QRD design change - what effects should I expect!

Hi everyone, Long time intermittant lurker, first time posted :) I've been considering building some diffusors for my rooms as i'm suffering a bit from flutter echoes, which I'd like to treat without using too much absorption. I've already using a bit of absorption and don't want to over do it in my fairly small room. I was considering a QRD design like this one:

However I was thinking of using smaller pieces of wood - perhaps 2cm*2cm instead of the 5cm*5cm suggested in this article - the reason being I have a very cheap source of the materail available to me. What would be the effect of this? I would still be covering the same amount of surface area on my wall and following the same formulae for calculating the lengths. It seems to me it would probably make the diffusors more efficient at higher frequencies? But that is just a gut feel and nothing thought out :) Thanks for the help & any recommendations! Cheers, Ewan

However I was thinking of using smaller pieces of wood - perhaps 2cm*2cm instead of the 5cm*5cm suggested in this article - the reason being I have a very cheap source of the materail available to me. What would be the effect of this? I would still be covering the same amount of surface area on my wall and following the same formulae for calculating the lengths.

Low and high frequency cutoff increased and lobing due to incomplete cycles. The BBC RD paper linked in your link gives all the relevent info. If you want to keep to same area, then use another pattern so there are no incomplete cycles. As a matter of courtesy would you:

Edit your profile to include your location. This is very important, because this is a worldwide resource, and as such, material costs and availability vary widely. For example, masonry is cheaper than gypsum in some parts of the globe, whereas it's the exact opposite in other regions. We're not asking for your address or credit card number, just a country will do. Nothing says "I didn't bother to read or follow these instructions" like leaving your profile location blank!

as detailed in Don't Even Think of Posting... In the sticky at the top of the forum. Andre

I've tried it with 2cm bits and it's a tremendous amount of work, you have to glue it well for it to hold. Ideally, I would cut each "piece" of the cake (a row of buildings) with CNC... Maybe it does worth the darn time :-) BTW, which wood are you planning to use? The thing IS going to weight (-: When you say cheap source for your wood, does this include all of the cutting?

As a matter of courtesy would you: as detailed in Don't Even Think of Posting... In the sticky at the top of the forum. Andre[/quote] I HAD done that...stupid computer didn't co-operate :roll: :roll: cheers for the help.

AdamZuf wrote:

Ideally, I would cut each "piece" of the cake (a row of buildings) with CNC... Maybe it does worth the darn time :-)

:mrgreen: I think the program(s) and setup cost alone will buy you already a set of original RPG ones. The idea of DIY is to save, not to spend extra money.

You must understand that going from 5x5cm pieces to 2x2cm pieces is not to be underestimated, in regard to time spent. Time is money, sometimes you don't save a dime from DIY, just gain knowledge- I can't see the profit in this case- and take it from someone who tried it. Ahhh no problem I can make a DXF myself if anyone needs help - if this is saved from the CNC operator it will cost a lot less. Plus you can get creative, as it's your own design 8) CNC is worth checking, if you care about looks, and the price is reasonable in the states. Routing yourself will take a lot of time - really, I've tried it. A router table would make things easier, but yet time consuming- as you can't cut all the depth at one shot, at least 2 or 3 times in order not to stress the router and bit. Using a jigsaw will not yield good looking results- but that depends on what's your threshold for "good" :D Another option is to make it not so fine looknig and covering with a nice fabric of yor choice. RPG also mentions that this raises the corresponding NRC values of the diffuser and makes it more linear. But for myself, I prefer clients to say "what the hell is it? I never seen something quite like it!" I never seen a QRD or Skyline in Israel :)