[terry j]

hey cheers andreas! Will have a look at the wikipedia,

Originally Posted by Lupo

What dutch forum?

Agreed that it needs to be cleared up! There's a lot to be said for repetition too. Will check out what the Cox and D'Antonio book says on the subject when I'm back home over the weekend.

I should buy 'the book', boy is it pricey!! Also agree that these things need to be cleared up. Too many experts on the internet I reckon!

Ok which dutch site? this one

SoundScapeS Akoestiek Thuis -- Bondgenoten voor Reflectiebeheersing

I must have been confusing, the guy who runs/made that site says in another forum that repetition is a good thing

As I do not ever want to misrepresent someone, I feel I need to quote him and provide the link. That way we can sort this stuff out??

However there's an unwritten rule that states that when using diffusers, you must apply a minimum of 4 or 5 periods of the design (that is: 4 complete panels wide). This is the reason you sometimes want to use a narrow panel when space is restricted: better to use 4 narrow panels than 2 wider ones to cover the same surface.

and

Periodicity indeed is a condition for homogeneous diffusion. The minimum number to be used would be 4 or 5 periods (full sequences) for a given surface to be appropriately diffused; more is always better in order to suppress the 'lobing effect' of a single or double period even more.

And this section approaches what we are talking about here, a repetition of a small one vs a large single higher N number that fills the space

One other important aspect to consider when applying diffusion is periodicity: for homogenous results any diffusive surface should at least be covered by a width of 4, or better still, 5 periods. Therefore it's sometimes better to design narrow periods (lower N-numbers such as QRD-7 or 11) in order to be able to have diffusive surfaces consisting of 4 or 5 periods next to each other.
Periodicity brings homogenous diffusion over the targeted working range. Applying one wide panel (period) is not a good approach, not even when it's a QRD-19 with a wide working range. In those cases it's better to apply 5 lower numbered periods of a QRD-7.

That is enough for now, the thread this all came from is here

appropriate diffuser behind Apogee - AudioWorld's StraightWire Forums

As you can see, here are two completely different interpretations of the same phenomenon. Gut feel is to believe cox and d'antonio.....

As you say, it is best if internet 'folklore' is replaced by truth. So hopefully we can find out eh??

The 2D fractal is neat! Though there are numerous things I could point out that could be done better. If you decide to do something like it, give me a word and I'll try to help you exceed the Swedish unit.

I give you the word, and point away!! (which word did you want????)

That's odd. It'll break up the room modes. Or..?

again to avoid misrepresentation, here is the line I was talking about

Diffusers are not effective below the (take your pic: Davis, Shroeder #1, Schroeder #2, 3 modes/Hz) cutoff frequency of a room.

It was avares, and here is the original post

Sonotube Diffusor

post 12

Hehe.. Talking about cables can be a quick affair. Speaker cables: big enough. Interconnects: shielded twisted pair. Done!

Ahh, a man after my own heart!

Originally Posted by Lupo

There's a graph in the master handbook of acoustics that looks something like this:

Cheers, will have a re-look (it is ONE book I do have!)

Though, I think there's something positive to having a dip in the high end. If the goal is to create an illusion of a room much bigger than what it really is, a dip in the high end RT is to expected from such a large room.

Ok then, if you are after a certain goal (like a drop in RT at the high end), HOW do you achieve that?

that is what I hope this thread will end up as, a documentation of the process to achieve certain goals.

Appreciate your input

On a side note, think I have managed to clear a few hours tomorrow, so will find out how many of those diffusors I can build in an afternoon with my new technique