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VilhoValittu
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- #21
Great question.
No — TDC is not active cancellation in the sense of injecting a delayed and inverted signal to cancel room modes in the time domain. There is no extra delayed copy of the signal being added anywhere.
What TDC does instead is decision control, not signal injection.
It analyzes the group delay behaviour of the measured system and identifies frequency regions where the response is clearly non-minimum-phase (typically room modes, reflections, or late energy that cannot be corrected cleanly with EQ).
In those regions, TDC simply reduces how aggressively magnitude correction is allowed. In practice:
the measured signal is not modified
no delayed or inverted signals are added
phase is not “fixed” or forced
only the amount of EQ correction is limited
You can think of it as a trust filter:
when the time-domain behaviour looks reliable, full correction is allowed;
when the time-domain behaviour looks unreliable, the correction is softened or suppressed.
This avoids the classic problem where EQ tries to “fill in” deep modal dips that are caused by time-domain cancellations — something that usually sounds worse and adds ringing.
So TDC doesn’t cancel modes — it prevents the filter from fighting physics.
The audible effect is typically less bass overhang, cleaner transients, and more stable imaging, even if the frequency response looks slightly less flat on paper.
