Anti-Mode Technology

Cumulative Spectral Decay Plots

These measurements are displaying the data measured in a typical 4m x 5m listening room. The subwoofer is placed in the front corner during first three cases, and the listening position to which the 8033 has been calibrated is varied. The first two cases (1B and 2B) have been corrected by 1-point measurement. The third case (3B) is calibrated by sophisticated multi-point Gradient method built in 8033 Anti-Mode for more global results. In near-wall situations the gradient method is recommended if first calibration does not yield satisfying results.

Case 1, listener at the opposite corner

Figure 1A: Initial response
Figure 1B: Corrected response for figure 1A:

Listener in the opposite corner

In the first case, the position of calibration is in the opposite corner from the subwoofer. The figure 1A presents the situation before calibration. There is the strongest modal peak at 53 Hz, and slowly decaying low frequency resonance at 34 Hz. Also the frequencies are emphasized toward 0Hz because of the narrow radiation angle caused by corner placement.

After-calibration measurement is in the figure 1B. The strongest peak at 53Hz has been countered quite succesfully, and the slow decay mode of 34 Hz has been improved for the first 200ms. Audible difference is obvious, although the frequencies above 80Hz remain slightly below the average level compared to range betwnn 16 and 80Hz.

Case 2, listener in the middle of the room

Figure 2A: Initial response
Figure 2B: Corrected response for figure 2A:

Listener in the middle of the room

In this case, the listener is in the midde of the room where low frequencies are usually cancelled by destructive reflections. The energy is shifted toward heavy modal concentration within midbass range at 63 Hz. Listening to the music, this standing wave will blur almost all transients, as it is narrow and has louder contribution still after 200ms compared to initial level of other frequencies.

The corrected plot in figure 2B shows that this devastating room mode has been counter-modelled efficiently and the decay is now actually faster all the way to 350ms, which is perhaps already better than neccessary for the global point of view.

Case 3, listener at the back wall

Figure 3A: Initial response
Figure 3B: Corrected response for figure 3A:

Listener on the backwall

Perhaps one of the most typical subwoofer-listener alignments is illustrated in the figures 3A and 3B. In the initial situation, the whole bass range is infested with several high-Q asymmetric room-modes. Proximity to the back wall is treacherous for automatic calibration algorithms, as the response will change rapidly for even the slightest deviations from one point. Therefore this situation is advised to be calibrated using the clever "Gradient method" which is also implemented in 8033 Anti-Mode.
 

The figure 3B shows that although the respone decay is still not completely uniform, a great improvement compared to the original has been achieved. The result is audibly now better for the whole region of the backwall except right in the corners. The gradient point for second phase was chosen 20cm toward the side wall, 10 cm toward the back wall and 10cm toward the floor.

Lifting target curves

Anti-Mode 8033 has three special "Lift" modes that allow the user to apply a digital low-frequency boosting filter together with a protecting steep digital subsonic filter. The maximum boost of Lift is around +7dB (peak vs. 80Hz). In the following measurements, also the noise-shaping Bessel lowpass is active at output, so the level of boost virtually looks ~3dB higher because of the output-LPF attenuation toward higher frequencies.

Here are the different frequency responses of the three different Lifting states of 8033. (Click to enlarge)

 

Flat target (no lifting, no subsonic)
Lift 25 Hz (boost between 15-25Hz with subsonic)
Lift 35 Hz (boost between 25-35Hz with subsonic)