Kartakoŭ

Hello Vasili!

Regarding the IR length, I totally get what you are saying and think that having an IR player capability with 20ms is really great for a preamp priced that fair.
As far as I know, this length is exactly what the Quad Cortex is offering as well. Albeit there are people criticising neural dsp for not having support for longer IR length's.
I have no technical knowledge but my belief, or experience is that I can hear or maybe more then this feel a difference between the exact same IR when it got 200ms and 500ms. There is a video from MLSoundLabs which try's to prove that there are differences as well. I honestly don't understand how a quad cortex could not offer a support of all necessary IR lengths if it's a substantial part to sound quality and feel.
I can just imagine that they can have a similar point of view that you articulated.
Nonetheless, I think that this a very interesting topic and that it is more than great seeing this option on a qc level at the Colossus preamp.

JesseJackson wrote: 11 Dec 2025, 19:06 I have no technical knowledge but my belief, or experience is that I can hear or maybe more then this feel a difference between the exact same IR when it got 200ms and 500ms. There is a video from MLSoundLabs which try's to prove that there are differences as well. I honestly don't understand how a quad cortex could not offer a support of all necessary IR lengths if it's a substantial part to sound quality and feel.
I can just imagine that they can have a similar point of view that you articulated.
Nonetheless, I think that this a very interesting topic and that it is more than great seeing this option on a qc level at the Colossus preamp.

Hey, thanks for the thoughtful question – I believe I understand why you're hearing that difference, and let me try to explain what's likely happening.

The Colossus supports IRs up to 20ms at 48kHz/24-bit. This length is sufficient to capture the essential character of the guitar cabinet itself – the speakers, the box, and the immediate acoustic response, as it can properly handle frequencies down to 50Hz (1/20ms = 50Hz), which covers the entire guitar frequency range. The first 20ms of an IR is almost entirely the cabinet's direct sound.

When you go beyond that (50ms, 100ms, 200ms, 500ms), you're increasingly capturing the room where the IR was recorded – the reflections, reverberations, and acoustic space. So when you hear a difference between a 20ms and 500ms version of the same IR, what you're hearing is more of that room character being captured. For a pure cabinet sound without room influence, 20ms captures what's needed. But I completely understand that some players prefer the sound of longer IR.

However, it's worth mentioning that with very long IRs, you can't remove those room artifacts, reverb, and reflections from your sound – they're permanently baked into the IR. With shorter IRs, you get a clean cabinet sound and can always add your own reverb or room simulation later if you want it, giving you much more control over your final tone.

As for why devices like the Quad Cortex limit IR length – it's usually about balancing processing power, memory, and latency. Longer IRs require more CPU resources. The Colossus handles 20ms IRs efficiently while keeping latency ultra low.

I hope it helps.

JesseJackson wrote: 11 Dec 2025, 19:06 Hello Vasili!

Regarding the IR length, I totally get what you are saying and think that having an IR player capability with 20ms is really great for a preamp priced that fair.
As far as I know, this length is exactly what the Quad Cortex is offering as well. Albeit there are people criticising neural dsp for not having support for longer IR length's.
I have no technical knowledge but my belief, or experience is that I can hear or maybe more then this feel a difference between the exact same IR when it got 200ms and 500ms. There is a video from MLSoundLabs which try's to prove that there are differences as well. I honestly don't understand how a quad cortex could not offer a support of all necessary IR lengths if it's a substantial part to sound quality and feel.
I can just imagine that they can have a similar point of view that you articulated.
Nonetheless, I think that this a very interesting topic and that it is more than great seeing this option on a qc level at the Colossus preamp.

Also, could you please share that MLSoundLabs video? It might be interesting to watch.

Thanks

This was the video I was referring to.

Thank you for your explanation, it is very good and helps a lot.
I think a unit like the QC should have all options. It should be able to play the very long IR's and the short ones. If you want to
add reverb, room, ambiance, etc., with other tools using the 20ms IR's either as first or second option. I would maybe call it a consumer and an expert mode for the IR section, then.
In consumer mode, having all the IR's with full length and coloration already, and in the expert mode, the 20ms IR's plus reverb, etc. options.

But regarding one point, I am still not quite sure. When you speak in terms of an IR primarily of the speaker, would it then be wrong to say that you have anyway baked in inside the IR the conjunction of the cabinet, because of the different impedance behaviour of the speaker? Like you have each time, a tiny bit of a different speaker depending on the cabinet he is sitting inside? I imagine this will probably be totally negligible for playing digital modellers. But, if you have this bond already anyway, wouldn't it then just be more stringent/consequent to capture the whole picture of this bond between speaker and cabinet/room?
So, would be saying that 20ms is approximately just the capture of the speaker, but being this speaker in conjunction with a certain cabinet, and longer IR's do have the capture of the behaviour of the speaker inside this certain cabinet, but with all the consequences going out from this, would be wrong? Maybe this is just nonsense or theoretically wrong. These are just the new first questions I wonder after you answered the last ones I had with your explanation.

Regards, Moritz

JesseJackson wrote: 13 Dec 2025, 00:36 I think a unit like the QC should have all options. It should be able to play the very long IR's and the short ones. If you want to
add reverb, room, ambiance, etc., with other tools using the 20ms IR's either as first or second option. I would maybe call it a consumer and an expert mode for the IR section, then.

Thanks for the video. Unfortunately, I have to say it contains numerous inaccuracies and deliberately false premises on which he bases his conclusions. The information in the video describes more his personal attitude toward reality rather than an attempt to describe reality itself.
The frequency response of a good tube amplifier cannot have such a sharp high-frequency roll-off. This is either manipulation or incorrect connection/use of the amplifier. To my opinion, this guy either doesn't understand the subject well, or wants to gather views by contrasting the viewpoint he's presenting against truthful information.

JesseJackson wrote: 13 Dec 2025, 00:36 So, would be saying that 20ms is approximately just the capture of the speaker, but being this speaker in conjunction with a certain cabinet, and longer IR's do have the capture of the behaviour of the speaker inside this certain cabinet, but with all the consequences going out from this, would be wrong? Maybe this is just nonsense or theoretically wrong. These are just the new first questions I wonder after you answered the last ones I had with your explanation.

If I understand your question correctly, you want to know whether a 20ms IR captures the behavior of different speakers inside cabinets. The short answer is yes, it does. The behavior of different guitar speakers fits well within the lower frequency of 50Hz. Everything below this frequency has vanishingly little effect on the actual guitar sound that you hear.