Troublesome 50Hz, 100Hz

lscangus

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Oct 24, 2018
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The corner bass traps that you can d.i.y. would be better if they are deep enough. They would not only address the two dips you have, they would also be working wide-band throughout your bass and mid-bass and will also shorten the decay time of the bass frequencies better than these resonators. They would also be cheaper as you will need a few of those resonators. Keep that in mind!
Totally understood. I wonder if it is possible by looking at the graph, to estimate how many of these resonator i need?
 

kodomo

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Apr 26, 2017
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Very easy to build. Just two 50x50mm from floor to ceiling. Then angle cut lateral ones to hold the earthwool. The cover with fabric as you like. Fill with knauf 044 ecosse earthwool.
 

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kodomo

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here it is in 3d, your carpenter can figure it out easily... If you like, make the lateral ones 10mm shallower and you can make a kind of front grill that can easily be put on and off and is easy to cover. If this is not comprehensible, I can draw that for you too.
 

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kodomo

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Think of this like a speaker grill. You have the grill with its frame and fabric and it will cover the trap. You can use anything you like, you can even make it magnetic attachment.
 

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lscangus

Industry Expert
Oct 24, 2018
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Very easy to build. Just two 50x50mm from floor to ceiling. Then angle cut lateral ones to hold the earthwool. The cover with fabric as you like. Fill with knauf 044 ecosse earthwool.

Hi Kodomo,

thank you so much for the detailed drawings. I wonder if the 80cm is a must? Whats the relationship of the depth to the desired bass response? Many thanks!
 

kodomo

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Hi Kodomo,

thank you so much for the detailed drawings. I wonder if the 80cm is a must? Whats the relationship of the depth to the desired bass response? Many thanks!

As a rule of thumb for porous absorbers, its thickness has to be at least 10th of the wavelength to be effective. I made your basstrap 80cm on the sides, so it reached 56cm depth. This would mean it will be effective down to 53hz as 53hz has a wavelength of 5.6meters and 1/10th of 5.6meters is 56cm.

Unless you have an active solution or a resonating membrane this is the actual thickness you need. The active solutions and resonating membranes are for targeting specific frequencies. The bass trap I have suggested would be fully effective down to 56hz. It will also be effective up until your upper midrange but as the corners have more bass accumulation, it will be most effective on those frequencies. Keep in mind it will be effective below 56hz too, not as much but still a lot more than those resonators.

As you have a measurement system, check the decay times. Here is mine, uniform at 0,4ms from bass to treble;
 

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lscangus

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As a rule of thumb for porous absorbers, its thickness has to be at least 10th of the wavelength to be effective. I made your basstrap 80cm on the sides, so it reached 56cm depth. This would mean it will be effective down to 53hz as 53hz has a wavelength of 5.6meters and 1/10th of 5.6meters is 56cm.

Unless you have an active solution or a resonating membrane this is the actual thickness you need. The active solutions and resonating membranes are for targeting specific frequencies. The bass trap I have suggested would be fully effective down to 56hz. It will also be effective up until your upper midrange but as the corners have more bass accumulation, it will be most effective on those frequencies. Keep in mind it will be effective below 56hz too, not as much but still a lot more than those resonators.

As you have a measurement system, check the decay times. Here is mine, uniform at 0,4ms from bass to treble;

Fantastic, what software you use to test the decay?
 

kodomo

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This screenshot is from REW and the it is taken via a calibrated umik1 at listening point.
 

lscangus

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Oct 24, 2018
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This screenshot is from REW and the it is taken via a calibrated umik1 at listening point.

Hi Kodomo! Thank you so much for all of the replies. I have now starting to source the needed materials for the bass trap. The material you have suggested is not available in Hong Kong, but i found a similar alternative like this one:

https://cdn01.rockwoolasia.com/site...thermalrock-s-data-sheet.pdf?f=20181204223136

What do you think? What sort of density are we looking at? the density varies alot. The higher the density the higher the absorption rate?
 
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kodomo

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Hi Kodomo! Thank you so much for all of the replies. I have now starting to source the needed materials for the bass trap. The material you have suggested is not available in Hong Kong, but i found a similar alternative like this one:

https://cdn01.rockwoolasia.com/site...thermalrock-s-data-sheet.pdf?f=20181204223136

What do you think? What sort of density are we looking at? the density varies alot. The higher the density the higher the absorption rate?

Higher density is good if your panels are shallow like 10cm or 20cm. When panel gets thicker than 30cm, it is better to go for lower density. For your basstraps with the dimensions I suggested, you would better use 40kg/m3 rockwool.
 

lscangus

Industry Expert
Oct 24, 2018
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Higher density is good if your panels are shallow like 10cm or 20cm. When panel gets thicker than 30cm, it is better to go for lower density. For your basstraps with the dimensions I suggested, you would better use 40kg/m3 rockwool.

Do i have to fill in the whole bass trap with the materials? If so, is higher the density the better?
 

kodomo

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Apr 26, 2017
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Fill the whole bass trap with lower density earth wool.

Contrary to direct logic, the higher density is not better for absorbing bass, lower density and depth together is what you need. This is common practice in recording studios, its variations are often called a super chunk bass trap.

Thinking higher density is better for absorption and using too much is also one of the reasons people do not like the sound of absorbers in their rooms. They use high density materials and end up loosing more mid and treble then they like. They blame the absorbers and end up thinking acoustic treatments make the sound flat and lifeless, but the reason was actually wrong application of absorbers.

If you have further question maybe pm would be better. This has become a conversation and maybe it is better to continue that way :)
 

christoph

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Dec 12, 2015
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Fill the whole bass trap with lower density earth wool.

Contrary to direct logic, the higher density is not better for absorbing bass, lower density and depth together is what you need. This is common practice in recording studios, its variations are often called a super chunk bass trap.

Thinking higher density is better for absorption and using too much is also one of the reasons people do not like the sound of absorbers in their rooms. They use high density materials and end up loosing more mid and treble then they like. They blame the absorbers and end up thinking acoustic treatments make the sound flat and lifeless, but the reason was actually wrong application of absorbers.

If you have further question maybe pm would be better. This has become a conversation and maybe it is better to continue that way :)
Please not via PM, I'm very interested in this topic
 

Hipper

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Jun 12, 2011
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I can't help thinking, as was mentioned earlier, that before going down the room treatment route - and I use lots of room treatment including bass traps and am fully in favour of you doing the same - you should make a real effort with positioning if you haven't already done so.

You seem to have a dedicated room and one of the big plusses is that you can do what you like regardless of what it looks like. Take advantage of that! I use this:

http://www.barrydiamentaudio.com/monitoring.htm

It works well for me. It's not perfect by any means and moving to correct one thing will cause problems in other areas, but if you can move the problem frequencies higher up the spectrum, they will be easier to deal with.

Also check this node calculator out:

https://amcoustics.com/tools/amroc

It works pretty well with a standard rectangular room.
 

lscangus

Industry Expert
Oct 24, 2018
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I can't help thinking, as was mentioned earlier, that before going down the room treatment route - and I use lots of room treatment including bass traps and am fully in favour of you doing the same - you should make a real effort with positioning if you haven't already done so.

You seem to have a dedicated room and one of the big plusses is that you can do what you like regardless of what it looks like. Take advantage of that! I use this:

http://www.barrydiamentaudio.com/monitoring.htm

It works well for me. It's not perfect by any means and moving to correct one thing will cause problems in other areas, but if you can move the problem frequencies higher up the spectrum, they will be easier to deal with.

Also check this node calculator out:

https://amcoustics.com/tools/amroc

It works pretty well with a standard rectangular room.

Hi Hipper!

Thank you so much for your contribution! I did follow the guide and also used the calculator. I have tried to position the speakers and also the listening spot to the optimum, it works i would say but the problem is still here. Hence i have gone for the route of treating the room more seriously. It is the first time i am dealing with a dedicated listening room and also a room this big! the room i had previously was no where near as big and wouldn't have such low resonance issue.
 

lscangus

Industry Expert
Oct 24, 2018
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Hi all!

An update to you all! First of all, thank you everyone for contributing and this is a great warm welcome as this is my first thread here in WhatsBest!

After great help form all of you and especially to kokomo, i have managed to purchase the right materials in right size etc etc. The materials comes in 1.2x2.4, so i have to basically do all the cutting myself ! Spent half a day during the weekend at the den myself cutting the materials, and stacking. Here is the progress! Apologies for the mess!!

Listening test:

Although it is no where near complete, it is around 700mm tall at the moment, taking away the original corner deflector i have, and subtitled this superchunk bass absorber at the corner already back a difference! And it is very positive! The bass is a bit clearer, the booming is still here for now ( as they are around 1/5 of their designed height ), but the decay has improved and somehow. To my surprise, the clarity of the mid and mid bass is a great improvement! I guess, I have to roll up my sleeve and start more cutting, really looking forward to it! Will keep you guys posted on the progress!
 

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Hipper

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Jun 12, 2011
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Excellent news. It is quite remarkable that once you sort out the bass everything sounds better. Those that don't do this will never know the benefits to be had, as I didn't until I was persuaded to try it. I'm so glad I did.
 

lscangus

Industry Expert
Oct 24, 2018
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Quite a bit of progress and cleaned up the room a bit.... will keep you guys updated
 

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Empirical Audio

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Oct 12, 2017
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The best way to get rid of the boom is to change the listener position to look into a corner and rotate the speakers and treatments into a corner. Works every time.
 

bpape

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Mar 28, 2019
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What Steve suggests can certainly help with mode related issues (and SBIR issues to a lesser extent) - but - the 'boom' generally is more of a decay time curve issue where moderate to broadband bass absorption can help. If you turn the room as suggested, just make sure you trap the corner you are facing and the corner behind you for sure.
 

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