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Room measurements with KEF R3

EEE272

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It is a bit a question of taste.
I would place two panels of 10-15 cm on the first reflection points (also in the back), as it will reduce the reverb time a bit.
Making the bass <100 Hz work with absorbers requires a lot of material, as others said as well. A second sub at some point might be a better choice.
I was surprised how much improvement a second sub represents.
 

ernestcarl

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How much treatment a room needs is often opposed to how much people usually want to have for aesthetic reasons... The best way to avoid this in the first place is to hide it all in the walls during the construction stage of a room. Unfortunately, most of us do not have the luxury to do such a project. No matter... since some room treatment is still better than none.

Very low sub bass frequencies are esp. difficult -- or just not practical -- to "absorb" with simple velocity type acoustic treatment products. I recently added maybe about +600lbs worth of very dense mineral wool to the lower half of the rear corners and wall of my basement listening room and found out that I was only able to get maybe a ~3dB reduction of a very specific 25Hz decay peak -- actually, I was a little surprised that it worked. But, it's not what most would even normally consider as a "problem" that needs tackling -- I was merely curious if I could reduce it at relatively low cost by buying the raw materials myself. ;)

DECAY COUCH MLP.png
The "faster" decay in the room above is maybe a little too much for others, but I like it esp. for multichannel purposes.

Was it worth it? Well, if I were only looking at the result exclusively of the sub bass response, then nope! It's definitely not worth it, to be honest. Observing the overall improvement of the sound in the room (and of my rear channel speakers -- allowed me to angle them much closer to the wall [something I always wanted to do] without increasing reflections), I'd say, yes. At the very least, I wasn't disappointed with the result, and the cost of the raw materials by itself wasn't exorbitant.

There's a bunch of youtube videos that show how a room sounds before and after treatment. This is one example from GIK:

 
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Marcin

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So I went to a hardware store today, like @ernestcarl suggested some time ago, and bought two packages of Rockwool 60x100x40cm. I wanted to buy 4 packages but my car is too small... I put them on the floor like below (red ones)
Room.png


This is how the measurements look like for L (brown) + R. Microphone straight at the speakers.
2022-01-23 16_17_40-Poczta.png


and RMS average compared to without the wool
2022-01-23 16_18_22-Poczta.png


I can already say that 40 cm is too thick for WAF... You can see that something is hidden behind the curtains. 30 cm is my max.

This wool has a density of 50 kg/m3. They also have packages of a different wool with density 110 kg/m3 that is sold in packages 60x100x20cm. I thought of trying this instead - stack it almost to the ceiling and leave 10cm air gap from the wall. Do you think it's worth trying? If it works I would just leave it there, behind the curtains. Just make sure to stretch all packaging gaps with foil.
 

ernestcarl

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So I went to a hardware store today, like @ernestcarl suggested some time ago, and bought two packages of Rockwool 60x100x40cm. I wanted to buy 4 packages but my car is too small... I put them on the floor like below (red ones)
View attachment 181261

This is how the measurements look like for L (brown) + R. Microphone straight at the speakers.
View attachment 181262

and RMS average compared to without the wool
View attachment 181263

I can already say that 40 cm is too thick for WAF... You can see that something is hidden behind the curtains. 30 cm is my max.

This wool has a density of 50 kg/m3. They also have packages of a different wool with density 110 kg/m3 that is sold in packages 60x100x20cm. I thought of trying this instead - stack it almost to the ceiling and leave 10cm air gap from the wall. Do you think it's worth trying? If it works I would just leave it there, behind the curtains. Just make sure to stretch all packaging gaps with foil.

It would be more informative if you could attach an mdat before and after treatment -- even just a single left and right sweep at the MLP, preferably microphone on 90 degrees calibration. You can get away with a thinner thickness if using higher density wool, for example -- some people add in different layers.


*Ethan Winer has an article which illustrates doing a similar experiment here using fiberglass which might be of interest: http://ethanwiner.com/density.html
 

abdo123

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@Marcin for such thickness (30 cm) you need to keep density as low as possible so the air can peneterate the material all the way through. not something to seriously worry about but if you have the option always pick the lowest density.
 
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Marcin

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Hmm, two different opinions on density.
So better unpack the one I have now 50kg/m3 and make 4 panels 20cm thick (wrap in foil)? Or buy 4 of the higher density 110 kg/m3?
 

ernestcarl

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It's going to depend on the material being used, but this is the data provided by Rockwool for the materials I previously checked for my own mini project:

Safe'n'Sound
Actual Density - 2.4 lb/ft³ (38 kg/m³)
1642957794710.png


Rockboard 60
Actual Density - 6 lbs/ft³ (96 kg/m³)
1642957881692.png


Comfortboard 80
Actual Density - 8 lbs/ft³ (128 kg/m³)
1642957931897.png

little less effective at some frequencies, but here I was primarily concerned with the low bass region (and my room had also a prominent ~130Hz mode affecting all speakers.

The only reason I got the latter variant instead of the 60 (I also purchased the safe'n'sound and layered the two boards) was because it was the only thing easily available to me.
 
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Marcin

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Rockwool panels are called different in my country. The one I have now is Rockslab Acoustic, it's rock mineral wool. The other one with higher density is called Steprock Plus, also rock mineral wool.

@abdo123 this is the converter kg/m3 - Pa.s/m2 I found on another forum.
Density 30kg/m3 - Pa.s/m2: 10.000
Density 40kg/m3 - Pa.s/m2: 15.000
Density 50kg/m3 - Pa.s/m2: 30.000
Density 75kg/m3 - Pa.s/m2: 50.000
Density 100kg/m3 - Pa.s/m2: 60.000

According to the calculator you provided the less density the better. When I compared 30 cm vs 20 cm with airgap the result is almost the same
1642961658842.png


@ernestcarl I will do the measurements you asked for tomorrow.
 

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abdo123

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Rockwool panels are called different in my country. The one I have now is Rockslab Acoustic, it's rock mineral wool. The other one with higher density is called Steprock Plus, also rock mineral wool.

@abdo123 this is the converter kg/m3 - Pa.s/m2 I found on another forum.
Density 30kg/m3 - Pa.s/m2: 10.000
Density 40kg/m3 - Pa.s/m2: 15.000
Density 50kg/m3 - Pa.s/m2: 30.000
Density 75kg/m3 - Pa.s/m2: 50.000
Density 100kg/m3 - Pa.s/m2: 60.000

According to the calculator you provided the less density the better. When I compared 30 cm vs 20 cm with airgap the result is almost the same
View attachment 181309

@ernestcarl I will do the measurements you asked for tomorrow.
The density for flow resistivity table you shared looks suspiciously overinflated. But glad you got the overall point.
 

hemiutut

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30 cm thick panels with a thickness of 5,000 Pa.s/m2 and
located in first reflections and at their maximum speed, the change will be from day to night.
to night.
If you can put the .mdat file without vs treatment.

Written with translator.

Greetings

PS:I insist that the wool used as filler for the 30 cm thick panels,
be of 5.000 Pa.s/m2
 
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Marcin

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The issue is that wool manufacturers in Poland don’t provide information about flow resitivity in Pa * s / m². I can only rely on converters and those may be misleading. For example on this page https://www.jochenschulz.me/en/blog/rockwool-glasswool-hemp-best-absorber-material there are different flow resitivity values for the same density. Let’s assume that the wool I have now is 15000 Pa * s / m² (as it is more less an average for this density).

I noticed that in the hardware store they have glass wool called Isover Akuplat+ that is 15.5 kg/m³. According to the above site it should be around 8000 Pa * s / m² (30-35 kg / m³ for stone wool). Comparing these two in porous absorber calculator the difference is significant in favor of glass wool.

@ernestcarl @hemiutut .mdat files attached. I also measured left speaker with with half-foam in BR port.
 

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abdo123

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The issue is that wool manufacturers in Poland don’t provide information about flow resitivity in Pa * s / m². I can only rely on converters and those may be misleading. For example on this page https://www.jochenschulz.me/en/blog/rockwool-glasswool-hemp-best-absorber-material there are different flow resitivity values for the same density. Let’s assume that the wool I have now is 15000 Pa * s / m² (as it is more less an average for this density).

I noticed that in the hardware store they have glass wool called Isover Akuplat+ that is 15.5 kg/m³. According to the above site it should be around 8000 Pa * s / m² (30-35 kg / m³ for stone wool). Comparing these two in porous absorber calculator the difference is significant in favor of glass wool.

@ernestcarl @hemiutut .mdat files attached. I also measured left speaker with with half-foam in BR port.
There is a significant difference in the 60Hz to 200Hz region with the rockwool installed, decay times are dramatically improved.

1643017894901.png



1643017906788.png


1643017933565.png
 
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Marcin

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Nothing really happened above 200 Hz. Is it due to the placement or due to foil wrapping?
 

abdo123

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Nothing really happened above 200 Hz. Is it due to the placement or due to foil wrapping?
foil wrapping most likely. you typically want your RT60 measurements to be somewhere between 250ms and 500ms for the entire spectrum and to have the treatment somewhat equally distributed across the entire room.

if you're planing on 30cm thickness or more then i would get the insulation material available with the lowest density, otherwise it won't make much of a difference on 20cm or lower.
 
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Marcin

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Thanks abdo123.
Now I have experienced the difference at least. Actually I can even hear that my voice is less reverberant in the room.

I think I will return Rockwool and try Isover instead. What do you think of wrapping it in non woven fabric (like for gardening)? It should be more breathable and reduce mids and highs reverberation. Or should I not try to reduce it?
 

abdo123

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Thanks abdo123.
Now I have experienced the difference at least. Actually I can even hear that my voice is less reverberant in the room.

I think I will return Rockwool and try Isover instead. What do you think of wrapping it in non woven fabric (like for gardening)? It should be more breathable and reduce mids and highs reverberation Or should I not try to reduce it?

usually you want to cover them with acoustically transparent fabric, a good way to measure what a certain fabric is doing is by simply covering the speaker with the fabric and measuring before and after. Keep in mind that this is not foam, it is a health hazard if it's left uncovered.

Your RT60 in high frequencies is 'okay' (400ms to 500ms), it can be reduced further up to perference down to 250ms, Since you use 30 cm thick material you won't experience extremes (theoretically) with high frequencies being absorbed too aggressively compared to ~100Hz to 400Hz.
 
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Marcin

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The fabric I'm talking about looks like this.
AGROWKNINA_5.jpg

It's recommended on other forums as good wrapping for wool so that it is not dusting.

Now I'm thinking that maybe mixing Rockwool with Isover would bring better results (like ernestcarl suggested)? Less dense at front and more dense at back.
 

hemiutut

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Thanks abdo123.
Now I have experienced the difference at least. Actually I can even hear that my voice is less reverberant in the room.

I think I will return Rockwool and try Isover instead. What do you think of wrapping it in non woven fabric (like for gardening)? It should be more breathable and reduce mids and highs reverberation. Or should I not try to reduce it?
If you can get Knauf TP116 of 5.000 Pa.s/m2, do not hesitate to contact us.
to try it.
In Spain a package of this wool is about 25-35 euros and if you can get it, you should try it.
panels for the corners of 40-60 cms better than better.
For panels up to 20 cms thick there is not much difference in using this wool.
from 5.000 Pa.s/m2 to 10.000 Pa.s/m2 although there is an improvement, but after
20 cms thick, there is no doubt that 5,000 Pa.s/m2 is better.

If you find a material of 3.000 Pa.s/m2, for panels of 40-60 cms thick.
is the most efficient for lower frequencies.

Written with translator

Greetings
 

ernestcarl

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The issue is that wool manufacturers in Poland don’t provide information about flow resitivity in Pa * s / m². I can only rely on converters and those may be misleading. For example on this page https://www.jochenschulz.me/en/blog/rockwool-glasswool-hemp-best-absorber-material there are different flow resitivity values for the same density. Let’s assume that the wool I have now is 15000 Pa * s / m² (as it is more less an average for this density).

I noticed that in the hardware store they have glass wool called Isover Akuplat+ that is 15.5 kg/m³. According to the above site it should be around 8000 Pa * s / m² (30-35 kg / m³ for stone wool). Comparing these two in porous absorber calculator the difference is significant in favor of glass wool.

@ernestcarl @hemiutut .mdat files attached. I also measured left speaker with with half-foam in BR port.

Sorry, I cannot comment if those are going to perform better.

Anyway, as noted by abdo, your measurements show a substantial improvement in the decay even with only the partial room treatment:

Left Speaker Decay
1643061026988.gif


Right Speaker Decay
1643061040357.gif

Improvements can actually be observed above 200Hz.


And severe ringing is reduced in the waterfall graphs:

Left Speaker
1643061091494.gif


Right Speaker
1643061096704.gif



While the frequency response might look worse in places, the overall sound heard should be clearer/cleaner.

1643061572172.png
 
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