Single Subwoofer Placement and Boundary Effect pg2

In the second simulation (Fig. 24) we see the results of locating the system at the juncture of 1 wall and the floor, first at r = .683m, then at r = 1.683m. No other boundary effects are considered or present in the analysis. As in the preceding simulation, the effect of boundary absorption is factored in to the analysis.

In the third simulation (Fig. 25) the system was placed squarely in a corner and as before, first at r = .683m, then at r = 1.683m. In this case, the effects of two walls and the floor, along with boundary absorption, factor into the system's response.

The power output of an acoustic energy source, such as the subwoofer modeled here, is a function dependent upon both the acoustic volume current and the resistive component of the radiation load. The magnitude of the resistive component of the radiation load is inversely proportional to the solid angle (4π, 2π, π, π/2 … steradian) of space into which the subwoofer fires.

We see the end results of this in the simulations: the power radiated into half-space (2π-steradian solid angle) is twice that which is radiated into full space (4π-steradian solid angle). Further, we see the increases in dB SPL levels we go from half space (2π-steradian) to quarter space (π-steradian, floor/wall junction) and finally to π/2 steradian space (in the corner). All of which nicely illustrates why pushing your subs into a corner increases the perceived output of your prized wall-shakers. (Note that this effect occurs in that portion of the frequency spectrum where the system's dimensions and boundary distances are small when compared with the wavelengths under consideration, eventually decreasing with increasing frequency).

At the frequencies we're dealing with when speaking about subwoofers, we can consider them to be omnidirectional radiators quite capable of exciting every room resonance whose eigenfrequency lies within the system's pass band.

Locating your subs for maximum bass slam and doing so by taking advantage of the room boundaries (especially corner placement) can work. Be aware, though, that given the very complex nature of any average listening room's acoustics - and the fact that there exists significant output at wavelengths possibly smaller than some or all of your listening room's dimensions - you'll be altering the measured or perceived amplitude elsewhere in your system's response spectrum. For example, you will likely see a dip in response at that frequency which has a quarter wavelength equal to the distance from the acoustic center of the subwoofer's driver to any of the room's boundaries. Once again, experimentation, in this case, with subwoofer placement will quickly tell you what works and what doesn't.