I was trying to make a subtractive-delay crossover (i.e. Lipshitz - Vanderkooy type) in Sigma studio using a Butterworth lowpass, the "Signal Subtract" (from Basic DSP/Arithmetic Operations) and a delay.
The derived highpass wasn't a highpass at all - it was looking like a low-shelf filter. Just as if the subtractor wouldn't subtract but add the signals instead ! I then replaced the subtractor with the "Signal Add" function and the result looked exactly the same ! I.e. my assumption is that the "Signal Subtract" doesn't do what it is supposed to - it does rather add than subtract.
I then inserted a "Signal Invert" before the adder stage - et voila: The crossover worked exactly as it should.
Is there a known problem with the "Signal Subtract" in Sigma Studio 3.4, build 0, Rev 724 ?