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Discussion Starter · #1 ·
Upon moving to Germany, I was pleasantly surprised to learn that both Praktiker and Toom (Germany's answer to Home Depot and Lowes) sell this stuff:




It comes in 1000mm x 625mm panels (approx. 49x24) in thicknesses of 20, 40, 50, 60, 80, and 120mm. The bags cost about 20 Euros ($28) each, and are about 480mm thick. So a bag of 40mm panels will get you 12 panels, while a bag of 120mm panels will get you just 4.


And so, being an enthusiast of Home Theater (or hauskino as they call it in Germany), I decided to go ahead and go the DIY route to acoustically treat my home theater.






Total cost of materials seen above is about 35 Euros, or $50. This was enough to do the entire front wall, and have two 40mm absorbers left over.


Here is a diagram of my room layout, and where I plan to put treatments.




Here is how my room looked before treatments.






As you can see, in the back I have the DVD towers and a book case. People always seem to have the diffusion toward the rear of the room. However, I wonder if I should have put them against the back wall instead of on the side walls?


The things on the side walls are covered foam sleep mats we bought from Ikea. I put them up there as a band-aid acoustic treatment until such time as I can build proper absorbers for the side walls. I also wanted to be able to play around with REQ.


Phase 1 is treatments on the front wall in order to make the front wall dead. For this phase, I chose a pack of 40mm panels (12 per pack), and 35mm wide boards to make the frames. This will coat probably 90% of the front wall with 1.56 of treatment.


Here is how Phase 1 looks completed.




In normal lighting (no camera flash), the gaps aren't as horribly visible as they are in this flash photo. And with the lights off, the absorbers make a very nice looking black background for the screen. Oh, and no, the whole thing isn't crooked. The ceiling really is that off. We are renting a very old house...


Here is how the sound has been affected. This is with the front wall dead, and the foam mats on the walls.




I'm not certain why, but it appears to me that the frequency response was smoother before I installed the absorbers... Another possibility for the discrepancy could be the fact that the first and second measurements were taken with different computers. I will be using my laptop for all future measurements.


Anyhow, I am hoping that once I get proper absorbers on the side walls, I will be seeing a better frequency response.


Here is a 1/48th octave frequency response chart:




I will say that I took these with a digital Radio Shack meter with the microphone pointed up, C weighted, fast response. Did I do it right, or should I have set it up differently?


Where I have seen (and heard) a huge difference is in the room's RT60.




Whereas before my RT60 was .45 seconds, it is now a much better .25 seconds. I know some people shoot for .35, but according to this post , I am actually a little high still. (My room is about 51 cubic meters in volume) I am hoping that I will be closer to .21 once I get proper absorption on the side walls. And, of course, everything below 200Hz needs work. I am hoping that once I do the corner traps, that number will also be brought towards where it should be.


As far as audible differences, the room is definitely much less echoey. On the downside, now that the sound is cleaned up a little, I seem to be hearing the deficiencies of my Primus 150 speakers. I think they are coloring male dialogue. However, moving my center channel up to the front of the table, and setting it on rubber feet seems to have helped. So I may have been hearing the table vibrating with the speaker.


Phase 2 will involve putting 120mm of treatment inside the windowsill to the outside. This is not for acoustic treatment within the room - this is to try to keep the sound from getting outside. I found that with the windows alone, there is about 20db of acoustic loss between the inside and the outside. I want to try to at least double that so that there is no chance the neighbors will be bothered. (Germans take quiet hours quite seriously. We have been told than mowing the lawn on Sunday will get the cops called)


A possible side effect of Phase 2 could be better bass response since I will be using thick material. However, I do not expect to see much improvement since everything I have read says bass trapping needs to be in room corners, not right smack in the middle of a wall.


Phase 3 will involve doing proper treatments on the sidewalls. For this, I plan to use 80mm of material, to create 3.13 of absorption on the side walls. Each wall will have 3 panels of 80mm absorbers, followed by one 40mm panel. (I had two 40mm absorbers left over from doing the front wall - 10 absorbers was enough to cover the front) This will treat 6' back towards the seating area with 80mm of absorption, and 2' more with 40mm of absorption. The absorbers are 1m tall (39). I will have them probably 6 off the floor, so that will make them up to ear height for both the front row, and a future second row.


The final phase will involve putting 120mm absorbers in the corners for bass management. These will be 2 absorbers high, so about 6 ½' of each corner will be trapped.


Unfortunately, you may all have to wait for quite some time to see the results of Phase 2-4. It is looking like I will be away from home for 6 months because of work. So don't be suprised if you see me resurrecting this thread around July of 2011...


So, am I going down the correct path? I'll have 6 months to read up and research before I go further.


Here is a recap of the main questions I came up with while typing this up:


-When measuring room response, I measured with my Radio Shack meter pointing straight up, fast response. Is this correct, or should I point it toward the speaker generating the test tone?


-Should I move the book shelf and DVD towers against the back wall to get better results with diffusion?


Enjoy!
 

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I'm just getting into room treatments, planning on doing DIY like yourself. I don't think you want the entire wall covered. The pictures I've seen of pro's room treatments has them spaced out around the room, and I think they try to set them at the points where the sound from the speakers hit the wall for the first time. Also, I think absorbers work better if you use a thicker frame and have the fiberglass at the front, leaving an air gap in the back.


Is that cork I see in the one pic? that could be a problem too.
 

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Discussion Starter · #3 ·
On the sides, the entire wall should not be covered in terms of floor to ceiling. However, it seems in many instances floor to ear level along the side wall from the front to the listening area is desirable. As I understand, for a 2-channel listening room, or in a room with a "seat of exellence", the walls (and sometimes ceiling) is covered with absorbers only at the first reflection points. But as Dennis Erskine put it in this thread , the entire front wall is treated for multi-channel listening.


I have read that an air gap is desirable for side wall treatments. That is supposed to help going down below 200Hz. If an air gap is not possible for whatever reason, thicker material can be used for similar results. Once the time comes to do the side walls, I will have to experament with air gaps on the sides.


I'm not sure where you are seeing cork... there is no cork in the room. If you are referring to the third picture, that is the actual mineral wool material.
 
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