It is possible to implement a Linkwitz-Riley-type crossover using RME audio interfaces with the TotalMix FX DSP capabilities. Devices of the type UCX-II, UFX-II etc., implement a so-called Room EQ section which is a 9-band parametric equalizer.

ff-ufx2-totalmix-setup.png

Linkwitz-Riley crossovers are constructed from cascading Butterworth filters: two 2nd order low-pass filters and two 2nd order highpass filters.

In Totalmix FX this is done at the output section, enabling Room EQ and assigning LF to the left and HF to the right channel of a stereo pair.

ff-ufx2-crossover-lo.png

ff-ufx2-crossover-hi.png

For our FaitalPro 12HX230 coaxial drivers, the HF sensitivity is 10dB higher then for LF. We therefore set the Volume calibration of the HF part to -10 dB.

We can measure the result by looping back (by analog cable) from the output to the input:

crossover-measurement.png

This is a measurement of the 1 meter on-axis driver response on white noise using the RME TotalMix-based crossover.

faital-ff-crossover-measurement.png

This is a measurement of the 1 meter on-axis driver response on white noise using the Max-based crossover implementation. The two implementations are equivalent.

faital-max_gen-crossover-measurement.png

Additionally, we discovered that the HF driver sits approximately 5 or 6 cm behind the effective radiation plane of the LF driver. Therefore we added a 0.2 ms delay to the LF signal (left channel) which improved the dip at the crossover frequency (1.7 kHz) considerably.