kyma•tweaky . Share . 3-BandPhaseContouringDiscussion

This sound was constructed after I studied the spec sheets on the new $19,000 Rupert Neve Masterpiece. (

I have never used the Masterpiece, and this design probably departs from what the Neve box actually accomplishes, but this certainly sounds interesting on some pieces of music, especially where there is lots of percussion and impulsive strikes.

This sound treats left and right channels independently for stereo processing. It splits the incoming signal into 3 bands using 12 dB/octave Butterworth filters. The mid-band has an optional phase inversion, ostensibly to flatten out the sum of the 3 filters. (+/- 2dB).

You can select each of the LPF, BPF, and HPF bands individually. Of those selected, their content is removed from the dry signal so that the processed material can be added back to the remaining dry signal without causing significant level shifts.

Of the bands selected, they are sent through a 3-pole All-Pass filter tuned to 200 Hz, with a variable Q control for Q between 0.01 and 1.0. This gives up to 270 degrees of phase shift at the higher frequencies. With a Q of 1.0 the phase shifting is essentially completed at 400 Hz. Lowering the Q moves that end frequency higher up.

The phase altered signal is recombined in some proportion with the input signal to the All-Pass filter using a fader control. At Phasing = 1 the output of the fader is pure APF, and at Phasing = 0 it is pure filter input signal.

The output of the fader is added back to the remnant dry signal for final output.

The band edges can be selected between 100 Hz or 200 Hz for the lower edge, and 1200 Hz or 2000 Hz for the upper edge.

This is a kind of screwball EQ that induces varying amounts of phase cancellation in the spectrum of the sound. It appears to enhance drums at some settings, and can cause some interesting spatial rearrangement of the material as well.

The Masterpiece specs simply state that the processed signal is added back to the dry signal. It does not specify that the dry signal has the selected filter bands removed first. It may or may not. I found that the effects were much more interesting with the dry subtraction performed here. I also have no idea how Rupert Neve accomplishes his variable phase rotation. But using a fader to combine the phase rotated signal with the filtered dry signal would certainly produce a varying amount of phase rotation, being up to 270 degrees at the higher frequencies when the Phasing control is equal to 1.

For me this is just an engineering stunt. But in the hands of a true artist, who knows what it could lead to?

Sure makes drums sit right up and make their presence felt in the music!

-- DavidMcClain - 20 Aug 2005

----- Revision r1.2 - 20 Aug 2005 - 22:38 GMT - CarlaScaletti
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