KERN SMOOTH vs Kobito ResSup

why this guide exists

most “soothe alternative” comparisons pit a $29 plugin against a $259 one, where the price gap does half the arguing. Kobito ResSup is different. it shipped in May 2026 as a dynamic resonance suppressor at $49, launched with a $29 discount code that put it (at least at release) right where KERN SMOOTH sits, with a feature list that overlaps mine more than anything else on the market. so this is the rare comparison where price is not the story and i have to be honest about where another developer’s tool is genuinely the better pick.

i make SMOOTH. i will still tell you where ResSup wins.

(reading one developer comparing his plugin to a competitor is worth exactly what you would expect. trust your ears and the demos, not me.)

what Kobito ResSup is

ResSup is a lightweight dynamic resonance suppressor: instead of statically EQing a sound, it detects frequencies that stick out too far in real time and gently pulls them down. the published feature set is genuinely capable:

• selectable band shapes: bell, band-pass, low/high cut, and low/high shelf modes for the suppression filters.
• spectral attack and release for timing the response across frequencies.
• Transient Protect to keep punch, and Harmonic Preserve to stop the source sounding over-processed.
• delta monitoring to hear exactly what is being removed, plus stereo, Stereo Link, and M/S modes.
• external sidechain input, so one signal can drive suppression on another.
• a VP (Vocal Pressure) toggle, added June 2026, that applies extra suppression to persistent resonances in the 800 Hz to 5 kHz range.
• described as light on CPU; sold and delivered via Gumroad; VST3 and AU for macOS and Windows.

that is a lot of plugin for the money. take the overlap seriously: both tools suppress resonances dynamically, both do M/S, both protect transients, both try to keep the harmonics intact. the honest comparison lives in the few places they actually diverge.

what SMOOTH does differently

SMOOTH is built around one architectural choice and one ecosystem choice.

ERB-domain bands

the human ear does not hear in linear frequency. the cochlea has roughly logarithmic resolution: critical bandwidths widen as frequency rises. SMOOTH’s 40 bands follow the Equivalent Rectangular Bandwidth (ERB) scale derived by Glasberg and Moore.[^1] bands are narrow where your ears are most sensitive (200 Hz to 5 kHz, where harsh resonances live) and wider where they are not. a 3 dB peak at 3 kHz triggers heavy suppression; the same bump at 80 Hz triggers proportionally less, because that is how you actually hear the problem. perceptual band placement is the lever SMOOTH pulls that most suppressors in this price range do not.

permanent price, standalone, and a free companion

SMOOTH is $29 with no intro clock, ships a standalone build alongside VST3 and AU, and comes from a catalogue where the mono-compatibility analyzer, KERN CHECK, is free forever. resonance work and mono-safety checking in one ecosystem, one of them at no cost.

where SMOOTH is behind

i will say it plainly: SMOOTH does not expose an external sidechain, and it does not let you pick the suppression filter shape per band the way ResSup does. if your workflow leans on either, that is a real reason to choose ResSup.

the comparison table

features compared, point by point

price and ownership

ResSup has a $49 base price, sold through Gumroad, and launched with a $29 discount code (verify whether it still applies at checkout). SMOOTH is $29 permanently, activated once via Lemon Squeezy and then offline forever. neither uses iLok, so the ownership question here is not about dongles. it is about the standing price and whether buying direct from the developer with a price that never moves matters to you. unless you catch a live ResSup code, the $20 gap is real money.

the suppression engine

both detect resonances and duck them dynamically rather than statically. ResSup’s distinguishing move is letting you choose the filter shape (bell, band-pass, cut, shelf) the suppression uses. SMOOTH’s distinguishing move is where the bands sit: on the ERB scale, so the resolution matches the ear instead of the FFT. these are different philosophies. ResSup gives you manual control over the shape; SMOOTH spends that complexity budget on perceptual placement and keeps the surface simpler.

transient handling

both protect transients, by design. ResSup ships a dedicated Transient Protect control. SMOOTH uses frequency-dependent attack times: high bands react faster than low bands, so transient sibilance gets a fast response while sustained body notes get a slower one. different mechanisms, same goal, both built to avoid the “deep dip after every hit” failure.

external sidechain

ResSup has it. SMOOTH does not. for spectral ducking, making the pad step out of the vocal’s way automatically from a sidechain feed, ResSup is the tool. this is the clearest single capability difference between them.

latency

i am not going to claim a latency edge in either direction, because neither of us publishes a number that makes it a clean win. ResSup’s latency is unpublished. SMOOTH runs a 4096-sample FFT in its standard mode (about 93 ms, fine for mixing, compensated by the DAW) and an opt-in LIVE mode at ~12 ms for tracking. if low-latency tracking matters, test both yourself on your system rather than trusting a spec sheet.

CPU

ResSup is described as light on CPU, with no published figure. SMOOTH targets under 3% on macOS at 44.1 kHz, single instance. both are designed to run across many tracks; neither will be your session bottleneck on a modern machine.

decision framework

get ResSup if

• you use external sidechain ducking and want it built into your resonance suppressor.
• you want to choose the suppression filter shape (bell, band-pass, cut, shelf) per band.
• you catch a live launch code and want maximum flexibility for the money right now.

get SMOOTH if

• you want perceptual (ERB) band placement, so suppression concentrates where the ear localizes the problem.
• you want a permanent $29 price with no intro clock and a standalone build alongside VST3/AU.
• you want the free CHECK mono-compatibility analyzer in the same ecosystem.
• you prefer a simpler surface and a fully documented algorithm from a solo developer you can email.

honestly, get either if

• you just need a capable dynamic resonance suppressor for vocals and bright instruments and you are not leaning on sidechain or filter-shape selection. both will do that job well. this is not a case where one is clearly the right answer.

frequently asked questions

frequently asked questions

is KERN SMOOTH a real alternative to Kobito ResSup?

yes, and the reverse is also true. they are unusually close: both are dynamic resonance suppressors in the same budget class, both do M/S, both protect transients, both try to preserve harmonics. the real differences are architectural and ownership-side. SMOOTH spaces its 40 bands on the ERB (perceptual) scale and is $29 forever; ResSup offers selectable filter shapes plus an external sidechain and is $29 only during its intro before rising to $49.

how much does Kobito ResSup cost compared to SMOOTH?

the ResSup base price is $49. it launched with a $29 discount code and was briefly free for early users; whether that discount still applies, check at the Gumroad checkout. KERN SMOOTH is $29 permanently, no intro clock and no upgrade fees. at the $49 base that is a $20 gap; if the launch code is still live, the two are level.

do either of them need iLok?

no, neither uses iLok. ResSup is sold and delivered through Gumroad. SMOOTH activates once via Lemon Squeezy on first launch, caches locally, and then runs offline forever with no further online checks. so iLok is not the deciding factor here the way it is against Soothe; the ownership difference is permanent pricing and buying direct from the developer versus a marketplace.

does ResSup have anything SMOOTH does not?

two things worth naming honestly. ResSup exposes an external sidechain input, so one track can drive resonance suppression on another. SMOOTH does not currently offer external sidechain. ResSup also gives you selectable band shapes (bell, band-pass, cut, shelf) for the suppression filters. if either of those is core to how you work, ResSup is the better fit.

what does SMOOTH have that ResSup does not?

ERB-domain band placement (40 bands mapped to how the cochlea actually resolves frequency, not linear spacing), a permanent $29 price, a standalone build alongside VST3 and AU, a free companion mono-compatibility analyzer (CHECK), and a fully documented algorithm. SMOOTH also has an opt-in LIVE low-latency mode.

which should I buy?

if you need external sidechain ducking or want to pick the filter shape per band, get ResSup. if you want perceptual (ERB) band placement, a permanent price with no intro clock, a standalone version, and the free CHECK analyzer in the same ecosystem, get SMOOTH. on the routine job of taking a resonance out of a vocal or a bright instrument, both do it well and the choice is about workflow and ownership, not capability.

references

a note from the developer

most weeks the competitor in one of these guides is a $200+ plugin from a company with a marketing budget, and the honest answer is “mine does most of the same job for a tenth of the price.” ResSup broke that pattern. it is a genuinely good, genuinely cheap tool from another small developer who picked the same problem i did, and in a couple of places (external sidechain, selectable filter shapes) it does something SMOOTH does not.

so the pitch here is narrower and more honest. SMOOTH’s case is ERB-domain perceptual processing, a price that never moves, a standalone build, a free mono-compatibility analyzer alongside it, and a published algorithm. if that is the combination you want, it is yours for $29 forever. if external sidechain or per-band filter shapes are what you need, buy ResSup, with my respect to whoever built it.

i am a solo developer in Copenhagen. if you have run both on the same source and your ears disagree with anything here, tell me: jonas@kernaudio.io.