Seeking advice on analysis of REW measurement

[feicipet]

Hi,

I had bought a MiniDSP measurement mic and proceeded to measure my room acoustics in it. I would like to get some advice on what I need to do to fix some of the more noticeable peaks and troughs in my room frequency responses. This is my first time measuring my room acoustics so I am very much a newbie at this. Thank you very much for any advice given.

My room measurements are in the file "Room Measurements,.png" in metric scale. Basically, my room is a slight L-shape with a width of 3.25-4.25m / 10.7-13.9 ft (depending on which end of the room I'm at) and depth of 5.5m / 18 ft. Height of the room is 2.54m / 8.3 ft. All walls are made with concrete while the ceiling is made with a dry wall material (fake ceiling).

My studio desk is at the narrower end of the room, I've attached a picture as follows:

Some notable facets of my room layout:

1. The acoustic panels that you see in the pictures are self made panels using wooden frames and Rockwool Safe n Silent Pro 350 slabs (90mm thick, 600mm width, 1200mm length). I have 2 of them at the front of the room and 4-5 more running along the left and right sides of my sitting position.
2. There are windows to the right of my sitting position but I've covered them up with the acoustic panels
3. There's also another window at the far end of the room behind my sitting position, I've left them uncovered except for a bamboo curtain
4. I do not have any ceiling cloud acoustic treatment currently
5. For bass trapping, I had simply bought 2 packs of Rockwool 350 (4 slabs each, creating a thickness of 320mm each pack) and threw them behind my studio monitors at the left and right corners in front of my sitting position (they're visible in the room picture above) - I did this just recently to test out how bass traps would improve acoustics in my room, if they work out I will build more permanent structures at the corners
6. I have an Ikea shelf rack of guitar amp heads right in the middle of my room behind my sitting position. They're not that densely arranged such that they create an artificial wall in the middle of my room, but I'm not sure if the amp heads are enough to create very significant reflections from my monitors. Here's a picture taken from my sitting position facing the back of the room.
   
   

In terms of measuring the room, I had done two rounds of measurement with the following parameters:

1. My listening position is slightly pushed back from my sitting position at my desk so as to create the equilateral triangle position (this is cos I had positioned my speakers a bit to the front in order to place them in front of my computer screens)
2. Each side of the equilateral triangle is 1.5m.
3. From my listening position, I took 6 REW measurements:
   1. Right at the listening position (labelled "center" in my measurements)
   2. About 10cm to the right, left, front and back (4 positions labelled "right", "left", "back" and "front" respectively)
   3. And finally one additional position to simulate myself sitting right at my editing position at the desk (not equilateral, labelled "lean", as in lean forward)
4. On the 6-Nov, I did one round of measurement and the average value in the All SPL window showed this:
   
   
   
   
5. This graph showed a pretty significant trough and peak between 60 - 120 Hz. All graphs are set to Var Smoothing.
6. At this point of time, I already had all of my acoustic panels installed but I had not yet put in the makeshift bass traps.
7. I didn't know better on what to do so I just ordered 2 more packs of Rockwool and then threw them behind the speakers to test and see how things would change.
8. So I did this yesterday and the measurement I took today shows this:
   
   
   
   
9. If I overlayed the 2 average lines, it would look like this (Green is before the bass traps, Orange is after):
   
   
   
   
10. So I guess the effect of adding the bass traps were:
    1. It remedied some sort of phase cancellation at the 20-30 Hz range.
    2. It somewhat stabilized the trough between 70-100 Hz range.
    3. But in general the trough and spike between 60-120 Hz range is still there.
11. I've uploaded the REW MDAT file (named "Nov 6 vs Nov 13.mdat"). This file contains both sets of measurements made on 6-Nov and 13-Nov.

Would very much appreciate it if someone could give some advice or pointers on what I should do next to improve my room acoustics.

Thank you!
Wong

 

[feicipet]

Hmm, it seems that my MDAT file attachment was blocked and I'm not sure what was the reason for it being blocked. Let me try again using a zipped version of the file.

 

[MediumRare]

First off, I’m terribly jealous, not only of all your gear, but your ability to use that stuff. Very cool!

I have a couple questions:
- what is the source of the frequencies below 40 Hz, as I doubt those speakers generate it?
- have you compared with the door closed and open?
- have you tried moving the screens together or moving the speakers farther away from them? I suspect that is the source of most of the nulls and peaks.

I think the first thing I would do is move the table farther into the room and the screens together so the speakers can be at least slightly behind them. You can also toe them out somewhat. That should change the cancellation dramatically. Also, suggest you move the rolling equipment rack on the left farther back, away from the speaker. Try it all out and remeasure. Even if it doesn’t work it will help determine what is causing the cancellations/peaks.

ps: I don’t know if the alarm clock etc. on the right speaker is resonating, but gosh there’s a lot of random stuff around that might be!

 

[ddude003]

Lets start out with the basics... It looks to me that this is a recording, mixing and maybe mastering studio... You need much more bass and wide band absorption... RT60 of 0.2 to 0.4, maybe 0.6 seconds... Possibly twice to three times more absorption coverage than you currently have... See http://arqen.com/bass-traps-101/placement-guide/ that gives a good guide to amount and placement... Speakers up off the desk with tweeters at ear level to where you sit... Once you have much more absorber coverage you can then start to think about managing the rest with EQ...

What speakers are those? Can you say what your signal chain is for the measurements?