Absorption coefficient /Density? -- RFZ panels

I asked him a few questions about the insulation I should choose and he told me that I shouldn't worry much about choosing the best product, since the differences in terms of real life efficiency will be minimal.

The absorption coefficients aren't just arbitrarily made up. They are real life measured phenomenon. To take what he is suggesting to the extreme, he is saying that if you hang a thin blanket on the wall, it won't sound much different than 4 feet thick of insulation. YES, use the proper material. I hope he consults his paying clients better than you. I suppose you are here shooting the $hit with us for a reason!

Also, today I was concerned about the 123Hz mode peak in my sweet spot. My friend suggested to move around the room and spot where it rings or disappears. I was surprised to hear it quieter in the corners of the room, though to be honest I couldn't reach the points where 3 surfaces meet (ie. wall/wall/ceiling). And that got me thinking... I mean, is there any chance - physics wise - that this - or any other - mode might not be affected by treating the corners ? And lastly, regarding the cloud, is there a good benefit of making it 8" thick rather than 4" ? I mean it is really meant for the 1st reflection mainly, not for the lower frequency modes, right? Or will it make a difference in the 123hz area also (assuming that it truly is an axial floor - ceiling mode) ?

Your room is an odd shape with a lot of furniture in it. Your modal response is damned near impossible to accurately predict. Low frequency response is best treated in the corners, period. You're never going to completely make any nodes/anti-nodes disappear, especially if just treating on your axial boundaries. Greg

The absorption coefficients aren't just arbitrarily made up. They are real life measured phenomenon.

I agree, but a method of measurement might demand covering of a whole huge wall for example, while we might use it for a 2' by 4' panel where other phenomena like diffraction might occur. I believe that this was his point.

he is saying that if you hang a thin blanket on the wall, it won't sound much different than 4 feet thick of insulation. YES, use the proper material.

No, by no means, no way! I'm afraid you are exaggerating. Our conversation was over choosing the right fibre product from the table I presented above. Nothing to do with blankets and definitely focusing on the thickness of my traps.

I hope he consults his paying clients better than you.

This is a bit unfair, so I feel I need to speak on behalf of him, since he can't do it himself. We've known each other since University and we meet every time I go to Cyprus or he comes to Greece. We are good friends. I asked him to help me in a 10 minutes skype call and he stayed for 49 minutes !There is no way he'd advise me differently than the way he would deal with this if it was his own project. He has worked for some time in Germany before starting his own business in Cyprus. As acoustic consultant in Cyprus he has dealt with numerous big projects that include luxury hotels and theaters. Along with his projects he is doing his distance learning post graduate in the Aristoteles University of Thessaloniki which according to the Webometrics Ranking of World Universities was included in the top 3% of the Universities of the planet https://www.iefimerida.gr/news/93528/%CF%80%CE%AD%CE%BD%CF%84%CE%B5-%CE%B5%CE%BB%CE%BB%CE%B7%CE%BD%CE%B9%CE%BA%CE%AC-%CE%B1%CE%B5%CE%B9-%CE%B1%CE%BD%CE%AC%CE%BC%CE%B5%CF%83%CE%B1-%CF%83%CF%84%CE%B1-%CE%BA%CE%B1%CE%BB%CF%8D%CF%84%CE%B5%CF%81%CE%B1-%CF%80%CE%B1%CE%BD%CE%B5%CF%80%CE%B9%CF%83%CF%84%CE%AE%CE%BC%CE%B9%CE%B1-%CF%84%CE%BF%CF%85-%CE%BA%CF%8C%CF%83%CE%BC%CE%BF%CF%85 (I know it's in Greek but with the help of Google translate it is readable :-) ) I certainly respect your point of view and take it seriously in account and of course I appreciate so much the fact that you are helping me with care with my little project. But it is true that in the music technology and Acoustics field there have been times that I realized specs don't always correspond to real life. To give a good example to that here is the link to the bobgolds.com absorption coefficients list we all certainly have got advise from when needed: https://www.bobgolds.com/AbsorptionCoefficients.htm The 3d line of the 2nd paragraph reads: "Differences in coefficients of less than 0.15 are not significant." Obviously this is exactly the point of my friend's advise. I mean if you look at the table I made, the different coefficients @125hz vary between 0,15 (Knauf Ultracoustic-p / Isover Piano) and 0,30 (Alpha Akoustiki izifon). That is exactly within the range of 0,15 deviance that bobgolds states as not significant. But apart from the cloud where I will definitely use the izifon, the latter won't be an option for the traps due to being too costy, so the variance of the absorption coefficients is really narrowed from 0,15 to 0,25 (isover ssp2) . That is a deviance of 0.10 which even smaller than the range of insignificance (0,15) that bobgolds is refering to. So, to conclude, , it seems that my friends advise makes sense according to bobgolds.com But of course that doesn't mean that you are wrong, in fact there has never been a question of who's wrong or right for me. I mean, like I said, I always take in account very seriously your advises, otherwise I wouldn't bother sketching up, uploading files, or writing huge posts like this one here :lol: . And to be honest, if I were to choose a product from equally expensive and of same gfr and density products I would definitely go for the one with the highest coefficient, no matter if within the 0,15 deviance in comparison to others.

I suppose you are here shooting the $hit with us for a reason!

Of course, there is no question about it! I believe I already answered that, I just would like to mention once again that there has never been a "who's wrong or right" issue and that I respect your sayings and appreciate your assistance very much! :D