thick MDF. We're adding 1/2" drywall up to 9ft on top of that. I wish I could slant them, but we can't.


I'd like to treat the room with columns (polys) to absorb and diffuse the sound, and acoustic paneling for additional high frequency absorption.

7 columns on the walls, and 1 in each of the 4 corners. Total of 11.
12 acoustic panels.

A)
Column Construction (Polys) : 9ft x 6ft (chord is 60", arc is 72", segment height as 16.9")

- Curved Surface is 54 sq. ft. of 4" Thick Johns Manville 1000 series 3pcf
- Corner Columns are 6" Thick - covered with burlap.

- Construction is 1/8" Pegboard wrapped around three 1/2" Oriented Strand Board bulkheads attached to four 9ft 2"x4"s.

- Interior is lined with 3" Thick R19 batt insulation on the flat surface directly opposite of the curved surface.


B)
Additional acoustic panels are located in between the columns. 2" Thick Johns Manville 1000 series fiberglass panels covered with burlap held to the wall with 1x3 wood boards. Eight panels are 4ft by 4ft and four panels are 5ft x 4ft


Using the 40x20x9 the room volume is 7200 cubic feet.

Total wall surface area is 1080 sq. ft.
Columns provide 594 sq. ft of absorption
Acoustic panels provide 208 sq. ft of absorption

802 sq. ft. total of absorption on the walls
74.3% of wall area is covered.

The Floor will have 14.5ft by 25ft of carpet covered wood for stadium style seating.
The drop ceiling is mainly absorptive with Owens Corning Frescor.



I'm thinking the columns will act as a resonant panel absorber, a polycylindrical absorber, and a diffusor (or reflector) for some mid range frequencies. Columns that straddle corners will have 6" of Fiberglass board on the surface to help absorber lower frequencies.


Axial Room Modes: 14.10, 42.32, 56.43, 70.53, 84.64, 98.75, 112.86, 126.96, 141.07, 169.29, 197.50, 225.72, 253.93


Anyone have any thoughts or ideas? Best use of resources? Glaring omissions? Doomed to sound awful? Any comments.

I've complied this design from Gearslutz, THX, and Dolby recommendations, and several books including Master Handbook of Acoustics, F. Alton Everest. Any insight welcome.

[Ethan Winer]

I'm not a fan of polys in small rooms, but your room is large enough that they might help a little. Large spaces mostly need absorption more than scattering. Especially if this will be a surround sound theater. I'd also skip having polys anywhere near the corners. Better to have the largest deepest bass traps you can manage.

--Ethan

[jacobfarron]

Thanks Ethan. Maybe a better idea would be to skip the column construction and just make the whole room absorptive. We're just trying to do some planning so we at least have an idea of what we'd like to do before calling the acoustic engineers in.

Could you recommend any reference material that applies specifically to mix theater / dub stage / cinema design? Or is that a rare skill? I can't find a book dealing with it.

[Pindebraende]

Nice to see a construct post about a mixing theater!
I will be watching this thread for sure!

Keep us posted Jacob.


Best wishes,

Mikkel

[jacobfarron]

I will. The design is bound to change quite a bit more. My boss wants more seating capacity - the only way to get it is to use a surround array instead of single speakers. They're also talking about sofit mounting the speakers. And I'm not sure the JBL 6328 we've specked will work for that. I'd love to move up to far field monitors from K&H or Genelec but that's half of our build budget right there.

I am still looking for a book that specifically relates to theater / cinema design. Anyone know of one? Not home theater, but the dub stage type.

[jayfrigo]

Jeff Cooper does a lot of dub stage work, though his book mainly deals with music studios. JEFF COOPER ARCHITECTS

A technique that works quite well in re-recording theaters is what I have jokingly referred to as "wedgie walls" for years. Wedged walls work in other applications as well, but they are especially good in mid-sized to larger dub stages.

The beauty is that you can design them for so many things, from helping with geometry, to trapping, to diffusion. You can make slat traps, tuned perf traps, resonant diaphragmatic absorbers, traditional bass traps with 703-airspace-hangers, chunk traps, broadband traps, pure reflection, simple mid/high absorption, or any combination thereof. Just because they look the same from the outside doesn't mean they are all the same underneath. Use whatever combination you need to accomplish your design goals within the whole-room plan.

Here are a few examples in smaller to medium-sized rooms that I've designed:

Mastering studio in Los Angeles

Mastering studio outside Boston

Multiple use college studio

And here are some examples in larger dub stages (not mine):

Universal stage with variation of this technique

Stage B at Wildfire Post, formerly Wilshire Stages

Warner stage D

[jayfrigo]

Originally Posted by jacobfarron

I will. The design is bound to change quite a bit more. My boss wants more seating capacity - the only way to get it is to use a surround array instead of single speakers. They're also talking about sofit mounting the speakers. And I'm not sure the JBL 6328 we've specked will work for that. I'd love to move up to far field monitors from K&H or Genelec but that's half of our build budget right there.

I am still looking for a book that specifically relates to theater / cinema design. Anyone know of one? Not home theater, but the dub stage type.

Using an array is correct for this application. You would not want a single pair of direct radiators for surround in a dub stage. I've never seen anything but surround arrays in real dub stages.

Also, if you really want to have a dub stage sound, you would need to get a Dolby curve in there on your B-Chain, and typically you would use JBL cinema speakers (the front three behind a perforated screen) rather than the esoteric music types listen above. If the room really is intended for dubbing, the only way to get translation is to leave the music methods behind and embrace film techniques. If you want playback consistency from stage to theater, that's how to do it. If the goal is more of a DVD style room, then regular speakers without the curve will work.

I'm in the middle of designing a theater classroom that will be constructed later this year for a college that offers both film/video production and audio production. We're using Genelecs in there because the room needs to be somewhat multi-purpose with the audio students, but we are using an array of 6 surrounds because of it's primary focus on film.

[jacobfarron]

Jay, thanks for the links and shedding some light on this. I'm already on revision 11 with the wedge type walls and a surround array. I'd like this room to have the "feel" of a dub stage, but realistically TV broadcast is our goal - just giving the producers a nice place to sit and screen the show. Like everyone else, our budget is limited. I'm wondering if I could make a surround array with 4 of the LSR6328's wall mounted. I doubt we'll actually have anything that must translate to cinema and I have to design for the business we have now (but I'd love to eventually have set of traditional cinema speakers, and Genelec mains and nearfields).

I have the book Surround Sound Up and Running, but it doesn't go into too much detail about the array. It looks like others have this problem as well - 110 to 120 degrees for rear surrounds leave out the producers desk or additional seating. So - when using an array, what are the angles of the speakers? A) Do the 2 closer to the mains remain at 110 while the rear 2 fire 180? or B) do all speakers fire 110 and the rear two are simply against the wall, which obviously makes the distance to mix futher, and I'm guessing introduces a lot of phasing issues or C) Do all array speakers fire at 180?

Also, I've been taking the 38% rule for mix position I've read about to mean the mix position is better situated towards the screen, rather then further in the room. Am I interpreting this complete backwards and the exact opposite is true?

[avare]

Originally Posted by jacobfarron

I have the book Surround Sound Up and Running, but it doesn't go into too much detail about the array. It looks like others have this problem as well - 110 to 120 degrees for rear surrounds leave out the producers desk or additional seating. So - when using an array, what are the angles of the speakers? A) Do the 2 closer to the mains remain at 110 while the rear 2 fire 180? or B) do all speakers fire 110 and the rear two are simply against the wall, which obviously makes the distance to mix futher, and I'm guessing introduces a lot of phasing issues or C) Do all array speakers fire at 180?

It seems that you are not certain what type of viewing environment you are designing for. Once you have decided that, the rest is following that standard. TV has point sources for surrounds. Cinema does not. Which one do you want? Do you want to arrange for video listening to a subset of the surround array to get both worlds?

If another perspective on the ambiguity might help, read over the NARAS Suround Sound Recommendations.

Also, I've been taking the 38% rule for mix position I've read about to mean the mix position is better situated towards the screen, rather then further in the room.[/quote]

With the size of room you are writing about, the importance of the 38% is not great. Besides, which seats will you put behind the "sweet spot" seats to be in the middle anyway?

Andre

[jacobfarron]

You're right - great at 1, or mediocre at both. Ultimately I'm the one who will work in there, and I'd like form to follow function and it be within ITU spec for TV. It's possible others are more concerned with the 'cool' factor, but I can't very well tell those paying for it that it's impossible to seat more than 4. Maybe I will have to use a subset of the array for video.

I don't know. I see Russ Berger Design Group did it Digital Audio Workflows Drive New Thinking in Facility Design | Studio Daily

RBDG designed a solution for this that keeps the producer position at its traditional location at the back of the control room and adds an additional set of surrounds hung above and at an angle to the producer desk, with appropriate time delays dialed in to allow the surround signal to arrive coincident with the LCR’s sound. They are also positioned on the same 100- to 120-degree plane as the surround speakers serving the mix position. The technique was used in three recently completed control rooms that RBDG designed at commercial post facility Reel FX in Dallas.

I can't quite visualize this.

[jacobfarron]

Avare, I'm reading through that paper, and the P&E Wing says it's alright to go to 150 degrees on surrounds? My entire problem revolves around not breaking 120 (110+ or - 10). If thats the case... maybe I can go 140 and be done with it. Will surrounds at 140 degrees "disqualify" the environment? I'm not asking to be a smart ass... I'm all about the specs, and the last thing I want to have happen is another mixer come in from out of town and say wtf is going on in HERE?

I need the surrounds to push back 3 ft. I'm not talking 40 rows of seats. Just 2 rearward! I'll try this out in the design. Total seating capacity of 9 people audience + the mixer, and a producer's desk on one side of the console.

I had no idea surround placement would be so difficult in what seemed like a large room.

[avare]

I'm all about the specs, and the last thing I want to have happen is another mixer come in from out of town and say wtf is going on in HERE?

In that case you are with the EBU/ITU spec which is 100 to 120°. That is the spec. The NARAS is a compilation of ALL standards. For television it is the EBU/ITU.

Andre

[jacobfarron]

Alright then. I've made a decision. It is what it is. Direct radiator - no array, no second row of seating. We do TV, not film. Just a nice large half empty room.

Thanks for keeping me in line!

Any thought on RBDG's work around though?

[avare]

Any thought on RBDG's work around though?

I have thought about it and done designs on paper using the same concepts as detailed from RBDG. It was independent of their work though. Personally, with all that I know of your room, which is this thread, I would use it as an optional system to turn on when the producer is there.

Andre

[jayfrigo]

Originally Posted by avare

It seems that you are not certain what type of viewing environment you are designing for. Once you have decided that, the rest is following that standard. TV has point sources for surrounds. Cinema does not.

Higher end TV, like 1 hour drama, TV movies, even network sitcom is more often done in rooms with arrays. DVD remastering is usually (but not always) direct radiators, as are smaller, single operator rooms that do the smaller post jobs, like A&E one-offs and Fox's scariest police chases type programs etc.

An array is still a viable and perhaps even preferable option depending on the nature of the work, whether it is dramatic, corporate and advertising, game audio etc., if the room will be multipurpose (any music centric stuff, like concert video?), how many people one must accommodate, if clients will attend and need to hear the surround image as well, etc... I would still need more info before declaring my opinion one way or the other.

Also, careful of the P&E wing specs - it's for direct radiators and music-centric, and the ITU spec is for direct radiators as well. If you are going array, those angles are no longer relevant, and the whole circle is abandoned in a strictly-for-film room since the channels behind the screen are flat and not in an arc. I know you aren't going for full film, but you still may want to consider how large you will be able to get your ITU circle if you plan to go 5 direct radiators, and then consider whether it will still meet all criteria.

Oh, and Russ Berger's work is always worthy of serious consideration. Solutions like his are not unique. I can think of at least a couple Storyk rooms that do something similar. However, you need to have other design elements present to prevent too much interaction.

An array in general does not need to accomplish the same things as an ITU circle. You aren't as worried about exact phase relationships since dialog is often in the center, with effects and music spread around elsewhere. It's not like music where the phase relationships of original spaces and instruments must be preserved among all 5 top channels.

In fact, some of the differences in time arrival from an array is exactly what one is looking for in dramatic TV and film. You often are using the surrounds to create atmospheres, or ambiences of the environments on screen. The array will combine things to create a general envelopment in an artificially created space. You are usually not trying to have a discrete panning location as you would in music, and certainly not one that has an originally recorded phase relationship to the center or even front channels. This is why I ask above about the nature of the work in the room. It definitely has an impact on which approach is more appropriate.

[avare]

You wrote about the main factor here Jay. All you, I and other readers know is what is in these posts. There are at least two questions that need clear, or at least clearer answers. The first is one we have discussed in generalities, that being, what is the intended market for the room? Second question is how many people is the room to seat comfortably?

One easy (my next post will explain my writing "easy") remark is that a 9' ceiling for that size room is too low.

Andre

[jacobfarron]

The intended market for this room is 30 minute and 1 hour episodic broadcast TV - mostly reality, and documentary, branching off into dramatic and others. We would also like to take a stab at the independent film market here since there are no local Dolby approved rooms. I need to seat about 8 audience people in addition to the mixer for both video and film style mixing. In my current design I'm looking at using an Argosy NC-24-RRC (Digidesign C|24 90-NC24-RRC by Argosy Console, Inc.) which had larger wings that could be used as a producers area at either side of the mixer. So the producers are covered. 1 Rows of seats behind the mixer, and 2 rows of audience seating in front.

I think it's within our budget to have a theatrical cinema system with arrays, as well as the standard ITU spec system. So the producers and I have the option of hearing either system, then for screenings with a small audience, we would only use the cinema system.

I'm really banging my head against a wall here trying to come up with an appropriate solution - does this sound reasonable?

The entire focus of this room was to seat more people than the local competition.

And again - I really appreciate all this advice. I can't get it anywhere else. Also, this thread is starting to become the same as one over at the Post Forum. But different people are replying to each.

[jacobfarron]

Hey guys, this is the current design without acoustic treatment. I'll try not to irritate everyone to death by minimizing the questions.
Room dimensions are 34'x20'x15' (drop ceiling, true structure ceiling is metal roof at 30ft)


Main questings at this time - There will be a wall constructed that seperates this 40' long space into 2 rooms. The slant walls you see in the front hold soffit mounted speakers.

1) Is it more beneficial to construct a straight wall (of drywall) perpendicular from side to side, making the corner bass trap with 6" of 3pcf fiberglass and supporting wood for the soffit,
or
Is it better to build the angle with framed drywall, then cover the surface with the 6" of fiberglass?

2) Can you recommend an RT60 time to shoot for in my ongoing calculations? Or is this a crazy question?

Also, to those who will say this... yes an acoustic consultant will validate or make appropriate changes to my design before we build. Just trying to be as economic as I can.

[avare]

Congratulations on the latest design.

1) Is it more beneficial to construct a straight wall (of drywall) perpendicular from side to side, making the corner bass trap with 6" of 3pcf fiberglass and supporting wood for the soffit,
or
Is it better to build the angle with framed drywall, then cover the surface with the 6" of fiberglass?

It six of one and half dozen of the other. Personally, I would angle the wall so that soffit mounted speakers are at the 30° mounting angle. Nothing hard and fast on that.

2) Can you recommend an RT60 time to shoot for in my ongoing calculations? Or is this a crazy question?

350 ms based on your dimensions and the EBU/ITU standard.


I have a big problem with the ceiling. The material at 15' will be acousitically transparent at low frequencies. The room modes will develop to the 30' dimension. Also, I have no idea how the absorbent material will actually absorb being basically suspended in free space, vertically. Jay, any ideas?

Andre

[jacobfarron]

After much discussion my mains aren't 30 degrees, rather 22.5 degrees at 20.5 feet back at mix position (THX spec for cinema) subtended angle is 45 degrees instead of 60.

I'll count on having the drywall guys build the angle into to the wall. I was worried about bass buildup, until I got up into the ceiling. There is currently a 1" MDF framed ceiling at 25', but the boss is having that taken down. Evidently they left it up above the drop ceiling in another room and it started to fall and became a costly repair. So... the only ceiling is an industrial metal roof with insulation under it - standard steel warehouse building. I don't think the low end can bounce off of that. It's really thin.

Jay, where can I find info about the "wedgie walls"?
Thanks for the input.

[avare]

the only ceiling is an industrial metal roof with insulation under it - standard steel warehouse building. I don't think the low end can bounce off of that. It's really thin.

Where in the world are you? It is now important discussing architecture. In my part the world warehouses typically roofs that are (going top down)

aggregate (gravel)
tar
35-100 mm (1.5 -4") regular weight or light weight concrete
depending on the specs reinforcing bar in the concrete
corrugated metal

What are details of your roof?


You will get more responses from people if you resize your images so people do not have to scroll sideways to read the text.
Andre

[jacobfarron]

I will resize. I'm in Orlando, FL. I doubled checked, the roof is in fact steel with no tar or gravel, with 4" of fiberglass type insulation under that. This is for what is basically a "warehouse" that I would guess is over 200'x300'.

Connected to that is an office building that has the same type of roof you listed. The theater would be constructed within the warehouse.

[avare]

Thanks. A concern now is noise isolation, if not from traffic or aircraft, but rain and thunderstorms.

Andre

[jacobfarron]

I had the opportunity to listen to a thunderstorm from inside the room a few days ago. The rain could not be heard. Thunder yes. And we're not under any aircraft flight path. But we are 40ft from railroad tracks. So when the train comes by about 4 times a day we have to take a 45 second break. Not ideal, but almost impossible to structurally isolate that. Our current mix room was designed by acoustic engineers with floating concrete floors and sand filled concrete block walls, lead lined doors, etc. The cost was very high, and you can still feel a slight rumble. So we've opted to not isolate to that extent with this room. It would quadruple the build price and only give us a few more minutes per day.

Otherwise, the room is very quite - less than Dolby requirements. No mechanical noise at all.

Since we've outlined a basic floor plan, over the next few months I should have time to evaluate different acoustic treatment ideas. I'd like to get more information about the "wedgie walls" Jay talked about.

[jayfrigo]

Originally Posted by jacobfarron

Since we've outlined a basic floor plan, over the next few months I should have time to evaluate different acoustic treatment ideas. I'd like to get more information about the "wedgie walls" Jay talked about.

Want to give me a call? We could discuss it easier than I could try to cover every possibility here. Sorry; bit tight on time for posting right now... Or if there's no rush, I might be able to post more next weekend.