Why five rumble engines, and not one

The first version of MrKicksy had one rumble engine. A pretty good one: a convolution reverb sourced from impulse responses we recorded ourselves in a Prague basement, with a sub-aware tail. It sounded great on the presets we built around it.

It sounded great on those presets only.

The producer we tested it with first, a working hardgroove guy who plays festivals, was complimentary for about ten minutes. Then he said the line that ended up reshaping the whole instrument: “It does one thing well. But a kick is more than one thing.”

He was right. A real kick, the kind that’s been mastered by somebody who knows what they’re doing, almost never has one rumble source. It has a room, plus a tail, plus a resonator quietly humming on the fundamental, plus sometimes a touch of feedback delay, plus sometimes filtered distortion in the lows. Stacking those produces a complexity that no single engine matches. You can hear it. You can’t synthesise it with one tool.

So we rebuilt the engine to run five generators in parallel, each with its own level. Here’s what each one does and why we picked it.

ConvRoom, convolution

The most straightforward one. You feed in an impulse response, a recorded sweep through a real room, and the engine convolves your kick with it. The result sounds like your kick was played in that room.

We ship five impulses: a tight studio booth, a medium basement, a tunnel, a hall, and a “fake big room”: an artificially-extended impulse that gives you reverb tail without the muddiness of a hall. The fake one is the one most presets use, because most clubs aren’t rooms with great natural reverb. They’re rooms with terrible reverb, and you want to replace their reverb, not double up on it.

ReverbTail, algorithmic

A normal algorithmic reverb, but tuned for the low end. The damping curve is biased so the highs decay fast and the lows decay slowly, opposite of a typical hall plate. The result is a tail that supports the kick without smearing the snare.

Tunable, predictable, cheap. The opposite of ConvRoom: convolution gives you authenticity. Algorithmic gives you control. You use them together when you want both.

Resonator, pitched harmonic series

This was the surprise. We added a Resonator engine because somebody asked for “the warehouse bloom”, that thing where a kick in a big concrete space picks up a slow, pitched, harmonic shadow that follows the fundamental for half a second after the click.

The Resonator emulates that with a bank of tuned bandpass filters at the harmonic series of whatever pitch you set. Tune it to E and the kick gets an E-tinted bloom. Tune it to a chord and the bloom feels harmonic with whatever’s playing on top. It’s the engine producers reach for when their track has a specific key and they want the kick to acknowledge it.

It’s also the engine most producers don’t know they wanted until they hear it.

FeedbackDelay, tempo-synced tape

Borrowed from dub. A short tempo-synced delay with high feedback, low-passed so the repeats don’t pile up in the highs. The result is a “rolling sub” effect: the kick sounds like it’s falling forward into itself.

You wouldn’t use this on every kick. You’d use it on tracks where the groove leans on a half-beat lag. Lots of UK garage uses something like this; dub techno uses it constantly; hardgroove uses it sparingly to add weight without slowing the BPM.

The amount of FeedbackDelay you add is one of the things the Analog↔Digital macro modulates, pull it back for clean modern kicks, push it up for the dub-techno end.

FiltDistort, filtered distortion rumble

A separate engine for what some producers call “the bass under the bass”, distortion run through a low-pass filter, generating sub-frequency content that wasn’t in the original kick. The result is a kick that feels bigger on a club PA without being louder.

This is the engine that’s easiest to overdo. A lot of factory presets use it sparingly, 10–20% on the rumble mix, and they sound massive. Crank it up and the kick starts to feel artificial. The listener can hear that something’s pumping that shouldn’t be.

It’s the most divisive engine. Some producers love it. Some never touch it. We’d rather give you the choice than not.

Why parallel, not serial

The reason we run all five in parallel, instead of putting them in a chain, is that each engine sounds best when it’s reacting to the dry kick, not to another engine’s output. A Resonator that listens to the output of ConvRoom is hearing a wet kick with smeared transients. It tunes itself to the smear instead of to the kick.

Running them all in parallel and mixing the wet sums at the end gives every engine a clean source to react to. You blend the wet returns. The dry kick stays dry until the master chain hits it.

This costs more CPU than a serial design, we measured about 25% more, give or take, depending on which engines you have lit. We thought that was worth it. The producer we tested it with agreed.

What this is for

The thing about MrKicksy that this engine architecture buys you: you can blend a real-room convolution with an algorithmic tail and a pitched resonator and a dub-style delay, all on the same kick, with independent levels, in one knob-twist each. That isn’t something a single rumble engine can fake. It’s also not something most producers would set up with five separate plugins, because by the time you’ve wired them all up and routed them through a bus, the kick has moved on.

Five rumble engines is more than the marketing copy needs. It’s also the reason the kicks sound like they do.