Quick question about mid and high absorbers

[Danny_79]

Hi all! I own a couple of these: https://www.thomann.de/se/the_t.akustik ... r_grey.htm I don't know how to upload photos here so i put a link there instead. Anyway, they're meant to go directly on the wall, they have clips which go in to other clips in the wall. But, could it be that they should have some gap to the wall like wall bass traps should have? I am not sure. Thanx in advance!

[Sam Spoons]

Spacing them away from the wall by up to 100mm (in the case of these panels) will lower the lowest frequency the panel will absorb so if you have the space and the skills then go for it.

[Hugh Robjohns]

Clearly they are designed to fix directly to a surface... but you could make that surface a small distance away from the wall, if you wanted, perhaps by fixing some timber strips to the wall, and then the panel to the strips.

As a general rule, acoustic absorbers are more effective, and have more efficiency to a lower frequency, if they are spaced from the wall by an amount equal to their own depth. So, a 2-inch thick panel should be 2-ibches from the wall... a foyr-inch panel four inches, etc, etc...

[PedroTheThird]

Calculate the wavelength of the lowest frequency you want to absorb. Divide it by four. This is the point where particle velocity is the highest and where simple porous absorbers perform the best (for that frequency and up).

[Philbo King]

I screwed 3 wood blocks to the back of my absorbers (rigid fiberglass in a wood frame wrapped in muslin). The blocks worked to space the panel away form the wall. That allowed me to put screwhooks into the block on each side so I could string picture hook wire across, to hang it with.

[PedroTheThird]

How much space did you use?

[Danny_79]

How much space did you use?

If i attach them directly to the wall the way they are designed, then it's about 2 mm or something

[PedroTheThird]

That's way too close. Based on the manufacterer's data (Deepest frequency: About 315 Hz) I would recommend a spacing of 22 cm.

[PedroTheThird]

Apologies, I made a mistake by confusing the numbers on the website. Though the correct distance to the wall is not that far off, just about 2 cm less (= 20 cm) if you decide to go with SOS' recommendation regarding minimum absorber depth (A tenth of the wavelength of the lowest frequency you wants to absorb properly). This should give you a good performance down to 350 Hz and some performance at lower frequencies.

How to calculate spacing:
f, Frequency (Lowest frequency you want the absorber to perform properly at, in Hz)
λ, Wavelength (of that frequency, in m)
v, Particle velocity maximum (λ/4, in m)
c, Speed of sound (About 343,4 m/s at 20⁰ C)
d, Absorber depth (in m)
s, Spacing between absorber and reflective surface (also in m)

λ=c/f
v=λ/4
s=v-d/2

[Danny_79]

Apologies, I made a mistake by confusing the numbers on the website. Though the correct distance to the wall is not that far off, just about 2 cm less (= 20 cm) if you decide to go with SOS' recommendation regarding minimum absorber depth (A tenth of the wavelength of the lowest frequency you wants to absorb properly). This should give you a good performance down to 350 Hz and some performance at lower frequencies.

How to calculate spacing:
f, Frequency (Lowest frequency you want the absorber to perform properly at, in Hz)
λ, Wavelength (of that frequency, in m)
v, Particle velocity maximum (λ/4, in m)
c, Speed of sound (About 343,4 m/s at 20⁰ C)
d, Absorber depth (in m)
s, Spacing between absorber and reflective surface (also in m)

λ=c/f
v=λ/4
s=v-d/2

No worries For the time beeing, that seems way to complicated but i am tired

[Drew Stephenson]

Some pictures might help? https://imgur.com/gallery/acoustic-treatment-he7dtDM

[PedroTheThird]

Some pictures might help?

You're right. Here's another one:

[Drew Stephenson]

Yeah, that's a much better one.

[Danny_79]

Some pictures might help?

You're right. Here's another one:

Yeap, it sure makes it easier