The School of composing

Each song should contain a recurring theme and should not be boring. It's two most important features

How to build your own the Bass trap ?

Bass traps, myths and reality. Common parametres for components

of this type are that made of foam or sponge for ease of manufacture.


Elements of this type are not absorbers, but diffusers and it's not a big benefit. The problem of low frequencies I described in the previous sections on the adaptation of the room. It is already known that low-frequency wave has a big length, so it has needs to absorb by a large element of absorption. The use of mineral wool or such materials is pointless, because this wave minimally penetrates the material and returned to the environment after rebound from such an element. It is noteworthy, for it is written for those elements. For each screen for the damping is the note on which frequency it affects. Most of the items purchased operate on the frequency of approx. 150 Hz and above, and what with the other lower frequencies ? The only good absorbers for low frequency, screens what are operating on the principle of resonance.

The wave reflected from the panel composed of mineral wool and the frame does not fulfill the role of the bass trap, because high frequencies are attenuated much more than low. This causes a disturbance of balance bandwidth for the reflected wave. 

Absorber 3


This type of panels we see in home studios as a cure for all evil 


A better solution to this problem is to use panels that operate on the principle of resonance.

The screen of this type, captures from the ambient the wave with specific frequency that into a such screen, gets into resonance, and next destroyed the his energy.


This energy is converted into heat. However, the cut-out single frequency does not improve the whole acoustics of the room. For this reason, you should perform several elements for different frequencies. Unfortunately acoustic wave will be change an own length for the influence of temperature. In one of the previous episodes I discussed the different screen with holes. See here !! The screen was suspended from the ceiling. This item reduces low frequencies that reach the listener. The space between the screen and the ceiling is high enough, the wave of great length what is kept in this part of the room. All kinds of the elements of small size of the holes do not fulfill their role because the wavelength will not allow this.


Another solution is to use the panel in the corners of the room, because the element prevents the effect of the tube and also acts as an absorber of low frequency energy. Loudspeaker in this case has the winding short-circuited by a capacitor. Mineral wool separates the wave and a cabinet corner. Wave energy is partially converted into electrical energy flowing through the capacitor

Absorber 4

Absorber 4a

or the corner absorber operating on the principle of wavelength dispersion after the passage of the smaller chamber to the larger. In a similar way it works as discussed earlier panel with holes.


Absorber 5



But back to the topic


The panels operate on the principle of resonance, so they should be tuned to specific frequencies. Here we will show you an example of such a panel.


This panel is designed for a temperature of 20 degrees in the room. Each cell is made doubly for better absorption of waves. It is a quarter-wave panel for the frequencies 40, 50, 60, 70, 80, 100, 120, 140, 160, 200, 240, 280 Hz. Main frequencies are 40, 50, 60, 70 Hz, the rest are harmonics of these frequencies. The height does not need to be 25cm, may be less e.g. 10 cm


This structure is in the shape of a rectangular prism, which chambers are provided for specific frequencies. Each chamber is opened on one side. The holes on the one side in each chamber allow you to capture the wave when the panel is suspended in a horizontal position, but the holes in the panel, you can skip. In the middle of each chamber is a partition, for the distance calculated by us for the wave. Behind the partition, we see the mineral wool filling.



How to calculate wave velocity for a specific temperature of the room ? 


v=(331,5+(0,6 x T)) 

T - temperature of the room 


example for 20 deg.

v=(331,5+(0,6 x 20)) = 343,5 m/s


We calculate the wavelength for a given frequency 




For a wave with a frequency of 40Hz chamber should be greater than 8.5 m, but we base on the construction of the chamber quarter-wave, or 1/4 wavelength. 


Combating the reflected wave of low frequency is not easy, but remember for the rest of the band. Good room to listen to is the one that has the smallest of level of the reflected wave and this wave is uniform in terms of frequencies. 


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