UpM1xer User Manual

Introduction

UpM1xer is a stereo-to-surround upmixing plugin for professional audio production. It takes a standard two-channel stereo input and distributes it across up to 16 output channels, covering formats from basic quad (4.0) through full 9.1.6 immersive audio. The plugin uses spectral analysis to separate primary (coherent) and ambient (diffuse) content from the stereo signal, then routes these components to the appropriate channels in the target surround layout.

UpM1xer is designed for music mixing, post-production, broadcast, and immersive audio delivery. It runs as a VST3, Audio Unit, or AAX plugin on macOS, and as a VST3 or AAX plugin on Windows.

Getting Started

Installation

The installer places the plugin files in the system-wide plugin directories.

macOS:

/Library/Audio/Plug-Ins/Components/                    (AU)
/Library/Audio/Plug-Ins/VST3/                          (VST3)
/Library/Application Support/Avid/Audio/Plug-Ins/      (AAX)

Windows:

C:\Program Files\Common Files\VST3\                    (VST3)
C:\Program Files\Common Files\Avid\Audio\Plug-Ins\     (AAX)

Launch your DAW and scan for new plugins. UpM1xer will appear in the spatial/surround or utility category depending on your host.

Basic Setup

1. Insert UpM1xer on a multichannel track or bus configured for the desired surround format.
2. Select the output format from the format selector in the plugin header (e.g. 5.1, 7.1.4).
3. Choose an Engine preset and Stem Profile that suit your source material.
4. Adjust the Immersion knob to taste — start around 50% and work from there.

Output Formats

UpM1xer supports 21 output configurations:

The format selector only shows formats that fit within the DAW's output bus channel count. For example, on a 7.1 bus (8 channels), formats requiring more channels such as 7.1.2 and 7.1.4 are grayed out and cannot be selected.

Logic Pro note: The 5.1.4, 5.1.6, 7.1.6, and 9.x formats are not available in Logic Pro. Logic's Dolby Atmos bed tracks are limited to 7.1.2 (10 channels), which does not provide enough discrete buffer positions for independent rear height channels (Ltr/Rtr) or wide speakers (Lw/Rw). Use 5.1.2 for a 5.1 layout with heights, or 7.1.2 / 7.1.4 for full Atmos immersion within Logic.

Channel Roles

• L / R — Front left and right
• C — Center
• LFE — Low-frequency effects (subwoofer)
• Ls / Rs — Side surrounds (approximately 90 degrees)
• Lss / Rss — Rear surrounds (approximately 135 degrees)
• Lw / Rw — Wide front speakers (between front and side surround, approximately 60 degrees). Present in 9.x formats.
• Ltf / Rtf — Top front height channels
• Ltm / Rtm — Top middle height channels (between top front and top rear). Present in 5.1.6, 7.1.6, and 9.x.6 formats.
• Ltr / Rtr — Top rear height channels

When the selected format has fewer channels than the maximum, the plugin automatically redistributes content. For example, if the format lacks a center channel, center content is folded into the front left and right at the appropriate coefficient.

Engine Presets

The Engine selector determines how aggressively audio content is distributed across the surround field. There are six engines, each with a distinct spatial character:

Subtle

Minimal widening with the strongest stereo compatibility. Most content remains in the front pair, with only gentle ambient energy pushed outward. A good starting point for material that needs to stay close to its original stereo image.

Natural

Balanced width and depth. The front stage retains clear definition while surrounds and rears receive a moderate share of ambient content. This engine suits most full-mix program material.

Wide

Emphasizes front and side spread for a cinematic sense of breadth. The side surrounds are more active, creating a wide horizontal soundstage while keeping the front image stable.

Deep

Rear-field bias for stronger behind-the-listener envelopment. Rear surround channels are driven harder, making this engine well suited to ambient recordings, live concert material, or any source where a sense of being immersed from behind is desirable.

Elevated

Vertical emphasis with an open, spacious feel. Height channels receive a larger share of ambient content, which lifts the perceived sound field upward. Best used in 5.1.2, 5.1.4, 5.1.6, 7.1.2, 7.1.4, 7.1.6, or any 9.x layout where physical height speakers are available.

Expansive

Maximum distribution across all channels. Content is spread aggressively to surrounds, rears, and heights alike. The front image becomes less dominant and the overall field becomes more uniform. Useful for ambient beds, atmospheric sound design, or deliberate effect.

Steering

Each engine preset includes an internal steering intensity that controls how wide the front soundstage is rendered. Steering works by scaling the side (stereo difference) component of the primary signal — higher steering values spread the front image wider between L and R, while lower values pull it tighter toward the center.

Subtle uses the lowest steering (narrowest front image), while Expansive uses the highest (widest). The Immersion knob also scales steering — at 0% immersion, steering is zero and the front image collapses to the original stereo balance. At 100%, steering reaches the full value defined by the selected engine.

The engine-driven steering described above shapes the front image. For active, source-level placement of audio anywhere around the listener, see the Source Placement (POSITION tab) section — the puck and width controls there steer the entire upmixed image to a chosen direction in the room, on top of the engine's front-stage steering. Stem profiles can also further modify the engine steering on a per-source basis (see below).

Stem Profiles

Stem Profiles optimize the spectral analysis and routing for different types of source material. Selecting the correct profile allows the engine to make better decisions about what content belongs in front, what belongs in the surrounds, and what should drive the height channels. Each profile also adjusts the engine's steering intensity to suit the source — for example, the Vocals profile uses tight steering to anchor the voice in the center, while Pads/Ambient uses wider steering to spread the front image.

Full Mix

General-purpose profile for complete program material. No frequency-range biases are applied, and transient detection operates across the full spectrum. Use this for stereo mixes, master bus processing, or any source that contains a full range of content.

Drums

Optimized for percussive sources. Kick and snare transients receive boosted detection weighting, and center routing is biased toward the low-mid range to anchor the kit in the front. Height channels below 3 kHz are attenuated to preserve the punch and immediacy of drum hits.

Vocals

Designed for vocal stems and dialogue. The speech band (300 Hz to 3 kHz) receives emphasis in the center extraction algorithm, anchoring the voice firmly in the front-center speaker. Reverb tails and room ambience are allowed to flow naturally into the surrounds.

Harmonic

Tuned for tonal and instrumental material — guitars, synths, strings, keyboards. Transient detection is slightly boosted in the attack range around 2 kHz, and overtones in the 6 to 12 kHz region are given increased height eligibility for a shimmering overhead quality.

Pads/Ambient

Maximizes the diffuse field for sustained, evolving textures. The extraction threshold is lowered so that more content is classified as ambient rather than primary. Transient detection is suppressed, and height eligibility is increased across the spectrum.

Bass

Focused on low-end stability. Center routing is biased below 1 kHz to keep bass content anchored, and high-frequency routing is reduced to avoid placing bass harmonics in the surrounds or heights.

Spatial Controls

Immersion

Controls how much upmixing is applied to the signal. At 0%, no spatial processing occurs — the output is the original dry stereo signal. At 100%, the full engine behavior is applied. This is not a simple wet/dry mix or a volume control. Immersion scales the engine's internal DSP parameters together: how much content is classified as ambient (and therefore sent to the surrounds and heights), how wide the front-stage steering is, and how much energy reaches the surround and height channels. Higher immersion means more content is pulled out of the front stereo image and distributed across the surround field. Turning up all the mixer faders would just make every channel louder without changing what is in each channel; turning up Immersion changes the spatial decomposition itself.

Group Controllers

The group knobs (Front, Surround, Rear, Height) are linked directly to the channel mixer. Turning a group knob proportionally scales the faders of all channels in that group:

• Front — Controls L, R, and C faders together. Default is 100 (unity).
• Surround — Controls Ls and Rs (side surround) faders together. Default is 50.
• Rear — Controls Lss and Rss (rear surround) faders together. Default is 50.
• Height — Controls Ltf, Rtf, Ltm, Rtm, Ltr, and Rtr faders together. Only visible when using a layout with height speakers (5.1.2, 5.1.4, 5.1.6, 7.1.2, 7.1.4, 7.1.6, 9.1.2, 9.1.4, 9.1.6).

Group knobs provide a quick way to balance the overall spatial shape without adjusting individual channel faders. The mixer faders update in real time as you turn a group knob. All group knobs are DAW-automatable.

Group knobs vs. Engine Presets: Group knobs and mixer faders control the volume of each channel after the upmix has been rendered. Engine Presets control the content — they change how the spectral analysis separates and distributes audio across the surround field during rendering. Boosting the rear fader makes whatever is already in the rears louder; switching to the Deep engine actually routes more ambient energy into the rears in the first place. Use engines to shape what goes where, and faders to fine-tune the balance.

Transients

A bipolar transient shaper that redistributes transient energy between front and surround channels. At the center position (50), no transient shaping is applied. Turning the knob left (toward 0) softens transients in the front channels and redistributes that energy into the surrounds and rears. Turning the knob right (toward 100) emphasizes transients in the front channels while reducing them in the surrounds and rears. The effect is energy-conserving: transient energy removed from one speaker group is added to the other, similar to how a transient shaper plugin works but applied spatially across the surround field.

Note: When Exact Mode is enabled, the transient knob only affects the surround and rear channels. The L/R front channels are not affected because Exact Mode continuously corrects them to maintain fold-down identity with the original stereo input. The spatial redistribution of transients across surrounds, rears, and heights remains fully effective — the difference is audible in surround playback even though the front channels are locked.

Input and Output Controls

Input Gain

Adjusts the level of the incoming stereo signal before it enters the upmix processing chain. Range is -18 dB to +18 dB. Double-click the fader to reset to 0 dB.

Output Gain

Adjusts the final output level after upmix processing. Range is -18 dB to +18 dB. Double-click the fader to reset to 0 dB.

Link Out

When the LINK OUT button is engaged, Input and Output gains are inversely coupled. Raising the input gain automatically lowers the output gain by the same amount, and vice versa. This maintains a consistent monitoring level while adjusting the drive into the upmix engine.

Mono Input Mode

The MONO button below the input meter tells UpM1xer that the incoming signal is a mono source (e.g. a mono vocal, bass, or dialogue stem on a stereo track). When engaged:

• Stereo input is summed to mono — left and right channels are averaged to a single signal before processing, eliminating any stereo artifacts from a duplicated-mono track.
• Spatial routing is activated — the engine overrides its correlation analysis to route energy into the surround and height channels, creating a spatial image from the mono source. Without this, a highly-correlated mono signal would remain locked to the center.
• The input meter displays as mono — a single full-width bar replaces the stereo pair, confirming the summed signal.

Profile interaction

When MONO is engaged, the stem profile's decomposition curves have reduced impact because the correlation override dominates the primary/ambient split. However, height eligibility and steering settings from the selected profile still apply, so choosing the correct profile (e.g. Vocals, Bass) still matters for vertical placement and panning behavior.

Channel Mixer

The mixer section provides per-channel control over all active output channels.

Channel Strips

Each active channel has its own strip containing:

• Level meter — Real-time signal level display
• Fader — Individual channel gain. Default is 0 dB. In normal mode, pulling the fader fully down silences that channel. In Exact Mode, faders operate as soft controls (see below).
• M button — Mute. Click to mute a single channel, or click and drag across multiple M buttons to mute several channels at once.
• S button — Solo. Click to solo a single channel, or click and drag across multiple S buttons to solo several channels at once.
• dB label — Displays the current fader value. Click to type a precise value.

Channel Linking

Stereo pairs can be linked so that fader, mute, and solo actions on one side are mirrored to the other. Link buttons appear between paired channels:

• L / R (front stereo pair)
• Lw / Rw (wide pair — 9.x formats)
• Ls / Rs (side surrounds)
• Lss / Rss (rear surrounds)
• Ltf / Rtf (top front heights)
• Ltm / Rtm (top middle heights — 5.1.6, 7.1.6, 9.x.6 formats)
• Ltr / Rtr (top rear heights)

Clear Buttons

• CLR M — Unmutes all channels at once.
• CLR S — Removes solo from all channels at once.

Diffusion

Diffusion controls the amount of decorrelation applied to the surround and height channels. Higher diffusion creates a wider, more spacious perception; lower diffusion keeps the surround channels more correlated with the front image.

Diffusion Mode (AP Button)

Toggles between two decorrelation algorithms:

• AllPass mode (AP on) — Time-varying decorrelation that evolves from frame to frame, producing a natural, organic sense of space. Recommended for most material.
• Static mode (AP off) — Fixed decorrelation pattern. Produces consistent, deterministic results that do not change over time. Useful for reproducible mixes or situations where time-varying effects are undesirable.

Master Diffusion

Sets the baseline decorrelation amount for all surround and height channel groups. Range is 0 to 100. At 0, no diffusion is applied (surround channels retain maximum correlation with the front). At 100, maximum diffusion is applied.

Trim Controls

Click the TRIM button to reveal per-group offset sliders:

• Surround Trim — Offsets diffusion for side surrounds (Ls/Rs)
• Rear Trim — Offsets diffusion for rear surrounds (Lss/Rss)
• Height Trim — Offsets diffusion for height channels (Ltf/Rtf/Ltr/Rtr)

All trim sliders are centerd at 50, which means "follow the master exactly." Values above 50 add diffusion relative to the master; values below 50 subtract from it.

Per-Group Shelf EQ

Each channel group (Surround, Rear, Height) has an independent two-band shelf EQ, accessed by clicking the EQ button beneath the corresponding group knob. The EQ popup shows a frequency response display and controls for a high shelf and a low shelf filter.

Each shelf has four controls:

• Enable (ON/OFF) — Toggles the shelf filter on or off. Both shelves default to off.
• Freq — Sets the corner frequency. High shelf range is 1 kHz to 16 kHz. Low shelf range is 20 Hz to 1 kHz.
• Gain — Sets the shelf gain from -12 dB to +12 dB.
• Slope — Sets the filter steepness: 6, 12, 18, or 24 dB/oct.

The EQ is linear-phase and adds no additional latency. Use it to shape the tonal character of the surround, rear, and height channels independently — for example, rolling off harsh high frequencies in the rears or adding warmth to the height channels. All EQ parameters are DAW-automatable and saved with presets.

Note: When Exact Mode is enabled, shelf EQ modifies the surround, rear, or height channels after upmixing but before fold-down correction. This means the ITU downmix will include the EQ changes and will not be a sample-perfect reconstruction of the original stereo input. The EXACT button changes to an orange color when this condition is detected. If fold-down fidelity is critical, disable shelf EQ.

Exact Mode

What It Does

Exact Mode guarantees 100% ITU downmix compatibility: the multichannel output, when folded down to stereo using standard ITU-R BS.775 coefficients, reconstructs the original stereo input sample-for-sample. The fold-down residual is below -120 dBFS — effectively bit-perfect.

This means that no audio information is lost or altered by the upmix process. A listener receiving a stereo downmix of the UpM1xer output hears the original stereo master, unchanged. Listeners receiving the multichannel output hear an immersive spatial presentation. Both audiences are served from a single multichannel deliverable.

Note: The fold-down guarantee requires the standard spectral engine. In Low Latency mode, Exact Mode is automatically bypassed because the time-domain engine's internal processing delay breaks the sample-accurate alignment needed for correction. The EXACT button turns orange when this conflict is detected.

The fold-down guarantee also assumes no post-upmix EQ is applied. If any per-group shelf EQ is enabled, the EQ'd energy in the surround, rear, or height channels alters the fold-down sum. The EXACT button changes to orange when this condition is detected.

The ITU-R BS.775 Standard

ITU-R BS.775 defines the standard method for converting multichannel audio to stereo. The standard stereo downmix (LoRo) is:

Lo = L + clev*C + slev*Ls
Ro = R + clev*C + slev*Rs

Where clev (center mix level) and slev (surround mix level) default to 0.707 (-3 dB). LFE is excluded from the fold-down. These coefficients are embedded in Dolby Digital, Dolby Atmos, and MPEG metadata and are applied automatically by consumer decoders and professional monitoring systems.

Faders in Exact Mode

All channel faders are functional in Exact Mode. Moving a fader changes the spatial balance, and Exact Mode redistributes the correction across all contributing channels to maintain fold-down identity.

However, faders in Exact Mode behave as soft controls rather than hard cuts. Because the fold-down equation must always be satisfied, pulling a fader fully down does not fully silence that channel. The correction algorithm distributes compensating energy back across all channels (including the attenuated one) in proportion to their fold-down coefficients.

For example, in a 7.1.4 layout the fold-down equation for the left side is:

Lo = L*1.0 + C*0.707 + Ls*0.707 + Lss*0.707 + Ltf*0.5 + Ltr*0.5

L has the highest fold-down coefficient (1.0) and receives roughly one-third of any correction error. Even with the L fader at zero, the correction puts signal back into L to satisfy the fold-down identity.

Use faders in Exact Mode for balance adjustments rather than hard muting. To fully silence individual channels, disable Exact Mode first.

Wides and Top Middle in Exact Mode

The Wide channels (LW, RW) and Top Middle channels (Ltm, Rtm) are not part of the ITU-R BS.775 stereo downmix specification. Consumer decoders, broadcast playout systems, and DAW stereo fold-down monitors do not include these channels in any standard fold-down formula. As a result, no internal compensation can guarantee that signal in these channels will be inaudible after a stereo fold-down — the host's downmix has no row in its matrix to subtract them.

To preserve the broadcast-grade fold-down guarantee that Exact Mode promises, LW, RW, Ltm, and Rtm are automatically silenced and their mixer strips are greyed out whenever Exact Mode is engaged. A 9.x output with Exact Mode active is therefore mathematically equivalent to a 7.1.4 (or 7.1.2) bed for fold-down purposes — exactly matching the standard ITU spec and how every consumer decoder and stereo monitor will reproduce it.

If you need to use the Wide or Top Middle channels for creative immersive content, disable Exact Mode. The full 9.x routing is then available, but the stereo fold-down is no longer guaranteed to be sample-accurate.

This behaviour matches the convention used by other broadcast-grade upmixers and ensures that delivery for streaming, broadcast, or any platform that ingests both stereo and immersive masters will reconstruct identically.

Reference Stereo Monitoring (REF ST)

When Exact Mode is enabled, the REF ST button becomes available. This folds the multichannel output back to stereo in real time using the ITU-R BS.775 coefficients. With Exact Mode active, this reference stereo output should be indistinguishable from the original input.

When to Use Exact Mode

• Broadcast and streaming delivery — always. The stereo fold-down must match the approved stereo master.
• Film and post-production — recommended when a stereo version is a deliverable alongside the multichannel mix.
• Music production — use when fold-down fidelity is required. Disable when maximum creative freedom over individual channel levels is preferred. If intended stereo mix is not derived from the ADM BWF file (i.e sent separately to distributors) exact mode is usually not necessary.
• QC and mastering — enable Exact Mode and use Ref Stereo monitoring to confirm null.

Sub Bass Generator

The SYN button opens the Sub Bass Synthesis popup, which controls a time-domain sub-octave synthesizer on the LFE channel. Unlike simple subharmonic generators, this uses a frequency divider technique that tracks the input's bass fundamentals and synthesizes a sub-octave signal that follows the dynamics of the source material — kick drums remain punchy and defined rather than smeared into a continuous drone.

The sub bass generator works in both standard and low-latency modes.

Character Modes

Four character modes shape the tonal quality of the synthesized sub-octave signal:

• SINE — Clean sub-octave with a steep low-pass filter. The smoothest option, producing a pure fundamental with minimal harmonics. Ideal for music and dialogue where a transparent sub presence is needed.
• TRI — Moderate filtering that retains some harmonics from the frequency divider. Adds a subtle edge to the sub tone while remaining musical.
• SQR — Lighter filtering for a punchier, more aggressive sub character with pronounced harmonics. Best suited to percussive material where sub impact needs to cut through.
• MULTI — Blends two frequency divider ratios (octave-down and fifth-below) through a shaped filter. Produces the densest, most harmonically rich sub tone.

Controls

• MIX — Blends between the normal LFE channel content (0%) and the synthesized sub-octave signal (100%). At intermediate values, both signals are blended proportionally. Default is 100%.
• DRIVE — Pre-saturation applied to the input before the frequency divider. Higher values add warm harmonics to the input signal, which helps the divider track more aggressively and produces a thicker sub tone. Range is 0–11, default 0.
• TUNE — Shifts the bandpass filter center frequency, tuning the sub response up or down. The knob displays the approximate sub-octave output frequency in Hz (range ~33 Hz to ~120 Hz, default ~47 Hz). Use this to match the sub response to the key of the source material or to emphasize a particular frequency range.
• LFE fader — A horizontal fader at the bottom of the popup that mirrors the LFE channel fader in the mixer. Adjusting it here is the same as adjusting the mixer strip fader directly. Useful for balancing LFE level while the popup is open.
• S (Solo) — Solos the LFE channel, allowing you to hear only the sub bass output in isolation. This mirrors the solo state of the LFE mixer strip.

Source Placement (POSITION tab)

The POSITION tab in the visualiser area provides a 2D top-down "puck" interface for steering the upmixed image to a specific location around the listener. It works on top of the upmix — the engine continues to produce its full multichannel output, and Source Placement steers and focuses that output toward the chosen direction.

The Pad and the Puck

The circular pad shows a top-down view of your speaker layout, with the listener at the centre. Speaker dots are positioned around the perimeter at their physical azimuths (L at -30°, R at +30°, side surrounds at ±90°, etc.). The orange puck represents where the source will be placed. Drag it anywhere inside the circle, or double-click on the pad to recentre.

When the puck is at the centre, the upmix passes through unchanged. As you drag the puck outward, a green highlighted area appears showing where the audio will be focused. Speakers inside the green area become the dominant carriers of the source; speakers outside it fade. At the edge of the pad the source becomes a directed image, but no audio is lost — the upmix's content is redirected into the highlighted speakers rather than discarded.

Width Fader

Below the pad, the WIDTH fader controls how wide the green area becomes:

• 0% — narrow: only the closest speaker(s) carry the audio
• 50% — the green area covers half the speaker ring
• 100% — full circle: the green area covers everything; no fading happens because every speaker is included

Drag the fader vertically, scroll the mouse wheel over it, or double-click to reset to 50%. The fader is automatically disabled when POSITION is OFF.

Position / Distance / Width readouts

The bottom row of the panel shows three live, editable values:

• Position — azimuth in degrees (0° = front, 90° = right, 180° = behind, 270° = left)
• Distance — distance from centre as a percentage (0% = centred, 100% = at the speaker line)
• Width — width as a percentage

Each value can be double-clicked to type a precise number, dragged vertically to nudge, or scrolled with the mouse wheel.

EXCL L/R, EXCL C, RESET

These buttons exclude audio from L/R or C. When enabled they ensure that the upmix is not sent to those channels and that the audio is distributed elsewhere — distinctly different from muting L, R, or C in the channel mixer (where the actual upmixed audio content would be silenced and lost).

The exact behaviour depends on whether POSITION is enabled:

• POSITION OFF — the excluded channels' content is redistributed:
  • EXCL L/R: L and R are silenced, their content sums into C at -3 dB.
  • EXCL C: C is silenced, its content splits equally into L and R at -3 dB.
  • EXCL L/R + EXCL C together: all front content (L, R, C) is redistributed across the side and rear surrounds.
• POSITION ON — the excluded channels become unavailable as steering targets. The puck never routes audio onto them, so the steering kernel naturally picks the closest non-excluded speakers instead. The original front-channel energy is still carried by the steering's mono fold and lands at the puck's direction.

RESET sets Position to 0°, Distance to 0%, Width to 50%, and clears EXCL L/R and EXCL C.

POSITION ENABLED / DISABLED

The button at the bottom-right of the panel is the master enable for source steering. When DISABLED (grey), the puck and Width controls have no audible effect — the upmix passes through as if the panel didn't exist. The pad shows "Press POSITION to steer audio" and the Width fader greys out. When ENABLED (bright green), the puck position and Width steer the upmixed output. EXCL L/R and EXCL C still work in either state.

Interaction with Exact Mode

The positioning function is disabled when working in Exact Mode, as steering would break Exact Mode's bit-identity fold-down guarantee. The POSITION tab is greyed out and unavailable; switching Exact Mode on auto-selects the 3D Cube tab, and switching it off auto-restores the POSITION tab.

Visualisers

The visualiser area sits to the left of the channel mixer and offers four real-time tabs, selectable from the tab bar at the top: POSITION, 3D Cube, Transients, and Radar. The POSITION tab is described in detail in the Source Placement section above; the remaining three are passive visualisations of what's happening at the output.

3D Cube

A three-dimensional representation of the speaker layout. Speaker positions are shown as coloured dots within a wireframe cube, with brightness and glow intensity reflecting real-time signal energy in each channel. Drag to rotate the view, scroll to zoom in and out. Muted or soloed channels are visually indicated.

Transients

A scrolling per-channel bar graph showing transient energy over time. Each active channel has a horizontal lane with bars whose height represents the rate of change (transient intensity) at that moment. The display scrolls horizontally, providing a time history of dynamic activity across all channels. The sensitivity of this display is linked to the Transients knob.

Radar

A top-down polar plot showing speaker positions around the perimeter, with energy lobes radiating from the centre toward each active speaker. This view provides a quick read of the overall spatial balance from above. Height channels are distinguished from the ear-level layer.

Preset System

Preset Browser

The preset browser appears at the top of the interface. It displays the current preset name with arrow buttons to step through available presets. The menu button provides access to Save As, Export, Import, Init (reset to defaults), and Delete functions.

Comparison Slots (A/B/C/D)

Four comparison slots store independent snapshots of all plugin parameters. Click a slot button to recall that snapshot instantly. The Copy button duplicates the active slot's settings to the next slot, making it easy to set up A/B comparisons by tweaking one slot while preserving the other.

Slot A is initialized with the current settings when the plugin loads.

Low Latency Mode

The LOW LAT button switches UpM1xer from its default spectral processing engine to a dedicated time-domain engine optimized for near-zero latency.

How It Works

The standard engine uses spectral analysis with thousands of frequency bins to achieve high-resolution spatial processing. This produces the best quality but introduces approximately 85 ms of latency.

Low Latency mode replaces the entire spectral pipeline with an engine that uses fewer, broader frequency bands — providing near-zero latency while maintaining a musical spatial image. Height channels use allpass filters for decorrelation rather than spectral phase processing.

What Stays the Same

All user-facing controls remain fully functional in Low Latency mode:

• Engine presets (Subtle, Natural, Wide, Deep, Elevated, Expansive)
• Stem profiles (Full Mix, Drums, Vocals, Harmonic, Pads/Ambient, Bass)
• All spatial knobs (Immersion, Center, Steering, Rear Emphasis, etc.)
• Diffusion controls including both Golden Ratio and Allpass modes
• Shelf EQ for surround, rear, and height channel groups
• Mixer faders, mute, and solo
• Output format selection

Note: Exact Mode is not available in Low Latency mode. The time-domain engine introduces a small internal processing delay that cannot be precisely measured, which breaks the sample-accurate time alignment that Exact Mode requires for fold-down identity. When both are enabled, the EXACT button turns orange and the fold-down correction is bypassed. If you need exact fold-down compliance, use the standard engine.

When to Use Low Latency Mode

• Live performance and real-time monitoring — when the 85 ms processing delay of the standard engine is unacceptable.
• Tracking sessions — monitor through the spatial mix without latency while recording.
• Live broadcast — minimize end-to-end delay in signal chains where every millisecond counts.
• Creative effect — Low Latency mode uses broader frequency bands than the standard spectral engine, producing a distinctly different spatial character. This lo-fi quality can be used as a creative effect in its own right.

Interface Modes

Easy Mode

The EASY button switches to a compact view that hides the full mixer section and diffusion controls, presenting only the essential spatial knobs and simplified I/O controls with the LINK OUT option. The window resizes to a smaller footprint. Full mode restores all controls and the larger window size. The plugin remembers each mode's window size independently.

Light Mode

The LIGHT button switches the interface to a light color scheme for use in brightly lit environments. All controls and meters update their color palette accordingly.

Metering

Input and Output Meters

Meters with fast attack and slow release envelope following. Scale markers indicate standard reference levels (-40, -20, -12, -6, 0 dBFS). The inline fader within each meter doubles as the gain control.

Per-Channel Meters

Each channel strip in the mixer section includes its own level meter. Meters automatically zero when the plugin is bypassed (the process block counter stops incrementing when the DAW disables the plugin, preventing stale display values).

Latency

In standard mode, UpM1xer uses a 4096-sample FFT window at 48 kHz (approximately 85 ms). At 96 kHz, the window doubles to 8192 samples. The DAW compensates for this latency automatically via the reported latency value.

In Low Latency mode, the plugin uses IIR filters with near-zero processing delay. The DAW will report minimal or zero latency compensation when this mode is active.

Low Latency mode sounds quite different to normal mode. It could also be used as a creative lo-fi effect.

License Status

The plugin footer includes a license indicator dot and a license button that shows your current license state at a glance.

License Dialog

Click the license button in the footer at any time to open the license dialog, where you can enter or change your license key, view activation details, or check your current license status.

Credits

UpM1xer is developed by max1mus audio.

For feature requests and bug reports, use the dedicated buttons in the plugin footer.