DIY - Room Acoustics..

[Ramesh RN]

Elango, can you share some details about nice digital clock in your room. Cost and from where you bought it

 

[sud98]

An other concern, assumption and hesitation of placing absorption on side walls is that it may eat away highs as the absorption is directly in the path of speaker reflection.. From reading posts / discussion from here and other forums, bare side walls seem to help widen sound-stage (or) at-least from the research that Toole or others have been quoted many times.. For now, am not very convinced to try absorption on side walls.. Will try someday..

What is curtain method of PVR?.. Haven't heard off.. But curtain being fabric and on side walls might dampen the high freq..

Since most of your absorption is in the ceiling, they wont typically affect the reflections of mid to high frequencies as they are a bit more directional in nature. All sound waves hitting your side walls esp. from L and R speakers will lead to distortion as they will reach your MLP soon after the original sound wave.

You could build a plywood frame with a a single sheet of rockwool and some air gap and cover it with spandex with a colour of your choice. That way it will still look nice for a living room and will also serve the purpose.

 

[elangoas]

Elango, can you share some details about nice digital clock in your room. Cost and from where you bought it

Thanks.. That was a small DIY.. It is a 10inch tab (Swipe slate +) with a screensaver app to display date & time through the day.. I bought a refurbished tab from ebay.in abt 2 ~ 3 yrs back for Rs 3,000 and installed the Lucid daydream app from playstore.. I think the tab runs on Android 5.0.. In the screen saver settings, i had set it to display date/time and battery indication all the time when charged / not being charged..

I mounted it to corner of a room with a Rs 15 plastic stand.. It is plugged to near by power-point all the time.. Whenever battery is low, i just switch on the power.. When it is full charged, i switch off the power.. Been working like this for more than 2 yrs now..

I have also done this to an other tab which lost its touch functionality.. Been using that as a digital clock too..

The tab also serves a night bulb (due to LCD screen) when all the lights in the room are switched off, an additional benefit ..

Here is a close look at the tab..

 

[elangoas]

I doubt if it is really your living room

It is a Semi Living room / HT room.. No choice, had to make these things for a better audio/video experience.. I know it looks shabby.. Will sort it out once acoustics are shaped in the room..

 

[elangoas]

Since most of your absorption is in the ceiling, they wont typically affect the reflections of mid to high frequencies as they are a bit more directional in nature. All sound waves hitting your side walls esp. from L and R speakers will lead to distortion as they will reach your MLP soon after the original sound wave.

Thanks Sudhir.. Let me share from what i have read and digested so far.. Some are still grey area for me..

So, as you would also be aware, speaker radiates in all direction until it reaches a freq range (mids) and then becomes more directional (highs)..

From what you have said, if we absorb on side walls at first reflection points, it should help absorb mids and part of highs too.. I have seen on AVS forums, especially on the HT of the month articles, that they use very less to no absorption on sidewalls / they uses diffusors ( might be because of big room).. Sometimes absorption (mids)+ diffusion (highs) together on sidewalls..

I have also seen mention of absorption at contra-lateral reflection points on side walls is beneficial for a more cleaner sound-stage.. I would like to try both someday and see for myself which i prefer..

You could build a plywood frame with a a single sheet of rockwool and some air gap and cover it with spandex with a colour of your choice. That way it will still look nice for a living room and will also serve the purpose.

Thanks for the idea.. Will evaluate it..

 

[Ramesh RN]

Thanks.. That was a small DIY.. It is a 10inch tab (Swipe slate +) with a screensaver app to display date & time through the day.. I bought a refurbished tab from ebay.in abt 2 ~ 3 yrs back for Rs 3,000 and installed the Lucid daydream app from playstore.. I think the tab runs on Android 5.0.. In the screen saver settings, i had set it to display date/time and battery indication all the time when charged / not being charged..

I mounted it to corner of a room with a Rs 15 plastic stand.. It is plugged to near by power-point all the time.. Whenever battery is low, i just switch on the power.. When it is full charged, i switch off the power.. Been working like this for more than 2 yrs now..

I have also done this to an other tab which lost its touch functionality.. Been using that as a digital clock too..

The tab also serves a night bulb (due to LCD screen) when all the lights in the room are switched off, an additional benefit ..

Here is a close look at the tab..

Nice Idea Elango

 

[elangoas]

I have some (very little) loose rockwool remaining from the earlier DIY traps which i made, though to make use of it for absorption on contra-lateral reflection points..

What should be the dimensions of the absorber at contra-lateral reflection points?.. Width & height ?..

 

[elangoas]

There seems to be not much rockwool left to complete an absorber.. Am now considering acoustic foams for reflection points for it is easier to work with and can add some room decor..



I found the above acoustic foams on amazon.in - https://www.amazon.in/gp/product/B07PRQXKZ5/ref=ox_sc_act_title_1?smid=AX6N6WBU1YXRB&psc=1

The images says maximum diffusion, but don't think / not very sure if foams can act as diffusor.. Thy have good absorption properties >250Hz, which is needed in the room..

Given that freq until 300 Hz or so is dependent on room dimension / resonance, which is fairly taken care by sufficient absorption in the room, thinking if these 2 inch foams (pyramid) should get it done to handle reflections..

Anyone here used foams to cut reflections points?..

 

[sud98]

Reach out to mmt directly and get their full acoustic properties. A lot of them give just average nrc which is not useful.

 

[elangoas]

Reach out to mmt directly and get their full acoustic properties. A lot of them give just average nrc which is not useful.

Thanks Sudhir.. I just checked the MMTacoustix website directly, they had mention of Density and absorption chart.. Seems low density foam, 40 Kg/m3 from this link - https://mmtacoustixonline.com/collections/pro-acoustic-foam/products/pyramid-acoustic-foam-bangalore

From the absorption chart at the bottom of the above link, there is no mention of thickness at which the NRC is achieved.. Hope it must be 1 (or) 2 inch inches only..

 

[elangoas]

Ordered abt 54 Sq.ft of 2 inch MMT acoustic pyramid shaped foams to be used at different places in the room.. each piece of foam of 12 x 12 inch, making it 1 Sq.ft area.. Cost me abt Rs 9,200 (after 15% discount) for 54 pieces of foam + 2 cans of MMT adhesive spray to fix the foams to walls..

I ordered these directly on MMT acoustix wbesite, there by getting 15% discount on the total value of the order crosses >10K, than i could get on amazon.in for the same order size..

Will update the thread with pics after i receive the material..

Here are some NRC details of the foam..

 

[sud98]

Just check with them if you can spray it on a finished wall or they need an unprepared wall (only plaster).

You should look at at conduits for your various wires and use this to serve a dual purpose of hiding them as well as proving better room acoustics.

Are you looking at first and second level reflection points or any other areas?

 

[elangoas]

Just check with them if you can spray it on a finished wall or they need an unprepared wall (only plaster).

Thanks Sudhir.. Will check with him.. I also thought of using sand paper on finished wall to make it little rough and it might stick to walls better..

You should look at at conduits for your various wires and use this to serve a dual purpose of hiding them as well as proving better room acoustics.

Sure.. Yes, thinking of how to make the room better aesthetically.. I have punctured the walls & ceiling so much, thought of wall paper to make it better and also plan to hide wiring as much as possible..

Are you looking at first and second level reflection points or any other areas?

Below is an image which fairly represents the reflection points in the room..

1) For now, giving a miss to ipsi lateral reflection points (1st reflection points on sidewall)..
2) Will be doing Contra-lateral reflection points - for absorption on sidewalls.. Right speakers reflection of left wall..
3) Rear wall behind listening position - A part of rear wall..
4) And frontwall too besides speakers and above the AT screen, wherever possible..

Surrounds being perpendicular to L-C-R, there is every chance that the front-wall receives some reflection from surrounds.. Same with height speakers 1st reflection points on front wall.. This should fairly eliminate any reflection hitting the front wall (L-C-R)..

This is the plan..

 

[generalxxxstark]

Ordered abt 54 Sq.ft of 2 inch MMT acoustic pyramid shaped foams to be used at different places in the room.. each piece of foam of 12 x 12 inch, making it 1 Sq.ft area.. Cost me abt Rs 9,200 (after 15% discount) for 54 pieces of foam + 2 cans of MMT adhesive spray to fix the foams to walls..

I ordered these directly on MMT acoustix wbesite, there by getting 15% discount on the total value of the order crosses >10K, than i could get on amazon.in for the same order size..

Will update the thread with pics after i receive the material..

Here are some NRC details of the foam..

Do you think they're of higher quality compared to the ones on Aliexpress? I'm contemplating getting a couple of 6x3 feet ones and they're very inexpensive to the MMT ones.

 

[elangoas]

Do you think they're of higher quality compared to the ones on Aliexpress?

Not very sure on that.. Could you share a link to the ones aval on aliexpress, just to check what is offered..

As far as foams are concerned, I don't think there would be significant difference w.r.t sound absorption is concerned.. Do check the density, thickness of the material and absorption properties of the material.. A high density foam will have low (or) very low absorption in the bass range..

I'm contemplating getting a couple of 6x3 feet ones and they're very inexpensive to the MMT ones.

MMT also have few on amazon & on their website.. How much is the cost difference for the same thickness of the material?..

 

[generalxxxstark]

Not very sure on that.. Could you share a link to the ones aval on aliexpress, just to check what is offered..

As far as foams are concerned, I don't think there would be significant difference w.r.t sound absorption is concerned.. Do check the density, thickness of the material and absorption properties of the material.. A high density foam will have low (or) very low absorption in the bass range..



MMT also have few on amazon & on their website.. How much is the cost difference for the same thickness of the material?..

Just searching on Aliexpress for acoustic panels/foam shows quite a lot of options. The pyramid foam for about 24 pcs of 30x30x5 cm seems to be priced between 10 to 15$ with density also ranging from 20 to 40 kg/m3. Some sellers didn't disclose any specifications though.

I'll be waiting for your opinions on the MMT ones..

 

[sud98]

Won't there be issues of shipping and customs with aliexpress. The price is tempting as mmt is almost 175 rs per sqft compared to this around 35.

 

[elangoas]

Just searching on Aliexpress for acoustic panels/foam shows quite a lot of options. The pyramid foam for about 24 pcs of 30x30x5 cm seems to be priced between 10 to 15$ with density also ranging from 20 to 40 kg/m3. Some sellers didn't disclose any specifications though.

Ok i checked this one.. https://www.aliexpress.com/item/400...chweb0_0,searchweb201602_5,searchweb201603_53

Though it is 12 x 12 inch dimensions, they are 1 inch thick.. MMT foams are of the same dimensions too, but are 2 inch thickness that i have ordered..

I'll be waiting for your opinions on the MMT ones..

Sure.. Will share product images when i recive them.. Yet to receive them. May be today or tomorrow should get them..

Won't there be issues of shipping and customs with aliexpress. The price is tempting as mmt is almost 175 rs per sqft compared to this around 35.

Exactly.. Just incase, these products classify for duties, i think that would be too much..

 

[elangoas]

Just some math.. I had ordered 54 MMT foams, each 2 inch thickness.. Approx 108 inch total..

From the above aliexpress link, foams are 1 inch thick of 24 panels, so 24 inch thickness.. To get to 108 inch thickness, you got to multiply by 4 (or) 5.. So that makes it $65 alone for product ,then shipping, then customs + VAT any.. The total amount may come close to MMT foams price..

 

[Sandip Das]

I am using same shape foam but not made by mmt.. buying it local market in kolkata. size is 2 ft. x 2ft. x 2inch