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I stole this from a dead thread posted by 'darkmoebius' on DIY Audio. I heard the the effects of these traps in several listening rooms at the RMAF-2005 and was very impressed. The traps are really $pendy, and it seems like they could be kloned.
Any how, I'm researching perforated metal material and am going to fab up some of these for experimentational purposes.
Here are the dimensions of the Daad traps
DAAD2
absorbents of sound for reflections
posterior laterals and p/resonances above of 120Hz
diameter max. 22cm - 110cm
DAAD3
absorbents of sound for all
the primary reflections above of 70Hz
diameter max. 28cm - 110 cm
DAAD4
absorbents of sound for all
the reflections anteriorers above of 50Hz
diameter max. 39cm - 110 cm
A new type of bass trap/diffuser room treatment
Italian company Acoustica Applicata has created what it claims to be a new form of bass trap/diffuser, called the DAAD..(see closeup pics here), which greatly outperforms the industry standard ASC Tube Trap (which AA manufactured/distributed for years) and RPG Diffusers
According to this long description of the DAAD's conception/evolution, there are 3 important factors to DAAD's superior performance: 1) the external metal screen/grate (closeup pic) serves the diffusing purpose, 2) the internal resistive/absorptive material sandwich, and 3) the oval/lobe shape of the traps as the link above shows
To save the impatient a little time, I've culled some of the most important concepts/claims from their literature
Regarding the external screen/diffusor.....
Regarding the absorptive insulation....
Regarding the shape of the trap...
Italian company Acoustica Applicata has created what it claims to be a new form of bass trap/diffuser, called the DAAD..(see closeup pics here), which greatly outperforms the industry standard ASC Tube Trap (which AA manufactured/distributed for years) and RPG Diffusers
According to this long description of the DAAD's conception/evolution, there are 3 important factors to DAAD's superior performance: 1) the external metal screen/grate (closeup pic) serves the diffusing purpose, 2) the internal resistive/absorptive material sandwich, and 3) the oval/lobe shape of the traps as the link above shows
To save the impatient a little time, I've culled some of the most important concepts/claims from their literature
Regarding the external screen/diffusor.....
The truth is that we had to realise rather quickly that the ‘density’ of the reticule is actually really influential. If there were too many and narrow holes, the ‘s’ became excessively hissing, and if they were too large, vocals sounded darker.
But these changes did not only affect high frequencies, because low frequencies also behaved differently. If the cover grille allowed more air to go through and reach the inside of the trap, it worked by absorbing larger quantities of frequencies if they were higher than 100 Hz, but it became poorly effective below that number. Whenever we used a more dense cover grille, the amount of absorption diminished drastically but the trap could also work at lower frequencies. In other words, the different types of cover grilles determined the quantity and quality of absorption at low frequencies. This has its logic in a trap that works through differences in pressure. For example, in the case of a dense cover grille, the amount of air reaching the resistive material is small if compared to a grille that has fewer but bigger holes. The quantity of resistive material inside is fixed. Therefore, air that enters the trap through denser and smaller holes ‘sees’ a greater quantity of sound absorbent material and has a higher pressure. In this way the trap absorbs a smaller quantity of sound because it has less air to deal with, but it activates itself at lower frequencies. On the other hand, if it has bigger holes, the trap receives more air and absorbs a greater quantity of sound, but, because of the fact that the pressure is lower, it activates itself at higher frequencies
The pressed and micro-perforated metal sheet turned out to be a very ‘powerful’ and flexible material. Whenever it was put in place instead of the original cloth covering the Tube Traps results were better. We were still not satisfied however
Tube Traps covered with a pressed metal sheet offered both good control over resounding frequencies and an acceptable amount of sound diffusion at high frequencies, but...didn’t allow music to breathe the way we wanted.
But these changes did not only affect high frequencies, because low frequencies also behaved differently. If the cover grille allowed more air to go through and reach the inside of the trap, it worked by absorbing larger quantities of frequencies if they were higher than 100 Hz, but it became poorly effective below that number. Whenever we used a more dense cover grille, the amount of absorption diminished drastically but the trap could also work at lower frequencies. In other words, the different types of cover grilles determined the quantity and quality of absorption at low frequencies. This has its logic in a trap that works through differences in pressure. For example, in the case of a dense cover grille, the amount of air reaching the resistive material is small if compared to a grille that has fewer but bigger holes. The quantity of resistive material inside is fixed. Therefore, air that enters the trap through denser and smaller holes ‘sees’ a greater quantity of sound absorbent material and has a higher pressure. In this way the trap absorbs a smaller quantity of sound because it has less air to deal with, but it activates itself at lower frequencies. On the other hand, if it has bigger holes, the trap receives more air and absorbs a greater quantity of sound, but, because of the fact that the pressure is lower, it activates itself at higher frequencies
The pressed and micro-perforated metal sheet turned out to be a very ‘powerful’ and flexible material. Whenever it was put in place instead of the original cloth covering the Tube Traps results were better. We were still not satisfied however
Tube Traps covered with a pressed metal sheet offered both good control over resounding frequencies and an acceptable amount of sound diffusion at high frequencies, but...didn’t allow music to breathe the way we wanted.
The resistive material inside of Tube Traps is glass wool that has excellent properties as a sound absorbent. Its thickness is calculated on the basis of the volume of air inside the trap. If one introduces compressed air inside a Tube Trap (thus creating a practically reversed situation compared to normal utilization), the air that comes out of the trap is almost non-existent. In other words, the added air is, for the most part, converted by the glass wool into heat through a powerful friction. But, if you think this through, this also means that it will take longer for the trap to return to its original pressure state. If one considers a long sequence of sound transients, it is quite likely that a device with a considerable quantity of sound absorbent material will succeed in handling the first difference in pressure, but then won’t have time enough to get ready for the second and some of the following ones. Therefore, a slow trap works only in intermittence.
... In order to get what we wanted, we had to experiment with other materials and thicknesses that allowed air to penetrate the trap quickly and get out again after a given time. These new materials shouldn’t create excessive friction to the air passing through them, in order not to slow down the functioning of the entire acoustic device with regard to the timing of music transients that follow each other. What we wanted was a ‘fast’ trap! After some substantial additional research we finally found a satisfactory combination of two materials.
... In order to get what we wanted, we had to experiment with other materials and thicknesses that allowed air to penetrate the trap quickly and get out again after a given time. These new materials shouldn’t create excessive friction to the air passing through them, in order not to slow down the functioning of the entire acoustic device with regard to the timing of music transients that follow each other. What we wanted was a ‘fast’ trap! After some substantial additional research we finally found a satisfactory combination of two materials.
So all we had to do now was to define the final shape of our new acoustic device.
The shape of a lobe seemed the most suitable one, for the following reasons:
1. its internal volume being equal to a cylinder, a lobe-shaped device ‘penetrates’ the corners of a room more deeply, thus capturing the resounding frequencies more easily
2. its shape facilitates the simultaneous use of different materials for the resistive layer of the device;
3. like a cylinder, but unlike a flat panel, a lobe device allows one to have an inner volume with air and a thickness able to create ‘acoustic shade’. In other words, it provides a very good ratio between the space used and the results that are reached;
4. like a cylinder, but unlike a flat panel, a lobe device can be rotated on itself. Having lobes with different diffusion characteristics allows one to position them in several ways and to change room acoustics according to one’s personal needs or tastes
But the most interesting and lucky discovery actually came when we realised how the chosen lobe shape tended to ‘remix’ energy: once it receives a sound wave, the DAAD works on it in a way that not only delays its re-release but also diffuses it homogeneously all around it.
We were about to reach the finish line. All we had to do now was to find the right ratio between the thickness of the resistive material and the degree of ‘permeability’ to air of the pressed metal sheet
We only thought to have reached our goal after we decided to reduce the thickness of the resistive material, when the device was put in a condition to work faster. The presence of the pressed metal sheet and the shape of the trap obviously allowed us to use sound absorbing material with more moderation. It is the combination of these three things – the shape, metal sheet, and quality and thickness of the resistive material - that allows DAADs to behave both as a fast acoustic trap for resounding low frequencies and as a diffusion–diffraction device that turns early reflections into more delayed ones.
The shape of a lobe seemed the most suitable one, for the following reasons:
1. its internal volume being equal to a cylinder, a lobe-shaped device ‘penetrates’ the corners of a room more deeply, thus capturing the resounding frequencies more easily
2. its shape facilitates the simultaneous use of different materials for the resistive layer of the device;
3. like a cylinder, but unlike a flat panel, a lobe device allows one to have an inner volume with air and a thickness able to create ‘acoustic shade’. In other words, it provides a very good ratio between the space used and the results that are reached;
4. like a cylinder, but unlike a flat panel, a lobe device can be rotated on itself. Having lobes with different diffusion characteristics allows one to position them in several ways and to change room acoustics according to one’s personal needs or tastes
But the most interesting and lucky discovery actually came when we realised how the chosen lobe shape tended to ‘remix’ energy: once it receives a sound wave, the DAAD works on it in a way that not only delays its re-release but also diffuses it homogeneously all around it.
We were about to reach the finish line. All we had to do now was to find the right ratio between the thickness of the resistive material and the degree of ‘permeability’ to air of the pressed metal sheet
We only thought to have reached our goal after we decided to reduce the thickness of the resistive material, when the device was put in a condition to work faster. The presence of the pressed metal sheet and the shape of the trap obviously allowed us to use sound absorbing material with more moderation. It is the combination of these three things – the shape, metal sheet, and quality and thickness of the resistive material - that allows DAADs to behave both as a fast acoustic trap for resounding low frequencies and as a diffusion–diffraction device that turns early reflections into more delayed ones.
Here are the dimensions of the Daad traps
DAAD2
absorbents of sound for reflections
posterior laterals and p/resonances above of 120Hz
diameter max. 22cm - 110cm
DAAD3
absorbents of sound for all
the primary reflections above of 70Hz
diameter max. 28cm - 110 cm
DAAD4
absorbents of sound for all
the reflections anteriorers above of 50Hz
diameter max. 39cm - 110 cm
) would work well around parts of the rest of the room, as long as they're less than 3 feet high. I've got one corner near the seats that would really benefit from one of these.
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