Serum 2 filters are where most of my presets get won or lost. Not the wavetable. Not the effects chain. The filter type and how it’s routed.
I’ve been building Serum packs at Monosounds since 2022, and since the Serum 2 update landed in March 2025 the filter menu has roughly doubled in usefulness. Two filter slots instead of one. Eleven new types, including analog-style emulations that actually saturate like hardware. Per-oscillator routing.
That’s also a lot of menu to scroll through at 2 a.m. So here’s the map I wish I’d had: what each category sounds like, how dual routing works, and exactly which filter I grab for acid bass, smooth pads, and vocal-ish formant leads.
What Changed in the Filter Section
Serum 1 gave you one filter and that was it. If you wanted a high pass after your low pass, you went to the FX chain and burned the single filter slot there.
Serum 2 gives you two filter slots that run serial or parallel. And each of the three oscillators can be sent to filter 1, filter 2, both, or neither. That routing alone changed how I build bass patches more than any new filter type did.
The knobs themselves will feel familiar: cutoff, resonance, drive, mix. Everything is a drag-and-drop modulation target, same as the rest of the synth. If modulation routing is still fuzzy for you, I break the whole system down in my Serum 2 modulation guide.
Serum 2 Filters by Category
Xfer doesn’t group them exactly like this in the menu, but after three years of preset work, this is how I actually think about the serum 2 filters:
- Clean digital filters. Low, high, band, peak and notch types at 6, 12, 18 and 24 dB per octave. Surgical, no added color. Great when the oscillator should do the talking.
- Multi filters. Morphing types that sweep from low pass through band pass to high pass on one knob. One LFO on that morph gets you movement a static filter can’t do.
- Analog-style emulations. The headline of the update. These saturate, and resonance behaves nonlinearly, like a hardware ladder filter. More on these below.
- Formant filters. Vowel shapes. The fastest route to talky leads and vocal-ish textures.
- Comb, flange and phase filters. Resonator territory. Metallic, hollow, pitched artifacts. Small doses.
- The weird bin. Ring mod, sample-and-hold flavors, downsampling types. You use them twice a year, and both times they save the patch.
The New Analog-Style Filters
Serum 1’s filters were famously clean, and that was the complaint: crank the resonance on a digital 24 dB low pass and the low end thins out while the resonant peak turns harsh.
The 11 new types in Serum 2 fix exactly that. Push resonance and the bottom stays thick. Push drive and the filter itself distorts instead of just getting louder. Cutoff and drive interact, so the same knob position sounds different at different input levels. That’s the hardware behavior everyone was layering third-party plugins to fake.
My test for any new filter: same patch, same cutoff, A/B a clean Low 24 against an analog-style type. On a saw bass with resonance at 40%, the clean filter sounds like a demo. The analog one sounds like a record. It’s not subtle.
The honest tradeoff: they cost more CPU than the clean types. Not brutal, but noticeable when you stack them with big unison. I’ll get to workarounds at the end.
Dual Filter Routing: Serial vs Parallel
Serial means filter 1 feeds filter 2. I use it when one filter shapes tone and the other cleans up. Classic move: a formant filter into a low pass, so the vowel character stays but the fizzy top end gets rounded off.
Parallel means the signal splits, hits both filters, and sums back together. This is Reese and neuro territory: a driven band pass on one side, a low pass on the other, and the phase interaction between them does half the sound design for you.
Then there’s the per-oscillator assignment, which is quietly the best part. Send oscillator A to filter 1 and oscillator B to filter 2, and you’ve got a split-band bass inside one preset. Sub stays clean and untouched, top layer gets filtered and driven. No layering two synth instances, no bus routing in your DAW.
One thing worth knowing: there are also filter modules in the FX section, and with Serum 2’s multiple FX buses you can filter each bus separately. That’s a different job, though, post-processing rather than synthesis. I cover when to use which in the Serum 2 effects guide.
Which Filter for Which Sound
Here’s my cheat sheet. These are starting points from actual presets I’ve shipped, not gospel. Move the numbers until it sounds right in your track.
| Sound | Filter pick | Starting settings |
|---|---|---|
| Acid bass | Analog ladder 24 dB | Res 65%, drive up, fast env on cutoff |
| Smooth pad | Clean Low 12 | Res 10%, zero drive, slow LFO on cutoff |
| Formant vocal lead | Formant type | LFO or macro on vowel morph |
| Pluck | Clean Low 24 | Env decay 250 ms, env amount 60% |
| Reese / neuro bass | Parallel LP + BP | Drive on the BP side only |
| Techno stab | Analog Low 12 | Res 30%, drive 3 o’clock, short env |
| Metallic texture | Comb | Key tracking on, mix 40% |
Acid Bass
The 303 recipe hasn’t changed in 40 years: 24 dB ladder-style low pass, resonance high enough to sing (60 to 70%), and an envelope slamming the cutoff on every note. In Serum 2, pick one of the analog ladder types and add drive; the filter distortion is what separates acid from just a squelchy saw.
Set the envelope decay between 120 and 200 ms depending on tempo, envelope amount around 50%, and modulate resonance with a macro for live tweaking. Most of the acid patches in our Technocraft techno collection are built exactly this way, so crack one open if you want to see the routing in place.
Smooth Pads
Pads are where people over-filter. You don’t want resonance, you don’t want drive, you want a gentle 12 dB slope so the harmonics fade out instead of getting chopped off.
My default: clean Low 12, cutoff around 800 Hz to 1.5 kHz, resonance under 15%, and a slow LFO on cutoff, around 0.1 Hz or a synced 8-bar rate at 120 BPM. The movement should be felt, not heard. If your pad sounds like it’s breathing loudly, halve the LFO amount.
Formant and Vocal Sounds
The formant types simulate the resonances of a human mouth. The trick is to modulate the vowel position, because a static vowel just sounds like a band pass with an accent.
Map an LFO to the formant morph for a talking rhythm, or put it on a macro and ride it during the drop. Serial routing shines here: formant filter first, then a clean low pass around 4 kHz to tame the sibilant fizz these filters generate up top.
Bass for Club Genres
For tech house and techno bass, the filter is doing the groove work: short envelope stabs, key-tracked cutoff so high notes open up naturally. I wrote a full patch walkthrough in my tech house bass guide for Serum 2, and there’s a deeper preset roundup in the techno bass presets guide if you’d rather start from finished patches.
And if you want free reference material, the 250+ patches in our free Serum 2 preset pack use every category on this page, basses, pads, formant leads included. Open them and look at which filter is loaded and why.
Keeping the CPU in Check
The analog types plus 16-voice unison plus two filter slots will spike any laptop. My rules: unison between 3 and 7 covers almost everything, oversampling at 2x not 4x while writing, and only one analog-style filter per patch unless the patch really earns the second.
If you’re still glitching, Xfer’s support page has official CPU guidelines, and freezing finished tracks is free. The clean digital filters are noticeably lighter, so use them anywhere the analog color isn’t the point.
FAQ: Serum 2 Filters
Are the Serum 1 filter types still in Serum 2?
Yes. Serum 1 presets load in Serum 2, filters included, and the classic types are all still in the menu. The 11 new types sit alongside them, so old patches sound the same until you decide to swap.
What’s the difference between serial and parallel routing?
Serial chains filter 1 into filter 2, so the second filter processes an already-filtered signal. Parallel splits the signal, runs both filters side by side, and sums them. Serial for shaping plus cleanup, parallel for split-band designs and phase interaction.
Which Serum 2 filter is best for bass?
For driven, aggressive bass, one of the analog ladder types with drive up. For clean sub-heavy bass, route the sub oscillator around the filters entirely and only filter the top layer. There’s no single best; the routing matters more than the type.
Do the analog-style filters use more CPU?
Yes, moderately. On my machine an analog type costs roughly half again what a clean equivalent does. Cut unison before you cut the filter, dropping from 16 to 7 voices saves far more than swapping filter types.
Start From Patches, Not From Zero
Reading about filters only gets you so far. The fastest way to internalize this stuff is to reverse-engineer working presets and watch what the filter section is doing.
If you want a shortcut, grab our 250+ free Serum 2 presets, no strings attached. Tear the patches apart, swap the filter types, and hear what each one actually does to a sound you already like.
I run Monosounds.studio and make the packs myself. Ten-plus years of producing, 97+ releases, 16,000+ downloads. Every Serum 2 preset we ship passes a CPU check on a mid-range laptop and gets used in a real track before release. If it does not survive a mix, it does not go in the pack.
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