Best way to absorb below 100Hz

[Glenn Kuras]

Broadband will work but you could always go with something tuned.
GIK or Realtraps?

Understanding Different Bass Trapping - GIK Acoustics

[John White]

Using any absorber may affect the "as good as it gets" part. Using a porous absorber of any resistance will significantly affect the overall response/decay times unless a NE style room (which is unlikely).

There are some great threads that may help you here which discuss Helmholtz / Pressure Based absorbers. These types of absorbers or even some kind of hybrid may have less of an impact on the decay times above 100Hz.

[DanDan]

A deep fibre back wall with a layer of wood laths in front would work well and look good. Use Newells 543 pattern or boggy's numbers for the laths/gaps.
This is easy to do, cheap, guaranteed to work well.
There are more space efficient Bass traps which are not critically tuned, i.e. safe for DIY. If you can get hold of the correct materials, i.e. Caruso Isobond and Steel, then the VPR design is worth considering.
Perforated Panel with Porous Absorber trap
DD

[Protone]

Thanks guys, all very informative replies! I´ll check those links.

[Protone]

Hi!

after doing some research I decided to go with insulation covered with wood laths, like DanDan suggested.

I just have one question about the insulation. There are no air flow resistivity specs available for most of the insulation products here in Finland, so I´m not sure what to get.

Most "fluffy" one I have found so far is Isover KL37. I think it´s 14kg/m3. The other one I already happen to have is Paroc Extra, 30kg/m3. But I don´t know how that diffence effects the air flow resistivity, and the absorbtion charasteristics of my 400mm thick wall.

So the question is, is 14kg/m3 noticeably better below 100Hz than 30kg/m3, when the thickness of the wall is 400mm (16")?

[Mctwins]

Originally Posted by Protone

Hi!

after doing some research I decided to go with insulation covered with wood laths, like DanDan suggested.

I just have one question about the insulation. There are no air flow resistivity specs available for most of the insulation products here in Finland, so I´m not sure what to get.

Most "fluffy" one I have found so far is Isover KL37. I think it´s 14kg/m3. The other one I already happen to have is Paroc Extra, 30kg/m3. But I don´t know how that diffence effects the air flow resistivity, and the absorbtion charasteristics of my 400mm thick wall.

So the question is, is 14kg/m3 noticeably better below 100Hz than 30kg/m3, when the thickness of the wall is 400mm (16")?

Don't forget to show before and after measurement when choosing the treatment. If there isin't any changes then it don't work.

Without any measurements we can only guess!

[DanDan]

Protone, you may be able to find an equivalent or something to make a better guess with here.
Common Gas Flow Resistivity numbers.
DD