Diffusor in Diffusor

[betserd]

I want to build a QRD diffusor with smaller diffusors inside like the flutter free strips inside a normal diffusors.

When I calculate the performance of a diffusor with a (theoretical) width of 56cm the performance would be from 581 to 20976 Hz, so that will be a mighty great diffusor!

I'm only stuck with the effect of the smaller diffusor on the depth of the big diffusor. Should the depth be calculated up to the surface of the smaller one or including the deepest well of the smaller one?

Hope someone can help me out on that.
thanks,
Bastiaan

[andrebrito]

Check the RPG Difractal

Andre

[Glenn Kuras]

This is a diffusor that we do not have on the market yet, but what we did was build little polys inside of the QRD to cure those problems. I will post some pictures and see if I can get Jason, our diffusor God, answer some questions for you.

[betserd]

Originally Posted by Glenn Kuras

This is a diffusor that we do not have on the market yet, but what we did was build little polys inside of the QRD to cure those problems. I will post some pictures and see if I can get Jason, our diffusor God, answer some questions for you.

Thanks Glen, that is really appreciated, hope to get a good answers! Looks very nice those poly's in the diffusor! Calculating the depth of that one basically is the same problem. Did you guys use the top of the poly as the depth of the diffusor or the Average depth of the poly?

Originally Posted by andrebrito;

Check the RPG Difractal

Andre

Andre, that is the basic idea of the diffusor. I only want to know what effect the inner diffusor has on the depth of the outer diffusor. It's not somethingI can easily check..

[Nordenstam]

Originally Posted by betserd

Calculating the depth of that one basically is the same problem. Did you guys use the top of the poly as the depth of the diffusor or the Average depth of the poly?

Think of each well as a delay line. The depth/volume of each well sets the delay time. If you calculate the volume the poly removes from the well and add that back again to increase the depth correspondingly, the effective depth/delay will be the same as when it started.

[betserd]

Originally Posted by Lupo

Think of each well as a delay line. The depth/volume of each well sets the delay time. If you calculate the volume the poly removes from the well and add that back again to increase the depth correspondingly, the effective depth/delay will be the same as when it started.

Is that also true for a smaller qrd diffusor in the diffusor? The added volume adds to the depth of a well? I read once that only the highest frequencies will react to the smaller diffusor and the lowest (the ones dealth with by the big duffusor) see the smaller one as a flat surface. Anyone knows a definetive answer on that?

[andrebrito]

The outside diffuser has a high frequency limit, the nested diffuser acts only for very high frequencies. The outside diffuser is a simple QRD but the wells are not flat basically.

You can look at all the RPG DIFRACTAL information at:

RPG Diffusor Systems

[Nordenstam]

[QUOTE=betserd;4218348]Is that also true for a smaller qrd diffusor in the diffusor? The added volume adds to the depth of a well?[QUOTE=betserd;4218348]

The smaller diffusor substracts from the volume of the bigger well. If you calculate the volume of the small diffusor and substract that from the big well, you'll end up where it started. OTOH, if you add the same small diffusor to every well, the end effect will be uniform across the diffusor - a slightly raised lower design frequency of the big diffusor.

Originally Posted by betserd

I read once that only the highest frequencies will react to the smaller diffusor and the lowest (the ones dealth with by the big duffusor) see the smaller one as a flat surface. Anyone knows a definetive answer on that?

That's the theory of double-diffusers, yes. Sound waves range from 17 meters at 20Hz to 1.7 centimeters at 20KHz. For an irregular surface to affect sound, the irregularities need to be at somewhat similar scale as the sound waves striking it. A wave several feet wide will not care if there are very small irregularities present in whatever object it strikes.

[Jason Jones]

Originally Posted by betserd

I want to build a QRD diffusor with smaller diffusors inside like the flutter free strips inside a normal diffusors.

When I calculate the performance of a diffusor with a (theoretical) width of 56cm the performance would be from 581 to 20976 Hz, so that will be a mighty great diffusor!

I'm only stuck with the effect of the smaller diffusor on the depth of the big diffusor. Should the depth be calculated up to the surface of the smaller one or including the deepest well of the smaller one?

Hope someone can help me out on that.
thanks,
Bastiaan

How you figure the depth in this particular design (with respect to the inner diffusers) really won't matter much as long as you are consistent. Though, the thing that I would think about regarding the diffuser within the diffuser is at what frequencies the small diffuser is kicking in at. How do you have that figured now in your design?

Also, I don't know how much surface you are trying to cover, but you will probably save yourself some work if you make each diffuser a little wider.

Jason

[Tom H]

Nice idea, you can also build seperate high freq and lower freq diffusers and place those on opposite walls from each other. That way you can also eliminate flutter over a very broad freq range.

Depends on the room and what you are trying to achieve.

[T1M0N]

Originally Posted by Jason Jones

Though, the thing that I would think about regarding the diffuser within the diffuser is at what frequencies the small diffuser is kicking in at. How do you have that figured now in your design?


Jason

Any more opinions on that? Should the inner Diffusor start at the HF limit of the outer one? Could there be an octave in between? Or overlapping ranges?

[Nordenstam]

I think you'll find that it's impossible to avoid an octave gap in the diffractal design.

[Jens Eklund]

New type of diffusor

[Northward]

Originally Posted by Nordenstam

I think you'll find that it's impossible to avoid an octave gap in the diffractal design.

Yes! And another point is the usefulness of diffusing at such high frequencies to start with (say, higher than 5kHz).

There is, in my experience, absolutely no practical beneficial effect of diffusing higher than the 'usual' mid-range frequencies. Can't hear a difference, can't measure a difference.

Can notice a definitive budget difference though.

Just build a nice, effective diffusor that will take care of that mid-range, place it accurately, and move on.

[Michael Loomis]

Originally Posted by Glenn Kuras

This is a diffusor that we do not have on the market yet, but what we did was build little polys inside of the QRD to cure those problems. I will post some pictures and see if I can get Jason, our diffusor God, answer some questions for you.

So, Glen, when do you expect to have these ready for market? ANy idea of price yet?

Michael

[Glenn Kuras]

Originally Posted by Michael Loomis

So, Glen, when do you expect to have these ready for market? ANy idea of price yet?

Michael

I don't think it is going to happen. The price on these just is way out of line. Think of a Porsche GT!! Instead we went with non curved, the Q7D. More like a Porsche 911. lol I think the curve concept is super cool, but the benefit has to meet up with the price.

[Sebg]

What about getting the curved blocks cut from EPS and then working out how to get a timber veneer to stick to the surface of the EPS...?

[12ax7]

Originally Posted by Glenn Kuras

I don't think it is going to happen. The price on these just is way out of line. Think of a Porsche GT!! Instead we went with non curved, the Q7D. More like a Porsche 911. lol I think the curve concept is super cool, but the benefit has to meet up with the price.

Maybe I'm just demonstrating my noobosity and ignorance here...

...But why couldn't diffusers such as this be made with something akin to the VacuForm process?

.

[dainja]

Originally Posted by 12ax7

Maybe I'm just demonstrating my noobosity and ignorance here...

...But why couldn't diffusers such as this be made with something akin to the VacuForm process?

.

What are the setup costs for this type of process?

[12ax7]

Originally Posted by dainja

What are the setup costs for this type of process?

I'm not sure, but I have seen them used in the film industry to make multiple duplicates of props, scenery, etc.

...And while those folks aren't exactly scared of spending money when necessary, they tend to try to be cost-efficient.

.

[Amioa]

there are vacuum formed diffusers already, several different ones, made in Spain, America and the UK, they are cheap but tooling is expensive and finish can be variable.

[boggy]

Originally Posted by Jason Jones

.......Though, the thing that I would think about regarding the diffuser within the diffuser is at what frequencies the small diffuser is kicking in at. How do you have that figured now in your design?
........

Some simple rule for fractal diffusers is that lowest working frequency of small difuser must be the same as highest working frequency of big diffuser....

Hope this helps,

Bogic