DIY - Room Acoustics..

[elangoas]

My two cents. The more absorption you setup the more speaker energy is lost so needs more headroom.

As @sound_cycle said, the BBA is only absorbing the freq (whichever is resonating / extending the decay time..) that has been already produced by the speaker..

Also a side effect will be the room will become hotter.

Didn't pay much attention to this.. Did read that absorbed energy is turned to heat.. If it induces heat, by how much would the room temperature increase?.. Just for clarity..

So start with a smaller thickness esp. In the ceiling and keep increasing till you have an optimal amount.

If smaller panels, then need to cover more area.. Will check the possibility.. Thanks..

I don't think you would need to do that much. I'd try chunky bass traps on the top corners alone before doing the full ceiling.

Ok.. I was checking the waterfall in 100Hz intervals from 10 - 500 Hz, did find few freq in 300+ ms decay time above 80Hz.. Hence was thinking thicker panels..Will share the waterfall metrics..

I used to have the backwall right behind the listening position. There is no option to BBA in that case, so you might need to try that too.

My listening position is also against backwall.. So, hard to have an BBA there.. May be 3 inches at best i can.. not more than that..

I have 8 4x2 feet 4" + 2" air gapped panels and that's all I need*. I do however run Dirac.

Thx for the info.. Would like to know the BBA density that you had used, also if the decay times has improved after adding the panels..

 

[elangoas]

Here is the Decay time bet 10 - 500Hz.. I had extended the "time range" window to 500ms..

Here is 10 - 250Hz..

Between 180 - 250 Hz, there is a big chunk to clear..

Think the best decay time is below 300 ms for modal responses, not sure if small rooms usually would have this..

 

[prateekatasniya]

My two cents. The more absorption you setup the more speaker energy is lost so needs more headroom. Also a side effect will be the room will become hotter. So start with a smaller thickness esp. In the ceiling and keep increasing till you have an optimal amount.

No...
Why will the room be hotter ?
Low frequencies need thicker absorption.

 

[prateekatasniya]

Here is the Decay time bet 10 - 500Hz.. I had extended the "time range" window to 500ms..

Here is 10 - 250Hz..

Between 180 - 250 Hz, there is a big chunk to clear..

Think the best decay time is below 300 ms for modal responses, not sure if small rooms usually would have this..

Clear everything above 100hz first.. That will be relatively easy corner bass trap might do the job

 

[sound_cycle]

Here is the Decay time bet 10 - 500Hz.. I had extended the "time range" window to 500ms..

Here is 10 - 250Hz..

Between 180 - 250 Hz, there is a big chunk to clear..

Think the best decay time is below 300 ms for modal responses, not sure if small rooms usually would have this..

Hi
The standard metric for reverb time (~ ringing time) is time taken for the sound to decay by 60 dB (therefore the 60 in RT60).

So get REW to display a vertical range of 60 dB, with the with the tallest mountains touching the top of the graph.

Then adjust the time to see how far the mountains march towards you.

Where they are squished up and have "their face pressed to the glass" is where the energy did not die out.

You dont want all of it to die and vanish very quickly.
With bass the the longer it sticks around is what we describe as “muddy” or “boomy.” Which overwhelms the other (nice) stuff in our music.
So we slather the rockwool. But it comes at a cost, it hits out at the treble/ highs viciously and a room where the high end dies young is what we describe as “dead” or “muffled”. (This is my situation, because I got the treatment in before the mic. and the measurements, which is why I cannot post a graph till I undo it all and then figure out what I really need (if you recollect you have asked me this on other threads before too). I think I have overcooked it - for the highs in my room, and I thought I was being conservative with the amount of treatment I added).

What you are aiming for is for the mountains which are 60db high to have "noses" that are not longer than 500 ms. And you do not want all the noses to be equally long, to get it even at all frequencies, ideally. Can this be realized in my room with treatment alone, across all frequencies ? My conclusion was no, not really, therefore the DRC.

What is humming in the 10 - 50 Hz, an a/c or a fridge or is it an artefact ?

ciao
gr

 

[prateekatasniya]

Hi
The standard metric for reverb time (~ ringing time) is time taken for the sound to decay by 60 dB (therefore the 60 in RT60).

So get REW to display a vertical range of 60 dB, with the with the tallest mountains touching the top of the graph.

Then adjust the time to see how far the mountains march towards you.

Where they are squished up and have "their face pressed to the glass" is where the energy did not die out.

You dont want all of it to die and vanish very quickly.
With bass the the longer it sticks around is what we describe as “muddy” or “boomy.” Which overwhelms the other (nice) stuff in our music.
So we slather the rockwool. But it comes at a cost, it hits out at the treble/ highs viciously and a room where the high end dies young is what we describe as “dead” or “muffled”. (This is my situation, because I got the treatment in before the mic. and the measurements, which is why I cannot post a graph till I undo it all and then figure out what I really need (if you recollect you have asked me this on other threads before too). I think I have overcooked it - for the highs in my room, and I thought I was being conservative with the amount of treatment I added).

What you are aiming for is for the mountains which are 60db high to have "noses" that are not longer than 500 ms. And you do not want all the noses to be equally long, to get it even at all frequencies, ideally. Can this be realized in my room with treatment alone, across all frequencies ? My conclusion was no, not really, therefore the DRC.

What is humming in the 10 - 50 Hz, an a/c or a fridge or is it an artefact ?

ciao
gr

The thick bass treatment should be covered with something which reflect mid and high frequencies.. Like dry wall ..
Low frequencies pass through it .. and higher frequencies are reflected.. Then treat the room with 2 inch thick panels to treat the mids and highs..

 

[elangoas]

Clear everything above 100hz first.. That will be relatively easy corner bass trap might do the job

Sure.. Yup, that will be the target..

The standard metric for reverb time (~ ringing time) is time taken for the sound to decay by 60 dB (therefore the 60 in RT60).

So get REW to display a vertical range of 60 dB, with the with the tallest mountains touching the top of the graph.

Then adjust the time to see how far the mountains march towards you.

Thanks for the info.. Will re-do the waterfall when i get back home & share here..

Where they are squished up and have "their face pressed to the glass" is where the energy did not die out. You dont want all of it to die and vanish very quickly.

Perfect..Got it..

(This is my situation, because I got the treatment in before the mic. and the measurements, which is why I cannot post a graph till I undo it all and then figure out what I really need (if you recollect you have asked me this on other threads before too). I think I have overcooked it - for the highs in my room, and I thought I was being conservative with the amount of treatment I added).

Ok.. Got it..Not a problem.. I was just asking for the sake of comparison, to see how the response is in a bigger room like yours..

What is humming in the 10 - 50 Hz, an a/c or a fridge or is it an artefact ?

Not sure.. I don't have A/c at home.. Fridge is away from listening position.. If i change the position of sub-woofer, that peak below 20Hz reduces.. Still figuring out..

 

[sound_cycle]

The thick bass treatment should be covered with something which reflect mid and high frequencies.. Like dry wall ..
Low frequencies pass through it .. and higher frequencies are reflected.. Then treat the room with 2 inch thick panels to treat the mids and highs..

Do we use drywall commonly in India ? Just curious.

You are right about using a combination of diffusion and absorption, but I did not figure out how to get that with simple/easy DIY. If you can point me to some resources I would like to try that out.

How did you figure out the 2" requirement ?

ciao
gr

 

[elangoas]

Why will the room be hotter ?
Low frequencies need thicker absorption.

When energy is absorbed, it is converted to heat.. So sud98 suggested to take that in to consideration.. However, we don't know by how much the room temperature would increase..

 

[sud98]

When energy is absorbed, it is converted to heat.. So sud98 suggested to take that in to consideration.. However, we don't know by how much the room temperature would increase..

If you are planning to build the corner trap, look at an old thread by FM santhosh, who built it using a wooden triangular frame and then getting 'Twiga' panels cut and put one on top of the other. If you build it 1'*1' you will get around 8-9 inches of depth.

 

[prateekatasniya]

Do we use drywall commonly in India ? Just curious.

You are right about using a combination of diffusion and absorption, but I did not figure out how to get that with simple/easy DIY. If you can point me to some resources I would like to try that out.

How did you figure out the 2" requirement ?

ciao
gr

Yes... Dry wall is very common for ceilings.. 2 years back . I got my ceiling done.. 40 rupees per square foot..( inclusive of everything)
Cost of gypsum board alone is around 15 rupees per sqft.
Made a mistake of not installing rockwool above it

Two inch thick Rockwool panels- checked the specs.. 2 inch panels have nrc of almost 1 or above over 500 hz.
And around 0.7 at 250hz
Might vary with different brands.
Once the dry wall is done.. you can gradually place one panel at a time and check the effect ok REW.

Few diffusers should surely be placed strategically.

 

[prateekatasniya]

When energy is absorbed, it is converted to heat.. So sud98 suggested to take that in to consideration.. However, we don't know by how much the room temperature would increase..

That won't make much difference..
And if total room is covered.. Then room will remain cool for a longer time when ac is used as it also Acts as a thermal insulator.

 

[elangoas]

If you are planning to build the corner trap, look at an old thread by FM santhosh, who built it using a wooden triangular frame and then getting 'Twiga' panels cut and put one on top of the other. If you build it 1'*1' you will get around 8-9 inches of depth.

Thx.. Yup.. Saw his thread and he has used 96 kg/m3 density rockwool, loaded it in the front room corner.. Think, he couldn't take measurements before & after due to speaker issue..

Anyways, not planning for corner trapping.. Covering more surface area in the room seems to be better.. Will check the material aval & do some math for total surface area of ceiling / walls in the room & see what would work best..

Cost of gypsum board alone is around 15 rupees per sqft.
Made a mistake of not installing rockwool above it

If you have absorption on ceiling and cover it with gypsum board, aren't you blocking the absorption?.. Most people seem to use fabric to cover the BBA, for the waves to pass through and get absorbed..

 

[prateekatasniya]

Thx.. Yup.. Saw his thread and he has used 96 kg/m3 density rockwool, loaded it in the front room corner.. Think, he couldn't take measurements before & after due to speaker issue..

Anyways, not planning for corner trapping.. Covering more surface area in the room seems to be better.. Will check the material aval & do some math for total surface area of ceiling / walls in the room & see what would work best..



If you have absorption on ceiling and cover it with gypsum board, aren't you blocking the absorption?.. Most people seem to use fabric to cover the BBA, for the waves to pass through and get absorbed..

Low frequencies pass through gypsum board..
I wanted to do this mainly for bass.. High frequency absorption is sufficient in my room..
Carpet , furnishing etc.
Didn't need ceiling absorption.

 

[elangoas]

Low frequencies pass through gypsum board..
I wanted to do this mainly for bass..

I doubt, if the absorption will work that way..

 

[elangoas]

Re-scaled the waterfall setting the highest peak as maximum value, and -60dB from the peak as lowest value for Y axis..

Also, referred to REW guide from AVS forum and adjusted the values accordingly.. They had suggested to set it to 300Hz max freq, also suggested to look at spectogram value, as it would record the highest peak value.. So in that case, it was showing 89db as the highest and the lowest value of the scale to be, -40dB from peak.. Hope i did the limits and values right.. Below -40dB from peak value is noise floor - below image (per REW guide)..

The highest peaks are all multiples of height mode (60Hz, 120hz, 180hz, 240hz).. This seems to be more damaging the graphs..

Per the guide, 450 ms is recommended view, also suggest to extend it to 600ms for ringing.. some part of the freq have extended decay time 600ms (between 180Hz - 250Hz), which per the guide is "serious ringing".. Hmm

Update : on material aval.. Dropped in to rockwool supplier place to check material aval..

The least density they have is 48kg/m3, in standard size of 3ft x 1.5 ft, thickness (100mm/50mm) being the variants.. They also have loose rockwool, which they weren't sure on the density and i guess would be difficult to work with..

48 kg/m3, 50mm thickness - Rs 130/Sq mt
48 kg/m3, 100mm thickness - Rs 404/Sq mt is the price, they had suggested to offer best pricing at the time of final purchase + 18% GST + transportation charges + labor charges (To be decided)..

Are the rates of the panel nominal?..

 

[prateekatasniya]

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Re-scaled the waterfall setting the highest peak as maximum value, and -60dB from the peak as lowest value for Y axis..

Also, referred to REW guide from AVS forum and adjusted the values accordingly.. They had suggested to set it to 300Hz max freq, also suggested to look at spectogram value, as it would record the highest peak value.. So in that case, it was showing 89db as the highest and the lowest value of the scale to be, -40dB from peak.. Hope i did the limits and values right.. Below -40dB from peak value is noise floor (per REW guide)..

Per the guide, 450 ms is recommended view, also suggest to extend it to 600ms for ringing.. some part of the freq have extended decay time 600ms (between 180Hz - 250Hz), which per the guide is "serious ringing".. Hmm

Update : on material aval.. Dropped in to rockwool supplier place to check material aval..

The least density they have is 48kg/m3, in standard size of 3ft x 1.5 ft, thickness (100mm/50mm) being the variants.. They also have loose rockwool, which they weren't sure on the density and i guess would be difficult to work with..

48 kg/m3, 50mm thickness - Rs 130/Sq mt
48 kg/m3, 100mm thickness - Rs 404/Sq mt is the price, they had suggested to offer best pricing at the time of final purchase + 18% GST + transportation charges + labor charges (To be decided)..

Are the rates of the panel nominal?..

What will be the final cost? Only then we can judge if the price is good.
Labour charges for what ? Installation ?

 

[elangoas]

What will be the final cost? Only then we can judge if the price is good.

This will depend on the # of panels we would need.. They made approx calc from what i told them to be done on ceiling.. So they calculated for 10inch thickness.. Approx it came up to 16K with GST..

Labour charges for what ? Installation ?

These suppliers offer installation support.. I though better to employ them as they would have expertise of various installation and challenges..

 

[prateekatasniya]

This will depend on the # of panels we would need.. They made approx calc from what i told them to be done on ceiling.. So they calculated for 10inch thickness.. Approx it came up to 16K with GST..



These suppliers offer installation support.. I though better to employ them as they would have expertise of various installation and challenges..

Means around 20k including installation?
Ceiling area?

 

[elangoas]

Means around 20k including installation?
Ceiling area?

Yes.. I thought of full ceiling earlier, but not full ceiling now..But front wall where it meets the ceiling..