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Discussion Starter #122 (Edited)
Hi prof, Ply wood cuts very cleanly if you use the right tool with the right blade :bigsmile:.. I use A special 30deg Laminate blade 180mm x 60teeth cuts All PLY perfectly no chiping perfectly clean cuts :T... I will post A picture of the clean cuts and blade needed...

No its not that easy you just cant use any old substrait, remember I needed A membrane with A curtain mass to meet A transmission loss at A fairly high mid frequency IE: Membrane stops reflecting/diffusing at 700- 900hz so below 750-900hz the membrane allows high freq sound to passes through to be absorbed...

There is A mathematical formula to work out the mass of A said substrait ,the math formula is also in the Master Handbook of Acoustics(4th edition) ..

So The reason I used thin 2mm ply wood is because it closely meets the criteria/mass required and with A small set air gap between the back of the ply and ultratel fiberglass(705) & applied attached in A certain way to the Vains as not to make the 2mm ply any more rigid in any way, the thin ply will transmit/pass the sound through at A mid frequency, which is what it needs to do...

Hope this helps Cheers....
 

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Sorry, I didn't notice any saw or blade...I was admiring the warm and sunny background...it's about to hit freezing and start to snow here Chicago today.
 

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Hi prof, Ply wood cuts very cleanly if you use the right tool with the right blade :bigsmile:.. I use A special 30deg Laminate blade 180mm x 60teeth cuts All PLY perfectly no chiping perfectly clean cuts :T... I will post A picture of the clean cuts and blade needed...
Ah..yes..Having the right blade would make all the difference..
I used to work for a furniture manufacturer.. many years ago..and I remember they used a special blade for cutting laminate..The edges were so cleanly cut that you could cut your finger on them if you weren't careful..

I can't believe how critical these membranes have to be to perform correctly..:dontknow:
 

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Discussion Starter #126
Sorry, I didn't notice any saw or blade...I was admiring the warm and sunny background...it's about to hit freezing and start to snow here Chicago today.
Hi Eric,
Yes it is often sunny here in the state of "Victoria" Australia and else where in Australia inc the state of SA where Prof lives, A little to sunny as it hardly ever rains thats why my back yard looks A bit like A Dusty Desert:yikes: it has'nt always been that way here but we are in A drought.... It does snow but only up in the High country never down in the flat plains...

Do you prefer Sun or Snow Eric ? I would gladly swap some sunny weather for some snow LOL...

Cheers mate...
 

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I'm a cool weather person, but this 35 degree sideways rain and 30MPH winds just peel the life out of you.

Chicago is funny, we can have weather change so drastically in one day, that we've had T-shirts and shorts on at noon, and snow that same night! Honestly, I'm really tired of it...but I have family here.

Oh, back on subject, I did manage to hang the *heavy* 4" deep QRD on my back wall as you suggested. I have one hanging, and the other the stain is drying.

Yeah, I know they are MDF, but I figured I'd stain them a warm cherry red to match the oak stair treads I turned into flutter breakers. So I have one 4" QRD and one "stair tred" QRD up on the wall, and I'm working out an aesthetically pleasing layout to hang the rest of them. Photos to come later. Right now, I'm much more interested in your project!
 

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Discussion Starter #129
Tonight I Glued & fitted the Veins of the Abffusor into place and Dry fitted the thin ply that form the wells... I am about to start fitting the ply permanetly to form the wells, Its going to be A very tedious job clamping each set of Veins untill the Ply is set permanently in place.....

Cheers....
 

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Discussion Starter #132
That is so much effort. :unbelievable: I cant wait to hear what difference it makes.
Yes it is A huge effort to make this Abffusor, 88 components in all to make just one, and I still have 2 more to build :wits-end:....

You can only assembel A little at A time in A curtan sequance so it is long and tedious...
It took 6 hours just to set 7 wells in place :yikes:...
Cheers....
 

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Discussion Starter #133
I admire your persistence Jason..I think I would have given up long ago..:thud:
Thanks Prof, The way I look at it is To do it your self saves big $$$$ and the performance is often better than what you can buy for A reasonable price, For instance the RPG Diffractal is over $2000au A piece in Australia (making these nested Diffusors next), RealTraps Diffusor/Abffusor is $1400au & mine will outperform this Diffusor and cost one third as much.. So you see what I mean by the Huge savings if you can DIY, But I understand not everyone can...

Cheers....
 

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Thanks jason..

I had a look at their website...Some very interesting materials they carry..
I was most surprised to see they have GOM.! I didn't think it was available in Australia..
Something to keep in mind, should I ever re-build my theatre..:)
 

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Discussion Starter #138 (Edited)
Getting close now to finnishing the first/Prototype Abffusor..
There is A fair amount of 2"705 being used for Absorbtion about 1200mmx1200mm sheet..

Because most of the wells being so deep I used my Wagner spray gun with A Matte Black Water based paint To paint the Abffusor, Making sure as to apply A very thin coat to the Actual membrane itself....

Just need to finnish up putting the Fiberglass in the back and closing it in with Muslin cloth then fitting the external metal frame after its painted....:daydream:

I believe the total weight should be no more than 15Kg but I will check for sure once assembled

Cheers....
 

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That looks fantastic after being painted black! Such a Pro looking job!

I picked up a cheap ($32 USD) HVLP spray gun somewhere many years ago...and never got it working right. The other day I took it apart and put it together again, which gave me a better idea of how it works (I've never used one before). It was a life saver for spraying the Warm Cherry stain on my two diffusers:



Not nearly as pro looking as yours, but they seem to do their job!

Now, after seeing yours, and reading your design thoughts...yours totally make sense! So the thickness and density of the parts were chosen so there would be a specific frequency that would pass through the paneling material and be absorbed, correct? And everything above the "cut off" would be then be diffused as normal. Clever!

And here, I was just going to stuff some 2" between my diffusers and the wallboard since mine are "floating" off the wall, suspended by some 2" X 2" I cut from some larger pieces of scrap. LOL
 
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