What is a Cox Box?
A cox box is the electronic unit the coxswain plugs into during every session. It amplifies the cox's voice through speakers along the boat spine, counts stroke rate live from a magnet on the stroke seat slide, and (on GPS-enabled units) shows boat speed, 500m split and distance covered. The Nielsen Kellerman CoxBox has been the international standard since 1985; the Australian-made Coxmate GPS is the local favourite across Aussie sheds.
Inside the cox box
A cox box is a small handheld unit about the size of a thick paperback, built around a battery, a voice amplifier circuit, a microcontroller for stroke rate counting and timing, and a display screen. It connects to four external components:
- A headset microphone worn by the cox and plugged into the box via a short cable.
- Speakers mounted along the boat spine - typically one per rower in an eight, fewer in a four.
- A stroke rate sensor: a small magnetic switch on the stroke seat slide rail that triggers each time the seat passes a fixed point.
- A power button, mode selector and timer controls on the unit face, plus a charging port.
GPS-enabled units add a GPS antenna inside the case for boat speed, 500m split, distance covered and session data logging that can be pulled off the unit after the row.
Cox box models on the Aussie market
Nielsen Kellerman (NK) is the dominant manufacturer worldwide, and the Australian-made Coxmate GPS is the popular local alternative across Aussie sheds. The current line-up:
- NK CoxBox Mini: entry-level voice amplifier with stroke rate and timer, smaller and lighter than the Pro. Around AUD 1,000.
- NK CoxBox Pro: the standard senior club workhorse - larger display, storable presets, longer battery life. Around AUD 1,200 to 1,300.
- NK CoxBox GPS: Pro features plus GPS-derived boat speed, 500m split, distance and session logging. Around AUD 1,400.
Competing options include the Coxmate GPS (Australian-designed and -built, widely used across NSW, Victoria and South Australia and a particular favourite at sheds where local support matters), NK Speedcoach GPS 2 (the smaller GPS-only unit popular with single scullers and used as a secondary display in coxed boats), and various Empacher amplifier units. Most senior Aussie boatsheds run a mix of NK and Coxmate across the fleet.
How crews use the cox box on the water
In training the cox uses the box to call drills, manage rate changes through rate-ladder pieces, and time intervals against the squad session plan. The stroke rate display lets the cox verify the crew is hitting the prescribed rate during steady state, AT and rate-locked work rather than working from feel alone.
In racing the cox box becomes the cox's tactical instrument. Rate changes, pressure shifts and race plan calls go through the microphone, and the display verifies in real time that the crew has actually executed each call. At King's Cup or the Australian Rowing Championships the cox calls the third 500 push by the boat speed showing on the display, not by guesswork. Coach tools let the coaching staff review session data after the row when GPS-enabled units have logged the piece.
Maintaining a cox box through an Aussie season
Cox boxes spend their working life in a wet, salty, dirty environment - Yarra mud, West Lakes salt, tidal estuary grime, summer heat in an unventilated shed. Maintenance basics:
- Rinse the loom connectors with fresh water after every session, especially anywhere salt water is involved.
- Charge on a regular cycle - modern lithium-ion cox boxes get 8 to 10 hours per charge, but a flat unit on a regatta morning is a disaster.
- Replace headset microphones the moment they crackle, cut out or pick up wind badly. Spares should live on the boatshed equipment shelf.
- Store dry - never leave a cox box in a wet kit bag overnight or in the bottom of a damp boat after the session.
Most senior Aussie boatsheds maintain cox boxes alongside the rest of the fleet with a tracker showing which unit is in which boat, current charge state and any known faults. Boat booking software can extend to cox box assignment so coxes know which unit they are using and whether it is charged before they push off the pontoon.
Where the cox box came from
Nielsen Kellerman built the first cox box in 1985, replacing the megaphones and battery-powered amplifiers that coxes had relied on since the 1960s. The original CoxBox combined voice amplification with the first electronic stroke rate display, and it changed the role of the cox overnight - rate calls became precise rather than estimated, the whole crew could hear the cox clearly even into a headwind, and the cox could time pieces against the same clock the coach was timing from the bank. NK has dominated international rowing ever since. The Australian-made Coxmate GPS arrived later as a strong local alternative and has been particularly popular at Aussie schools and senior clubs from the early 2000s onward.
Cox box FAQs
What does a cox box do that megaphones could not?
Three things at once. It amplifies the cox's voice through speakers mounted along the boat spine so every rower hears every call clearly even into a headwind on the Penrith course. It counts stroke rate live from a magnetic sensor on the stroke seat slide and shows it on the cox box display. And it doubles as a piece timer. GPS-enabled units (NK CoxBox GPS, Coxmate GPS, NK Speedcoach GPS) add boat speed, 500m split, distance covered and session logging that can be reviewed on a computer after the row.
What does a cox box cost in AUD?
A new Nielsen Kellerman CoxBox runs roughly AUD 1,000 to 1,400 depending on model and importer. The CoxBox Mini is the entry-level unit, the CoxBox Pro is the standard senior club model, and the CoxBox GPS adds GPS-derived boat speed and session logging at the top of the range. The Australian-made Coxmate GPS is the popular local alternative and is widely used at Aussie schools and senior clubs from West Lakes through to Lake Barrington. Most boatsheds run a fleet of cox boxes assigned to specific boats and tracked alongside other equipment.
How does the cox box connect to the boat?
The boat is fitted with a permanent wiring loom that runs from speakers down the spine back to a multi-pin connector near the cox's seat. The cox box clips into the connector via a single plug. The cox wears a headset microphone (or holds a handheld mic on older setups) that connects directly to the box. The rate sensor sits as a small magnetic switch on the stroke seat slide rail. One unit, one loom, one mic, one sensor - all four need to work for the cox box to do its full job.
NK CoxBox Mini, Pro or GPS - which one suits an Aussie boatshed?
The Mini is the basic unit: voice amplifier, stroke rate, timer. Smaller, lighter, cheaper. Typically used in school learn-to-row programmes and lower-grade fleet boats. The Pro adds a larger display, storable presets and longer battery life - the workhorse senior club unit across most Aussie boatsheds. The CoxBox GPS adds GPS-derived boat speed, 500m split, distance covered and post-session data download. Most King's Cup-grade clubs and AGSV / CAS / GPS 1st VIII programmes run Pro or GPS units in their racing boats and Minis in the lower fleet.
How do you keep a cox box alive through a season?
Cox boxes live in a wet, salty, dirty environment - rivers like the Yarra, salt at West Lakes, mud at any tidal estuary. Rinse the loom connectors with fresh water after every session because salt and silt corrode the contacts within weeks. Charge the battery on a regular cycle - modern units are lithium-ion with 8 to 10 hour run time. Store dry, never overnight in a wet kit bag. Replace headset microphones the moment they crackle or cut out. Most Aussie sheds maintain a tracker showing which unit is in which boat, current charge state and any known faults, with replacements ordered ahead of regatta season rather than during it.
Related
Continue through the rowing glossary: the coxswain who plugs the cox box in, the ergometer where the same Concept2 PM5 monitor handles rate counting off the water, stroke rate for the cadence the cox box measures, the stroke seat where the rate sensor lives, rowing boat types for which boats need a cox at all, or browse the rest of the glossary. Also worth a look: coach tools for crew lineups and boat booking and equipment tracking across the shed.
Tracking the cox box fleet should not need a spreadsheet.
Row HQ tracks boats, equipment, faults and assignments across the boatshed - which unit is in which boat, charge state, known issues, and who has it on Saturday. Built by rowers.