SONOSAX SX-R4+ professional audio recorder, built around SONOSAX preamps, made for stand-alone field work
The SX-R4+ is designed around the world-renowned SONOSAX microphone preamplifiers: ultra low noise, high headroom, and the “natural” capture quality that SONOSAX is known for. It’s a true stand-alone 16-track production recorder compact enough for bag work, yet engineered as a serious location tool with disciplined metadata, redundancy, and professional sync.
A major part of the SX-R4+ appeal is that it delivers this performance in a machined aluminum chassis with a genuinely portable footprint (200 × 50 × 144.5 mm) and very low weight for its class (960 g without battery / 1.2 kg with 48 Wh battery).
The machine is also built for real set pace: it boots in 4 seconds and is ready to record immediately. Its 2.4″ pressure-based touchscreen remains usable in challenging conditions when gloves make capacitive screens impractical, you can still operate the UI reliably using a pen/stylus.
Fast operation and user-assignable shortcuts
Beyond raw audio performance, the SX-R4+ is built to stay fast on set. Key functions and the most-used menus can be assigned to quick-access “hot spots”, so the operator can jump straight to what matters without digging through layers.
Depending on the context, a simple press or a long press on a designated area of the touchscreen can trigger an action or open a specific menu. The same principle applies to the front-panel rotary/push control: press and long-press can be mapped to different functions for immediate access during takes.
This customizable action concept extends to compatible SONOSAX expansion accessories equipped with buttons and/or rotary controls, allowing operators to assign shortcuts and functions to external controls to match their workflow.
Recording, redundancy, and metadata
The SX-R4+ records up to 16 tracks as uncompressed BWF with iXML metadata.
It supports 44.1 to 192 kHz at 24-bit or 32-bit and offers 0.1% pull up/down for NTSC workflows.
For reliability on set, the SX-R4+ uses dual SD cards and can record to both simultaneously in Mirroring mode for instant redundancy.
Inputs & digital expansion including the 26-pin AES input connector
4 × XLR-3F inputs, individually configurable as:
Analog mic/line (electronically balanced) with phase reverse, 48 V phantom, LF cut, and front-panel level control
Digital AES3 or AES42 (transformer balanced) with individual ASRC, plus phase reverse, LF cut, and front-panel level control
2 × balanced line inputs on TA-3 with front-panel level control
TA-3 AES3 I/O (transformer balanced) that can be switched as input or output
3M MDR 26-pin connector: 4× AES inputs + command bus
On the right side panel, the SX-R4+ includes a 3M MDR 26-pin multipin connector that carries 4 × AES3 inputs (AES 1–2 / 3–4 / 5–6 / 7–8) and the SX-R4+ command bus for system expansion.
Internally, the recorder implements four independent AES receivers, each with its own ASRC, allowing connection of non-synchronized digital sources. These AES receivers can be allocated either to the 26-pin AES inputs or to the XLRs when configured as digital (AES3/AES42).
Powering
Removable 14.4 V / 48 Wh smart battery (SMBUS capable)
External 9–18 V DC on Hirose 4-pin, SMBUS capable and electrically isolated
12 V regulated DC output for accessories (up to 7 W)
Expansion ecosystem
SX-AD8+ preamplifier: The SX-AD8+ expands the SX-R4+ input capability to up to 12 microphone inputs, enabling larger bag setups while keeping SONOSAX preamp quality across the rig.
SX-LC8+ linear fader control surface + USB MIDI controller: The SX-LC8+ adds 8 linear faders with function switches for more comfortable mixing control in the field. It also supports a USB MIDI mode for workflows/systems that accept MIDI control.
SX-RC8+ front panel expansion + AES breakout + power distribution: The SX-RC8+ adds 8 rotary faders with function switches to extend mixing facilities. It also works as an AES breakout box for the SX-R4+ multipin AES input connector (providing 4 × TA-3 AES connectors for easier connection of AES sources such as digital wireless receivers). In addition, it provides power distribution (Hirose connectors), an additional headphone output, and a slate microphone capability.
SX-RX8+ wireless-focused expansion module: The SX-RX8+ is an 8-channel HF extension module designed to integrate multi-channel wireless workflows with the SX-R4+. It includes a 98 Wh battery slot that can power the receivers and also help power the recorder, plus assignable encoders/push controls. Like the SX-LC8+, it can also be used via USB MIDI with other systems supporting MIDI control.
Options (choose one recorder configuration)
Base (no option)
4-channel output module on XLR-5M (user-configurable output modes, including analog/AES combinations)
Dante I/O (AoIP integration; PoE capable for single-cable power + audio)
Sennheiser AMBEO VR mic on DIN 12-pin
Summary
Inputs / Outputs
4x XLR-3F inputs, individually configurable as:
– ANALOG: mic/line levels, electronically balanced, with phase reversal, 48V phantom, LF cut and level control on the front panel
– DIGITAL: transformer balanced AES3 or AES42 with ASRC, phase reversal, LF cut and level control on the front panel
2x Line inputs, electronically balanced on TA-3 with level control on the front panel
4x AES3 balanced inputs on multi-pin connector
1x AES3 balanced input with ASRC on TA-3 connector (shared with AES3 output)
2x analog unbalanced line outputs on TA-3
1x AES3 balanced output (user independent sampling frequency) on TA-3 connector (shared with AES3 input)
Up to 12x Mic inputs when connected to the SONOSAX AD8+
Optional audio over IP on RJ45 connector, such as Dante
Performance
135 dB (A-weighted) overall dynamic range from analog input to recorded file (114 dB (A-weighted) dynamic range with USA version)
90kHz overall frequency response @192 kHz recording
40 bits processing
Recording capabilities
up to 16 tracks recording on 2x SD cards (SDHC, SDXC)
uncompressed BWF with iXML metadata
44,1 up to 192 kHz @ 24bits or 32bits, Pull up/down 0.1% for NTSC world
– For development reasons, both bootloader and firmware files unfortunately have exactly the same name; to differentiate between them, the bootloader is only 100 KB, while the firmware is over 700 KB.
– Up-date one at a time starting with the bootloader, then reboot the SXR4+ and proceed the same way with the firmware.
– When the up-date is completed, reboot the SX-R4+ normally and the apply a full “Factory Settings” in the System Info menu.
– DO NOT RELOAD previously saved user settings, as this may cause memory corruption. You will need to redo all your settings from scratch.
Fixed scratch record (wasn’t working with SX-LC8+)
Fixed bug in input menu: for XLR as analog, the 2nd channel buttons were hidden but still active
Added an IP address in the web application (so that the SX-R4+ can join an existing network).
Fixed stability issues.
Added SX-RX8+ functionnality
Improved SD card wirting performance
Dante operation is limited to the following:
The optional DANTE card handles up to 16 channels. Input and output channels can be operated at the same time in pairs of channels.
16 channel recording using DANTE is only available up to 96kHz, limited to 8 channels at 192kHz.
Please note that you’ll need to factory reset your recorder when switching between 3.x and 4.x releases (recorder + user settings and format all SD cards).
Update filename to copy on SD card must be “R4P_UPD.BIN” (some browsers rename it)
a FULL FACTORY RESET (step 4 of the firmware update procedure) must be applied from the service menu (so that user settings are also cleared)
Backup your files then format all your SD cards before applying update. The SX-R4+ reads the SD card content when it is inserted. The recent 4.1 firmware adds some new functionality (related to Dante tracks and SX-RX8+) that are not supported by previous versions.
SX-R4+ with the “4CH OUT on XLR-5M” option only:
after switching the unit off and on again, the optional board appears to be functional, but does not provide any audio signal (either in AES or analog). Workaround :deactivat and then reactivate the option outputs.
CHANGELOG
Enhanced graphics rendering, allowing more channels to be recorded at high sample rates
Added SX-LC8+ operation
Fixed track name bug: when set to 12 chars, a memory corruption could occur if used with the snippet list
Fixed track filename creation on SD2 (file was created when configured as MIX only and without any armed track)
Added SX-RC8+ potentiometer position noise reduction button (see SETUP/SYSTEM/MISC/RC8+)
This noise reduction can be used when the SX-RC8+ position is noisy
Added solo channel selection in inputs (use rotary encoder push to select a channel, the other, or a stereo)
Removed <BEXT> tag in iXML (unused and deprecated)
Fixed metadata project name: when modified while recording, it was not set properly
Fixed playback issue with (very long) take: seeking wasn’t working correctly
Fixed sound report: takes were not always sorted
Fixed pop noise when closing a fader assigned to LINE OUT
Fixed gain menu interlock when using SX-AD8+ solo events
Minor interface enhancements (format card indicates SD card identification)
Operation with SX-AD8+ or SX-RC8+ can sometimes results in spurious touch screen events when modifying SX-AD8+ or SX-RC8+ pot position. A fix will be posted soon, please disable bottom touch 1/2/3 push buttons simple touch events (menu SETUP / SYSTEM / PUSH BUTTONS) as a temporary workaround.
Under some rare circumstance, a crash can occurs causing screeen freeze and/or icons pixel corruption. We identified that problem when engaging AES inputs at startup, but can imagine that it can happens in other -very rare- cases. To overcome that problem, please disable meters peak hold (menu SETUP/METERS and set HOLD TIME parameter to zero).
CHANGELOG
Fixed option card operation: configuration was not restored after a power cycle, audio was corrupted
Fixed XLR input performance: low frequency noise floor (in the range 1..100Hz) wasn’t totally flat
Modified headphones limiter: attack time was too high
Enhanced note edition: selecting an empty snippet resets the note field
Enhanced web interface: unarmed tracks are less visible than armed ones, added SD & power alarms
Enhanced push-button solo action: now every channel can be selected (instead of channel pair) for AES, LINE and AUX AES inputs
Option card 4 channels out is not working properly: configuration is not restored correctly after a power cycle and audio is corrupted with click noises. A fix will be released soon, use version 2.5 if you need the 4 channel outputs of the option card.
CHANGELOG
Fixed SD card ERROR and SPEED ERROR
Enhanced note snippet list. Selecting an item will add it to the note (vs replace it). Selecting it again will remove is from the note.
Metadata tape can now be freely edited (12 chars max). When set, all audio files are stored in the path /PROJECT/WORKING DAY/TAPE. When empty, files are stored in /PROJECT/WORKING DAY and tape value is the working day
Added metadata take type menu, allowing to select the following: FALSE START, NO GOOD, CIRCLED, WILD TRACK, PICKUP, REHEARSAL, ANNOUNCEMENT, SOUND GUIDE. Take type is stored in the iXML metadata according to specification release 2.01
Added configuration save/restore to /from SD card (see menu SETUP/SYSTEM/BACKUP/RESTORE). Sub-menu SAVE OPTIONS allow user to select what should be saved in the configuration file
Added main screen peak-meters pages (horizontal, vertical)
Added limiter to headphones output (HEADPHONES/SETUP)
Added limiter to mix tracks (MIX/SETUP)
Increased headphones and output preset count from 4 to 8
Added headphones presets selection from main screen when level is locked (use rotary encoder)
Added RF64 (https://en.wikipedia.org/wiki/RF64) encoding. This format is automatically used if max file size is > 4GB (set it in menu SETUP/RECORD SETTINGS/MAX FILE SIZE). Max file size is now 45GB, but default value remains to 4GB for compatibility reason
Added input delays (up to 96k, disabled at 176.4 and 192k)
Added project name selection list. Up to 8 project name can be defined in (METADATA/PROJECT)
Increased track name and note snippet list length from 8 to 32
Added “SHOW F. START” button in TAKE LIST menu, allowing to view false start takes
Decreased default alarm level
Modified default behavior for input gain long press knobs: now toggle phase reversal (instead of track arm)
Added link in sound report title, allowing to download data as CSV file
Full rework of the web interface, which allow now to modify monitoring, outputs, user settings, as well as metadata, last takes or track arming
Various minor bug fixes and interface modification, such as meters hold returns smoothly, added reset button in filetag menu, fixed battery time to empty, …
A faulty SD card ERROR or SPEED ERROR can occurs during record. It happens mainly with low track count (1-3) and high sampling frequencies, more frequently to the SD2 card slot.
CHANGELOG
Added SX-AD8+ and SX-RC8+ operation from SX-R4+
Fixed timecode accuracy (was not accurate when cycling power with 23.976 and 30 fps). Also fixed some drift when switching from EXT JAM SYNC to the same frame rate.
Fixed SD card filename bug (same filename in a folder).
Fixed phase reversal input level issue: when using fader mude, a phase change using a push button assigned function can corrupt the input level
Fixed take number generation: wasn’t correct when scene changed during recording
Modifying metadata of an existing take with the HTML web interface results in a bad filename of next take to be recorded
23.976 & 30 fps timecode formats are not accurate after a power cycle
Version 2.4 is a fix for version 2.3, which has a major bug.
INFO It is important to apply a full factory reset as described in the simplified update procedure to prevent running new firmware with an old configuration.
CHANGELOG
Fixed timecode bug (was not correct on SD2)
Fixed SD card ‘SPEED’ error
Fixed monitoring bug
Fixed take edition bug (metadata wasn’t saved properly)
Fixed alarm level (was active even when disabled)
Fixed take number generation (wasn’t correct if a take was shot with identical scene name)
Fixed sound report (false start takes were displayed and projects were not filtered)
Fixed system instability involving 4 channels output option card and sampling frequency changes
NOTE Official version jumps from 1.4 to 2.1; version 2.0 only exists as beta. If you’re running version 2.0, please update to version 2.1.
KNOWN BUGS
XLR inputs levels remain fixed to MUTE. In fader mode, the input level can be modified using the rotary encoder in the input menu. However, if the input level is MUTE, input level change does not work. Workaround: do not mute inputs before entering fader mode.
Record sometimes fails on a SD card with the ‘SPEED’ error on the card. More frequent with low track count (1-2) on high speed cards.
CHANGELOG
Fixed playback channels swap
Fixed playback timecode (wasn’t displayed)
Fixed timecode accuracy
Fixed 176.4/192k operation
Fixed record start: under some rare condition, record start could be ignored
Fixed power failure filetag: was identical to previous take
Fixed ambient light sensor calibration and auto dim mode
Added User Settings menu
Added timecode date in user bits
Added system time zone
Added fader operation mode
Added SD2 Mix Only recording
Added 24bits WAV file recording/playback
Added note field in Tag Last Take menu
Added track coloring
Added meter range user selection
Added sound report file generation
Improved monitor/mix menu: presets are now independent from each others
Improved audio performance and behavior
Improved various menus (Inputs, Monitoring/Mixing, filetag, push buttons, date/time, split Record Tracks menu into Rec Tracks and Mix menus)
Version 1.4 is a fix for version 1.3, which has a major bug.
KNOWN BUG / INFO
Sampling frequencies of 176.4k and 192k not yet supported
WAV file creation time may be incorrect due to timezone
USER SETTINGS menu is not implemented
Modifying playback position can result in channel swap
CHANGELOG
Fixed file system (setting file to hidden was incorrectly implemented)
VERSION 1.3 November 2015
KNOWN BUG Applying a false start will corrupt the file system, making some files unreadable. Please update to version 1.4.
NOTE Once updated, press AND HOLD REC button until boot screen appears to power up the SX-R4+.
CHANGELOG
Fixed monitor presets: wasn’t restored at boot time
Fixed take list menu: selected take timecode wasn’t correct
Fixed pop noise during playback start
Fixed AUX AES output: channel status is now in pro mode
Fixed various minor bugs
False start files are now hidden
Full re-work of the metadata menu: scene is 10 alpha-num chars, added tag last take, added user editable snipped list for track names and notes
Full re-work of the push button assign menu (SETUP/SYSTEM/PUSH BUTTONS)
Added file size selection: fow now limited to 4GB (until WAV64 is implemented)
Added RECORD TRACKS menu
Added encoder long press new menu with various useful links and tools: timecode, track names, track arming, screen lock, headphones lock, display brightness, daylight mode
Added timecode set manual
Added quick power-down (to be enabled in menu SETUP/SYSTEM/POWER DOWN SETUP): press and hold REC button in rec ready to power down unit.
Added solo in headphones menu
Added a second reference level: user can now configure ‘orange’ level and ‘red’ level
Added a config save button (SETUP/SYSTEM) to force configuration save (done at power down)
Player: loading a take no longer begins automatically playback; encoder can be used to modify playback position (1 step = 1%), to change headphones level, enter pause or stop states.
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