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Massive bass reverberation

NTK

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You can try DIY the BBC very low frequency modular absorbers. I've also included a link to their broadband design.


Below is the low frequency absorber design, and its measured absorption coefficients (from page 10 of the BBC report).
bbc_1.jpg
 

bpb

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I've had quite a bit of success with room treatments from following the guidance at acousticinsider.com.

You could check out videos such as this -

The over-simplified summary seems to be to add as much absorption material as the room (and aesthetics) will allow!

I think Jesco at acousticinsider.com would consider 10cm panels on the thin side.
 
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Matias

Matias

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I've had quite a bit of success with room treatments from following the guidance at acousticinsider.com.

You could check out videos such as this -

The over-simplified summary seems to be to add as much absorption material as the room (and aesthetics) will allow!

I think Jesco at acousticinsider.com would consider 10cm panels on the thin side.
I have read all he published and watched all his videos. Great guy!
 
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Matias

Matias

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Besides that, congrats on the room. I'm envious of your current set of problems.
Thanks. I thought I would be in heaven but this room is actually a lot worst in the acoustics side than my previous living room... But I will get there, eventually.
 

caught gesture

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For a good overview of all problems in your room (if you not already aware). I think that you are going to need more of those “fridges” floor to ceiling in all four corners at least. 41.33 Hz (E1) is going to require some depth of treatment to tame. 40Hz is a wavelength of 28.25 ft or 8.6m!

The lower the problem frequency the more material thickness you need because the thickness must be at least 1/4 of the half wave-length to achieve an absorption effect (also considering the effectiveness due to the flow rate/density of the material used to try and achieve as near to absorption rate of 1.0 as possible). The panels you have mounted on the wall could also be easily improved by just mounting them on a bracket to leave an air space behind them. That improves their efficiency at little extra cost.
 
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ppataki

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No, not yet. Below the measurement if it helps.


I already think those panels are think and heavy, making them thicker still would be hard. Plus the expense of wasting them and ordering new ones. I would prefer to add stuff than replace right now.
@Matias
Might be a bit off-topic but just for fun I have created some filters for you based on your measurements to completely flatten your frequency response
See below your measurement file + the wave file I have generated (you can use a convolver to try it)
I see in the simulated spectrogram curve that low frequency post-ringing will be significantly reduced, hence it might be worth a try
If you want to elevate the lows and lower the highs you can use some shelf filters accordingly on top of the convolver
Regarding the convolver, I personally prefer Convology XT (just make sure to enable "Normalize" + set the Mix knob to 100%)

 
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Matias

Matias

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The panels you have mounted on the wall could also be easily improved by just mounting them on a bracket to leave an air space behind them. That improves their efficiency at little extra cost.
That is something I can easily try. What kind of bracket would that be? Could you send a picture?

My panels are currently mounted with hardware like those below, used in frames, and screws with washers in the wall.

D_NQ_NP_2X_995627-MLB31645878570_072019-F~2.jpg


Edit:
For a good overview of all problems in your room (if you not already aware).
I know of the amcoustics.com website, great tools. Now that I remembered that spacing the panels would not get near the trouble area. Below I simulated a panel with no gap, 5 cm, 10 cm and even going crazy 20 cm away from the wall. It would not be effective, at least in simulation.

0 gap.jpg
5 gap.jpg
10 gap.jpg
20 gap.jpg


And even making them extra thick 20 cm still far away from my trouble area.

20 thick.jpg


As a rookie with panels, my conclusion playing around with simulation is that they are not the solution for my 40 Hz bass problem.
 
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Matias

Matias

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I just added an updated render of the room in the 1st post. I was designing it with Homestyler.com before the build, and just updated it with the panels, fridges and rug. I am quite proud of this render project, not bad for a noob. :)
 
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Curvature

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For a good overview of all problems in your room (if you not already aware). I think that you are going to need more of those “fridges” floor to ceiling in all four corners at least. 41.33 Hz (E1) is going to require some depth of treatment to tame.
Right. Because you see those in every professional installation.

This is not how low end control is done.
 

caught gesture

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Right. Because you see those in every professional installation.

This is not how low end control is done.
How would you do it? Limp mass membrane, tuned Helmholtz resonator, or something else? I’ve seen plenty of control room builds documented where masses of rock wall is hidden behind false walls in order to control low end. I’m interested in your take on the problem.
 

Thomas_A

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You should aim for panels covered with perforated boards to tame down to 100 Hz. Below 100 Hz use several subs and EQ.
 

caught gesture

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That is something I can easily try. What kind of bracket would that be? Could you send a picture?

My panels are currently mounted with hardware like those below, used in frames, and screws with washers in the wall.

View attachment 231469

Edit:

I know of the amcoustics.com website, great tools. Now that I remembered that spacing the panels would not get near the trouble area. Below I simulated a panel with no gap, 5 cm, 10 cm and even going crazy 20 cm away from the wall. It would not be effective, at least in simulation.

View attachment 231471View attachment 231472View attachment 231473View attachment 231474

And even making them extra thick 20 cm still far away from my trouble area.

View attachment 231475

As a rookie with panels, my conclusion playing around with simulation is that they are not the solution for my 40 Hz bass problem.
You are right, of course. They will not address the 40 Hz issue but there are other room mode issues above 100Hz, some close together, where it might help.

When I constructed my listening room, I made all my panels, cloud, bass traps, etc. For mounting the panels away from the wall I used something like
1663417330261.png

I’m sure you could come up with a more elegant solution. There are plenty of differing lengths of hooks and fixings which can be inserted into a strip of wood screwed to the back of the panel which can get your panel away from the wall.
 
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Matias

Matias

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You should aim for panels covered with perforated boards to tame down to 100 Hz. Below 100 Hz use several subs and EQ.
Subs extend and distribute bass, and EQ I already use. Both do nothing to absorb long decays.
 

Curvature

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How would you do it? Limp mass membrane, tuned Helmholtz resonator, or something else? I’ve seen plenty of control room builds documented where masses of rock wall is hidden behind false walls in order to control low end. I’m interested in your take on the problem.
Helmholt resonators could have been installed into the walls before construction. It would bd incovenient now.

I think large tuned diaphragms would do good work. Modex series by RPG, for example. No more broadband absorption needs to be applied.
 

DJBonoBobo

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@Matias

This is what your measurements look like when using var smoothing:

1663418696169.png


No wonder it sounds boomy still, don´t you think? I suggest using var smoothing and higher Q-values for bass EQ and focus on reducing the most offensive peaks. Those are still very high after your current EQ. Also, i think you pushed the upper bass too hard with EQ and i highly recommend trying better positions for your speakers and/or listening position. I would focus on smoothing out the 70-300Hz region first with better positions, as good as it gets. Then cutting the peaks with EQ. At last tuning the treble to taste with low Q filters.
 

caught gesture

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Helmholt resonators could have been installed into the walls before construction. It would bd incovenient now.

I think large tuned diaphragms would do good work. Modex series by RPG, for example. No more broadband absorption needs to be applied.
You are right. I remember reading about the Frauenhofer VPR which the modex series seems to be based on. This was after I had constructed massively thick bass traps and I kicked myself at the time for not investigating a DIY version to build instead. A steel plate sandwiched between two sheets of CIB. The components are expensive but the results excellent. Good call!

Edit: I found the construction details of materials needed if DIY is appealing. Others on this thread might be able to add more detail or advice on construction (although it looks very straightforward. The Caruso-ISO-Bond comes with adhesive on one face I think so maybe the elastic adhesive might not be needed).


Modex Plate (150cm x 100cm)

galvanized steel plate 1mm to 2,5 mm
-----------------------------------
Elastic Adhesive
-----------------------------------
CIB - 100 mm thick WLG 035



Modex Broadband (150cm x 100cm)

Front Cover (perforated metal or wood, even fabric may work with some braces)
-----------------------------------
CIB - 30mm to 50 mm thick WLG 035
-----------------------------------
Elastic Adhesive (I've read Sika Bond T2 was sucessfully used a couple of times)
-----------------------------------
galvanized steel plate 1mm to 2,5 mm (a little smaller than the CIB eg. 140cm x 90cm or 145cm x 95 cm)
-----------------------------------
Elastic Adhesive
-----------------------------------
CIB - 70mm to 100 mm thick WLG 035
 
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dasdoing

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better look at spectogram or waterfall

anyways, the first room mode is terrible in smaller rooms. and it can only be cured with a thick absorbtion at the backwall....with thick absorbtion calling for lower density material
 

DJBonoBobo

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From @Matias mDat: Spectrogram without EQ:
1663419177531.png


With EQ:
1663419198986.png
 
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