weiss said:
IIRC the Neumann filters were using 6db/oct ?
What exactly would i have to do to sonically come closer to an elliptical filter compared to a 6db hpf in the sides? is it even possible?
An elliptic EQ is strictly identical to inserting a 6dB/octave in the S component.
Inserting a higher-order filter results in a different response.
For a 1st-order (6dB/oct) HPF, a left-panned bass sound will result in a -6dB low-shelved signal on left, and a -6dB Low-passed version of the signal on the right. So, the LF energy that was concentrated on the left channel is now shared between the two outputs.
For a 2nd-order (12dB/oct) HPF, the signal on left is unchanged, but the right signal is very different, with a hump at the filter's cut-off frequency. No doubt it sounds different.
Depending on the speaker's position and directivity pattern, it can result in significant perceptual differences.
The graph represents the outputs after matrixing, HPF and de-matrixing.
Dark blue and red are the left and right outputs with 1st-order filtering of the S component. Note that dark blue is hidden by green that is identical.
Green and cyan show same outputs with 2nd-order filter in S component.