DIY - Room Acoustics..

[elangoas]

Planning to do false ceiling for my living room of 14 ft (W) x 11ft (L) x 9.7 ft (H), with plywood (Carpenter to visit and yet to provide estimate)..

Carpenter visited my place last weekend.. He seems disinterested in work as i told him it is not for aesthetic reasons of the room and the priority is to place acoustic panels above the wooden structure on ceiling.. He roughly said 20 ~ 30K.. .. Will wait for him to give complete quote..

Meanwhile, i was trying to calculate total surface area of the room 14(W) x 11(L) x 9.7 (H) ft.. Surface Area = 2wl + 2lh + 2hw = 793 sqft..

If 38% of the area is good for absorption, then it makes it roughly 301 sqft.. That will be approximately my entire front wall (154 Sqft ) and entire ceiling (154 Sqft)..

Am considering this as an alternate solution if ceiling absorption isn't possible (due to cost) and also to keep the panels away from my kids reach (on the front wall)..

The std rockwool panel size aval is 1 mtr (1000 mm) x 0.6 mtr (600mm)..

Am thinking of treating 1/3rd of my room height from ceiling (with 6/8 inch thick panels wall mounted high on all the walls).. Is this good / bad / too much absorption?..

 

[sud98]

Carpenter visited my place last weekend.. He seems disinterested in work as i told him it is not for aesthetic reasons of the room and the priority is to place acoustic panels above the wooden structure on ceiling.. He roughly said 20 ~ 30K.. .. Will wait for him to give complete quote..

Meanwhile, i was trying to calculate total surface area of the room 14(W) x 11(L) x 9.7 (H) ft.. Surface Area = 2wl + 2lh + 2hw = 793 sqft..

If 38% of the area is good for absorption, then it makes it roughly 301 sqft.. That will be approximately my entire front wall (154 Sqft ) and entire ceiling (154 Sqft)..

Am considering this as an alternate solution if ceiling absorption isn't possible (due to cost) and also to keep the panels away from my kids reach (on the front wall)..

The std rockwool panel size aval is 1 mtr (1000 mm) x 0.6 mtr (600mm)..

Am thinking of treating 1/3rd of my room height from ceiling (with 6/8 inch thick panels wall mounted high on all the walls).. Is this good / bad / too much absorption?..

You might want to check out building an alumnium frame for the ceiling. Might end up much cheaper.

 

[elangoas]

You might want to check out building an alumnium frame for the ceiling. Might end up much cheaper.

If the false ceiling would hold only the heights and absorption panels, would have gone for it.. Since planning to integrate the subwoofer on ceiling, though of wooden frame / fixture to hold the entire thing more robust.. Will check the feasibility..

 

[prateekatasniya]

If the false ceiling would hold only the heights and absorption panels, would have gone for it.. Since planning to integrate the subwoofer on ceiling, though of wooden frame / fixture to hold the entire thing more robust.. Will check the feasibility..

Why subwoofers in ceiling ?

 

[elangoas]

Why subwoofers in ceiling ?

Since i couldn't have them on floor (living room) at the right location (1/4th distance from side walls)..

 

[prateekatasniya]

Since i couldn't have them on floor (living room) at the right location (1/4th distance from side walls)..

Did you try 1/2 distance from side walls?

 

[elangoas]

Did you try 1/2 distance from side walls?

I have two subs at 1/4th & 3/4 of room width and 1/2 room length, on ceiling.. This has reduced all peaks below 80Hz, except height mode peak..

 

[elangoas]

Came across this table on Airflow resistivity of rockwool..

Also used porous absorber calculator - http://www.acousticmodelling.com/multi.php

I tried comparing absoprtion of rockwool for three types of density, loose rockwool, 48Kg/m3 and 96 Kg/m3 for same thickness (300mm).. 12 inches / 1ft..

Loose rockwool - unknown density (am assuming the density & air flow resistivity would be lower than rigid slabs) - Approx 10,000 (Pa.s/m2)
For a 48 Kg/m3 Density of rockwool, from the above table, air flow resistivity is approx 20,000 (Pa.s/m2)
For a 96 Kg/m3 Density of rockwool, from the above table, air flow resistivity is approx 55,000 (Pa.s/m2)

Loose rockwool seems to be more efficient, per the assumption of lower density and lowest value of air flow resistivity.. If i were to make an abosrber of 3ft x 1ft, for the entire room width of 14ft, place it high on front walls near ceiling, would i benefit from reduced decay times & taming the low freq absorption?..

 

[sound_cycle]

Hi

Came across this basotec thing recently. Ordered a small quantity. I've got 16 sq ft of the 50mm thing. Will see how it works out. Impressive on the graph I must say.

ciao
gr

 

[sound_cycle]

Am thinking of treating 1/3rd of my room height from ceiling (with 6/8 inch thick panels wall mounted high on all the walls).. Is this good / bad / too much absorption?..

 

[saikatbiswas82]

Are you planning for absorbers only?

 

[elangoas]

Hi

Came across this basotec thing recently. Ordered a small quantity. I've got 16 sq ft of the 50mm thing. Will see how it works out. Impressive on the graph I must say.

Are these Acoustic foams?.. How much do they cost?.. Where do you plan to place these in the room..

From the graph, they seem to absorb less below 500Hz.. Hope you have considered this point..

Are you planning for absorbers only?

Hope this Q was for me.. If so, yes (for now)..

The plan is to get the bass reasonably right in the room with little variance till say 500Hz without any EQ (Audyssey XT32)..

1) Reduce Decay time in the room
2) Improve the modal responses to the extent possible..

 

[elangoas]

Made some progress with wooden structure on ceiling as planned earlier.. Had to chase the carpenter to get this done..

Located a scrap wood dealer near home..

The scrap wood is sold Rs 38/Kg.. So for my entire ceiling of 14ft x 11ft area and planned partitions, had to pick approx 120Kgs of wood to build the frame..

Approx cost of raw material - Rs 4,500 + Rs 300 to ship it to my location.. Totally Rs 4,800/-..

Explained the carpenter with details on spacing from ceiling and two columns of wooden structure to hold 6 speakers..

Labour cost for two carpenter - Rs 1,500 and hardware (L-brackets, screws) Rs 1,000.. Totally Rs 2,500/-..

The wooden structure is now 16.5 inches from ceiling.. Usable space is approx 16 inches..

As planned earlier, thought of stacking 16 inch thick rockwool inside the wooden frame, wherever possible..

Next steps is to -

1) Mount all 6 speaker enclosure ( 4 enclosure for heights & 2 for subwoofer) to wooden frame in the empty columns and fix it securely..
2) Then spread close knitted stainless steel mesh above the wooden structure to hold rockwool.. FM @sud98 Idea, to make it look neat..
3) Once all the above is done, the wooden frame will be pinned with black spandex to hide the rockwool & stainless steel mesh inside and to absorb the projection screen light reflected to ceiling..

 

[saikatbiswas82]

Hope this Q was for me.. If so, yes (for now)..

Yes. The question was intended for you. Thanks for responding.

I'm following everyone who are into room treatment. I appreciate everyone and trying to gather as much info as I can on this confusing subject (room treatment).

 

[elangoas]

Yes. The question was intended for you. Thanks for responding.

I'm following everyone who are into room treatment. I appreciate everyone and trying to gather as much info as I can on this confusing subject (room treatment).

Ok Great.. Hope you too are trying to add room treatment..

w.r.t absorption, yes, It was confusing initially.. But then somewhere we get know details, it gets clearer on the approach..

 

[saikatbiswas82]

Ok Great.. Hope you too are trying to add room treatment..

w.r.t absorption, yes, It was confusing initially.. But then somewhere we get know details, it gets clearer on the approach..

I think I need to do some treatment in my room keeping the WAF in mind. I'm getting some reflection from back wall (i.e. the wall which my speakers are facing directly)

 

[srinisundar]

Nice work...

Made some progress with wooden structure on ceiling as planned earlier.. Had to chase the carpenter to get this done..

Located a scrap wood dealer near home..

The scrap wood is sold Rs 38/Kg.. So for my entire ceiling of 14ft x 11ft area and planned partitions, had to pick approx 120Kgs of wood to build the frame..

Approx cost of raw material - Rs 4,500 + Rs 300 to ship it to my location.. Totally Rs 4,800/-..

Explained the carpenter with details on spacing from ceiling and two columns of wooden structure to hold 6 speakers..

Labour cost for two carpenter - Rs 1,500 and hardware (L-brackets, screws) Rs 1,000.. Totally Rs 2,500/-..

The wooden structure is now 16.5 inches from ceiling.. Usable space is approx 16 inches..

As planned earlier, thought of stacking 16 inch thick rockwool inside the wooden frame, wherever possible..

Next steps is to -

1) Mount all 6 speaker enclosure ( 4 enclosure for heights & 2 for subwoofer) to wooden frame in the empty columns and fix it securely..
2) Then spread close knitted stainless steel mesh above the wooden structure to hold rockwool.. FM @sud98 Idea, to make it look neat..
3) Once all the above is done, the wooden frame will be pinned with black spandex to hide the rockwool & stainless steel mesh inside and to absorb the projection screen light reflected to ceiling..

 

[elangoas]

I think I need to do some treatment in my room keeping the WAF in mind. I'm getting some reflection from back wall (i.e. the wall which my speakers are facing directly)

Then try adding panels behind the speaker.. But before that, measuring the response at your listening position will give you more clarity on next steps.. just my 2 cents..

 

[saikatbiswas82]

Then try adding panels behind the speaker.. But before that, measuring the response at your listening position will give you more clarity on next steps.. just my 2 cents..

What a timing. Just received DBX RTA mic today. Waiting for the DSP and cables to arrive

 

[elangoas]

15 years of HT usage, never paid attention to room acoustics, wasn't even concerned why acoustic panel are added to the room.. All this changed, when i wanted to add dual subs to the room and started making baby steps to room acoustics..

This is my first attempt at room acoustics - DIY absorber -

Dimensions of the DIY absorber - 57 inches (W) x 24 inches (D) x 11 inch (H)..
Material - Uncompressed Mineral Wool (Loose Rockwool)
Density of the material - <36 Kg/m3 (Gently compressed by hand should be lesser than the least density compressed by machine)..
Flow resistivity of the material - <=10,000 Pa.s/m2
Target freq >= 90hz, until the room transition frequency..

To be placed under the listening position couch..

Picked uncompressed mineral-wool @ Rs 1,180 per bag (40Kgs).. I picked 3 bags too add some more DIY abosrption in the room..

Also picked packing wood from a near by scrap wood dealer.. Rs 700 (30/Kg, approx 25Kgs wood).. But, used less for the absorber..

My younger brother and dad are semi-skilled with DIY wood and metal fabrication.. Took help from them..

Since it was uncompressed mineral wool, wanted to avoid bulging when stuffing the wool inside the absorber.. So added a steel mesh with plastic coating.. More stiffer material to keep rockwool in position inside the absorber..

Wrapped the absorber on the outside with black spandex material and pinned it to the frame with stapler.. Spandex fabric is the same that is used for Acoustic transparent screen.. Had some unused material..This should help from rockwool not seeping from the absorber..

Kept one of the sides open to stuff the loose wool in the absorber..

And finally covered that too with plastic coated steel mesh..

And the final absorber.. It consumed about 60% from a single bag.. Approx 25Kgs of rockwool..

Total cost for the DIY absorber - Less than Rs 3,000/-..

Why uncompressed Mineral wool, why not panels?.. Whenever i happen to read about acoustic panels, i used to observe the density of the material used, which seems to be one of the important factor.. I also came across the Air flow resistivity of rockwool..

From the above graph, i assumed that if the density of the absorber is less, lesser is the flow resistance value and hence the bass should flow thru the absorber and get absorbed.. Higher the density of absorber, higher would be flow resistance value and the bass may not be able to flow thru the absorber effectively, and hence less absorption in the lower frequency range.. Hence used uncompressed mineral wool, so i can go thicker and absorb effectively in the lower freq range..

Will be adding it to the room over the weekend..