The Parallax User Guide

The Parallax is a three-band stereo enhancer for shaping width where it matters. Instead of making one broad stereo decision for the whole signal, it lets you treat the low, mid, and high frequency regions independently — so the low end can remain focused while the midrange and top open around it.

Use it on individual tracks, buses, mix buses, or toward the end of a master when the stereo field needs a deliberate adjustment. There is no fixed place for it in a chain; the useful place is wherever its stereo decision supports the record.

The two central ideas are simple:

• Perspective scales your overall width decision.
• Integrity reacts only when widened material begins to lose phase coherence, gently bringing it back toward unity.

Quick Start

1. Begin with the Default preset.
2. Set Low, Mid, and High width for the balance you want.
3. Keep Low at 100% or narrow it slightly when the bottom needs more focus.
4. Use Perspective as the final, global width trim.
5. Raise Integrity only after you have widened one or more bands beyond 100%.
6. Check Mono, then compare with Bypass at a matched level.

The Three Bands

Low, Mid, and High control stereo width independently from 0% to 200%.

• 0% removes the Side information for that band, making it mono.
• 100% leaves its original stereo width unchanged.
• Values above 100% increase width.

This is Mid/Side width processing: the Mid content is preserved while the Side content for each band is scaled. The Parallax does not use delay, Haas processing, or phase trickery to create width.

Low Split and High Split

Low Split and High Split determine where the three frequency regions meet. The crossovers blend smoothly rather than switching abruptly from one band to another.

• Low Split: 60–1,000 Hz; default 300 Hz
• High Split: 1,000–12,000 Hz; default 3,000 Hz

Move the split points only when the musical balance needs it. If the bass feels too broad, lowering the Low Split can confine your low-band decision to a smaller region. If air or percussion needs room without widening the vocal range, raise the High Split and work primarily with High.

Perspective

Perspective is the master width control. It scales the three band-width settings together from 0% to 200%, preserving their relative relationship.

At 100%, Perspective changes nothing. Lower it to pull your complete stereo decision inward; raise it to push the entire image outward.

Perspective does not create depth, move elements front to back, introduce delay, or change the Mid channel. Think of it as the final trim after you have balanced Low, Mid, and High — not a replacement for choosing the right per-band widths.

Integrity

Integrity is a reactive safety net for width above 100%. It measures the stereo relationship of the processed signal and intervenes only when two things are true:

1. A band has been widened beyond 100% after Perspective is applied.
2. The material in that moment is losing phase coherence.

When both conditions occur, Integrity gently pulls that band's width back toward 100%. It never narrows a band below unity, and it never changes any band at or below 100%.

Integrity is sensitivity, from 0% to 100%, not an amount of stereo width, a correlation meter, or a tone control: 0% turns the restraint off; higher settings make it respond more strongly when widened material begins to become unstable.

The pink glow around the Integrity control shows the restraint actually being applied at that moment. It is not simply an indication of the knob position.

Mono

Mono is a true processed-signal mono check. It collapses all three bands to 0% width, regardless of your Perspective or Integrity settings.

Use it before committing to a wider setting. You are listening for what remains when the Side information is removed: kick, bass, vocal, core groove, and essential tonal balance should still make sense.

Mono is not automatic protection. It is a deliberate listening tool, and it remains on or off exactly as you set it.

Response Display

The response display has three distinct visual layers:

• Blue shows the Low, Mid, and High width settings you have chosen.
• Pink shows the resulting width across frequency after crossover blending, Perspective, Integrity, and Mono are considered.
• Grey shows the incoming spectrum.

The display is not a correlation meter and does not measure stereo width in the source. It is a clear view of the decision The Parallax is making. Let it help you understand the settings, then judge the result by listening.

Presets, A/B, and Bypass

The Parallax includes five fixed factory presets:

• Default
• Open Sesame
• Open Air
• Wide Spread
• Down Low, Up High

Use them as starting points, not rules. The preset selector is intentionally simple: there are no user presets, saving, renaming, or deleting. Recalling a preset changes Low, Mid, High, Perspective, Integrity, and the split frequencies as one edit; Mono and Bypass stay where they are.

A/B stores two complete width states. Use it to compare two actual directions — perhaps a conservative low-end focus against a wider high-frequency approach — without rebuilding either one. A/B compares the seven width, Perspective, Integrity, and split settings; Mono and Bypass are deliberately left untouched.

Bypass crossfades smoothly to the untouched input so comparisons do not click. The processing and Integrity tracker remain ready underneath, so re-engaging Bypass does not create a cold or delayed response.

Practical Workflows

Subtle width

Leave Low close to 100%, add a small amount of width to Mid or High, and keep Perspective near 100%. This is often enough to make the image feel less constrained without changing the identity of the record.

Focused low end, open top

Narrow Low slightly or leave it at unity, then open Mid and High. Use the split controls to make sure the transition occurs where the music needs it. This is especially useful when kick and bass need a firm center while percussion, guitars, pads, or ambience can extend outward.

More ambitious width

Push one or more bands above 100%, then bring up Integrity to the degree that the material needs. The goal is not to keep the width as wide as possible; it is to let the record open without losing the parts that make it feel solid.

Open Sesame, Open Air, and Wide Spread are useful references for more assertive starting points. Down Low, Up High is a direct way to hear the benefit of narrowing the low band while expanding the upper regions.

Final compatibility check

Use A/B to compare two choices at the same level. Then engage Mono. If the record loses its center, drive, or tonal balance, reduce width, adjust split points, or let Integrity work a little more. Return to stereo and Bypass before making the final call.

Zero-Latency Operation

The Parallax adds no processing latency and has no tail. Its crossover design is built for real-time use, so it can be practical on tracks and buses as well as in a final stereo-field decision.

Updates, Licensing, and Support

The Parallax is available as AU and VST3 for macOS. The About overlay shows the installed version and provides links to this User Guide, the product page, the Mainline Audio site, and support.

Some host browsers may still show the earlier descriptor "Stereo Imager." This refers to the same plug-in; the customer-facing product description is Three-Band Stereo Enhancer.

For current downloads, release notes, and support, visit the product page or support@mainline-audio.com.

Final Perspective

The goal of The Parallax is not maximum width. It is intentional perspective: a tighter foundation, a more open upper field, and a stereo image that remains believable when the record is heard in mono. Make the band decisions first, use Perspective as the final trim, and let Integrity be the restraint — not the substitute for listening.