Polycilindrical abffusor

[Kan Kaban]

Hi.

I´ve been researching on Cox/D´Angelo´s book about "BAD" panels (RPG Inc.). Read every thread on Gearslutz about this. Also, got help from some people around. But, I still need some help from someone... PLEASE.

The idea is to make a binary (amplitude) panel, but instead of planar, made with many cylindrical bamboo pieces as the reflective surface, similar to this ones: http://www.gearslutz.com/board/bass-tra ... otype.html

As you can see, there are many reasons to try this. Diameters can´t be regular, as nature does it´s fine job with aperiodic diameters on bamboo. Those exampled pieces are between 97mm to 103mm. Also, horizontal & vertical positions can be used. This could be an interesting alternative to the usual cylindrical BAD panels you see everywhere.

1. We need a Maximum Length Sequence of 195 "cells". (13 x 15 cells panel), since total coverage will be a 4,5 by 4,5 meters walls. May we take the sequence from a larger one?. I´ve found a couple of Matlab programs, but 195 cells are not coming from 2^N-1, where N must be an integer.

2. Cells are square 10cm (variable) diameter by now, as this is the size we have right now in stock. Cut off freq is near 3.4k (Is that enough?), so, what other diameters could you recommend besides this one?.

3. Is possible to cover 90% of the listening room (4,5 x 4,5 mts) with this kind of abffusors?. (for a 5.1 listening room). We are aiming to build an inside "cube" made from this panels, instead of hanging them from the walls.

4. I know of Reflex program, but don´t know if this will be enough to replicate the hole abffusor characteristics. Right?.

Thanks in advance guys. Please drop some lines for us. This is not a commercial project, we will invest our personal $ on this...

Cheers!.

[Soundman2020]

Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things!

(Also, I think you mean D'Antonio and Cox, not D'Angelo... )

It seems to me you are confusing QRD diffusers with BAD panels: they aren't the same, and don't work on the same principle. The first photo you show on the Gearslutz thread is not a BAD panel, as Boggy pointed out, since it has no holes or slots in it and doesn't follow a random binary sequence. It is also not a QRD diffuser, since the wells are not defined due to the round shapes, and the depths are all the same (or similar). And the shape of the bamboo is cylindrical, not poly-cylindrical, so it isn't a poly diffuser either!

It will diffuse, no doubt about that, and it looks pretty cool, but it isn't BAD, it isn't QRD, and it isn't poly. I'm not sure quite what it is, or how it will behave, but since it is a repeating pattern of the same sized and shaped elements, I would expect heavy lobing.

As Jens pointed out, the wells are very shallow and curved, and the elements are curved, so the diffusion is only going to happen at high frequencies. I'm not sure how you would figure those out though: maybe the best way to find out is to get it tested in an acoustic lab. I'm not aware of any theory that would predict the outcome accurately.

Is possible to cover 90% of the listening room (4,5 x 4,5 mts) with this kind of abffusors?. (for a 5.1 listening room).

I wouldn't do that, no. A listening room needs different treatment for each frequency range, starting out with major bass trapping at the low end: Those panels won't to anything for bass, nor low-mids, nor high-mids. With those sizes and depths, they will only affect highs, and even then the lobing is going to be pretty major: The more panels you put together, the worse it will get. Covering the entire room is going to create some pretty ugly lobing patterns at very specific frequency ranges in the high end, with some scattering to about one octave below the cut-off. You say cut-off is 3.4 kHz, so you will get scattering down to maybe 1.7 kHz, but still not low enough to be useful. Listening rooms have the biggest problems below about 300 Hz, where those panels will do nothing at all. There normally aren't a lot of problems in the frequency range that you are talking about, so you'd be creating problems by covering the room with those, instead of solving the problems that really need it.

They look really nice though! It would be cool to have a couple of those in the room, even if they do nothing at all!


- Stuart -

[Kan Kaban]

Hi. Yes, D´Antonio changed to the error with word´s dictionary... sorry for that Mr. D´Antionio.

The first panel you saw, was not made for acoustics. The panel we´re working on is an poly-cylindrical hybrid project. Do you know any correct way to model an hybrid surface?.

[Soundman2020]

The panel we´re working on is an poly-cylindrical hybrid project. Do you know any correct way to model an hybrid surface?.

Just like Cox and D'Antionio did, you'd have to work through the math and the theory yourself. I'm not aware of anyone who has done that before, so you'd be inventing a new system, and you'd have to do what they did when they came up with the original concepts for QRD: Theorize, then test, the refine, the repeat until you have both the equations and the actual laboratory results in good agreement.

Also, please read the forum rules for posting (click here).


- Stuart -

[Kan Kaban]

Also, please read the forum rules for posting (click here).

Hi Stuart.

Why do I have to read your posting rules?. Is there something else above a normal forum?.

[Kan Kaban]

Ahhh eres Chileno... claro. Gracias por tus comentarios, nada como re-confirmar los que ya uno sabe, no?. Suerte.

[Soundman2020]

Why do I have to read your posting rules?. Is there something else above a normal forum?.

Yes. If you click, you'll find out what. Especially the part in big blue letters.

- Stuart -

[Kan Kaban]

Why do I have to read your posting rules?. Is there something else above a normal forum?.

Yes. If you click, you'll find out what. Especially the part in big blue letters.

- Stuart -

Really?. Ohh, those letters, yes. You want my personal info, location, all that. What for?.

[Soundman2020]

Well, if you read the rules, you'll find out why we ask for that, and also the reasons for everything else we ask for... it's all explained in there.

- Stuart -

[Soundman2020]

... four years later, and still no compliance with the rules...

and...

Ahhh eres Chileno... claro. Gracias por tus comentarios, nada como re-confirmar los que ya uno sabe, no?. Suerte.

... no, I am not Chilean, and I didn't appreciate the snide comment against Chileans in any case... especially from someone who does not like to follow the social rules of the places he/she visits...


- Stuart -