Calculate subwoofer housing - the best tips

The self-built sound system includes in particular the own subwoofer. It is not difficult to build it. However, you should be particularly careful when calculating the housing, as this is essential for the right sound. You can read how this works in this practical tip.

Build a subwoofer yourself: this is how your system sounds optimal

Even with little previous knowledge of the craft, building a bass box is not a big problem. However, the planning and calculations are much more extensive and complicated than building itself. These are necessary so that the loudspeaker actually outputs the desired sound in the end.

The simplest variant: calculate closed housings

The easiest way to build the subwoofer is a closed, airtight housing. All you need is three simple formulas and a calculator. First, however, you should use this tool to check whether your chassis is suitable for installation in a closed housing.

1. Next you have to decide what is more important to you: Should the sound be more cracking and impulsive or warm and full?
2. If there is a lot of space, select Qtc = 0.577 (Bessel characteristic). This is how you achieve ideal phase behavior and very dry and reserved bass reproduction.
   If you listen to all kinds of different music, a Qtc of 0.7 to 0.9 is the ideal compromise (Butterworth characteristic). This is how you achieve a dry to full bass reproduction.
   As a techno or house fan or if there is not enough space at the installation location, choose Qtc> 0.9 (Tschebycheff characteristic). So you get the greatest bass output with increasing Qtc and worse and worse impulse fidelity. In principle, values ​​over 1.2 are not recommended.
   
3. Calculation of the optimal housing volume: Vb = Vas / ((Qtc² / Qts²) - 1) Attention: the larger the housing volume, the greater the deflection of the chassis at lower frequencies, since the braking effect of the enclosed air is smaller. With very large housings, there is a quick risk that the driver will be overloaded without additional protective measures such as a subsonic filter.
4. This results in a new resonance frequency: fc = (Qtc * fs) / Qts
5. If you want to dampen the housing tightly with glass wool, for example, the volume is reduced by about 20 percent: Vnew = Vb / 1.2
6. You should also take the space requirements of the chassis into account.
   The following rule of thumb applies: 2 liters for 16 and 5 liters for 38 drivers.
   This volume must be added to Vb.
7. When using two woofers, you only need to double the volume. The sound pressure rises by six decibels due to the double membrane surface and the double output.

We have summarized everything you need to know about importing speakers in the next article.