[Cuki79]

Originally Posted by Paultergeist

For those of us who may be less-enlightened....."IR" stands for.......?

IR= Impulse response filter. This type of filter is now used for amp speaker & cabinet simulation (Line 6 Helix, Kemper, Atomic FireAmp...) or reverb (Logic Pro X Space designer)

An impulse response filter basically adds multiple delayed versions of your signal with different weight/strenght/amplitude and phase. For long delays it behave like the echos of your sound coming from the different reflexions on the walls (reverb). For shorter (few 10 ms), you can see it as the different path of the vibration from the strings, to the bridge, to the different areas of the top and then of course to the microphone. Those muliple paths create the different resonant vibrations of your top and therefore the identity of your guitar. So a custom IR filter, like one made by Tonedexter reproduce that (and also the rosette woofy air resonance).

For the record, I think Tonedexter is 2048 "paths" (8096 "paths" in slot 22) and Fishman Aura is around 2000 (says Larry Fishman in an interview).

Here is a fast demo with a Martin D-35SA

1) is mic
2) is pickup (fishman goldplus)
3) is homemade IR v1 applied to the pickup
4) is homemade IR v2 applied to the pickup


Note that I only used 1minute of recording of the guitar (only strumming) to create these IRs. I could probably do better with longer recordings. Also note that I did not EQ yet. So you have a typical bass boost that have been also discussed in previous threads. Fishman IRs usually have a big low cut filter added. And to my ear since I don't own one, Tonedexter as a strong high cut filter.

The same technology was patented by Fishman, Yamaha and Audiosprokets (Tonedexter) with different "flavour". Nonetheless, the main idea was published in scientific papers before. It's probably the reason why you have IR modeling pedals everywhere now (Mama bear, Zoom...).

Cuki