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SOL-4 Mastering Limiter

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SOL Studio Audio  /  Mastering Tools

SOL-4 — Transparent Limiter
with No Hidden Behavior

“Uncompromisingly clean — but it never strips away the harmonics your music needs.”

A professional mastering limiter that shows you exactly what it’s doing, sounds exactly as neutral as you want it to, and gets out of the way.

Version Update Sale

Buy Now — $39.90

Regular $69.90   Sale $39.90

VST3/AU Windows 10 / 11 macOS 10.13 – 15 (Apple Silicon & Intel) 64-bit

Oversampling

8x

Maximum quality mode

Latency

0 ms

Zero-latency capable

Processing

M/S

Full mid/side domain

LUFS

M / S / I

K-weighted display

True Peak

Safety

Independent final guard

Presets

13

Factory + user saves

Version 2.5.10 Update

More loudness. Less pumping. The same transparency.

SOL-4 now distributes peak control across a spectrally adaptive Slow M/S stage, a fully linked Fast stage, and an independent final True Peak safety guard. The result is greater usable loudness, clearer transient definition, and more stable recovery under demanding material.

SOL-4 Mastering Limiter version 2.5.10 interface

Slow / Fast Dual-Stage Limiting

Slow shapes the main M/S envelope while the linked Fast stage catches residual peaks. Drums stay clearer and low-frequency pumping is reduced as loudness rises.

Independent True Peak Safety

A final safety stage follows the oversampled limiter path and controls predicted inter-sample peaks in normal lookahead operation, with improved agreement to external meters.

FAST and SAFE GR Meters

Dedicated meters reveal how much reduction is happening in the linked Fast stage and the final safety stage, alongside the existing Mid/Side GR display and history.

Optional FAST CLIP

A visible, optional peak-shaving stage can remove up to about 0.49 dB before Fast. OFF preserves the original clean path; 4x or 8x oversampling is recommended when ON.

Expanded Drive and OUT TRIM

INPUT GAIN now spans -15 to +20 dB. OUT TRIM provides -12 to 0 dB of post-limiter attenuation for accurate loudness-matched comparisons.

Refined Presets and Workflow

All 13 factory presets have been reviewed for the new architecture. FAST CLIP remains OFF by default, and the live latency value is now always visible on the Options bar.

Core Design

Built for mastering engineers who trust their ears.

Every parameter in SOL-4 does exactly what it says. No secret sauce and no hidden saturation. Any added colour is explicit: FAST CLIP is visible, optional, and OFF by default.

Zero Latency Mode

Disable lookahead and oversampling for 0 ms reported latency. Ideal for monitoring and real-time adjustment; switch back to lookahead for the strongest inter-sample peak protection at final delivery.

Spectral-Dependent Release & Crossover Solo

Low/high energy analysis continuously adapts release timing without splitting the audio into bands. Crossover Solo auditions the low Mid region so the analysis boundary can be set by ear.

M/S Domain Processing

All limiting happens in Mid/Side space. The S-Floor Link parameter gives continuous control over stereo width preservation — from fully independent to fully linked.

Delta Monitoring

Hear exactly what the limiter is removing. Complete silence means no gain reduction. Audible content tells you precisely how hard the limiter is working — and what it costs.

Transient Preservation

Protect the initial attack of transients without allowing peaks to exceed the ceiling. Drums and percussion stay impactful, even at high gain reduction.

Auto Release Modulation

Automatically extends release time during dense passages to prevent inter-modulation distortion, then shortens during sparse material. Fully adjustable.

Dual-Stage + True Peak Safety

The Slow M/S and linked Fast stages share gain reduction before an independent final safety guard controls predicted inter-sample peaks in normal lookahead modes.

Detector Weighting

Four K-weighting modes determine how aggressively the limiter responds to high-frequency content. From subtle (0.25) for acoustic material to flat (FLAT) for drum-heavy tracks.

A/B Comparison + Undo

Two independent parameter slots for instant side-by-side comparison. Full undo/redo history. Non-destructive workflow at every step.

Dithering & Noise Shaping

Built-in TPDF dithering for 16-bit and 24-bit output, with four noise shaping curves (FLAT, HF1, HF2, HF3). SOL-4 handles the complete final delivery chain — limiting, true peak control, and word-length reduction in a single plugin.

Resizable Interface

Six zoom levels from 50% to 150% cover compact and high-resolution displays. Gold, Silver, and Bronze themes change appearance only, and compact screens can start at an automatically reduced size.

Metering Suite

Everything you need to see. Nothing you don’t.

SOL-4’s metering gives you immediate, accurate feedback on what’s happening.

K-Weighted LUFS — M / S / I

Momentary (400 ms) and Short-term (3 s) maximums plus an Integrated accumulator above the -70 gate. All three are visible together and reset with one click.

GR History Graph

Scrolling gain reduction history for Mid and Side channels. Three scroll speeds (SLOW / MED / FAST) let you zoom from full-song overview to individual transient detail.

Knee Curve Display

Live input/output transfer curve. The full knee width is always visible regardless of the KNEE setting — readable from 0 to 12 dB.

MID / SIDE Solo + Output Meters

Audition Mid or Side channels independently. Post-processing Left/Right level meters, peak hold, and the dedicated FAST/SAFE reduction meters keep every limiter stage visible.

Pricing

SOL-4 Mastering Limiter

Version Update Sale

Regular $69.90

$39.90

  • —  SOL-4 VST3 plug-in (Windows 64-bit)
  • —  SOL-4 AU & VST3 plug-in (macOS 10.13–15, Apple Silicon & Intel)
  • —  PDF User Manual
  • —  13 factory presets
  • —  Free updates within version 2.x
  • —  Support via info@solstudio.online
Purchase on Gumroad

Requires Windows 10 or 11 (64-bit), or macOS 10.13 or later (Apple Silicon and Intel).
Not compatible with Pro Tools.
No subscription. No iLok. No internet connection required after purchase.