Room Treatment Options?

After much thinking, a number of re-reads of this thread and some procrastination, I finally built a couple of panels and did some testing.

Here is a pic of the two panels stacked in a 4' x 4' configuration at the back of the room behind the center seat:



The front of the panels is 2'8" from the back of the room in this picture the idea was to get them out where they would be more efficient.

They hold 6" of 3lb fiberglass board.

The positions tested were at the back as shown above, at the front of the room above the aquariums, in the rear right corner and in the dining area on the table. Wherever possible, I tried to get them out from the wall to increase efficiency.

Below is a pic of them at the front position:

The measurements:

I have included a non-treated base line (purple) in each plot for reference. I took this measurement with the treatments safely out of the way in the bathroom so they would not influence the baseline. I did a quick calibration to make sure everything was correct and then did all the measurements without any changes.

Rear room position, Centered behind the meter:


Front position above the aquarium:


In the Corner:


On the diningroom table in a 4x4 configuration:

Discussion:

Surprises.

1. All positions did pretty much the same thing with only minor variation.
2. The 40Hz null is gone and the 25 to 30 Hz region is improved.
3. Nothing really touches the 52Hz mountain. :explode:

Observations.

The front position did narow and reduce the 52Hz peak slightly, though I do not know that it would make much difference to the sound of the room. The other positiona actually increased the peak a little. What the does this tell me about the related room mode(s)??

The front and corner positions, the only two that I can realistically use, also narrowed and reduced the 75Hz null.

In addition to eliminating the 40Hz. null there is also a reduction in the 80Hz and 120Hz. Are they all part of the same room mode?

The real test comes next. I want to build another two panels to see if there is further effect or if I suffer the same fate as the last person who tried this.

Fred

Hi Bryan. I guess I should have reposted the room info. The measurements are of the sub only and is in the position shown in the diagram at the beginning of this thread: on the side wall facing forward.

Just for giggles, try re-running the test with no panels but shift the mic about 6-8" to either the right or left.

Click to expand...

I will certainly do that in the near future, What I was after with this set of measurements was to see the effect of treatments in different positions so I went with a consistant mic placement.

I do, however have multiple position measurements I have done in previously. Out of interest, I went back to look for comon elements across measurements from diferent mic positions.

The positions are: center left and right seats and 1.5' forward of these three positions (38% distance point in the room). The sub was always at the side position either facing forward or into the room. Measurements were taken across days, so mic positions would have varied by inches as well.

What I found was peaks and nulls at almost the same positionsacross all measurements. What changed was db level.

34-35Hz -peak varying by mayby 10db
37-40Hz null varying from nothing to 6db down.
52-53Hz peak varying by maybe 3db
72-77Hz null varying from nothing to -15db
80.7-83Hz peak varying by maybe 3db
93-97Hz null down 15-20hz varying a bit
103-104Hz peak missing in some measurements
114-124Hz peak sometimes a shelf

The 40Hz null is the most variable and the 52Hz and 80Hz peaks are the most consistant.

I am wondering if those that are the most consistant are the most reinforced by multiple modes?? That would make them the most difficult to treat, and the ones likely to respond the least to a single treatment placed in the room. Am I on the right track here?

OK, I see your point, they are very much related to the sub and mic position. But the fact that various peaks and nulls react differently to different treatment positions should tell me something more about the nature of those peaks and nulls. Those differences are accounted for by one variable, treatment location. What does that tell me?

For example, the 40Hz null is affected pretty much the same way no matter where in the room I put the treatment (in a horizontal position). That tells me that I have a 40Hz reflection that is bouncing around in the room in all sorts of (horizontal?) directions. I can trap it once, and it is largely gone; multiple directions, single source (??).

Contrast that with the 52Hz null. When I put the traps centered in the room behind the mic, it actually increases the peak by around 1.5db. That tells me that there is some cancellation going on in the room length direction that is getting absorbed by the trap more than whatever is adding to that frequency.

Putting the trap in the dining area, centered on the wall does nothing, telling me, that in this area (side to side), either there is no reflection at 52Hz, or the trap is absorbing both in and out of phase reflections equally.

I guess what I am getting at is that I would like to move away from the "throw it at the wall and see what sticks" approach, which could end up quite costly, to a more analytical or deductive reasoning approach.