Sorry friends, i haven't logged on in a while, was busy getting the acoustic treatment done
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Purna, Vinay - thanks a lot for your suggestions. Vinay, i have read almost all of your posts on this subject from the other threads and have learnt a lot from them - thanks.
Finally the solutions i took/taking are the following:
1. I decided not to treat the entire room, the plan was to get the panels done and then screw them at vantage points ( i can experiment with placement). To see why i convinced myself that partial treatment was sufficient for my modest needs (apart from the obvious cost factor), see this great before/after video
Acoustic panels effect: cheap room treatment - YouTube
2. Decided that this will be mostly broadband absorbers but also to install low freq absorbers at the corners. The plan would be similar to this:
Acoustics Forum • View topic - Studiotips Corner Absorber
Also lookd at these:
Acoustics Forum • View topic - Studiotips SuperChunk
and
Acoustics Forum • View topic - Corner Absorption Comparision test
3. I used 2 inch thick fiberglass boards of 48 kg/m3 density from Twiga. Bought them from Himal supplies in Bangalore (thanks Santosh for posting their contact number on one of your threads. For easy ref the number is 080-26665441
4. One point to note is that 48 kg/m3 fiberglass boards are not really that flaky and one needn't worry too much about the dust getting all out. This is just my observation but please do wear protection (mask etc - i did). Use gloves while handling as it can get itchy.
5. i made huge plywood frames of 4 ft wide, 6 ft high, 2.5 inch deep and put supporting planks every 2 feet in the height section. So that let me mount fiberglass boards of 2 ft x 4 ft one above the other - supporting planks provide ..well support.
6. I wrapped the fiberglass with yellow colored cushion foam half inch thick and a very low 23 density (don't know the unit). Low density should let sound pass through. This is available in all mattress/furnishing shops. You get it in 3 ft x 6 ft dimensions. Used 2 to wrap one fiberglass board and glued the two using Fevicol 505 adhesive (it seems this adhesive is purpose built for foams). Used very little glue and used it to bind the two pieces of foam together. This meant the fiberglass boards were all sealed up and no chance of anything leaking out.
7. The frames have beadings (just a very thin flat wood piece) that run the entire length of the frame to ensure the mounted fiberglass stays put inside. The beadings are mounted on the front of the frame and after mounting the fiberglass, on the back of the frame as well to keep the fiberglass boards in place.
8. The frame was now ready to be wrapped in good (and not so good) fabric. I bought some very good looking jute finish (not jute, it's just the finish) fabric to cover the front and some kachcha fabric (they call it kora cloth) to wrap the back side. The good fabric cost me Rs 470 per meter and the kachcha Rs 50 per meter. The meter is the length, the breadth is fixed and is called "panna". One must be very careful with the breadth. It should be enough to wrap the breadth of your panels - otherwise you end up wasting a lot of cloth. Most good fabric have a width of 54 inch which is not ideal but i could manage to cover 4 feet wide panel (plus the 2.5 inch depth of the panel) using some help that i will describe next. The kachcha cloth is used to wrap the backside of the frame. This is not essential but i thought this will be an additional layer of protection and would help make the panel look as "professional" as possible.
9. The corner traps are triangular and mounted with 2 layers of fiberglass (4 inch thick total) using the method described in the link posted above. It has an airgap behind the fiberglass which is sealed in all directions, behind by the wall, top/bottom by plywood. None of my panels have plywood face. Plywood is apparently good for bass traps but since im not covering all walls, didnt want to lose any mid/high absorption in whatever portion i do cover. It seems plywood reflects most high freq.
10. Totally i got done, 3 panels of 4ft x 6ft (2 for the back wall and one for the side wall, other side wall has a window and is covered with very thick curtain), 2 corner traps of 2ft x 6 ft for back corners and 2 corner traps of 2 ft x 4 ft for front wall behind the tower speakers.
11. I used the services of a very skilled carpenter. Without his real world experience this would never be where it is given my "only theoretical expertise". He took 2 days to complete the wood work and i paid him Rs 2500 that he asked for.
12. I wrapped the fiberglass with the yellow foam myself. I initially expected fiberglass dust/flakes to be a problem but that was never the case, it was the terrible smell of the foam adhesive. This is not something that you can take if you aren't used to it - i struggled for 2 days after it was over. If you know someone who works with this on a daily basis (sofa/seat makers etc) it might make sense to just leave it to them. But then again, i'm being cruel :sad:
13. I used the services of a cloth wrapping expert. He was recommended by the cloth shop and i initially hesitated thinking i might be able to do it myself. But boy am i glad i used him. He was a god send. I would never be able to do what he did and he used every last mm of the fabric (note that the width of the cloth was only slightly larger than the width of my panel) and did a fantastic job. Learnt a lot from this guy and am going to use him for carpet laying as well - he is a master-of-many skills i hear and i don't have any reasons to doubt. He is in Mysore but in case someone wants to use him, his number is 9035278874.
14. In the end, i now have the panels up and the results are VERY impressive to even my inexperienced ears. The room is not boomy at all now and the sound is so much more coherent.
15. I plan to install Armstrong optra ceiling tiles for the false ceiling. It comes in black color and has a stated NRC of .95. I was quoted a price of around Rs 400 or so for a tile of 2 ft x 2 ft, so should come to around Rs 100/sq ft. I'm buying this from Armstrong main dealer (or is it a branch of Armstrong itself) in Bangalore. They are located opposite Surana college near South end circle, Jayanagar.
16. In the next month or so, i should have both the ceiling and carpet done. For carpet i'm thinking i'll put a half inch thick thermofoam (the black thing you get in foam shops). I hear this is good but please let me know if you have any other ideas.
I will post pics shortly. Have some in my cellphone that i plan to post here.
Please let me know if you think i should do anything else.
Almost all ideas here were taken mainly from this forum and from few other sites.
Thanks Santosh, Vinay, Purna - your work has been an inspiration to get this started.
