GM Arts
Fractal Fanatic
Here’s the thread where Cliff proposed using a 0.06 mSec delay on one of two cabs, with a recommendation for using different cab models. http://forum.fractalaudio.com/cliffs-notes/91932-my-secret-realistic-cab-sounds.html
Cliff was pretty clear about what it does, but reading through some replies, it seems to have been lost. Even worse, some other threads seem to imply that this delay is now a mandatory requirement for good tone, and if I understand one post correctly, this delay is required alone on a single (mono) signal path!
So here’s what it actually does. Firstly, this is about mixing 2 signals: one without delay, and the other with a very short delay.
0.06mS is way too short to be perceived as a repeat; the effect is filtering caused by mixing these two signals. To keep things simple, we’ll apply an equal mix of the same signal and another delayed by 0.06mS. An easy way to experiment with this in the Axe-FX is with a Flanger block, with depth and feedback set to zero, and mix set to 50%. Adjust the delay to 0.06mS (not 0.6mS) to hear the effect with a mono signal.
This produces a notched frequency response with complete signal cancellation just above 8KHz, with the -3dB point one octave lower at just over 4KHz. The signal is restored over the next higher octave (8KHz to 16KHz), but bear in mind that most Cab IRs will not have much response there anyway, so this effect is mostly a blocking filter over the range 4KHz to 8KHz.
So if you have a cab IR that has some response over this range, it will be perceived as a loss of some treble response. For many, this will remove harshness in a way that’s difficult to achieve with other filters.
Others may find this effect too much. You can soften this effect by decreasing the delay and/or changing the mix ratio. Decreasing the delay raises the frequency at which this cut occurs. For example, a 0.05mS delay blocks response over the octave 5KHz to 10KHz. Lowering the mix % decreases the depth of the notch. Similarly, applying a delay to a different Cab IR than the un-delayed block will “jumble” and reduce the final response to some extent.
If you increase the delay (typically from 1mS and above), you’ll hear the combing effects as multiple notches become low enough to hear in the range of “guitar frequencies”. This sounds like a flanger or chorus without modulation, which shouldn’t be a surprise given we’re experimenting with a Flanger block.
So why does this delay sound produce a tone more amp-like? Most players prefer their amp tone off-axis, meaning that they’re avoiding the direct harsh sound directly in front of the speaker, where high-frequencies are beamed. This filter simulates that effect. It’s also similar to standing slightly off-axis when using multiple speakers. Sound travels at roughly one foot per millisecond, so there is a very short delay between sound from different transducers. As Cliff stated, it also emulates recording techniques with mics placed at different distances from the cab.
How to calculate? To find the frequency where this rolls-off high frequencies at -3dB, it’s simply: Hz = 1000 / 4 /delay in mSec . So for 0.06 mSec: 1000 / 4 / 0.06 = 4167Hz. Complete cancellation occurs at double this frequency, 8333Hz, and builds back to -3dB a double this frequency again, 16666Hz. Bear in mind that with higher delays, there will be audible effects from additional notches above this calculated frequency.
I hope this helps those who are interested.
Cliff was pretty clear about what it does, but reading through some replies, it seems to have been lost. Even worse, some other threads seem to imply that this delay is now a mandatory requirement for good tone, and if I understand one post correctly, this delay is required alone on a single (mono) signal path!
So here’s what it actually does. Firstly, this is about mixing 2 signals: one without delay, and the other with a very short delay.
0.06mS is way too short to be perceived as a repeat; the effect is filtering caused by mixing these two signals. To keep things simple, we’ll apply an equal mix of the same signal and another delayed by 0.06mS. An easy way to experiment with this in the Axe-FX is with a Flanger block, with depth and feedback set to zero, and mix set to 50%. Adjust the delay to 0.06mS (not 0.6mS) to hear the effect with a mono signal.
This produces a notched frequency response with complete signal cancellation just above 8KHz, with the -3dB point one octave lower at just over 4KHz. The signal is restored over the next higher octave (8KHz to 16KHz), but bear in mind that most Cab IRs will not have much response there anyway, so this effect is mostly a blocking filter over the range 4KHz to 8KHz.
So if you have a cab IR that has some response over this range, it will be perceived as a loss of some treble response. For many, this will remove harshness in a way that’s difficult to achieve with other filters.
Others may find this effect too much. You can soften this effect by decreasing the delay and/or changing the mix ratio. Decreasing the delay raises the frequency at which this cut occurs. For example, a 0.05mS delay blocks response over the octave 5KHz to 10KHz. Lowering the mix % decreases the depth of the notch. Similarly, applying a delay to a different Cab IR than the un-delayed block will “jumble” and reduce the final response to some extent.
If you increase the delay (typically from 1mS and above), you’ll hear the combing effects as multiple notches become low enough to hear in the range of “guitar frequencies”. This sounds like a flanger or chorus without modulation, which shouldn’t be a surprise given we’re experimenting with a Flanger block.
So why does this delay sound produce a tone more amp-like? Most players prefer their amp tone off-axis, meaning that they’re avoiding the direct harsh sound directly in front of the speaker, where high-frequencies are beamed. This filter simulates that effect. It’s also similar to standing slightly off-axis when using multiple speakers. Sound travels at roughly one foot per millisecond, so there is a very short delay between sound from different transducers. As Cliff stated, it also emulates recording techniques with mics placed at different distances from the cab.
How to calculate? To find the frequency where this rolls-off high frequencies at -3dB, it’s simply: Hz = 1000 / 4 /delay in mSec . So for 0.06 mSec: 1000 / 4 / 0.06 = 4167Hz. Complete cancellation occurs at double this frequency, 8333Hz, and builds back to -3dB a double this frequency again, 16666Hz. Bear in mind that with higher delays, there will be audible effects from additional notches above this calculated frequency.
I hope this helps those who are interested.