Something Cool I've Been Working On

Does this mean that these new UltraRes IRs can be extracted out of wav files?

Will the UltraRes versions be choosable for the in the Axe II already available cab IRs, or will this only be for future IRs?

Just curious.
 
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Cliff - I'm wondering if you're considering deploying ultra-res as a new option within the cab block
if this is the case, and given that your innovation has little additional CPU impact
would this new res option only come as a mono option, or could a stereo ultra-res option be a possibility??

I'm thinking this because there is quite a CPU gain to be had from using a stereo cab block rather than a pair of mono blocks running at the same resolution..
 
FractalAudio said:
It's not a mathematical mistake and nothing to do with windowing.

That peak in the bass response might be the speaker, it might be the room. Looking at the actual IR it appears to be the speaker as there are no discernible early reflections.

The frequency resolution of an IR is the sample rate divided by the number of samples in the IR. The window function has nothing to do with frequency resolution (except for making it even less). So a 1K IR at 48 kHz sample rate has a frequency resolution of roughly 48 Hz. If a speaker has a resonance (formant) at, say 80 Hz with a Q of, say, 3.0, then 48 Hz is insufficient to capture that resonance accurately. You need a frequency resolution of several Hz to accurately recreate that resonance. I chose 80 Hz and a Q of 3 because that's what that response looks like. The Q could even be higher than that.

It doesn't take much mental energy to realize that if you have a narrow formant at a low frequency then you need fine frequency resolution to reproduce that. An 80 Hz formant with a Q of 3 only spans about 25 Hz. Obviously a frequency resolution of 48 Hz is not going to be able to reproduce that.

Windowing only smooths the response even more. This is basic FFT theory. The less time-domain information you have, the less frequency domain information you have and vice-versa. This is the uncertainty principle. I always window IRs with a Hann window.

EDIT: I broke out my impedance measurements for that Vox cabinet and the speaker resonance is 80 Hz.
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Scary. I think I understood most of that. I think I even remember what FFT stands for, lol.
 
When and how will these ir's be available? Will they be part of a Firmware update or will they have to be downloaded and placed into the user slots?
Cabs are the biggest influence in my tone.
Thanks, I can't wait!
 
FractalAudio said:
Normalization is your friend. Rectangular windows are simply truncation and are generally regarded as bad practice due to extremely high sidelobe levels. The choice of window is subjective. I actually use my own custom window that is not really a Hann window but that's proprietary information. My window preserves more frequency detail while still suppressing Gibbs phenomenon. Windowing trades off frequency resolution for sidelobe suppression. My window is optimized for the unique statistics of IRs. For a random process I tend towards Bessel-Kaiser windows. IRs have unique statistics that aren't addressed by any of the standard textbook windows.
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Sounds good!............Is Good!..............Damn Good.............Good For You..........Good for me!
 

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Ah, if OH's IRs are of sufficient length to be compatible, then carry on. I'd just hate for Kevin to have gone through all the hundreds of hours he's been spending on producing his (excellent) IRs for naught...
 
FractalAudio said:
Normalization is your friend. Rectangular windows are simply truncation and are generally regarded as bad practice due to extremely high sidelobe levels. The choice of window is subjective. I actually use my own custom window that is not really a Hann window but that's proprietary information. My window preserves more frequency detail while still suppressing Gibbs phenomenon. Windowing trades off frequency resolution for sidelobe suppression. My window is optimized for the unique statistics of IRs. For a random process I tend towards Bessel-Kaiser windows. IRs have unique statistics that aren't addressed by any of the standard textbook windows.
Click to expand...

...so THAT's how Ace Frehley did it! Whaaaa? Just kidding!

Cliff: You had me at hello. Soooo, when do we get to drink this Kool-Aid?

A thousand thank you's for pushing the tech forward. All I worry about now when I play is whether to wear Red Nike's, Blue Addidas, or Black Converse....Fractal does the rest.
 
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