6 Years, room finished.....now we're selling the house

[Guest Peter the Greek]

I had a nice build thread over on AVS that was well documented. But given the changes with stupid photo bucket, it needed rebuilding. Instead of doing that, I figured I’d provide a more succinct version here.

Soundproofing and Room Construction:

Everything you need to know can be found here:

http://www.soundproofingcompany.com/soundproofing101/

Dennis Erskine’s comments on why/how:

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There are two standards, or recommended best practices, for sound isolation depending upon the objective:

1. In room ambient noise level. This is defined as NR or NC 21 or lower (STC does not count since it ignores sub 125Hz frequencies and was never intended for this application in the first place ... so don't use it). In simple terms, with all environmental elements (HVAC, fans, equipment, etc.) running the ambient noise level in the room should be NC/NR 21 or lower. Using dBSPL as an example, if the ambient noise level is 32dB in room, you must lower that to 21dBSPL. 30 to 35 is typical of a residence. Basically, you need to lower the noise floor by 11dB. [NOTE: you cannot use dBSPL for accurate measurement against the NC/NR curves; but, you will get close.] Thus, your isolation strategy is to reduce noise entering the room, or noise from stuff YOU put in the room.

2. Avoid noise contamination outside the space. The generally accepted metric here is that you will not increase ambient noise levels outside the room by more than 3dB. Let's put this in simple context: the dynamic range is from 22dB to 105dB ... 115dB for low frequency. Thus, if your ambient noise level in an adjacent room (or neighbor's apartment) is 33dB, your sound isolation strategy needs to address a requirement to reduce noise transfer by 79dB. Once again, using dBSPL will get you close; but, that is not the method used to determine NR/NC. For reference, a baby screaming or crying loudly is on the order of 130dB ... I'm sure OSHA will try to regulate that level of noise pollution at some point.

Neither of these goals is easily achieved and likely not by anyone other than very skilled and experienced individuals and contractors. One can, however, see the effort to prevent noise pollution in adjacent spaces is a much different challenge than keeping in room ambient to NR21!

How to build a wall by Dennis Erskine:

I have never been particularly fond of the "leave a gap, fill it with caulk" approach to ceiling/wall intersections.

Presuming the ceiling and walls are decoupled using isolation clips and channel, then anything else attached to the wall/channel is also decoupled. My preference is to adopt a construction method which is less prone to leaving air gaps (now or in the future). Therefore, what I prefer be done, is the ceiling drywall (first layer) be installed followed by the first layer on the walls. Caulk any gaps. Now install the second layer on the ceiling followed by the second layer on the walls. By default that will make all wall/wall and wall/ceiling intersections lap seams not butt joints. The lap seams are less likely to allow open gaps and air leakage than a butt joint. To the crown question, the crown is then installed as one would in any other room.

This method may reduce the springiness at the intersections but will not adversely affect the flex, or vibration, required for a CLD material (like Green Glue) to do its job properly. In the overall scheme of things, an air gap will go further to degrade wall performance than any loss of flex at the joints.

 

General design by Dennis Erskine:

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I started this sticky some while ago because this forum is a beehive of individuals building DIY home theater projects. I thought it would be useful for those who are starting on such projects to discuss the errors, omissions and "oh oops" that have been made by others to avoid making the same mistakes. Hopefully this has helped.

Our firm is a design/build/install organization with the ability to completely turnkey a project. Clearly, our business doesn't fit the profile of a DIY forum (with the exception of the designs we produce which many DIYers have utilized). Because we can turnkey an entire project, we have a view of the total project and can control the entire process...which is why we prefer turnkey engagements (but don't insist on them). Today, I thought I'd add just a few "errors" I've encountered with "disjointed" projects (the designer, builder, installer are different groups) and those where the lack of experience has resulted in some hair pulling.

1. Projector Mounting:
---- throw distances incorrect for projector/screen combination
---- projector mounted outside the range of it's vertical offset resulting in picture distortion
---- projector mounted higher than the top of the image area on the screen (a real problem with masking screens)

2. Seating
---- Radius seating (curved rows) where the seating radius is smaller than the radius of the seating platform.
---- Radius seating where the radius of the seats has the viewers on the ends of the rows looking straight ahead to the opposite side of the screen (most manufacturers will custom make the radii)
---- Front row viewing angle has the viewer looking upward more than 10-12 degrees to the center of the screen (uncomfortable).
---- Second/third rows don't have an unobstructed view of the entire screen area.
---- First row is too close to too large a screen, second row is too far for an immersive experience.
---- Elevated second row platform plopped on the floor as a island in the back of the room.
---- Attempts to put too many seats in the room, making it crowded, expensive, uncomfortable for "general" use and looking like you've tried to put 50lbs of potatoes in a 5lb sack.

3. HVAC
---- Even in Fargo, ND in the middle of the worst winter, you MUST consider the cooling and ventilation requirements of these rooms.

4. Room colors
---- I don't like black "man caves" any more than your wife; but, light colors (tans, off white) and bright colors WILL ruin your picture.

5. Screens
---- Screen too big for the room. Screen widths should never be more than 80% of the room width. Keep the screen at least 3' off the floor (if not more) and don't mount it within inches of the ceiling. Big is not always better.
---- Screen too large for your projector budget. A dim picture is not wanted and will result in low utilization of a room you put a bunch of money into.
---- With all the "arm waving" and "oh, my goodness, it will ruin your sound" I hear about AT screens, the FUD factor will result in the big non-AT screen and then the speakers end up stuffed in the corner of the room. If you want to argue about the "damage" an AT screen will do to your sound, here's news flash ... what an AT screen might, or might not do, won't even begin to compare with the damage the corner stuffing will do.

6. Sound Isolation
---- I've said it many, many times before. You can read all of Ted's goodies, buy all the right stuff, and have little to no sound isolation when you're done. This is really, really anal stuff. 1/2 way is zero results. Get help.
---- The primary object of sound isolation is to keep the room quiet...not to keep adjacent rooms quiet (if my wife isn't in the theater with me, let her eat cake...hope she doesn't read this). Once you've done this proud work, why is all the equipment in the room room?
---- Now that you have this very quiet room and you can watch movies really, really loud, tell me...will you hear the smoke alarms go off in your house? (and, you were wondering if you bought enough bass traps from Ethan).

Nuff for now.

HVAC according to Dennis

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You can look at the Bar registers.
One other point, the HVAC contractor will be determining CFM (cubic feet per minute). That's fine, let them have at it; however, YOU tell them that regardless of the CFM required per diffusor, you want no more than 250 FEET PER MINUTE velocity.

(8'' is apparently quieter, provides greater air flow velocity, etc).
Your HVAC contractor is concerned with volume. They will calculate room requirements as Cubic Feet per Minute (CFM). They will size the ducts according.

From a noise perspective, we are concerned with Feet Per Minute (FPM) or velocity. To keep your diffusors (registers) from creating a lot of air flow noise, you do not want more than 250 FPM through a slotted or bar type diffusor. Therefore, let the HVAC contractor size the system but you insist upon the velocity...which will mean larger ducts and larger diffusors.

From a capacity perspective, the HVAC contractor needs to look at the demand of the room to be on the same order as a kitchen (that's if you cannot calculate latent and sensible BTU requirements). For example, six people sitting in the room will require 3000 BTU's/hr. (exclusive of equipment, etc).

 

 

Hush Box Glass:

Glass pane mounted 7 to 15 degrees is what is used along with an AR coated optical glass

http://www.edmundoptics.com/onlineca...w=21&PageNum=2

 

[Guest Peter the Greek]

Acoustics:

 

Bass trapping – this room didn’t have a single peak at the seating position and the nulls were eq’ed. How was this achieved? The riser trap and another similarly sized bulkhead trap above the screen. The soffits were lined with pegboard and the wall on the right had two 150mm pegboard traps behind the main acoustic panels

First reflections – a combo panel of 150mm Quest AI QPerf (50mm thick) followed by 150mm of Ultratel covered in HVAC foil tape

Surrounds – surrounded in BAD panels

The balance of the panels were absorbers either faced with 3mil plastic laminating film or unfaced Ultratel. All panels are 50mm thick with 2 layers of 25mm Ultratel with the 3mil plastic in between

Calibration by Adam Pelz

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Most of my clients will have a DSP 322ua or at least a DSP-30 dedicated to the subwoofers, so I am doing quite a bit more than kicking subs around and moving chairs! But not everyone reading this thread has that equipment, and many would not even have something like Audyssey, so quite often, the only tools available are a basic calibration of speaker levels and distances, and moving speaker and listeners to the proper position.

If the subwoofer is jammed in the corner, energizing all of the room modes, and the couch is up against the back wall, pushing the start button on the auto room correction is not going to be very effective. Yes, it will likely improve, but the goal is to make the experience the best possible.

A standard audio calibration goes like this.

1. Show up on time.
2. Drag 80lbs of test equipment into the cinema.
3. Sit and listen with the client to his reference material, explain the process.
4. Set up test equipment and take both physical and acoustical measurements.
5. Verify system. This includes checking polarity of every driver in the system, near field response of each speaker, off-axis response, menu settings on the AVR or Pre-Pro, impedance plots, checking distortion levels, etc. No sense calibrating broken gear.

From here, the structure is more fluid. From the acoustical and physical measurement of the room, we determine best seating location to avoid putting the listener in the middle of a null. We can determine subwoofer locations the same way. A basic calibration happens (distance and level matching), and I start listening in stereo. Toe-in, angles, distance from front wall, how much first reflection I want based on earlier off-axis response plots and client feedback. Hours later, once satisfied with stereo, the center channel is integrated. Surround speakers next. End of Day 1.

Second day is all about subs and creating a smooth transition between the mains by use of level matching and phase. Moving the subs into 1st and 2nd measured room modes will help smooth the response plot at the seating position. If I have DSP, then parametric EQ is also used. A "house curve" is added.

Listen, listen, listen to my reference material, tweaking until I am smiling. The client is then allowed back into the room, and we listen some more, and I explain the changes and why. Now that he is better educated, we listen some more, and make final changes based on his listening preferences.

I have started Day1 with the subs after all of the initial measurement and verification. All depends on the mood that day.

Placing speakers on something heavy:

 

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You've got a concrete slab, you make a box and fill it with sand, which weighs more then your speaker. Sit the speaker on it and its de-coupled? I fail to see how this transfers energy into the room rather than into the slab and into the house?

Dennis said:

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Good question. The damping does not re-direct energy, it simply converts kinetic energy to heat reducing the transfer into the remainder of the home's structure. The high mass of the stage, and the positive attachment of the sub to that stage, is the mechanism which works to improve efficiency. When the driver moves forward, the cabinet wants to move backward. Preventing this backward motion is helpful. It takes mass to do that.

That doesn't mean we have overcome the equal but opposite reaction...it means we're doing a better job of managing what's going on.

 

 

Plans / Layout - done by Shawn Byrne

I didn't use all of this and made a few changes along the way, which are pretty evident

 

 

 

 

 

Edited April 21, 2018 by Peter the Greek

[Guest Peter the Greek]

Framing detail:

 

Double stud walls - 25mm gap between the existing house frame an the HT room frame:

 

 

 

[Guest Peter the Greek]

HVAC Duct Designs

 

[Guest Peter the Greek]

Underfloor gyprock and greenglue to help with keeping footfall from the room above out:

 

[Guest Peter the Greek]

The room has a split bulkhead mitsubishi AC unit as well as its own 24/7 ERV

 

This is the ERV. It is made by Airchange Australia

 

 

AC mounted in void space next to the room

 

Edited April 21, 2018 by Peter the Greek

[Guest Peter the Greek]

First ply layer

 

[Guest Peter the Greek]

Second layer of gyprock (Firechek) on

 

[Guest Peter the Greek]

Floor isolation

This stuff is called Angel step, its a visco elastic membrane that Acoustica sell

 

That black box is the main AC supply. You can see the area around it used as a bulkhead bass trap

 

 

[Guest Peter the Greek]

Chipboard floor down

 

Isolated from the walls. So it sits on the Angelstep and a 5-10mm acoustical sealant around the edge.

 

[Guest Peter the Greek]

Some details of the soffits:

 

 

 

[Guest Peter the Greek]

Bass trap riser build:

 

 

 

 

 

 

 

 

 

 

Edited April 21, 2018 by Peter the Greek

[Guest Peter the Greek]

Door build and detail. I'd not do this again, it was over the top. Two interconnecting doors would be as good and easier:

 

 

 

 

Hinges from Hingefit in Melbourne

 

 

Door hung and then filled with 10mm Greenglue / MDF layers

 

 

 

 

Edited April 21, 2018 by Peter the Greek

[Guest Peter the Greek]

Stage build:

 

Notice hoe it doesn't touch the walls

 

 

 

 

Filled with sand:

 

 

 

 

Edited April 21, 2018 by Peter the Greek

[Guest Peter the Greek]

Floor down:

 

 

[Guest Peter the Greek]

 

Column design. This is my little brainchild, I was quite proud of these:

 

 

 

 

The rectangle ones are for balancing subs to be placed on the side walls

 

 

These were lined with Ultratel and stuffed with fluffy

 

 

 

Edited April 21, 2018 by Peter the Greek

[Guest Peter the Greek]

Bass trap above screen wall

 

[Guest Peter the Greek]

Various acoustic panels

 

 

 

 

 

Edited April 21, 2018 by Peter the Greek

[Guest Peter the Greek]

Soffit details:

 

 

Rear bulkhead bass trap

 

 

[BATMAQN]

Love a bit of construction this is the bomb Peter what a shame to sell up now. 

[Guest Peter the Greek]

Back wall detail:

 

 

 

 

[Guest Peter the Greek]

Entryway WIP leading into the room:

See the spiffy threshold (polished stainless) perfect for the drop seal to seal against

 

 

 

Angled tiles lead up to the room, given it was about 40mm higher than the rest of the house/floor

 

Edited April 21, 2018 by Peter the Greek

[Guest Peter the Greek]

DIY screen build:

[Guest Peter the Greek]

600 x 600 panels for the ceilings. These were all BADS, 50mm thick with the laminating film in between

 

 

[Guest Peter the Greek]

Detail of how the ceiling went together