Diffusor rolling....with books

amit11

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Jul 7, 2014
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Pune
Hi Friends,

Just sharing some thoughts and little experimentation i was doing.

To improve the sound, i used to try with keeping some rugs, or pillows or even canvas paintings in between the speaker space. Yes they used to modify the sound to some extent based on the material of the item. A big canvas 5 X 4 feet was less better than 3-5 small square pillows spaced out in between the speaker space. I observed that the canvas used to rob-off the low end and the high-ends were more focussed. Regarding the square pillows, the material of the pillows also used to change the sound experience. After few trials lasting for few hours or couple of days, I used to finally remove them and realized that sound is better without them even though i lose some aspects in comparison to them.

Then I recently came across the word 'Diffusor'. I had heard it but very very less compared to above experimentation. Then I realized what i was doing in these few years was mainly using 'Absorbers'. Absorber makes sense to use since it will absorb extra bass and make the sound coherent.. right?.... But then something was not just right about those absorbers I was using.

Then on some sites I started exploring what are diffusors, of what material they are made. But confusion was still there that they are not absorbing then how will they make a positive impact, and that too they are made of hard materials like wood. Skyline diffusor, quadratic diffusor.. then words like quarter wave length theory, then 4 inches depths of well in the quadratic diffusor, then even more words like matching well depth with the quarter wave length, uneven well spacing based on prime number etc... aroused more curosity. I also saw on youtube where someone also suggested that normal books can also act as a diffusor.. thought it might not be perfect but still it can.

So that aroused even more curisoity to try out without burning the pockets. So i started first with some books keeping on the floor (in between the speakers and where the floor & wall edges run with each other). That was a relevation for me. No bad effects like the 'absorbers' i used to use. Based on how many books we keep, how we arrange them, some a bit towards outside, some a bitwards the inside etc.. this made slight-slight differences in the sound heard. Also the material of the book, especially the outer cover also could make a difference.

Then I thought if I can stake 2 layers (like 2nd floor, 1st floor) that would help even more. But the books used to fall down when i staked the 2nd floor). So an idea cam to buy some rack. But the rack shelves should not be solid else that itself would impact sound. So an idea came to buy a rack (we used to use as show rack in the past). It was made of metal wires and nothing like a solid shelf. So it was airy-airy in all 3 dimensions. I purchased from a local kitchen utensil shop and told i can return if i do not like it... :)


So with this new item, I dumped my books on 2nd floor and even 3rd floor... :).. yes that made even more difference and i was happy.

The in couple of days as my ears got further tuned, i realized that dumping the books is not the way. If i keep some spacing in between them it helps....

Then i started researching on the quadratic diffusors... and especialy words like quarter wave length, well-depth etc. So i started to experiment on spacing the books based on gap between them... for example 4 inches, 6 inches etc... Yes.. that made the sound better (atleast to me)... In 1st floor and 2nd floor I kept the books in a triangle fashion with 6 inch (roughly) gap starting between them.. and then on 3rd floor i kept multiple books like a skyline with very less space between them. To my understanding the 1st and 2nd floor helps to diffuse low end and 3rd floor helps to diffuse the high end to some extent.


I know it may sound stupid but mixing some theory and practical helped me to get a better sound, if i may say so.... Now i keep on experimenting with the books position, spacing between them which influences the sound.... kind of tone changer... or diffusor rolling (like tube rolling).

Attaching one pic and one calculation working sheet which helped me to get a better understanding.

Thanks for reading...

Regards,
amit11.
 

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jenson

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Nov 25, 2010
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Indore
I also see great improvement in mid to high range if you hang a jaipuri 125 gm razai in center, placement above the book shelf you have. Tames bass quite a bit.

You may also consider pulling the speaker atleast 1 feet from the back of speaker to back wall.
 

Analogous

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Nov 17, 2017
Messages
1,747
Points
113
Location
Bangalore
Hi Friends,

Just sharing some thoughts and little experimentation i was doing.

To improve the sound, i used to try with keeping some rugs, or pillows or even canvas paintings in between the speaker space. Yes they used to modify the sound to some extent based on the material of the item. A big canvas 5 X 4 feet was less better than 3-5 small square pillows spaced out in between the speaker space. I observed that the canvas used to rob-off the low end and the high-ends were more focussed. Regarding the square pillows, the material of the pillows also used to change the sound experience. After few trials lasting for few hours or couple of days, I used to finally remove them and realized that sound is better without them even though i lose some aspects in comparison to them.

Then I recently came across the word 'Diffusor'. I had heard it but very very less compared to above experimentation. Then I realized what i was doing in these few years was mainly using 'Absorbers'. Absorber makes sense to use since it will absorb extra bass and make the sound coherent.. right?.... But then something was not just right about those absorbers I was using.

Then on some sites I started exploring what are diffusors, of what material they are made. But confusion was still there that they are not absorbing then how will they make a positive impact, and that too they are made of hard materials like wood. Skyline diffusor, quadratic diffusor.. then words like quarter wave length theory, then 4 inches depths of well in the quadratic diffusor, then even more words like matching well depth with the quarter wave length, uneven well spacing based on prime number etc... aroused more curosity. I also saw on youtube where someone also suggested that normal books can also act as a diffusor.. thought it might not be perfect but still it can.

So that aroused even more curisoity to try out without burning the pockets. So i started first with some books keeping on the floor (in between the speakers and where the floor & wall edges run with each other). That was a relevation for me. No bad effects like the 'absorbers' i used to use. Based on how many books we keep, how we arrange them, some a bit towards outside, some a bitwards the inside etc.. this made slight-slight differences in the sound heard. Also the material of the book, especially the outer cover also could make a difference.

Then I thought if I can stake 2 layers (like 2nd floor, 1st floor) that would help even more. But the books used to fall down when i staked the 2nd floor). So an idea cam to buy some rack. But the rack shelves should not be solid else that itself would impact sound. So an idea came to buy a rack (we used to use as show rack in the past). It was made of metal wires and nothing like a solid shelf. So it was airy-airy in all 3 dimensions. I purchased from a local kitchen utensil shop and told i can return if i do not like it... :)


So with this new item, I dumped my books on 2nd floor and even 3rd floor... :).. yes that made even more difference and i was happy.

The in couple of days as my ears got further tuned, i realized that dumping the books is not the way. If i keep some spacing in between them it helps....

Then i started researching on the quadratic diffusors... and especialy words like quarter wave length, well-depth etc. So i started to experiment on spacing the books based on gap between them... for example 4 inches, 6 inches etc... Yes.. that made the sound better (atleast to me)... In 1st floor and 2nd floor I kept the books in a triangle fashion with 6 inch (roughly) gap starting between them.. and then on 3rd floor i kept multiple books like a skyline with very less space between them. To my understanding the 1st and 2nd floor helps to diffuse low end and 3rd floor helps to diffuse the high end to some extent.


I know it may sound stupid but mixing some theory and practical helped me to get a better sound, if i may say so.... Now i keep on experimenting with the books position, spacing between them which influences the sound.... kind of tone changer... or diffusor rolling (like tube rolling).

Attaching one pic and one calculation working sheet which helped me to get a better understanding.

Thanks for reading...

Regards,
amit11.
Interesting experiments @amit11
I too have been using books as diffusers (or partial absorbers?) of sound to treat uncontrolled reflections from the side walls (areas of first reflection)
I love having my books around (old friends) and aesthetically they are to me better than panels.
Hopefully we will see more acoustic treatment panels with good art work coming to the market.
 

Subbu68

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Joined
Mar 13, 2022
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643
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Location
ABU DHABI, UAE
Interesting finds @amit11

Knowingly or unknowingly I had been having book shelves with random books on the sides of speakers a little behind them and that impact was felt when we emptied the shelves for cleaning. Now I have a sofa to one side and some heavy plants to the other side and a heavy sofa facing the speakers. Things seem to be under control but haven't done any study like you.

Keep educating us ...
 
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