More small panels vrs less large panels

[Arksun]

Can lots of smaller panels be as effective as single larger panels, or does the airgap between them (albeit small) affect their ability to absorb those lower frequencies?

I've attached little MSPaint pic to illustrate the point. Are singular uniform sections with no spacing at all that much more effective, or would both versions yield roughly similar results over same area and thickness?

[takman]

Well, kind of depends on the application...

but...

IMO...better to have one larger panel for most cases...also easier to build one larger panel then 3 small ones...

The plus to having 3 seperate panels is that you get cover a slightly larger area..good for say a 3 piece ceiling cloud....1 over one speaker, 1 over you and the other over the other speaker..and you can space them slightly to get the coverage you want...

the larger panel will absorb more...because with the 3 panels, you have account for the gap between the panels, and the framing for the panels themselves ( which wont be doing any absorbing of course)unless you are just wrapping them with no frame...which i dont suggest...

anyways..the difference between the two would be small...but still a difference nonetheless

[Arksun]

Originally Posted by takman

unless you are just wrapping them with no frame...which i dont suggest...

Aside from possible mounting issues, what other reasons are there that no-frames would be bad? If its stacked in free-standing corners it shouldn't be a problem I woulda thought (plus the added benefit of absorption across entire surface)

[aleatoric]

Originally Posted by Arksun

Aside from possible mounting issues, what other reasons are there that no-frames would be bad? If its stacked in free-standing corners it shouldn't be a problem I woulda thought (plus the added benefit of absorption across entire surface)

A frame is for aesthetics and mounting.

A properly wrapped 703 panel without a frame looks fine, it just lacks that razor sharp perfect 90 degree look of a framed panel.

Acoustically there is no real benefit either way. If there was a acoustical benefit though it would certainly lean towards "no frame" as a panel without a frame lacks any sort of hard surface.

[takman]

Originally Posted by Arksun

Aside from possible mounting issues, what other reasons are there that no-frames would be bad? If its stacked in free-standing corners it shouldn't be a problem I woulda thought (plus the added benefit of absorption across entire surface)

just mounting and asthetics.....i like the clean look a frame gives....plus without a frame its kinda floppy....The 50kg density i used, when propped up against a wall without a frame, was rigid enough to stay there...but it bowed in the middle a bit......just didnt look good...

but really...i dont think all these details add much to the overall differences in absorption..

with your drawing there...i think its going to be fine either way...just one would be more work than the other ( if you made a frame that is)

[Millo 3.1]

Originally Posted by SAC

The short answer is: Yes. The efficiency of a sound absorbing material can indeed be affected by its distribution and location.

And example would be 10 absorber panels, each 2ft x 2ft, when placed in a checkerboard pattern on a 80 ft^2 (8'x10') surface will absorb more acoustic energy per panel than a single 40 ft^2 (4'x10') uniform contiguous absorber positioned in the same 80 ft^2 surface area.

The increase in efficiency is due to the diffraction of energy around the perimeters of the spaced absorbers as well as the absorption of the energy by the increased area of the panel edges (if available). This is often referred to as the 'area effect'.

This is also the cause of the higher than expected absorption exhibited by reflective diffusors.

Wow, so you're saying that for broadening a sweet spot in one RFZ it is better to use two 2'x4's than make one 4'x4'? There go my plans... LOL!

[SaSi_SiDi]

In general, it is a better strategy to use more smaller panels than a single huge one or very few large ones.

A single, say, 24sqf panel covering exactly an area of 20sqf of wall compared to 3 panels with 2x4ft dimensions has the following differences:

1. The single panel provides a localized absorbtion area while the 3 separate panels can be expanded to cover a, say, 40sqf area. It has been tested (can't recall if I saw that in the realtraps or Gik site) that the expanded coverage is more effective.

2. The alternation of absorber / wall / absorber causes some sort of diffusion which benefits the room.

3. If the traps are "cleverly" made, i.e. no frame to the sides or large holes added to the sides for the panel to "breathe", this adds to the effective absorbing area. This detail by itself can become the most important difference and benefit of multiple panels if frames are properly executed, as it can add from 20 to 50% of additional area.

Regarding aesthetics, I will not put any comments as this has more to do with the craftsmanship and personal taste.

However, having just completed one of the two traps I am building for the front corners, I will say that large traps are pretty difficult to handle, build, and mount. I am building two traps with each having gross size of 9 x 3.5ft. The one that is finished (pics to be posted tomorrow) is huge, heavy and - I anticipate - a bitch to mount.

I am strongly considering to make the second one in smaller pieces, like 2x4 and stack them one on top of the other. That way I will be able to mount them by myself.

[Millo 3.1]

Originally Posted by SAC

As I am not exactly sure of your meaning, I will error on the side of caution and respond by saying "Not exactly".

Depending on exactly what you mean by replacing a 4'x4' panel with 2-2'x2' panels... I did not say that simply dividing a contiguous absorptive surface into a contiguous absorptive surface with a greater number of integral frames or panes will increase absorption.

Simply dividing an absorptive surface area into a many framed surface without alternating reflective (wall) surfaces will not have an appreciable effect.

The alternating area of absorption, integral edges and surface reflection create the additional effective absorption and interference phase patterns that result in greater net absorption.

Ron Sauro's continuing research into this is most welcomed!

And it gets even more interesting... as among other issues, shape also plays a factor with absorptive and diffusive panels - with rectangular panels exhibiting greater absorption than circular panels........

I was simply thinking of putting two 2"-thick, 2x4's side-by-side, held by a frame on the back, to treat first reflection points in my small room, effectively ending with a 4x4 on each side and the ceiling. What I seem to be able to gather from discussion is that the area on the side of the panels is more important than initially thought, and that might get better results from leaving a [wall] gap between the two 2x4's. My room is small and I'm not sure it's even possible to do so w/ the superchunk OR corner-straddlers I am planing to install, but if doing the separate 2x4's is so much better than joining them together in a 4x4, then I'll consider the option.

Thanks.

[Nordenstam]

Originally Posted by SAC

This has been suspected for quite some time, as (in particular), many diffusors which were constructed of highly reflective materials had exhibited much greater absorptive losses than the surface acoustical impedance suggested. Thus, obviously more factors were at play than simply that for which "absorptive coefficient" values could account.

According to this, tests in '94 and '00 showed that the primary source of the incidental absorptions observed in diffusers where due to flow of energy from wells in resonance to adjacent less energetic wells.

.. and welcome to the forum!


Andreas

[PaulP]

Originally Posted by Millo 3.1

I was simply thinking of putting two 2"-thick, 2x4's side-by-side, held by a frame on the back, to treat first reflection points in my small room, effectively ending with a 4x4 on each side and the ceiling. What I seem to be able to gather from discussion is that the area on the side of the panels is more important than initially thought, and that might get better results from leaving a [wall] gap between the two 2x4's.

I think absorbers for side reflections may be a slightly different matter.
Spaced absorbers may absorb more but what you're really worried about on
the sides is reflections than will conflict with the source. A space between
two panels could give you higher absorption and some diffusion but it may
also give you a reflection you don't want. The same would apply to the
first reflections on the ceiling and the floor. Anywhere else I don't see a
problem.

Paul P

[Millo 3.1]

Originally Posted by PaulP

I think absorbers for side reflections may be a slightly different matter.
Spaced absorbers may absorb more but what you're really worried about on
the sides is reflections than will conflict with the source. A space between
two panels could give you higher absorption and some diffusion but it may
also give you a reflection you don't want. The same would apply to the
first reflections on the ceiling and the floor. Anywhere else I don't see a
problem.

Paul P

a-ha! I had thought about that, even thought about NOT framing them with metal frames b/c of that reflection... I had thought about them for aesthetic purposes and for the ceiling cloud, for mounting purposes. To the experts: please be patient as I am absolutely ignorant on the matter (LOL!), trying to learn more. OK, it seems my plan for these reflection points are still valid. In terms of superchunks and the other low-freq absorbers I am thinking of building/preparing/assembling, my latest thoughts/plans include no or limited framing.


Thanks so much to everyone...

[Nordenstam]

Originally Posted by SAC

Else, how would one account for the greater then expected losses in diffusors made of reflective material?

See post number twelve. The primary absorption mechanism in diffusors is the movement of energy from wells in resonance to adjacent wells not in resonance. There's a lot of air movement back and forth across the boundaries. A normal wall structure will not have resonating wells next to non-resonating areas.

[Nordenstam]

Cool! The findings in the new studies seems to build on the previous work, not replacing it. The afformentioned movement between wells is good, but it doesn't explain why the air is absorbed when it moves back and forth across the well edges. Your explanation above seems to cater nicely for that part! Along with the usual boundary effects(increases with rought surfaces etc).

It still makes a diffuser a lot more effective at absorbing than a single edge in a room. There'll be more movement on the surface of a QRD due to the well resonances, compared to any normal corner construction in a room.

[Millo 3.1]

Originally Posted by SAC

Whoa!

So now you are worrying about edge reflections on CORNER mounted bass traps? Especially as the frame (if any) would be mounted flush and adjacent to the wall surface....

Be careful before making generalized conclusions! (And remember too that sound has 'size'.)

Superchunk bass traps are mounted into the corner such that the edges are against the wall...

So, at the risk of being a smart aleck, exactly how would these edge characteristics help you with Superchunk 'bass' absorbers?

And even if the edge was exposed, and not flush to the wall surface as in a corner bass trap, the edge of a 4' thick corner straddled trap would not offer ANY significant absorptive loss until the normal (90 degree) incident wavelength frequency was at or above 844 Hz! At 45 degrees, the effective frequency would be 598 Hz!

...And the absorptive losses are not the only. nor necessarily the primary, factor in the loss!

Else, how would one account for the greater then expected losses in diffusors made of reflective material?

In addition to increased absorptive surface area, the edge reflections create diffraction which act as a virtual source for out of phase reflections that combine (superpose) to create acoustic energy losses.

So the leap to eliminating a frame may NOT have the effect you desire!

Both absorptive and diffractive issues are at play here.

I fear the rush to overly simplify the total behavioral characteristics of a system to one factor while excluding other significant characteristics while also treating all applications as being the same may lead many to making very false conclusions.

Ok, thanks... I guess I expressed myself badly regarding the superchunks. Regarding the rest: interesting.