Can someone tell me if it's better to build first reflection panels, front wall panels, rear wall panels using 3" Rockwool or would it be better to double up and make them 6" thick? I will be placing these on stands so they stand off the walls a few inches and can be adjusted closer or further away. Also, would 3" or 6" ceiling cloud panels be better? The room is roughly a cube. 12' x 12' x 11' tall.
6" is better so long as you don't compromise on coverage. What I mean is don't make, say, 10 6" panels instead of 20 3" because the latter would probably be better. Whatever thickness you choose, a 1x gap is usually the best place to start.
I should just mention that, when using rigid, it's fine to go up to 8" thickness. Especially for a cube room, you absolutely can not go overboard with absorption. Just remember that, in addition to your up to 8" of rigid, you can fill that gap in with fluffy also; though I know you're making movable panels so this bit of advice might not apply.
Yeah, I agree with Hexspa (I usually do ) but I'll add my 2cents: So I think Hexspa's point about coverage over thickness is most important!
What thicker panels will do for you is to extend the low frequency effectiveness so the thicker the better as long as you don't skimp on coverage.
The thing about the gap or spacing the panels from the wall is that it also extends the LF effectiveness. It's like getting free absorber thickness by simply moving the absorber away from the wall. When the gap is equal the panel thickness, the theory is that the LF efficacy will extend one octave down. There is however a trade off when compared to alternately using a panel twice the thickness without a gap, but the advantage is relatively small, especially when you consider the cost is double.
So what ever thickness you choose, gapping whenever possible or practical, will always improve LF effectiveness. But you can take this gapping thing too far(?) if you go more than equal thickness. The result will be that in trying to achieve even lower LF absorption, you may create a "hole" or a loss in the absorptive frequency band between the normal panel (against the wall) and the lower end of the spaced panel.
(actually, there is really NO LF cuttoff and the LF absorption will actually extend to zero Hertz regardless of the thickness! BUT the amount of LF absorption can also be infinitesimal too. So yes, thicker is better and gapping is a good idea too. BTW, the above concept is not considered when you hear opposition to porous absorbers pointing out that you need 7 foot thick absorber to control 40 Hz. I remember Ethan saying that even a washcloth will absorb SOME LF... ha ha ha)
Now, having said that, there can be situations where you may want to target lower frequencies using larger gaps without regard to the "lost frequencies". This is where acoustic measurement will help you fine tune the placements of your panels. I believe Hexspa has done this so he hopefully can add to this if need be.
Yes, I've worked in some targeted treatment in this space. This happened partly by coincidence since I have a short wall of the hallway which acts as the kitchen wall. The width of the hallway perfectly coincided with 1/4 wavelength of the antinode that boundary was creating. It just so transpired to line up perfectly with my recording zone.
As far as randy's nearly cube room goes, 3' is going to be the optimal thickness of absorber. You can easily do 15" fluffy and gap it just over 1x and that'll help with that frequency. Since the room is cube, I wouldn't recommend solely rigid unless you absolutely can't afford to lose the floor space. You could also do 6-8" rigid in front of 24" of fluffy too. That might be even better than a straight 36" of fluffy.
Your advice on "The result will be that in trying to achieve even lower LF absorption, you may create a "hole" or a loss in the absorptive frequency band between the normal panel (against the wall) and the lower end of the spaced panel. " Is something I haven't heard before cause I am sure I have read that the larger the gap the more LF it absorbs.
So from your statement, am I right by saying the mid frequencies are the bad between the normal panel and the lower end of the spaced panel? I am a little confused here?
So, for the RFZ we don't need the gap any larger than the width of the panel itself? So if it is 10cm thick panel, we only space it at 10cm away from the wall? I am presuming it is important not to loose that band of frequencies in the RFZ compared to the back wall, while the back wall we could potentially aim for more LF absorbtion.
1. "The result will be that in trying to achieve even lower LF absorption, you may create a "hole" or a loss in the absorptive frequency band between the normal panel (against the wall) and the lower end of the spaced panel. " Is something I haven't heard before cause I am sure I have read that the larger the gap the more LF it absorbs.
"So from your statement, am I right by saying the mid frequencies are the bad between the normal panel and the lower end of the spaced panel? I am a little confused here?"
See page 55, there is a graph showing the response of and example of spacing.
2. "So, for the RFZ we don't need the gap any larger than the width of the panel itself?"
In general yes. But I should point out your RFZ panel is providing two functions. It's primary purpose is to absorb mid to high frequency reflections. A 2" panel mounted flush to the wall will achieve this. It's secondary function can serve to absorb lower frequencies to help control modal response and ringing the same as bass traps but because of placement and lack of foil, paper or plastic on the front, they are not as effective as corner mounted bass traps BUT DO help; especially in smaller near cubic shaped rooms.
The second function is the reason you want to use thicker panels and space them away from the wall. If you choose to space them more than the panel thickness, I would suggest experiment with measurements to see what spacing is optimum due to tradeoffs.
But seeing that I got 2 side panels in my RFZ the ceiling panel will provide more LF absorbtion if I have a larger gap.
I also have always wanted to ask, how to figure out how to know the cause or solution to dips and peaks in the frequency zone? Even bass suck outs, it seems there isn't a book handy which explains problems at a certain frequency. I have seen Hexpa and you explain quite a few of them with two concepts always being the same, more panels and panels at the spot where room modes occur.
My question is based on, is there any more solutions? If so perhaps a book that dissects all the frequency problems. And what is the best way to find out where room modes are?
Hexpa's comment below
"130Hz, C3, has the wavelength of your ceiling height. Your 460cm dimension is just 8Hz, or 68cm away from C2 (527.47cm). Whenever you have same and double dimensions, you're bound to have modal (antinode) buildup where they line up.
If you want to tame that range, treat those dimensions more - probably the ceiling is easier. Also, your 340cm dimension's 3/4 wavelength matches that of your 260cm ceiling. Therefore, you can treat that one a bit less in order to take advantage of the nulling effect at that frequency. I've done this in my room and it works."
Where can i study this phenomenon to understand better is there a write up anywhere? Or any more issues like these that occur that we need to understand?
I'm just glancing over this thread but I understand your question to be about SPL response at your listening position. To me, this is mostly about placement. Placement includes where your listening position itself, your speakers and your treatment, and even your room's dimensions.
There are many - perhaps thousands - of reflections of any given sound in a typical bedroom space. However, below the Schroeder Frequency, your room acts like a resonator - similar to blowing in a glass bottle - and it's less about reflections and more about standing waves. The combination of reflections, standing waves, and direct signal make up your SPL at any given point.
While there are a few orders of modes: axial, tangential and oblique, the axial modes are the primary movers of that squiggly line we obsess about. The knowledge of how to calculate these is widely available. You also need to analyze for speaker-boundary interference (speaker placement) and listener-boundary interference (stuff between you and the speakers or within about 10' from you). The sum of these two factors dictates, along with your room's dimensions, where to put your auxiliary treatment.
Long story short, you first measure the physical boundaries of your room. The more rectangular it is, the easier. From there, you predict peaks and nulls at the respective frequencies. Once everything is in but without treatment, take a measurement and see how you're faring. Begin installing treatment, measuring as you go. Once you've got a baseline installation established, measure again and see whether your predictions are manifest or if new surprises have popped up. Determine the cause of any problems using frequency-to-wavelength conversion minding that halves and wholes create peaks and odd quarters create nulls. It's really not that hard once you do it a few times. Just make sure to think it through. I'm not sure where you can learn this since I just started doing it here based on the information I picked up and a desire to optimize the value of my resources. I'll be making more videos on these topics so I'll let you know when it's up.