How does the millisecond of an IR affect tone, performance, and usage? Many of the impulse response bundles have multiple folders with various ms options . . . Which to choose and why?

 

Depends entirely on the IR, the simplest response is 2 samples long (an IIR lowpass filter). For reverbs this depends on the reverb tail length. Modelling responses normally vary from 16 to 128 bytes.

Longer ones can carry a better frequency response, but they also incur latency of the impulse length. For reverbs etc. it doesn't matter since there's predelay.

So... it depends!

 

Just have a look here :

 

Many of the Own Hammer (and other) IR packs have 200ms and 500ms options. Is there any reason/advantage to having 500ms? The vid above suggests even 200ms is long.

 

500ms needs more CPU and give more details on the tails and better low end definition (most cant tell the difference). Can be useful if your sound has tons of time based FX like delay, reverb etc in front of the amp. I don't think I really can tell in a blind test the difference between using 200ms and 500ms but it's theoretically better. It's like mixing in 192kHz vs 96kHz but end result is converted to 44.1kHz, there are tons of technical and theoretical reasoning to support that 192kHz is way way better sample rate, but 99% of people can't really tell in a listening/blind test.

200ms is more than enough in most cases.

 

Last edited: Feb 28, 2024

I agree, theoretically better, but for a guitar cab impulse, in a mix, Pete Thorn shows small IRs are ok.

 

At the beginning of hardware guitar cab IRs, they were LESS than 20ms
Even today, Helix is (was ?) 42ms

Yes, less low end and less "room".
But enough for most guitar usages

Some additional reading :
https://line6.com/support/topic/46062-ir-length-discussion/

On my side, i prefer to add "room" myself with a reverb.
Some modern cab sim (even hardware) added a mic position far/close setting

For those ppl who like "roomy" vintage sound, it adds something for sure.

Some demo (distance at 20 seconds) :

Another :

 

It seems a guitar amp cabs at 500ms is not necessary or even desired, but maybe other types of IRs a longer length helps?

 

With 500ms, you enter "reverb" territory
But not quite enough anyway.

To me, 50ms to 100ms is enough for guitar cab close mic.
And you add "distance" with IR loader or reverb.

 

One reason for creating this thread was to learn more about length of IRs. The other get enough info to figure out if I can delete some of these IRs . . . lots of folders with lots of .wav files. I'm leaning towards dumping the guitar cab IRs that are 500ms.

 

I only use OwnHammer IRs.
And only use their "Summary" folder in 44kHz.
So each release weight only 10-20 IRs

 

unless you use a pocket calculator to mix- numbers are meaningless. Its all in your ears. - you need to listen to the difference and use what sounds appropriate. The numbers are there for a "label" for you to remember them the next time you want to use them. oh yeah i used 500ms on that last mix and liked that, lets give that a shot on this one..

 

sorry but buy an amp, and a delay and a reverb pedal, and experiment.
the sounds will soon become evident and you will have a physical example of your virtual software to be able to give you context. its what the shadows did and pink floyd and every other band that got a great sound.

all software is an emulation of the real world.

 

well, of course, the longer the files, the more CPU cycles.

tone? is unreleated.

 

An AI virtual Emu playing the guitar through a Marshall clone..is it real, and if so is there an IR that covers this territory? Enquiring minds....

 

I'm afraid I can't do it justice in these brief words, would suggest you consult the film below, "Certified Copy" - it will answer all

https://www.imdb.com/title/tt1020773/?ref_=nm_knf_t_4

 

as pictured: