Impulse Response frequency response

John_A

I quite often find on my Helix that I'm EQing post everything to get rid of high frequency fizz.  Question is, if a Helix cab, or an IR accurately models a speaker why is there so much fizz there in the first place.  Most guitar speakers produce little above 5K, but I seem to have to EQ this out of my modelled sound.  I would have thought that running FRFR shouldn't make a difference, as the FRFR cab should only amplify what it gets and the IR should make that sound like a guitar cab

guitarfishbay

Mic choice, mic placement, room factors. Also the speaker system itself won't be perfectly flat, then there's the room it's being played in, placement in the room etc 

Little above 5k doesn't mean nothing, especially with distorted sounds that create a lot of high harmonic content. If you put a mic infront of a real cab you'd largely get the same result as if you made an IR of the same setup.

Applying a low pass filter is common practice.

John_A

Yes, I know when I was gigging a proper amp and micing I always had to Get rid of loads of top end to make it sound good.  Wonder why no one makes IRs that sound like an amp 20 feet away rather than close micd 

guitarfishbay

Because 20 feet away would have very little punch, close micing helps get the low end thump that sounds and feels good.  Also close micing is pretty much the sound of modern guitar, there aren't that many instances where a room sound is the primary sound these days.

As for pre-mixed IRs without too much high end, if you have any Ownhammer IRs try the OH1/OH1F or OH2/OH2F files with higher numbers.  Those files have a ribbon mic blended in, the higher numbers tend to be smoother whereas the lower number files are brighter.  YMMV but you might find those need less high end taken out of them.

I think one reason people don't do too much pre-EQ is that can kind of restrict what the end user can get out of them.  I'm not really aware of anyone who does good completely mix ready IRs, but on balance having tried multiple vendors I feel like OH's system of numbering from bright (lowest number) to dark (highest number) is the fastest way to navigate, plus in general their IR packs all sound very good.

I've only bought one Celestion Plus pack but my impression again was their system is also well set out and the pack I have (Creamback M magnet I think) actually has quite several fat sounding IRs that aren't too fizzy. 

It of course also depends on your guitar, pickups, and what amp/pedal settings you're using on your Helix. 

octatonic

That don't produce nothing over 5k, it is simply that above 5k is attenuated and mostly more attenuated the higher you go up in frequency.

This is the frequency curve of a Celestion Greenback.

guitarfishbay

Absolutely, then consider the go to mic for many people (and by extension IR makers) is the SM57 -


Or the MD421

John_A

Thanks for that.  I'm sure one of the main reasons people don't get on with modellers is that they can sound fizzy without careful EQing, which if you are just used to an unmic'd combo on the floor you mightn't realise.  

Roland

John_A said:

Yes, I know when I was gigging a proper amp and micing I always had to Get rid of loads of top end to make it sound good.  Wonder why no one makes IRs that sound like an amp 20 feet away rather than close micd 

guitarfishbay said:

Because 20 feet away would have very little punch, close micing helps get the low end thump that sounds and feels good.  Also close micing is pretty much the sound of modern guitar, there aren't that many instances where a room sound is the primary sound these days.

A mic at 20 feet would pick up a lot of room resonance and other reflected sound, which you wouldn't want. It's a lot easier to EQ out what you don't want than try to build it back in.