Invisible Room Treatment

jespera

Well-Known Member
Jan 12, 2018
235
183
115
Copenhagen
We moved into our current house three years ago and since then I’ve struggled with the acoustics in the front room where my main system resides.

The room is very reverberant and has a high pitch flutter echo as well. Even with furniture, curtains and rugs in the room. Muddying the sound and definition and loosing connection with the music.

We have also had trouble with the dinning room that also has very hard acoustics that makes conversations hard when there are many people in the room.

Recently I took the plunge and decided to do something about it. Specifically, to apply the system that a friend of mine had installed in his new house.

The ceilings are covered with 20mm of special mineral wool. This is in turn covered with a very thin acoustically transparent white plaster which makes the treatment virtually invisible.

The improvement is remarkable. Much much better definition, clarity and involvement. Improved transients and bass too. Highly recommended.
 

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LL21

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Dec 26, 2010
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Wow...great to know! Congrats! Will definitely keep this one in mind! Did you decide NOT to do the walls while you were doing the ceiling?
 

Ron Resnick

Site Co-Owner, Administrator
Jan 25, 2015
9,842
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965
Beverly Hills, CA
We moved into our current house three years ago and since then I’ve struggled with the acoustics in the front room where my main system resides.

The room is very reverberant and has a high pitch flutter echo as well. Even with furniture, curtains and rugs in the room. Muddying the sound and definition and loosing connection with the music.

We have also had trouble with the dinning room that also has very hard acoustics that makes conversations hard when there are many people in the room.

Recently I took the plunge and decided to do something about it. Specifically, to apply the system that a friend of mine had installed in his new house.

The ceilings are covered with 20mm of special mineral wool. This is in turn covered with a very thin acoustically transparent white plaster which makes the treatment virtually invisible.

The improvement is remarkable. Much much better definition, clarity and involvement. Improved transients and bass too. Highly recommended.

Very interesting! Do you think that wall-to-wall carpeting would have had a similar acoustic effect as your full-ceiling mineral wool treatment?
 

PeterA

Well-Known Member
Dec 7, 2011
8,802
5,339
1,235
North Shore of Boston
Took me a while to notice the stereo. I like the shelves with three turntables and tube amps. The record storage units must be attached to the wall quite strongly because I imagine those are heavy.

It’s a very interesting ceiling treatment. How thick would you say the plaster is? And is there any flexing or deformation with pressure?
 

jespera

Well-Known Member
Jan 12, 2018
235
183
115
Copenhagen
Took me a while to notice the stereo. I like the shelves with three turntables and tube amps. The record storage units must be attached to the wall quite strongly because I imagine those are heavy.

It’s a very interesting ceiling treatment. How thick would you say the plaster is? And is there any flexing or deformation with pressure?

The plaster is very thin << 1mm. Its sprayed on and subsequently polished down to near nothing. Its a specialist job. Not cheap either. Around 200 usd per m^2..

The resulting surface is soft. So dont slap flies on it or touch it — you can easily make imprints. This means that you can only really use this type of treatment on the ceiling.
 
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jespera

Well-Known Member
Jan 12, 2018
235
183
115
Copenhagen
Very interesting! Do you think that wall-to-wall carpeting would have had a similar acoustic effect as your full-ceiling mineral wool treatment?

When we took over the house, the previous owner had left a thick carpet in the room. That reduced the echo compared to a completely bare room but it was still problematic.

Also after the house was renovated and we’d moved in, i had played with big pillows and rugs and installed thick curtains without much effect.

The mineral wool appears to be much more effective than carpets and rugs.

In fact, i noticed:

a. bare mineral wool is super effective
b. Its effectivenes is reduced quite a lot after the plaster is sprayed on. Say 50%.
c. but it comes back to say 80% when the plaster is polished.

There is a 40mm variant thats more effective. Panels that hang from the ceiling are even more effective but much less invisible.

Bare mineral wool is of course ugly and wify will notice. Shell probably also notice that it leaves an itchy dust. So you need the plaster.
 
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jespera

Well-Known Member
Jan 12, 2018
235
183
115
Copenhagen
Wow...great to know! Congrats! Will definitely keep this one in mind! Did you decide NOT to do the walls while you were doing the ceiling?

Apart from the practicalities that prevent doing the walls and my observations, see above, I think the room and the speaker placement may suggest that its the first ceiling reflection that is most problematic.

The ceiling is completely bare wheress there is stuff along the walls and on the floor.

But beyond that, the room is big and long, approx 5x9x3.2 m^3 and im playing it on the long end with the speakers relatively close to the lower corners.

So i think first wall and floor reflections have a shorter delay than the first ceiling reflection that in turn isnt long enough to be ignored. Speculations fwiw.
 
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PeterA

Well-Known Member
Dec 7, 2011
8,802
5,339
1,235
North Shore of Boston
Apart from the practicalities that prevent doing the walls and my observations, see above, I think the room and the speaker placement may suggest that its the first ceiling reflection that is most problematic.

The ceiling is completely bare wheress there is stuff along the walls and on the floor.

But beyond that, the room is big and long, approx 5x9x3.2 m^3 and im playing it on the long end with the speakers relatively close to the lower corners.

So i think first wall and floor reflections have a shorter delay than the first ceiling reflection that in turn isnt long enough to be ignored. Speculations fwiw.

It looks like your speakers are set up on the short wall. Have you ever tried locating the speakers on the long wall and listening in the near field? The ceiling and floor reflections would be the same, but first side wall would be very different and you would have the back wall behind your listening seat to cause issues, but I would be curious about the different sounds.

Do you know what frequencies are most affected by this ceiling treatment? I am also curious about the effect of a smooth polished plaster surface compared to a slightly more rough texture. I have an old rough thick horse hair plaster finish over lathe on my walls and a matched plaster finish over sheetrock on my ceiling. I always suspected that the slightly rough finish and mass of the thick plaster sounds different from the typical skim coat (or sparse joint compound) over sheetrock in most modern construction.
 

jespera

Well-Known Member
Jan 12, 2018
235
183
115
Copenhagen
It looks like your speakers are set up on the short wall. Have you ever tried locating the speakers on the long wall and listening in the near field? The ceiling and floor reflections would be the same, but first side wall would be very different and you would have the back wall behind your listening seat to cause issues, but I would be curious about the different sounds.

Do you know what frequencies are most affected by this ceiling treatment? I am also curious about the effect of a smooth polished plaster surface compared to a slightly more rough texture. I have an old rough thick horse hair plaster finish over lathe on my walls and a matched plaster finish over sheetrock on my ceiling. I always suspected that the slightly rough finish and mass of the thick plaster sounds different from the typical skim coat (or sparse joint compound) over sheetrock in most modern construction.

No never tried the other way around for any extended time.

Im quite sure that the treatment has very little effect for low frequencies, and only really works for say 200-400hz and upwards. Its possible that there are exact specifications from the producer for that.

In this case the plaster needs to be very thin to be acoustically transparent for the mineral wool to be effective.
But yes, materials with diffusive character are definitely advantageous to completely smooth psurfaces.

In our old flat we had high ceilings, stucco and great sound.
 

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Lagonda

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Feb 4, 2014
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No never tried the other way around for any extended time.

Im quite sure that the treatment has very little effect for low frequencies, and only really works for say 200-400hz and upwards. Its possible that there are exact specifications from the producer for that.

In this case the plaster needs to be very thin to be acoustically transparent for the mineral wool to be effective.
But yes, materials with diffusive character are definitely advantageous to completely smooth psurfaces.

In our old flat we had high ceilings, stucco and great sound.
And a very nice kitchen system ! :)
 

QuadDiffusor

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Apr 3, 2017
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Congratulations Jespera, for an innovative and inobtrusive flutter/slap echo solution! I hope you don't mind me saying this, but I'm concerned for you and your family's health. Rock wool and glass fiber insulation is extremely hazardous as a respiratory carcinogen, and my advice would be to have it removed ASAP. Be VERY careful, please.

 

jespera

Well-Known Member
Jan 12, 2018
235
183
115
Copenhagen
Congratulations Jespera, for an innovative and inobtrusive flutter/slap echo solution! I hope you don't mind me saying this, but I'm concerned for you and your family's health. Rock wool and glass fiber insulation is extremely hazardous as a respiratory carcinogen, and my advice would be to have it removed ASAP. Be VERY careful, please.


Thank you for your concern. But Im not worried.

Its not a homecooked solution but aprofessional product with all sorts of certifications and approvals.

 

AMR / iFi audio

Industry Expert
Aug 21, 2019
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Its not a homecooked solution but aprofessional product with all sorts of certifications and approvals.

Did you get this wool by yourself in some kind of specialized construction shop or was the material purchasing process arranged entirely by the specialist you hired?
 

Lagonda

VIP/Donor
Feb 4, 2014
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Interesting, i have a couple of tons of the stuf right under my roof, the roof is made of asbestos by the way ! Am i going to die soon ? :eek:
 

spiritofmusic

Well-Known Member
Jun 13, 2013
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E. England
'Fraid so Milan. And just before you secure those MBL monos as well.
 

Lagonda

VIP/Donor
Feb 4, 2014
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'Fraid so Milan. And just before you secure those MBL monos as well.
Yes that elusive second set of 9011's ! You can bury me in the traveling cases, they are just the right size ! :rolleyes:
 

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