Absorption coefficient /Density? -- RFZ panels

How to use REW, What is a Bass Trap, a diffuser, the speed of sound, etc.

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musictracer
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Location: Macedonia, Greece

Re: Absorption coefficient /Density? -- RFZ panels

Post by musictracer »

The rar has no files to extract :(
I can download, extract and view it fine! Are you sure you followed the steps correctly?
instructions.jpg
That would make a huge difference!
It certainly does make some difference. I mean, it's a small room but I definitely can hear it sounding different in the absence of the carpet indeed.
I would suggest just leaving the fabric framing until the end when you've got the room tuned to your liking. Then build the accordingly.
Well, I would prefer to be a bit prepared by making room in case I need to add reflective surfaces. Otherwise I will need to remove a bit of insulation to fit them in. But maybe doing so would be fine if that's what you meant in the first place.
I realized we don't have any SketchUp or real pictures for your room. Care to share something?
There is a link to the sketchup file in the first post you replied to in this thread, but maybe you missed it :-). It is this one : https://files.fm/u/dx6hc5z5
Gregwor
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Re: Absorption coefficient /Density? -- RFZ panels

Post by Gregwor »

I can download, extract and view it fine! Are you sure you followed the steps correctly?
I've done this countless times in my life. This one doesn't extract anything.
Well, I would prefer to be a bit prepared by making room in case I need to add reflective surfaces. Otherwise I will need to remove a bit of insulation to fit them in. But maybe doing so would be fine if that's what you meant in the first place.
You could build your fabric frames using 1x2 framing. Worst case, you could just use more 1 by lumber as your slats. Plastic would work alright too. Thicker (still thin of course) plastic sheeting that has some density to it would work fine as well for reflecting high frequencies. It's really the width of the material that is going to determine the frequencies that it affects.
There is a link to the sketchup file in the first post you replied to in this thread, but maybe you missed it :-). It is this one
I have bad luck with your files man! This one also downloads as a rar that won't extract either! Seriously, I can't recall any linked files from anyone on this forum that I can't extract! Care to post some exported 2D pictures of your SketchUp for us? Sorry!!!

Greg
It appears that you've made the mistake most people do. You started building without consulting this forum.
musictracer
Posts: 28
Joined: Fri Feb 13, 2015 10:21 am
Location: Macedonia, Greece

Re: Absorption coefficient /Density? -- RFZ panels

Post by musictracer »

I have bad luck with your files man!
Here is a link with both files uncompressed in case you need them:
https://files.fm/u/8zurpv4q

Care to post some exported 2D pictures of your SketchUp for us? Sorry!!!
No prob!
1. left side.jpg
2. over back left side.jpg
3. above .jpg
4. over back right side.jpg
5. over front right side.jpg
6. over front left side.jpg
I know you requested 2D, but it is really hard to print them in a usable way in such a small space. I hope these help :-) .
Each trap is meant for one front corner.
You could build your fabric frames using 1x2 framing.
Maybe I get it wrong but you mean to make an extra frame for the fabric upon construction? That would increase the cost of money and time to get it. But to be honest the thing that concerns me the most is that I won't be making these on my own, but with the help of someone that has pretty little time, so it will be hard to get him dealing with my project again upon construction, this is why I insisted in prediction before construction.
Worst case, you could just use more 1 by lumber as your slats.
I don't get your point, sorry. Unless you mean to use leftover lumber as slats, is that right ?
Gregwor
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Re: Absorption coefficient /Density? -- RFZ panels

Post by Gregwor »

You sure are making your space work! It's cramped but I'm stoked that you're making music in there!
I know you requested 2D, but it is really hard to print them in a usable way in such a small space. I hope these help :-) .
It gives me a great idea of what you're dealing with! Thank you!

That big shelving unit may making your room sound great tricky though :?
Maybe I get it wrong but you mean to make an extra frame for the fabric upon construction?
Yes. That's what I was suggesting. If that's not possible, then just wait to put fabric on. You can quite easily experiment with strips of plastic (imagine vapour barrier for example) on your insulation. Once you get the room tuned to your liking with the plastic, you can easily add fabric yourself. All it takes is scissors and a staple gun! You won't need any special wood working tools or help doing that.
I don't get your point, sorry. Unless you mean to use leftover lumber as slats, is that right ?
Ignore this suggestion as it won't work for you. I thought you'd be doing the wood work yourself :thu:

Greg
It appears that you've made the mistake most people do. You started building without consulting this forum.
musictracer
Posts: 28
Joined: Fri Feb 13, 2015 10:21 am
Location: Macedonia, Greece

Re: Absorption coefficient /Density? -- RFZ panels

Post by musictracer »

You sure are making your space work! It's cramped but I'm stoked that you're making music in there!
Your words are quite encouraging, thank you! I've been dreaming of an acoustically balanced room for many years now... Hopefully I can get at least pretty close to it in there. :-)
That big shelving unit may making your room sound great tricky though
Well, I definitely have stereo imaging issues due to lack of symmetry, if that's what you mean, but I can't figure out how to resolve this in this space with this furniture.That being said, this unit is a bookshelf and I believe it kind of helps with diffusion ( or should I better say "scattering" in this situation).
Yes. That's what I was suggesting. If that's not possible, then just wait to put fabric on.
Yes, of course, I mentioned that before but maybe I didn't make it clear enough. My plan is to make the front fabric of the traps removable anyways , so that I can "edit" the panel if I want, ie. for replacing the insulation, or adding reflecting surface underneath. The fabric will be attached on the front wood frame by using velcro tape. One side of the velcro will be stapled on the front face wood frame of the trap, while the other will be sewed on the edge all around the fabric. I think it's the most convenient way.
imagine vapour barrier for example on your insulation
I googled that, and it seems to me it won't be hard to attach! I mean it looks pretty thin and light. I guess it works only for the high frequencies though, but maybe that's all I might need, don't know...
I'll keep that in mind, thanks for pointing out! :-)

Also, I had a talk with my dear old university mate who now owns his own acoustic consulting company in Cyprus. 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. Is that really the case, or do you think I should go for 7000 mks rayls like Stuart proposed in the first place - also in accordance to the porous absorber calculator?

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) ?
Gregwor
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Re: Absorption coefficient /Density? -- RFZ panels

Post by Gregwor »

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
It appears that you've made the mistake most people do. You started building without consulting this forum.
musictracer
Posts: 28
Joined: Fri Feb 13, 2015 10:21 am
Location: Macedonia, Greece

Re: Absorption coefficient /Density? -- RFZ panels

Post by musictracer »

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/%C ... E%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
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