Rockwool vs sand as filler for bass traps

[Bluu]

So, I've been reading a bit on DIY bass traps and one question I have pertains to the agent used to fill the trap. Some sites suggest using rockwool/mineralwool/glasswool and some others suggest dry sand. Can someone explain the pros and cons of either wool or sand? Also, if wool is better, where can it be sourced from in Bangalore?

TIA!
Cheers!

PS: I need this to cancel out heavy bass boom in my new room. If I can source sand/wool, I will get the corner pieces fabricated. My first plan is to see if placement and furniture can help. The problem currently exists only on bass-heavy tracks.

 

[Shivam]

Both sand and glasswool have different sound absorption coefficients. Even the variety of sand or the density with which the glasswool is packed can change the way the bass traps sound.

Ideal method is to first profile the listening room and identify the frequencies causing problems and the most problematic locations for the same in the room. Choose your material for the bass traps accordingly.

For a boomy room-
Try to control the standing waves first using carpets, furniture etc.
Bring the speakers out into the room. Get your listening position also a little to the inside of the room.

 

[Bluu]

Shivam,

1. The speakers are pretty far from the back walls. Any closer will be uncomfortable.

2. Listening position - I will try this and report back. However, room for play is very less.

3. When facing the speakers, the right wall has a bookcase but the left one is bare. I guess that is where the problem is stemming from. Also, the back wall is bare except for the equipment rack.

I will try to temporarily throw things like cushions, pillows etc to break up any flat surfaces and see if that helps.

Cheers!

 

[Shivam]

If the book-case is without any glass cover, then it is perfect. Just place random sized books and fill the bookcase. You can also put LPs if you use them and make stacks of 10 LP each and place some of them completely in and some to various degrees out form the inner wall of bookcase.

Try calculating your room-modes and find out the problematic frequency ranges. Speakers can be placed in such a way that these frequencies are not further reinforced.

On the left wall, you can hang a carpet with some interesting pattern. A lot of people in Europe, CIS and even Arabic countries do it. Looks beautiful.

For the corners, stack various heights of newspapers or magazines.

The secret is to create a lot different dimensions in your room rather than a simple cuboid.

 

[pdhanwada]

Rockwool is fine.

I am not sure if dry sand can be used for sound absorbtion. I did not come across any place dry sand is used.

With respect to hanging carpets from the walls, it does not help frequencies below 200. It is ok with high frequencies.

RealTraps - Home hosted by ethanwiner has lots of information.

Ethan winer says for bass treatment the more the better.

In small rooms try to do bass treatment in a generic sense. Trying to tame specific frequencies will not help. You will always find dips and highs in the frequency curve. More so once the frequencies go below hundred. Only way is to minimize them.

The more bass treatment you do it will be better.

Treat the corners and first reflection points you should be good.

Thanks
Pandu

 

[Shivam]

With respect to hanging carpets from the walls, it does not help frequencies below 200. It is ok with high frequencies.

The more bass treatment you do it will be better.

Treat the corners and first reflection points you should be good.

Thanks
Pandu

Dry sand is frequently used inside of tube-traps and places where resonance can be a problem. A lot of equipment racks, speaker stands and even some speaker cabinets have option to fill sand. Sand in itself does very little in terms of absorption but can be used very nicely for creating tube-traps tailored to a specific frequency range.

Absorption is not the only thing that is needed. Too much absorption will create a dead room. Actually hanging carpets from the walls helps in 'diffusion' and creates non parallel surfaces. Sound absorption from the carpet depends on the material used, weaving and thickness etc..

Room dimensions are very important to know before starting anything.

Yes, corners and the first degree modes need the most treatment. I suggest people to start keeping the books and newspapers in the corners first.

 

[hydra]

...

I will try to temporarily throw things like cushions, pillows etc to break up any flat surfaces and see if that helps.

...

This will help a lot with better imaging, but I don't think this will help with the bass issue.

I didn't know sand could be used for bass traps!

This will be an interesting thread! I think all the other room treatment threads here have to do with room treatment from the HT perspective, and not from the listening room perspective.

 

[pdhanwada]

Bluu,

I guess currently the room is not treated. You should feel the difference, of bass frequency db level from teh corner to the middle of the room without even using spl meter.

Corners are bass loaded where as the other parts of the room are not.

That will get nullified. It will balance out across the room.

Bass treatment and corner traps building is a must. I read some note some where on the net After doing bass treatment, it equalled the performance of inclusion of 1500 Dollar REL subwoofer. Meaning bass treatment = extra subwoofer.

Please go thru my thread where I made corner traps using Rockwool. It is cheap. All locally available material.

http://www.hifivision.com/av-enhancers-room-acoustics/10892-need-help-room-acoustics.html

Thanks
pandu

 

[sidvee]

I have seen sand used to fill raised wood platforms in home theaters. Reduces resonances in the wooden floor and tightens up the bass traveling through the floor. So sand does have effect on bass, but as as bass trap I am not sure. One thing is for sure though sand is definitely much safer than rock wool to handle.
Cheers,
Sid

 

[IndianEars]

Bluu,

Go with With what pdhanwada has said.

1. I am not sure if dry sand can be used for sound absorbtion. I did not come across any place dry sand is used.

Dry sand is used to make enclosures and like inert. Not Bass traps.

If you do make a bass trap using Dry sand, I would love toi see it being moved around even by a few inches ! :lol:

2. With respect to hanging carpets from the walls, it does not help frequencies below 200. It is ok with high frequencies.

In small rooms try to do bass treatment in a generic sense. Trying to tame specific frequencies will not help. You will always find dips and highs in the frequency curve. More so once the frequencies go below hundred. Only way is to minimize them.

The more bass treatment you do it will be better.

Treat the corners and first reflection points you should be good.

I cant thjink of better advice :clapping:

 

[pdhanwada]

I have seen sand used to fill raised wood platforms in home theaters. Reduces resonances in the wooden floor and tightens up the bass traveling through the floor. So sand does have effect on bass, but as as bass trap I am not sure. One thing is for sure though sand is definitely much safer than rock wool to handle.
Cheers,
Sid

I am pretty sure sand cannot be used for bass traps. There is very little porosity in sand. As far as ROck wool or glasswool is concerned, it absorbs the energy from teh bass frequencies, and makes them die down in itself.

Another problem with sand is its weight. Its specific gravity is 1600kg/cubic meter. Where as the heaviest rockwool cannot be greater than 96kg/cubic meter. Sand being heavier by 15 times.


If we work outside make all the traps outside, use sufficient cover on your hands you should be good. Not so difficult.

Thanks

 

[sunilj]

Hi Bluu,

Why don't we work with the 'real' deal - post the measurements and lets take it from there.

I did room treatment - 14'x11'x9'. Started by killing the near-field reflections on either side of the High/Mids. Then worked on the first reflection points directly opposite to the speakers (directly behind the listener). This did a great job of most except the bass.

For the basstrap - created a sandwich of 2" Strand (wood-fibre) + 2" Synth (poly-fibre) backed by a 4mm ply. This helped but I will need more. I understand that controlling bass in a small room is challenging and typically requires most, if not ALL corners to be straddled with bass-traps, think it was on 'GearSlutz' that I read that.

Anutone - makes you feel good
http://www.anutone.com/products/19_Infills/Synth Brochure.pdf

Hope this helps.

Regards,
Sunil

 

[Bluu]

Sid - Why is glasswool dangerous? Sorry if this is a noob question.

Others - Thank you for the inputs. I will try the basic approach of breaking up large surfaces first. I am on an extremely tight budget to do anything right now.

Bajaao.com has pretty awesome deals on Auralex panels. I have asked them if the bass traps can also be sourced.

Will post updates once I get a chance to try some things out.

Cheers!

 

[sunilj]

Bluu,

The DIY effort will outdo the Auralex on a cost-to-benefit ratio. The Auralex' are great nodoubt but in my opinion a DIY effort will cover more for the same cost, so would you rather do a complete-almost-there or half-great job for the same price.

The glass-wool particles unless completed bonded /covered /closed will come loose of the main fabric floating freely in your listening space. Also, there is the hazard of working with the damn thing...painful...think itch-baby-itch...what a b17ch !

regards,
Sunil

 

[Thad E Ginathom]

I will try to temporarily throw things like cushions, pillows etc to break up any flat surfaces and see if that helps.

I have a mental picture of you juggling cushions around your head as you listen hyeah:

Please excuse my foolishness. Very interesting thread.

 

[Shivam]

Sid - Why is glasswool dangerous? Sorry if this is a noob question.

Cheers!

Glasswool can cause a lot of minor scratches on your hands even if you accidentally handle it. The particles get embded into the skin and take days to come off.

Inhaling the fine glasswool dust is also an invitation to a lot of health problems.

If you must use glasswool then buy surgical gloves and use them and wear a good mask and eye protection. Don't talk while you work with it. Make sure that after you have packed them they don't come out of any place.

 

[Thad E Ginathom]

It gets in your clothes too. You can find cuffs and collars, etc, irritating and itching, even after washing. Like after the barber, but worse, and you can't guarantee to find or wash the bits out.

 

[sidvee]

Sid - Why is glasswool dangerous? Sorry if this is a noob question.

Bluu as i understand constant exposure to glasswool is carcinogenic (lungs and respiratory system). So if treatment is built improperly and fibres float in your room then it is a health hazard - this is besides the handling issues which are temporary anyways.
Cheers,
Sid

 

[sidvee]

I am pretty sure sand cannot be used for bass traps

pdhanwada, there are applications where it has been used. Like I said I have not seen it used before commonly, specifically as a bass trap, but here is an example, and there seem to be quite a few if you do a google search, though not sure how effective it will be.

Build an awesome bass trap

Cheers,
Sid

 

[himadri]

Hi
There is large enough material regarding diy bass traps on the net. Corner chunk traps are the easiest to make . See my diy on http://www.hifivision.com/av-enhancers-room-acoustics/21275-diy-bass-traps-smallish-rooms.html
P.S. If sealed properly rockwool is quite safe.
But in my experience, bass traps should be tried out after trying out the various speaker placement options http://www.hifivision.com/av-enhancers-room-acoustics/15655-stereo-speaker-placement-experience.html
cheers
himadri