Something Cool I've Been Working On

FractalAudio said:
The problem with conventional IRs is that they are too short to capture the detail in the low frequencies. There are those that maintain 20 ms is the maximum length you need to fully replicate the speaker. This would be about 1000 samples at 48 kHz.

I disagree with this as I have many IRs here that exhibit significant energy beyond 20 ms. I believe the room has some influence as the low-frequency modes of the room will impact the resulting sound. The amount of this impact depends on the room, the mics, distance, etc., etc. Or perhaps certain speakers have particularly high Qs in the low frequencies. Regardless, it is my opinion that you need IRs much longer than 20 ms to fully capture the "mic'd amp in the studio" sound.

My tests show that IRs of 8000 samples are required to fully capture the low-frequency detail. Unfortunately to process an 8K IR in real-time require copious processing power...

Fortunately I have developed "UltraRes (TM)" cabinet modeling. UltraRes cabinet modeling provides the frequency detail of a very long IR with little or no added processing power requirements.

The following image depicts the response of UltraRes cabinet IR processing:
The blue trace is the frequency response of the original (long) IR. It is a Vox AC-30 cab.
The green trace is the frequency response of the same IR truncated to 1K samples. This is "normal resolution" in the Axe-Fx and 2-4 times longer than what other products use.
The red trace is the frequency response using UltraRes processing.

I’ve shifted each trace by 0.5 dB to make comparison easier.

ultra_res.jpg
Click to expand...

I freaking love this!
 
FractalAudio said:
The problem with conventional IRs is that they are too short to capture the detail in the low frequencies. There are those that maintain 20 ms is the maximum length you need to fully replicate the speaker. This would be about 1000 samples at 48 kHz.

I disagree with this as I have many IRs here that exhibit significant energy beyond 20 ms. I believe the room has some influence as the low-frequency modes of the room will impact the resulting sound. The amount of this impact depends on the room, the mics, distance, etc., etc. Or perhaps certain speakers have particularly high Qs in the low frequencies. Regardless, it is my opinion that you need IRs much longer than 20 ms to fully capture the "mic'd amp in the studio" sound.

My tests show that IRs of 8000 samples are required to fully capture the low-frequency detail. Unfortunately to process an 8K IR in real-time require copious processing power...

Fortunately I have developed "UltraRes (TM)" cabinet modeling. UltraRes cabinet modeling provides the frequency detail of a very long IR with little or no added processing power requirements.

The following image depicts the response of UltraRes cabinet IR processing:
The blue trace is the frequency response of the original (long) IR. It is a Vox AC-30 cab.
The green trace is the frequency response of the same IR truncated to 1K samples. This is "normal resolution" in the Axe-Fx and 2-4 times longer than what other products use.
The red trace is the frequency response using UltraRes processing.

I’ve shifted each trace by 0.5 dB to make comparison easier.
Click to expand...


Well, here comes FW 12 guys!

With FW 11, the amp models had been licked. We still had cabs, the final frontier, that needed to be explored and brought under the axe thumb, right? Well here we are: Ultra Res IRs - coming to you soon courtesy of CC and Co.

I'm thoroughly impressed. Can't wait to hear the results in a recording and, most importantly, live.
 
This looks great on paper Cliff!!!, but where are the audio samples? :p

And the BIG question!, with UltraRes IRs be compatible only with the Axe FX or will this become something others can use?
 
Awesome work as usual, Cliff! This will surely add to the character of each IR. However, while the IR certainly is going to sound more natural, I'm sure, it may not always sound better or give you a more workable guitar tone in the end. Lot of the issues with recording a guitar amp IRL is precisely that of the resonating bass frequencies in the room. We are talking about a boost in bass frequencies of up to 5-10 dB with a Q factor of roughly 1/6 octave. Sounds to me like it may cause resonance issues in particular lower frequencies. Slow resonating frequencies are tougher to control than faster ones, especially at volume, and usually cause a boomy quality... Usually this is dealt with in mixing and with EQ... I'll have to listen to this to be fully convinced that this is a step forward across the entire range of guitar tones. It may definitely help certain types of tones, such as raunchy Vox or Marshall tones, while it can make higher gain tones and deep super clean tones boomier and not as tight as before. But what the heck do I know???? :) In either case I'm super excited to try this out!!! :encouragement: Your continuous strive for perfection makes us, all of us I'm sure, proud to be Fractalians! Great work Cliff! :encouragement:
 
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Every time I read one of Cliffs posts, I feel like an absolute idiot. It amazes me that there are people out there with enough brilliance to come up with things like this and actually understand all the math that goes into making it happen.

I look forward to hearing the difference that this new technology will offer us all in creating even more realistic IRs. Thanks for all you do FAS and for creating the best piece of gear any musician could have!
 
This is cool. Amazing (to me, anyway) that there's such a difference in low-frequency response detail. There are even some smaller peaks and valleys above 200 Hz that the standard IR smooths over altogether.

@Cliff: What subjective differences do you hear or feel when playing through an UltraRes IR? If it's significant, will it still be significant to those who start to roll off the low end somewhere above 100 Hz?
 
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