# Critique my Treatment Plan



## watson b (Feb 18, 2013)

Since I've upgraded my speakers I might as well do something with two boxes of 2" OC703 sitting in the garage for the past few years. What's the point of good speakers in a bad room, right?

So here is the layout:
13'5" W x 22'1" L x 8' H home theater
10" high x 20" wide soffit around the perimeter of the room (about half of the length is filled with HVAC and plumbing, the rest may or may not have pink stuff)
Drop-in acoustic tile ceiling with about a 10" air gap above to 2x10 floor joists. The joists are filled with pink R-22.
There is a pocket door to the left (there weren't many options to do it otherwise.)
The door to the right side is to the outside and rarely used, but the booger is it is a metal door and very close to a primary reflection.
Equipment cabinet is located on the left side wall near the front.
I don't like the couch position along the right wall, but my only other option would be a platform behind the primary couch and that is not realistic.

Floor plan:








Front panorama:








Here are my pre-treatment REW results. I was surprised they were not that terrible, but there is definitely some work to do on the low end.


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## watson b (Feb 18, 2013)

The plan (for now) is kinda generic since I will be replacing the sub and possibly moving it do a different position later (I have already moved it around and was surprised the smoothest response was in that corner). It's not a great sub and I have the crossover currently set at 40Hz. 

I want to implement some basic "best practices" until I finalize the setup and get more specific and spot-treat individual reflection points. Here is the plan:

1. 2" OC703 on the screen wall and possibly the first part of the front corners up to where it meets the door and equipment rack. The screen is Wilsonart laminate and I assume somewhat reflective on the high end, but I planned to treat behind it as well with the 703.

2. Ensure the empty soffits are loose-filled with unfaced pink fiberglass.

3. Corner bass traps (Roxul filled triangle type) in the back. I'm not sure if this should be a first step or not.

4. Ceiling: I am unsure whether the R-22 in between the joists should stay where it is, let it fall down on top of the drop ceiling, fill both spaces with fiberglass or maybe just treat the first reflection point above the ceiling.

Any input is appreciated.


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## Tonto (Jun 30, 2007)

That graf will change when you get a new sub & set the crossover higher, I suspect the drop off is a preformance issue with the sub. The 50 hz dip is the room & treating the 1st reflection points will help. You can always replace that door with an exterior wooden door. You can find excellent used (Chinese Mahogany) doors at mom & pop dealors at times. There is such a place in Thomasville, Ga that has a line on these--great buy's. Base traps in the rear is also an excellant place to start. Looks like a nice room you have there.


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## jim1961 (Apr 8, 2011)

Your graphs dont look that bad, I agree. 

The thing that jumps out first to me is the listening position looking like its mid way between the front and back walls. Usually you will get some pretty nasty nulls being exactly 50% from the front / back walls.

I would try putting the listening position around 35-40% from the back wall. Basically sliding everything back a few feet. 

In the end, let the measurements guide you.

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I would use 1/24th oct smoothing. 1/6th isnt revealing enough (one reason your graphs look better than they should). Also only measure one channel at a time. I wouldnt use left to right averaging except maybe in the bass region. An ETC will tell you better where reflections need to be dealt with than a FR graph.


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## watson b (Feb 18, 2013)

jim1961 said:


> Your graphs dont look that bad, I agree.
> 
> The thing that jumps out first to me is the listening position looking like its mid way between the front and back walls. Usually you will get some pretty nasty nulls being exactly 50% from the front / back walls.
> 
> ...


The listening position is a quandary, since it is in conflict with the ideal viewing position. I may experiment with moving the mic a few feet up.

The base graph is without smoothing as noted and is the average of the individual measurements as you suggest. The full range graph is really too noisy to be useful until about 1/12 and still shows some problems at 300, 400, 650, 1500 and 1800. 

Instead of chasing individual frequencies yet, I wanted to implement some basic treatments and then work from there. So adding in the door replacement and LP placement, is the initial plan too basic, overkill? I am trying to avoid doing too many things that will have little to no effect.


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## jim1961 (Apr 8, 2011)

watson b said:


> The listening position is a quandary, since it is in conflict with the ideal viewing position. I may experiment with moving the mic a few feet up.
> 
> The base graph is without smoothing as noted and is the average of the individual measurements as you suggest. The full range graph is really too noisy to be useful until about 1/12 and still shows some problems at 300, 400, 650, 1500 and 1800.
> 
> Instead of chasing individual frequencies yet, I wanted to implement some basic treatments and then work from there. So adding in the door replacement and LP placement, is the initial plan too basic, overkill? I am trying to avoid doing too many things that will have little to no effect.


I wanted to see the full range graph at 1/24th oct smoothing because it gives a better sense of what is actually occurring. Also, the right and left channels shown separately (but plotted on the same graph for easy comparison).

I seem to be missing what you are proposing as to a change to the door. 

I would leave the ceiling as is for now.

2" OC703 is only effective down to 500-600hz (flush against a rigid surface). I would go 4". And 4" OC703 with a 4" air gap behind it would be better still.


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## watson b (Feb 18, 2013)

jim1961 said:


> I wanted to see the full range graph at 1/24th oct smoothing because it gives a better sense of what is actually occurring. Also, the right and left channels shown separately (but plotted on the same graph for easy comparison).
> 
> I seem to be missing what you are proposing as to a change to the door.
> 
> ...


Below are full range 1/24. The door consideration was whether the insulated metal door near the front right corner would be a big problem or need be replaced with a sold core wood door (that may be a last resort kind of thing).









So my first few steps might be:
1. full-height 24x24x34 superchunks in the back two corners
2. 4" OC703 panels L, R and below screen with a 2" air gap behind (4" gap won't quite work, not sure if a 2" gap will still be effective enough to do it?)
3. loose-fill the soffit with pink stuff

Based on the results of that, in no particular order:
1. panels at first reflection points
2. 2" OC703 behind the screen (if mids are still a problem)
3. fully treat the back wall

So, do the first few steps still make sense or is one of these likely to be a waste?


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## jim1961 (Apr 8, 2011)

watson b said:


> So my first few steps might be:
> 1. full-height 24x24x34 superchunks in the back two corners
> 2. 4" OC703 panels L, R and below screen with a 2" air gap behind (4" gap won't quite work, not sure if a 2" gap will still be effective enough to do it?)
> 3. loose-fill the soffit with pink stuff


1. sounds good
2. 4" with a 2" gap is better than 4" with no gap
3. ???



watson b said:


> Based on the results of that, in no particular order:
> 1. panels at first reflection points
> 2. 2" OC703 behind the screen (if mids are still a problem)
> 3. fully treat the back wall


1. YES
2. I dont see this as likely to be helpful
3. YES


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## watson b (Feb 18, 2013)

jim1961 said:


> 3. ???


Mentioned in the room description, there is a 10"x20" gypsum board covered soffit around the ceiling perimeter of the room. I assumed this volume, especially at a corner boundary, is an effective place to trap bass, or at least make sure it's not a resonator. Below is a pic.


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## jim1961 (Apr 8, 2011)

watson b said:


> Mentioned in the room description, there is a 10"x20" gypsum board covered soffit around the ceiling perimeter of the room. I assumed this volume, especially at a corner boundary, is an effective place to trap bass, or at least make sure it's not a resonator. Below is a pic.
> 
> View attachment 41548


I see. I would do the other things first and then see where you are at.


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## watson b (Feb 18, 2013)

The front panels are done. They are 2)2'x7'x4" and 1)1'x12'x4" panel. I used 2 layers of OC703 and drywall corner bead for the frame. I suspect wood would have been much quicker and easier, but I had limited space to fit the 24" wide panels beside the screen and didn't want to lose the space from a 1x on both sides.

Not too complicated, but time-consuming. I am absolutely no competition for Bryan Pape; I would make about $0.50 per hour at my pace.

A sawzall blade cuts pretty well when you can't find your drywall hole saw.








Cut one leg of a 10' long piece to form a corner and joined to the other, all with rivets (100+ total :gulp.








Installed one or two cross pieces to hold the width and 4" pieces to join the two sides and hold the thickness.








Painted the metal on the front and sides to keep it from shining through.








Covered with speaker grill cloth from Parts Express using spray adhesive to the ends and along the back.








A finished panel. The edges aren't visible so I wasn't worried about how they looked.


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## watson b (Feb 18, 2013)

Next up is testing. Just for my own education, I will test flush to the wall and with a 3" air gap.


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## watson b (Feb 18, 2013)

The panels are installed on the front wall to the sides and bottom of the screen with a 3" air gap behind.


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## watson b (Feb 18, 2013)

SPL graphs of the L and sub taken with no panels, flush to the wall and with a 3" air gap behind.
Black is no panel, red is flush, and green is 3" air gap. There is not much effect below 200, but there is significant improvement in the peaks and nulls centered around 350 and 1200 with the air gap.






















Waterfalls improve significantly below 30 with either panel, but not a huge change with or without the gap.






















I suspect the ringing at 120Hz is some sort of electrical transient in the system as it doesn't decay and is an even multiple of 60Hz, but there is also a steep null near 120 on the SPL graph as well. There is no audible hum in the system.

I welcome any feedback on what these mean and what to do next, especially to deal with the peaks and nulls from 50 to 120. Moving the mic several feet in either direction from the LP makes little change on the nasty stuff. Next I plan to put superchunks in the back corners to see if that will help the lows.


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