Airwindows

PrimeFIR

TL;DW: PrimeFIR is a mostly linear-phase brickwall with a taste for the bizarre!

PrimeFIR in Airwindows Consolidated under ‘Filter’ (CLAP, AU, VST3, LV2)
PrimeFIR.zip (551k) standalone(AU, VST2)

It’s experiment time again! Inspired by the original filter in Baconpaul’s Six Sines FM synth (which I recommend the heck out of, by the way) I got busy trying to make a similar type of filter. This is not how I usually filter. I have a great distaste for the smearyness of linear phase and the weird vibe the pre-ring gives off, but it was amazing in Six Sines, partly because of the incredibly tiny and CPU-efficient window, and so I had a whack at the problem.

As usual I had a whack at it in pinata fashion, so rather than do it properly I came up with a way to implement the sinc function I needed for the brickwall, with a sin() based window, and for good measure I made the post-ring longer than the pre-ring just because I could, and made the window size variable so you could filter right down to moderately low frequencies, and that’s the first part of the experiment.

And then I thought it would be fun to calculate out the sinc function for what it would need to be if you took, not every sample, but every PRIME sample in that window, and used that. Only some of the samples, but across a much MUCH broader time window for the same number of filter positions. And also those positions wouldn’t be reinforcing each other, because they’re prime numbers. How hard could it be?

So, when you turn the ‘prime’ control over 0.5, you get a completely different filter, if that’s still an appropriate name for it. In theory it’ll filter down lower, except it completely fails to be a brickwall. It’s sort of like a shelf? And sort of phasey, and sort of diffuse, and it’s yours to play with. You’re hearing only a window of the prime-numbered samples peeking through and acting like it’s a filter or something resembling one.

And you’ve heard something like it before… because nearly twenty (!) years ago, my plugin Iron Oxide came out, and one of the things it does is build tone shaping out of prime-spaced successions of samples. No kidding: this technique hasn’t really been played with since Iron Oxide and variations on BrightAmbience. Here it’s a way to broaden the range of frequencies a brickwall filter can ‘reach’, except that since it’s such a sparse set of filter coefficients, it stops working like any normal brickwall filter and turns into something else.

If I wanted to make it be a similarly inefficient highpass, merely including an ‘Inv/Wet’ control wouldn’t be enough, I’d need to doctor the filter so instead it was accepting the nonprimes and omitting the primes, run the brickwall, and then subtract that.

This (not the prime version) is also what I’ve been trying for the last two reverbs, and some folks love that but others cried foul. I’m going to broaden my filter palette a bit for the reverbs, though now I know what this one can do (a sort of slick flashy effect) and will most likely turn to the Pear filter with nonlinearity for the next few reverbs. I’ve got about four different methods not counting simple biquads that will do different things. Even one (BezEQ!) that will produce gnarly artifacts for texture, for certain kinds of special effects.

For now, enjoy playing with the experimental PrimeFIR. It might just lead to an interesting sort of highpass for livening up things as significant as lead vocals… more on that later. Have fun :)

Airwindows Consolidated Download
Most recent VCV Rack Module
download 64 Bit Windows VSTs.zip
download Signed M1/Intel Mac AUs.dmg
download Signed M1/Intel Mac VSTs.dmg
download LinuxVSTs.zip
download LinuxARMVSTs.zip for the Pi
download Retro 32 Bit Windows VSTs.zip
download Retro PPC/32/64 Mac AUs.zip
download Retro PPC/32/64 Mac VSTs.zip
Mediafire Backup of all downloads
All this is free and open source under the MIT license, brought to you by my Patreon.

Date July 6, 2025
Author Chris
Comments 1 Comment

DeCrackle

TL;DW: DeCrackle isolates clicks and vinyl crackles to remove them.

DeCrackle in Airwindows Consolidated under ‘Utility’ (CLAP, AU, VST3, LV2)
DeCrackle.zip (523k) standalone(AU, VST2)

This was a lot of work, for a good purpose (cleaning up vinyl records), being asked for (ever since I did the livestreams developing this, I’ve been hearing about it) and getting put out as it is. There might well be good ways to inappropriately use it, and I might well get something out of it in its intended use, but all the same I have to establish expectations.

The fantasy of a decrackle plugin is that you can throw a scratchy ol’ record at it, and get a lovely noiseless version back out, that is perfect and has all the tone you want, with none of the noise. Seemed worth trying. I could try to isolate bursts of energy that were the right kind (more side energy than mid, energy higher than the average energy happening at the time, and so on) and mute them. Or, apply a filter, and snap to the filter while the click is happening, so the lows remain unaltered, then back to the raw audio right away.

Turned out to be a lot more tricky to get it to work… but there’s a problem. The whole idea was to let the audio through totally untouched, rapidly triggering the decrackle for every instant it’s needed. This is happening, but when there’s heavy crackle, the noise is so constant that there’s no way to play the raw audio between the crackles… and there’s always a lot of quieter crackle happening between the louder pops and clicks. So the concept worked, but it didn’t work in the sense of making all the noise go away. And since it barely touches or affects the rest of the audio, you get a powerful sense of whatever crackle remains… minus the REALLY loud bits, that get neatly removed as if they weren’t there.

Filter goes from bass-only to full frequency and is the audio you replace clicks with. You tune it to hide the transitions (full bass might not be the ideal setting, you’re looking for minimal disruption). Window is important: it’ll go from very narrow, to extremely wide. It’s set up so it can be abused to let through a big section of the click’s surroundings, which can be used for other purposes. Threshld gets lowered to increase the effect, and requires delicate adjustment: be careful about letting it kick in on actual music as that will sound bad. Surface goes from normal at zero, to intense treble filtering. It’s not purely a lowpass, it tries to respond to micro-crackles but not underlying high frequencies, and you can use it to subtly mute general surface noise in quiet sections. Finally, Dry/Wet has a special trick: if you set it to 0.0, full dry, it switches to delta monitoring so you can hear ONLY the clicks. If you hear music coming through that, you know Threshld has to be higher.

Since this probably isn’t going to excite would-be decracklers unless they’re really committed to keeping the tone of the audio at all costs, including ‘sounding like you didn’t bother decrackling’ (certain music might be more resilient to lower thresholds), I have an alternate suggestion for amusingly misusing DeCrackle.

Use high Window settings and full Dry to make it a neat little percussive gate which is also a highpass, and which isolates the attack (because it’s treating it as a click where it has to remove the entire onset of the sound). It will apply a fair amount of latency: DeCrackle is FAR from zero latency, unlike most of my plugins. That does let it gate around a peak while presenting the whole peak without cropping the front off.

Or, use the Dry/Wet to reinvent the attack of percussive sounds, from very high frequency spikes to bassy thumps. Filter controls how much of the attack is allowed to be bright, Window controls how much of the attack you grab, Threshld interacts with that and Dry/Wet blends how much of the attack is removed. This is going to work well for darkening and refining bright attacks on kicks you want to make heavier, since it interacts with the Filter up top plus the Window setting plus the processing latency of the plugin.

DeCrackle is a lot of tricky, hard-to-balance processing tuned to invisibly remove just the right crackles and clicks from only certain vinyl recordings. If it works for you like that, I’m thrilled! If it works when used on totally different things, I guess the trickiness of it makes the process more interesting or gives you more sophisticated results. Your mileage may vary. Hope you’re enjoying kBeyond, I’m working every day on following it up with even better stuff :)

Airwindows Consolidated Download
Most recent VCV Rack Module
download 64 Bit Windows VSTs.zip
download Signed M1/Intel Mac AUs.dmg
download Signed M1/Intel Mac VSTs.dmg
download LinuxVSTs.zip
download LinuxARMVSTs.zip for the Pi
download Retro 32 Bit Windows VSTs.zip
download Retro PPC/32/64 Mac AUs.zip
download Retro PPC/32/64 Mac VSTs.zip
Mediafire Backup of all downloads
All this is free and open source under the MIT license, brought to you by my Patreon.

Date June 29, 2025
Author Chris
Comments 8 Comments

kBeyond

TL;DW: kBeyond is a recital hall.

kBeyond in Airwindows Consolidated under ‘Reverb’ (CLAP, AU, VST3, LV2)
kBeyond.zip (609k) standalone(AU, VST2)

Turns out there’s a technology to beat all AI: the genetic algorithm. GA. And if you know how to steer it, you can do anything.

kBeyond is a first real example of what that can do. It’s two different reverb matrices in one plugin, the first generating early reflections and the second expanding them into an eerily believable acoustic space.

I did it by telling the genetic algorithm to try millions upon millions of different matrices, and evaluate them in various ways. Like, constructing all the end-result echoes from the Householder matrix, and then seeing how many of those combinations were primes (people are used to putting primes in the individual delays of the matrix, but it does nothing! It’s how many of the end results add up to a prime). Or measuring the gaps between echo returns, and seeing if they’re similar or all different (this increases the depth and naturalness of the sound). Or working out what the intersample peaking of the reverb will be, and preferring lower treble energy out of it. Or wanting the first echoes to happen almost immediately, which means there has to be a path through the matrix that is very short.

I put together a small hall out of this, without too much furniture or weird architecture (yes, I can specify that too) and it’s yours now. It’s using a 3×3 and a 6×6 Householder matrix inside, so before it even gets into regeneration it’s producing 1.25 million echo returns (previous kVerbs before VerbSixes? 3125, for not much if any CPU savings). It’s using Bezier undersampling to sound right at high sample rates with no penalty in CPU to speak of. It’s got just enough controls to adapt to many needs, but is essentially simple to use: keep things near default, tune your RT60 and loudness of early reflections and the filtering on the deep reverb to tune the brightness of the hall. Use Derez if you want to scale it up while darkening it.

There will be more grandiose spaces (heck, you have VerbSixes for that). But in certain ways, there won’t be more impressive spaces for a while, because whatever sound you put into kBeyond, it ought to sound like you’ve just gone on the road and into a hall and put up some mics. It’s not even a texture, it’s just there, invisibly, making things real.

Compare this to, say, ClearCoat, and you can see why I didn’t stop there.

Expect more. All the reverbs kinda need an update now that I can do this…

Airwindows Consolidated Download
Most recent VCV Rack Module
download 64 Bit Windows VSTs.zip
download Signed M1/Intel Mac AUs.dmg
download Signed M1/Intel Mac VSTs.dmg
download LinuxVSTs.zip
download LinuxARMVSTs.zip for the Pi
download Retro 32 Bit Windows VSTs.zip
download Retro PPC/32/64 Mac AUs.zip
download Retro PPC/32/64 Mac VSTs.zip
Mediafire Backup of all downloads
All this is free and open source under the MIT license, brought to you by my Patreon.

Date June 22, 2025
Author Chris
Comments 3 Comments

VerbSixes

TL;DW: VerbSixes is a calibrated reference reverb plugin for Householder matrices.

VerbSixes in Airwindows Consolidated under ‘Reverb’ (CLAP, AU, VST3, LV2)
VerbSixes.zip (604k) standalone(AU, VST2)

The only thing small about this is the interface, and there’s a reason for that.

VerbSixes applies Householder matrices to produce reverb, and it’s named VerbSixes because it escalates things up to the point of 6×6 matrices. Normally you get 4×4 matrices in conjuction with allpass filters which smear out the sound (example: my CloudCoat plugin is made up entirely out of allpass filters, as is MV). There’s a reason other matrix sizes aren’t popular: firstly, you can use multiple 4×4 matrices, and secondly the math is messier with other sizes. With the 4×4 you can feed all the delays into all the other delays at unity gain, just flipping the polarity.

A 3×3 matrix gives you 27 distinct echoes out of 9 different delay lines.

A 4×4 matrix gives you 256 distinct echoes out of 16 different delay lines, only 7 more, and the math is quite straightforward.

A 5×5 matrix, which I’ve been doing for all the kVerbs I’ve made, uses only 9 more delays to get 3125 distinct echoes… which is an impressive jump from 256, especially when you’re using the ability of a Householder matrix to feed back into the input again. That’ll quickly get you lots of echo density, though it’ll sound repetitive with smaller matrices like 3×3 or 4×4. 3125 with regen is a lot, though the math requires multiplications by -2 and 3.

A 6×6 matrix gives you 46,656 distinct echoes BEFORE regen. And all the math is either unity gain or times 2… which of course we know as BitShiftGain, a math operation that only changes the exponent and doesn’t alter the mantissa of the floating point number in any way (one of the secrets of the old Midiverb, which didn’t have floating point math capable of complicated multiplication).

VerbSixes comes with a built-in 6×6 matrix with a calibrated amount of regeneration, so it’s the most recent generation of Householder matrices, prepared to produce extremely lush fluid reverb, in spite of having no filtering or allpasses whatsoever. In fact it has no controls either: it gives exactly one RT60 no matter what the reverb is.

That’s because VerbSixes is also set up to demonstrate 5×5 reverbs. And 4×4. And 3×3… and ANY COMBINATION of those things.

So if you’re making a 4×4 matrix, generating variations on them with my program IntoTheMatrix, you can compare the results knowing they’re going to be consistent. They’re also pretty consistent with the other matrix sizes (to the best of my ability) and a full range of delay lengths (smaller spaces will tend to get louder). It’s a reference reverb maker, running all wet, and you can put it on an aux or just wallow in depth, and if you can get the VerbSixes code to compile and also run IntoTheMatrix, you can generate anything and try it.

Or you can use it just as a plugin, which is a 6×6 giant hall… times an entirely separate 4×4 matrix, so call it 256 giant halls laid end to end.

Just short of 12 MILLION echoes, even without regen. And they both have regen.

I’ll give you more reverbs based on this technique, but enjoy the new bigger-than-Cosmos space :)

Airwindows Consolidated Download
Most recent VCV Rack Module
download 64 Bit Windows VSTs.zip
download Signed M1/Intel Mac AUs.dmg
download Signed M1/Intel Mac VSTs.dmg
download LinuxVSTs.zip
download LinuxARMVSTs.zip for the Pi
download Retro 32 Bit Windows VSTs.zip
download Retro PPC/32/64 Mac AUs.zip
download Retro PPC/32/64 Mac VSTs.zip
Mediafire Backup of all downloads
All this is free and open source under the MIT license, brought to you by my Patreon.

Date June 15, 2025
Author Chris
Comments 1 Comment

Chris

PrimeFIR

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VerbSixes

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