Need Help On Room Acoustics

[sidvee]

pdhanwada - In your case my suggestion (just my opinion) would be:
1. Treat the first reflection points only - that would be side walls, floor, ceiling. Treat the wall behind the front speakers as well with absorbers.
2. Side walls & ceiling first reflection can be treated by absorbent panels.
- I think anutone panels will work well here and if possible you can attach them to the ceiling first reflection as well - this will take care of ceiling reflection.
3. Floor first reflection point can be treated by a thick rug, carpet etc.
- easy enough to do.
4. All 4 corners should have panels that are absorbent at-least upto 80hz and better if below - otherwise known as bass busters.
- not sure if anutone sells bass busters.
5. Next step would be to add diffusers to the rear wall.
- again I have seen some diffusers in anutone catalog but I have had no luck in trying to obtain them.
6. Finally your furnishings such as couches, curtains and other fabric covered items will also serve as absorbers.

IMO for smaller home theaters that do not need sound isolation it would be overkill to fill the room with absorption panels as it would require a significant increase in amplifier power to overcome the massive absorption (otherwise called as dead sounding room).
Hope this helps.
Cheers
Sid

 

[pdhanwada]

pdhanwada - In your case my suggestion (just my opinion) would be:

1. Treat the first reflection points only - that would be side walls, floor, ceiling. Treat the wall behind the front speakers as well with absorbers.
2. Side walls & ceiling first reflection can be treated by absorbent panels.
- I think anutone panels will work well here and if possible you can attach them to the ceiling first reflection as well - this will take care of ceiling reflection.

This is exactly I was planning to do. You confirm my ideas.

3. Floor first reflection point can be treated by a thick rug, carpet etc.
- easy enough to do.

Should we do only first reflection point treatment on the floor. My room size has increased from 17 to 22 ft and I checked my ceiling height it is 9 ft not 10 ft.

4. All 4 corners should have panels that are absorbent at-least upto 80hz and better if below - otherwise known as bass busters.
- not sure if anutone sells bass busters.

I have seen some diy bass traps in the net. I am not sure how easy or hard to make them. I will do more study/analysis and get your opinion.

5. Next step would be to add diffusers to the rear wall.
- again I have seen some diffusers in anutone catalog but I have had no luck in trying to obtain them.

cmsajith says in the previous post we need atleast 8 to 10 ft away from the diffusers. If that is so, front wall becomes more appropriate from them than the back wall. Anybody used diffusers let me know.

6. Finally your furnishings such as couches, curtains and other fabric covered items will also serve as absorbers.

IMO for smaller home theaters that do not need sound isolation it would be overkill to fill the room with absorption panels as it would require a significant increase in amplifier power to overcome the massive absorption (otherwise called as dead sounding room).

My room size has increased to 22 X 9 X 12' 3''. I need to move my back wall into the store room by 5ft making store room smaller. What is your defination of smaller home theater rooms.

This forum is awesome.
Thanks very much.

Hope this helps.
Cheers Sid

 

[sidvee]

This is exactly I was planning to do. You confirm my ideas.

Should we do only first reflection point treatment on the floor. My room size has increased from 17 to 22 ft and I checked my ceiling height it is 9 ft not 10 ft.

I have seen some diy bass traps in the net. I am not sure how easy or hard to make them. I will do more study/analysis and get your opinion.

cmsajith says in the previous post we need atleast 8 to 10 ft away from the diffusers. If that is so, front wall becomes more appropriate from them than the back wall. Anybody used diffusers let me know.

My room size has increased to 22 X 9 X 12' 3''. I need to move my back wall into the store room by 5ft making store room smaller. What is your defination - of smaller home theater rooms.

This forum is awesome.
Thanks very much.

Hi pdhanwada
Regarding the floor - when using a carpet - make sure it covers the first reflection point, but if it exceeds beyond that -like wall to wall - should be no issue other than adding a little more absorption.
DIY bass traps are not too hard to build, but I am not sure about all the materials and their availbility in India. Also I hate working with insulation material - like glass wool - find it very itchy and the fibres are dangerous if inhaled in large quantities.
Usually front wall should be covered in absorption and rear wall with diffusion - to create what is a LEDE effect - live end, dead end with front being dead and listener being in live end. In my experience 8-10' in not required for diffusion. Secondly for HT surround speakers which are in the rear benefit most from diffusion.
Your room is approx. 2400 cu.ft, which is what I would classify as small to medium. Usually in HT parlance large would mean spaces above 4000 cu.ft wherein total room treatment starts making more sense both for dialog intelligibility and steering surround effects not to mention bass impact. One more thing in such rooms - that are fully treated for HT - music does not sound very good (no-flames just my opinion after having been in many such rooms) - so if you want a dual purpose room - go easy on the absorption as I have stated in my earlier post.
Cheers
Sid

 

[pdhanwada]

Sidvee,

That answers all my questions for now. May would need help later when we start to implement things. This will also help me in budgeting.

Thanks
Pandu

 

[GeorgeO]

Pandu

There is some trial and error involved in all of this.

 

[pdhanwada]

Pandu

There is some trial and error involved in all of this.

I have seen this statement in many places across the web. But while the construction is on we cant test it. We can only test it after everything is done. How can we make it trial and error.

Only one thing I can think of is we can make the panels removable and see how it sounds. That too it will change the design of the interiors.

Thanks
Pandu

 

[pdhanwada]

Was going over the web last few days. I went thru the website george recommended. It is interesting. Also found another website named bills audio
cave

Acoustic Tweaks

In this author refers to the point that more thickness is needed for the acoustic panels. 2 inch thick panels do nothing on the low end and the waves keep bouncing the sound stage is disturbed. Minimum of 4 to 5 inch thickness is needed.

Another point mentioned is Keep the panels several inches away from the wall. That should provide good absorbtion. I am not sure How I can acheive this in my room. My rooms width is 12ft and 3 inches. 4 inches for the panel and 2 inches spacing between the wall and the panel makes it 6 inches. May be I can experiment on the spacing between the panel and wall later.

Another intresting point is the whole wall is not treated. Only Panels are hung at the point where ever required. He treats both first and the second reflection points only and the corners.

I found a distributor/dealer of Rock wool india who can supply rock wool at Rs 170 per sq meter for 2 inch thick which is 96 kg per cubic meter. 1 square meter turns out to be around 11 sq feet. Rockwool even if we use 2 2 inch thick one over the other we would end up spending about Rs 35 per sq ft apart from the framming and the labor charges. Did some research on rock wool vs glass wool and found out that both do a good job of sound absorbtion and there is no difference between materials until the 65 db mark.

Our Carpenter came over yesterday, I showed him the panels which I wanted to get done, He said that He is ok working on that. He has worked on it earlier and says to prevent itching gloves are needed.

I am encouraged by his comments and I am thinking about going the DIY acoustic panels way.

Comming back to the comparison between anutone vs DIY acoustic panels.

1. Anutone is expensive and the 50mm ones are still more expensive. But are easy to work with.

2. My house is finished with wall putty just by adding 100 mm panels, I should get the work done.

3. My HT room is situated on the pent house and no body will be affected except the carpenter. I will suggest him to complete one panel before moving on to the other one and keep them. Will make sure he wears a full handed shirt gloves and covers his nose with a filter.

4. Looking at the absorbtion qualities, I feel DIY way looks better than the anutone tiles.

Your opinions welcome.

Thanks
pandu

 

[sidvee]

Was going over the web last few days. I went thru the website george recommended. It is interesting. Also found another website named bills audio
cave

Acoustic Tweaks

In this author refers to the point that more thickness is needed for the acoustic panels. 2 inch thick panels do nothing on the low end and the waves keep bouncing the sound stage is disturbed. Minimum of 4 to 5 inch thickness is needed.
He is absolutely right - minimum 4" thick is required to start absorbing frequencies below 200hz

Another point mentioned is Keep the panels several inches away from the wall. That should provide good absorbtion. I am not sure How I can acheive this in my room. My rooms width is 12ft and 3 inches. 4 inches for the panel and 2 inches spacing between the wall and the panel makes it 6 inches. May be I can experiment on the spacing between the panel and wall later.
To create space behind the panel - you can have your carpenter attach 6" strips of wood behind the panel around the edges such that when the panel is attached to the wall there is a 6" air gap between the panel surface and the wall. This will increase absorption and is highly desirable.

Another intresting point is the whole wall is not treated. Only Panels are hung at the point where ever required. He treats both first and the second reflection points only and the corners.
Absolutely - if you remember my previous post I alluded to the fact that treating the whole wall will run the risk of creating a dead sounding room not to mention requirement of higher amp. power to hit required SPL
I found a distributor/dealer of Rock wool india who can supply rock wool at Rs 170 per sq meter for 2 inch thick which is 96 kg per cubic meter. 1 square meter turns out to be around 11 sq feet. Rockwool even if we use 2 2 inch thick one over the other we would end up spending about Rs 35 per sq ft apart from the framming and the labor charges. Did some research on rock wool vs glass wool and found out that both do a good job of sound absorbtion and there is no difference between materials until the 65 db mark.

Our Carpenter came over yesterday, I showed him the panels which I wanted to get done, He said that He is ok working on that. He has worked on it earlier and says to prevent itching gloves are needed.

I am encouraged by his comments and I am thinking about going the DIY acoustic panels way.

Comming back to the comparison between anutone vs DIY acoustic panels.

1. Anutone is expensive and the 50mm ones are still more expensive. But are easy to work with.

2. My house is finished with wall putty just by adding 100 mm panels, I should get the work done.

3. My HT room is situated on the pent house and no body will be affected except the carpenter. I will suggest him to complete one panel before moving on to the other one and keep them. Will make sure he wears a full handed shirt gloves and covers his nose with a filter.
My suggestion - see if he can work outdoors when installing the glass wool portion of the panel - that way none of the fibres will be indoors at all

4. Looking at the absorbtion qualities, I feel DIY way looks better than the anutone tiles.
If you do diy right and make them adequately thick they may even outperform commercial panels - at-least in performance if not aesthetics.Just my humble opinion no flames please.
Your opinions welcome.

Thanks
pandu

Pandu - Please see some of my comments in blue.
Cheers
Sid

 

[manishk13]

I have just finished my HT here are my 2 cents (I am not an expert but Venkat Sir, Santosh and Subhash guided me primarily) . Based on research and their broad advice here is what I did:

- To cover the reflections broadly, I put Anutone absoprtion panels starting at 1.5 ft from the floor till 5.5 ft (they come in 4 ft height). So 2 feet above and below the tweeter level is fully covered for relection (tweeter comes at about 3 feet height). The panels are backed by 22 mm channels filled with anutone synth (like glasswool). This was the sound treatment strategy

- The area above and below the absopption panels have been treated for sound proofing/isolation using another Anutone board called TUFBLOC. It is a thick, dense, heavy sound proofing matrial. It was also backed by synth. This was the sound proofing/isolationn strategy

- The above combination of absoption and islolation was done for the side walls and back wall (back means back of the listener)

- The front wall (screen wall) was fully treated for absorption backed by synth

- The ceiling was treated with Anutone's celing tiles - I chose black matt finish and also put a layer of synth over it just to be safe

- The room is 22 ft by 16 ft

- The total treatment costed Rs 75,000

- I am happy with the initial tests except one door from which sound is leaking

Regards
Manish

 

[santhosh]

I found a distributor/dealer of Rock wool india who can supply rock wool at Rs 170 per sq meter for 2 inch thick which is 96 kg per cubic meter. 1 square meter turns out to be around 11 sq feet. Rockwool even if we use 2 2 inch thick one over the other we would end up spending about Rs 35 per sq ft apart from the framming and the labor charges. Did some research on rock wool vs glass wool and found out that both do a good job of sound absorbtion and there is no difference between materials until the 65 db mark.

Our Carpenter came over yesterday, I showed him the panels which I wanted to get done, He said that He is ok working on that. He has worked on it earlier and says to prevent itching gloves are needed.

Pandu, please avoid Rock Wool, they powder a lot and is very difficult to work with.

I have just finished my HT here are my 2 cents (I am not an expert but Venkat Sir, Santosh and Subhash guided me primarily) . Based on research and their broad advice here is what I did:

...................................

......................I am happy with the initial tests except one door from which sound is leaking

Regards
Manish

Manish, is the room and equipment operational yet? Would like to drop in some time.

Also, about the sound leak problem, you have two doors with an air gap in between. Correct? Ensure all gaps are sealed (key holes, gap between door and floor etc).

 

[GeorgeO]

Santhosh

I would also like to come along with you whenever you make the pilgrimage..

 

[manishk13]

Dear Santosh, George

Yes it is broadly ready and it would be a privilege to have you. Lemme know when u wanna visit

Regards
Manish

 

[pdhanwada]

Steven P. Helm: DIY Bass Traps

Please go thru this link for DIY bass traps. They are made in the super chunbks design.

In this design you have the right triangle with 24, 24 and 34 inches corner full fillup.

May be we can change the length. I feel I can have couple of them behind the listner on each corner.

Is there any other better bass trap designs let me know. Two advantages are it sticks to the wall and secondly interior wise it looks better than the 6 in thick. I think it performs better than the acoustic panel bass trap.

Let me know your opinions.

Thanks
Pandu

 

[pdhanwada]

Last few weeks I have been studying about Room treatment.

Few Decisions I have made.

Currently my room is 17' 4" X 12' 3" X 9'. Initially thought of increasing the size to 22' ft in length. Gave up the idea as it involved more civil work, more expenditure etc. Also I thought 17 ft is not too bad of a size of a room. Also Will be creating Acoustic panels such that they can be removable.

Acoustic treatment design will consist of two parts

1. Broadband absorbers which will be positioned on the side, back and front walls.
2. 3 Super chunck bass absorbers.4th one I cant use as there is entrance door situated there.

All the acoustic panels will be 4 inches thick.

My side walls will contain 6 ft width X 4.5 ft Height panels. There will be three panels each of 2 X 4.5. These will be positioned based on the first reflection points. These will be hung 2 inches away from the wall. To hang them away from the wall I will be using a A nut bolt method where the screw will be embedded into the back part of the panel. The front part of the screw with the head will be inserted into the frame hanger which is fixed into the wall. This is like frame being hung on to the wall but the nail is on the frame not on the wall. Another advantage with this method is I can remove them and change the spacing between wall and panel by rotating the screw to 0,1,2 or 3 inches. I will be using 4 inch nut bolts.

My Back wall is pretty close to my seating position I will have a 6ft by 4.0 ft panels. I dont have too much space so I am planning to stick them to the wall leaving no space between the wall and panel.

My front wall where I hang my projector screen will be covered with absorbtion panels about 8ft X 5 ft. It will starting at 32 to 34 inches from the bottom and reaching up till the roof. My 32 inches from the floor will be covered by my new HT rack. Same with my front panels, I will stick them to the wall leaving no space between wall and panel.

Question : My Projector screen will be hanging over this absorbtion. The screen will always be pulled down. The spring action which the screen had is all gone. Will this be a problem for absorbtion not happenning. If so I might need to fix my screen such that It will go up as and when required.

My Front two corners will contain two super chunk corner bass absorbers. The dimensions of each being 17X 17X24 inches. I can only use one back super chunk corner bass absorbers of size 15 X 15 X 21 inches. On the other corner I have the entrance door situated.

I might treat my center of my ceiling with 4ft by 12ft with 12 ft being parallel to the speaker line and 4ft being the width. Not decided yet. Currently my room's fall ceiling is already done. Dont want to disturb it. If at at all I do it it would be such that I will run two Iron rails parallel to the Speaker line. Then hang the absorbers to the two rail lines. Before I commit to this I will test it without the ceiling absorbers and then decide about it.

Let me know your opinions.

Pandu

 

[pdhanwada]

Pandu, please avoid Rock Wool, they powder a lot and is very difficult to work with.

I stumbled upon this article in the gearslutz.com which talks about safety factor for each of ROCKWOOL,GLASSWOOL and orgranic products.

The Comparative Safety of Rockwool, Fiberglass, and Organic Fibers (a review) - Gearslutz.com

This is a detailed study of all the materials which was tested on animals for prolonged periods of time.

It says that safety of Rockwool > glasswool > cotton ,fiber etc.

I agree with you that utmost care needs to be taken care of whether it is rockwool or glass wool like wearing gloves, full sleeves, covering nose , working outdoors etc.

I checked out that glasswool is not available > 32 kg/cu m. Where as we can find rockwool in abundance until 144 kg/cum. Also it is cheap. I did quite an amount reading over the internet and have seen lot of people use Rockwool freely.

I was talking to the rockwool insul india representative. He says that there are lots of sub standard rockwool products available in india they become powdery pretty quickly. This particular rockwool which i am planning to use is being used in Rajdhani where lot of vibration and still doesnot get powdery. May be thats what you might be referring to.

With respect to my DIY panelling project, I am working on the design portion of it.

Thanks
Pandu

 

[pdhanwada]

Rain has letup. My acoustic treatment began yesterday.

I am going ahead the plan to treat the corners and the first reflection points on the side walls ceiling and backwall.

Corners are treated with superchunk bass absorber formula. Where as the first reflection points are treated with 4 inch thick panels filled with rockwool.

I am taking all possible measures to make sure that use of rockwool doesnot affect anybody's health by covering face, wearing gloves and having full sleeves.

Last Week Sidvee paid a visit to my place. I am very much thankful to him for his and advice. Sid wanted my rack to be very low. But I had to make one level higher for the sake of any future increase in my equipment. I dont to make any more racks anytime sooon. I agree with sid ideally racks should not be placed behind the speakers, so he suggested one having till 14 in height. But I am making it to a height of 22 inches. Only reason for that being my woofer is at 26 in height so any sound waves will be directed towards my rack will be pointing downwards.

Will put up pictures of the room treatment frame work tommorrow.

One of the principle I am following here is all the frames, super chunks I am getting them made in the format where they can be removed whenever needed.

Thanks for all yoour help.

 

[S_Sridar]

Hey Hey Hey hey,

I am into advanced soundproofing and sound blocking.

what is it that you want achieve ?

That is the first point to be taken into consideration.

Sound blockers, and absorbers are to be decided later. You have to first decide what you want to get done by the sound proofing system. And, finally, most soundproofing materials are well below that price.

 

[Kittu]

Hey Hey Hey hey,

I am into advanced soundproofing and sound blocking.

what is it that you want achieve ?

That is the first point to be taken into consideration.

Sound blockers, and absorbers are to be decided later. You have to first decide what you want to get done by the sound proofing system. And, finally, most soundproofing materials are well below that price.

Can you throw some light on this topic with more details ? and Step by step approach ?

Thanks in advance.
Kittu

 

[pdhanwada]

Hey Hey Hey hey,

I am into advanced soundproofing and sound blocking.

what is it that you want achieve ?

That is the first point to be taken into consideration.

Sound blockers, and absorbers are to be decided later. You have to first decide what you want to get done by the sound proofing system. And, finally, most soundproofing materials are well below that price.

Sridar,

I dont understand you. I didnot quote any price. Please point me if I had missed anything.

I am not working on sound isolation. I am working on onlysound absorbtion and that too thru DIY made panels of ROCKWOOL.

Thanks
pandu

 

[santhosh]

Hey Hey Hey hey,

I am into advanced soundproofing and sound blocking.

what is it that you want achieve ?

That is the first point to be taken into consideration.

Sound blockers, and absorbers are to be decided later. You have to first decide what you want to get done by the sound proofing system. And, finally, most soundproofing materials are well below that price.

Can you throw some light on this topic with more details ? and Step by step approach ?

Thanks in advance.
Kittu

Welcome to HFV Sridar. Nice to have a Room Acoustics expert amongst us. Appreciate it if you could start a thread on the topic and guide us members in our Home Theater Build projects. TIA.