I’ve never trimmed IRs. I need to try it out, I’m guessing you trim the tail to try removing reflections ?
Yeah, totally. The default length is Max, which varies depending on the source IR, but then you can choose 1024, 512, or 256 also. They will all alter the tone, but not in a bad way. You'll lose low end as you decrease the length, but you'll also lose reflections. The amount you need to trim to lose reflections is completely dependent on the IR you're using. What I do is I hit, e.g., the 9th fret of the 3rd string and let it sustain with vibrato, then I'll hit notes going up in 5ths from there; that seems always to exploit where room reflections will really show up in the sound. I'll make a quick recording of that, but you can also just use the looper immediately after your Input Block. Anyway, I'll just play that recording of sustained notes with wild vibrato in a loop, and decrease the IR length until the reflections go away. Then, I'll record a loop of me actually playing something I'd want to sound great with the tone I'm creating, and I'll start increasing Smoothing until the hollowness / phasiness goes away. With Smoothing I'll go just to that point, but I don't want to go further, because the high end can be too much at that point, and once you get it just at the level where the phasiness goes away, you can use various EQs for the rest of the sculpting.
Finally, I think Smoothing is best complimented by Proximity and Proximity Frequency. This is the really fun part. Now you've gotten your IR not to sound phasey, and you've also removed the room reflections, so it sounds kind of Tabula Rasa, but you've almost certainly lost low end. To me, Smoothing sounds like you've moved the mic very close to the center of the speaker, at the dome, but that only sounds like that on the high end. With a real mic, if you were to do that you'd gain not only high end, but also low end. So the Proximity parameter allows you to fine tune the low end. Here's what I do:
Increase the Proximity Level until the bass is overwhelming. Just make it too much to sound good. Now adjust the Proximity Frequency. If you're using the front panel of the unit, it's two pages to the right of the main IR selection / mixing page, at the bottom right corner. On Axe-Edit it's on the same screen. Now I adjust the Proximity Frequency until the
pick attack sounds just right. I emphasize pick attack because that counterintuitive. Pick attack is not primarily in the lows at all, but I find that Proximity changes the character of your pick attack greatly, and it can either kill the power and character of your pick attack, or enhance it to be even better. So I'll just move the knob until the pick attack is just awesome. But now you've got a boomy mess. So you now reduce the Proximity level to remove the boominess. You'll find it supports the tone in a nice way. Sometimes I'll spend a good deal of time jumping between Proximity and Proximity Frequency until I get everything right. It's incredible for every kind of tone I try to create, at any level of gain.
The thing with Proximity is, the method I use here is something that is really easy and intuitive if you're using a single IR, but it is more complicated if you're using many IRs. If you're of the mindset to use, e.g. one IR for definition / character, and a second for low end girth, then the fine tuning may be more time consuming, because the Axe-FX III currently only has a master Proximity Frequency parameter; it does not allow fine tuning for each individual IR. So I've found that, exploiting this parameter the way I like means using one IR for definition / character, even if it sounds thin, then really fine tuning the low end with Proximity and Proximity Frequency. And of course you can EQ from there if you'd like. But to me Proximity and Proximity Frequency allow greater low end control that simply finding a dark IR to complement the IR that covers the definition / character side of the tone.
