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Wish "Phase Correct" switch for TMA/IRP/CAB to fix IR phase cancellations

guitarnerdswe

Power User

FractalAudio

Administrator
Fractal Audio Systems
Moderator
Isn't that what the align feature is for?
No. When an IR is read from storage the first few hundred samples are scanned and the maxima is found. If the maxima is a negative value the polarity of the IR is inverted because it is assumed the polarity of the IR was inverted when captured. This can happen if the speaker is wired backwards, the IR is captured from the back of the cabinet, the back of a ribbon mic is used, or a polarity inversion occurs in the power amp or mic preamp.

A Tone Match can appear to be inverted because it's not a classic speaker IR. When exporting a TM to an IR this inversion will be removed when the IR is read.

There's two approaches I can use:
1. A single "Auto-Polarity" parameter that covers all four channels of the cab block.
2. Individual Auto-Polarity per channel.
 

yyz67

Inspired
Cliff, because a possible the inversion happens in the TMA, would it make more sense to put the switch ("phase invert" or "positive polarity") switch in the TMA rather than in the CAB/IRP blocks?
 

Rex

Legend!
Cliff, because a possible the inversion happens in the TMA, would it make more sense to put the switch ("phase invert" or "positive polarity") switch in the TMA rather than in the CAB/IRP blocks?
That would work for new tone matches and IR exports, but not for existing ones.
 

yyz67

Inspired
That would work for new tone matches and IR exports, but not for existing ones.
The Cab and IR Player blocks automatically "phase correct" IRs so that the peak signal is positive. A Tone Match may have the peak signal negative. When putting them in parallel this will lead to cancellation.
Looks like both CAB and IRP already phase correct any IR (incl TMs) to a positive signal. It's the TMA that can be negative (and thus not play well esp with other saved off TM IRs).

Unless I'm not understanding correctly, existing or new TMAs with a new switch (e.g. auto polarity on/off) could be fixed to either act like CAB/IRP (switch on) or as is (switch off) which could be pos or neg polarity.
 
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yyz67

Inspired
I take it back: what I said above won't work! But I think the TMA needs a switch as well to cover all combinations.

There's two approaches I can use:
1. A single "Auto-Polarity" parameter that covers all four channels of the cab block.
2. Individual Auto-Polarity per channel.
I vote for a switch per channel in case one of them is a TM IR. Also perhaps three values: ON (default=current behavior), OFF (raw IR polarity is unchanged), and INVERT (would swap the polarity of the raw IR). For a switch in the TMA block the default should be OFF (current behavior).
 
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