• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Do you think this Comsol simulation result of Bass Trap make sense?

NTK

Major Contributor
Forum Donor
Joined
Aug 11, 2019
Messages
2,657
Likes
5,820
Location
US East
Back for one more post.

The biggest benefit of simulations is that you can run lots of cases. Regardless of whether you have setup your sim correctly to give correct results, you can still try many different things to see how they affect the response. Try simulate bigger (or smaller) bass traps, put them in different places inside the room, try other rooms of different size, see how they response. One important thing people want from these analyses is to discover the trends (parametric analyses).

Theory says the most effective location for dissipative bass traps is where pressure response is minimum (i.e. the nulls), which gives velocity maximum. Try put some bass traps there and see if your sim gives a reasonably corresponding response.
 

raindance

Major Contributor
Joined
Sep 25, 2019
Messages
1,037
Likes
968
In my experience, floor to ceiling GIK soffit bass traps (recommended by GIK) in my room at the front wall left/right corners had almost no impact on the frequency I was trying to treat (46 Hz), but they evened out the mid bass and upper bass response. I don't have measurements to share, but they showed little, if any, impact on measured response at the listening position below 100 Hz except that the 46 Hz standing wave decay time was reduced in the spectrogram.

In short, low bass is challenging to fix unless you use some kind of resonant membrane / Helmholtz resonator / equalizer.

In the end, I disconnected the subwoofers so as not to excite the 46Hz mode as much because I found music more musically satisfying with the evened out mid to upper bass region.
 
OP
MengW

MengW

Member
Joined
Jun 30, 2022
Messages
63
Likes
44
In my experience, floor to ceiling GIK soffit bass traps (recommended by GIK) in my room at the front wall left/right corners had almost no impact on the frequency I was trying to treat (46 Hz), but they evened out the mid bass and upper bass response. I don't have measurements to share, but they showed little, if any, impact on measured response at the listening position below 100 Hz except that the 46 Hz standing wave decay time was reduced in the spectrogram.

In short, low bass is challenging to fix unless you use some kind of resonant membrane / Helmholtz resonator / equalizer.

In the end, I disconnected the subwoofers so as not to excite the 46Hz mode as much because I found music more musically satisfying with the evened out mid to upper bass region.
Thanks for your inputs.

I have been using AVAA for three years. The effect is still very satisfactory, except for the price.

It works for 15~150 Hz with surface of R0.2m x 0.5m 1/4 cylinder at 120 Pa*s/m specific acoustic impedance.

When turn on the power switch of AVAAs, the world is quiet.

50Hz decay about -15dB in 50ms, and decay to -30dB about 150ms.

1680193611374.png


1680194221940.png
 

alex-z

Addicted to Fun and Learning
Joined
Feb 19, 2021
Messages
910
Likes
1,685
Location
Canada
but from this simulation results, it is only effective above 110Hz.
That is due to positioning and surface area, the trap itself will be capable of moderate absorption in the 60-80Hz range. Speaking from practical experience using 11" mineral wool corner traps.

If you extend the same trap to cover an entire wall, but with 30cm thickness and 30cm air gap, the simulations hould look better.

I do a fair amount of home theatre consulting and absorbing deep bass is just not practical unless the owner is willing to give up 2ft of usable space. Multiple subs are a better solution, unless the room usage includes live recording of drums and bass guitar.
 

fluid

Addicted to Fun and Learning
Joined
Apr 19, 2021
Messages
691
Likes
1,196
I have never used COMSOL and don't have access to know how it works, but in reality a porous absorber is affected by gas flow resistivity and depth of the material, the thicker the material the lower in frequency the effect can be had. With the right combination of GFR and depth theoretically any frequency can be absorbed but it gets big for low frequencies. 80 Hz is a struggle for most practical setups outside of big studios. Air gaps work too. Porous absorbers are velocity devices and as such work better away from walls, they still work straddled over corners but the distance away from the wall limits things. I have two I made myself and use them over the front corners of my room, they certainly work to some extent.
 
Top Bottom