How To: Mirror EQ with VituixCAD

With VituixCAD, we have the ability to provide a mirror EQ function, that can then be passed to APO EQ for active processing. This allows for a speaker's frequency response to be fully compensated for without requiring many bands of parametric EQ.

VituixCAD Process

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Connect each driver and EQ blocks in the crossover section as shown. Ensure that the active peak/notch filters are “shorted” so that only the G(f) block is directly connected to the driver. Three PEQ blocks are show, you may include as many or as few as are needed.

1. Load all driver responses in the drivers tab. Set smoothing for each driver at 1/12 oct to avoid unnecessarily detailed correction with FIR EQ.
2. Connect each driver and EQ blocks in the crossover section as shown. Ensure that the active peak/notch filters are “shorted” so that only the G(f) block is directly connected to the driver. Three PEQ blocks are show, you may include as many or as few as are needed.
   
3. Using the Optimizer window, select “axial response of driver”, then select the driver to be optimized in the drop down menu top the right. Define the target slope and high pass or low pass function as desired.
   Some care of the target slope is necessary to avoid extreme gain requirement for the mirror filter. For example, a flat to 20kHz response for a 12” woofer will result in extreme gain requirement at high frequency. As well, target response at low frequency should be similar to driver low end roll-off as any EQ in the sub range requires many taps for a DSP system.
   In order to prevent over-correction of the EQ or compensation for measurement noise floor, selecting the frequency range in the optimizer will limit the range that is to have EQ applied. Uncheck “Free LF” and “Free HF” to have the EQ follow the slope of the response beyond the EQ limits. Checking either of these boxes will apply a flat 0dB/oct slope beyond the frequency limits.
4. Select the G(f) block for the driver, then press the “->TF” button to export the target transfer function. This will save the target response file and load it to the G(f) block. If the G(f) block hasn’t been selected, you must load the file manually by selecting the block and using the open button at the bottom of the main window.
   
   
   
   Optimizer Window
   
   
   
   
   
   High Pass Target
   
   
   
   
   
   Low Pass Target
5. Repeat Steps 3 and 4 for each driver in the system.
6. Enable active peak/notch filters and optimize the system for listening window, in-room response, power response as needed.
   
   
   
   Filter Schematic

Complete system with optimized responses

Complete IR export and utilize within APO EQ for active processing. See my instruction “filter simulation with EQ APO and VituixCAD” for details on this process.