wooden block diffusor

subatom · Post by **subatom** » Tue May 10, 2005 10:04 am

Is there a science to wood block diffusors? Is it anything like the quadratic residue? I assume there are some similarities, but there are no fins so the wells are not equal for any side. I'm really not sure that it should even be symetrical. I suppose it could be, but i'd like to build them for a live room anyway. I'm guessing that as random as possible would be ideal, but what do I know.

I did a few searches here, and haven't found anything looking thru my books. Any ideas?

philofparis · Post by **philofparis** » Tue May 10, 2005 4:20 pm

Hello subatom!
have a look at this document:

www.bbc.co.uk/rd/pubs/reports/1990-15.pdf

Philippe

AVare · Post by **AVare** » Tue May 10, 2005 11:36 pm

Philippe gave it to you. that is the most comprehensive on the web. Next strp is Cox and D'Antonios book.

Andre

subatom · Post by **subatom** » Wed May 11, 2005 12:44 am

Thanks guys!

Here is more reading on this for those that haven't already

http://www.acoustics.salford.ac.uk/rese ... eviews.pdf

impact_kent · Post by **impact_kent** » Tue May 24, 2005 11:01 pm

http://www.mhsoft.nl/DiffusorCalculator.html

Check out that link there, its an interesting little calculator and layout sheet based on the bbc article referenced above.

Perhaps someone knows what frequency range is a good range for diffusion, as that seems to be a key in doing it.

Thinking about building a few myself out of some nice flat plywood and some good straight 2x2s.

I'll let you know how they come out, hopefully I'll get started in a couple of days.

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AVare · Post by **AVare** » Wed May 25, 2005 12:09 am

Perhaps someone knows what frequency range is a good range for diffusion, as that seems to be a key in doing it.

I don't understand your question at all! Read the BBC papaer.

Adnre

impact_kent · Post by **impact_kent** » Wed May 25, 2005 3:31 am

sorry for being vague....

i'm just trying to figure out the calculator someone has made (based off of that BBC report) at the link in my earlier post.

It asks for a low and high frequency to specify a range..... i'm guessing the range of frequencies to be diffused.......

It then provides different block sizes and a layout chart.

Maybe its wrong. Figured it might be helpful in building one.

AVare · Post by **AVare** » Wed May 25, 2005 4:40 am

impact_kent wrote:sorry for being vague....

i'm just trying to figure out the calculator someone has made (based off of that BBC report) at the link in my earlier post.

It asks for a low and high frequency to specify a range..... i'm guessing the range of frequencies to be diffused.......

It then provides different block sizes and a layout chart.

Maybe its wrong. Figured it might be helpful in building one.

Read the BBC paper!

Puting it in lay terms, the lower the low frequency, the bigger the cell depth. The higher the high frequency, the finer the cell width.

It is all in the BBC paper!

Andre

impact_kent · Post by **impact_kent** » Thu May 26, 2005 11:52 pm

where is the best place for this type of treatment?

Ceiling i assume, as that's where I always see it placed.

How about on a wall, like, opposite a very dead wall?

Perhaps also covering a windows that leaks too much sound ;]

knightfly · Post by **knightfly** » Fri May 27, 2005 4:52 am

Generally, diffusion is best kept at least 10-12 feet from your ears; otherwise, there's a strong chance of getting specular reflections from the individual elements since there hasn't been enough distance for the individual reflections to "mix" -

If you don't have really high ceilings, an absorbent "cloud" is usually a better overhead treatment.

Also, (window leak comment) don't confuse treatment with isolation; the two are almost mutually exclusive, other than most absorbers cause a weakening of the containment structure at their specific location and effective frequency. This is why we "overkill" on containment whenever possible, so that after the treatments do their thing, our space is still isolated enough.

Remember, isolation is keeping the sound in or out - treatment/acoustics is making it sound GOOD... Steve

impact_kent · Post by **impact_kent** » Fri May 27, 2005 5:02 am

thanks steve for that... especially the part about allowing the diffused reflections opportunity to 'mix'

Yeah.... I was just thinking of possibly hitting two birds with one stone.... rather than sealing the window with rockwool and a piece of MDF, thought i could fill it with rockwool and cover it with a piece of hardboard with skyline style diffusion on it.

Anyway, I was just wondering if it would be beneficial (window or not) to have at the end of a 20 ft room, and whether it should be dead on the opposite wall.

drfrankencopter · Post by **drfrankencopter** » Sat May 28, 2005 4:52 am

Remember, isolation is keeping the sound in or out - treatment/acoustics is making it sound GOOD... Steve

True, and also note that by the time you have good isolation in your room, you tend to have massive/stiff walls that make things like bass mode problems really stand out. Its amazing how much bass a light partition wall 'absorbs' (more like transmits....)

Cheers,

Kris

AVare · Post by **AVare** » Sun May 29, 2005 12:09 am

more like transmits....)

Thank you Kris!

So many people, incuding at least one well one writer, keep refering to it as absorption, not what it really us: transmission.

Andre

knightfly · Post by **knightfly** » Sun May 29, 2005 5:47 pm

Absorption is just "transmitting" to somewhere ELSE - and flimsy walls are just another name for panel/membrane traps...

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