What is a Cox Box?
A cox box is the electronics package a coxswain runs every outing - voice amplification through the hull's speaker system, live stroke rate from a sensor on the stroke seat, and piece timing. GPS-enabled units add live boat speed and 500m split. NK CoxBox and Coxmate GPS are the two units most commonly seen at NZ rowing clubs.
What's inside a cox box
A cox box is about the size of a hardback novel. Inside the case sit a battery, an audio amplifier, a microcontroller and a display screen. The unit connects to four things in the shell:
- A headset microphone worn by the coxswain, plugged into the unit.
- Speakers mounted along the spine of the hull - typically one per rower in a coxed eight, fewer in a four.
- A stroke rate sensor - a small magnetic switch on the stroke seat's slide that pulses each time the seat reaches the catch position.
- Front-panel controls for power, mode and timer functions.
GPS-enabled models include an internal antenna and pull satellite data for live hull speed, 500m split and cumulative distance.
Models and pricing in NZD
Nielsen Kellerman (NK) is the most common brand at NZ university squads and competitive clubs. The current lineup, with rough NZ pricing:
- CoxBox Mini: voice amplification, stroke rate and a timer in a smaller, lighter case. The entry-level option for learn-to-row programmes and smaller school squads. Around NZD 1,100.
- CoxBox Pro: the senior standard at NZ clubs, universities and major school programmes. Larger display, programmable rate presets and longer battery life. Around NZD 1,400.
- CoxBox GPS: all the Pro features plus GPS-derived hull speed, 500m split, cumulative distance and full session logging for post-row review. Around NZD 1,600-1,700.
Competing units widely seen at NZ clubs: the Coxmate GPS (Australian-made, with a simpler trans-Tasman supply path and strong GPS performance), the NK Speedcoach GPS 2 (a smaller display-only unit favoured by scullers and used as a backup in coxed shells), and older StrokeCoach amplifier units still on a few school fleets. Clubs typically standardise on one brand across the fleet so spare parts and training stay simple.
How crews use a cox box
During training, the cox uses the box to deliver drill calls, manage rate through rate-ladder pieces and time work-rest intervals. The live rate display lets the cox confirm the crew is on the prescribed rate during steady-state work - whether the squad is doing a long paddle at 20 spm on the Avon River in Christchurch or AT pieces at 28 on Lake Karapiro before the Maadi build.
In racing, the cox box becomes the coxswain's tactical instrument. Rate changes, pressure calls and race-plan execution are all delivered through the microphone, and the cox confirms on the display that each call has taken effect. Coach tools let the coach review GPS session data after the row when a GPS-enabled unit was in the shell.
Maintenance and care
Cox boxes live in a wet, sandy, variable environment - NZ harbours, rivers and lakes through summer and a wet winter training season. The maintenance basics:
- Rinse all connectors with fresh water after every outing, especially after sessions on salt water at the Waitemata Harbour or the Otago Harbour.
- Charge the battery on a fixed schedule - current units run 8-10 hours per charge on lithium-ion.
- Replace headset microphones at the first sign of crackling or wind cut-out.
- Store the unit dry - never leave a cox box in a wet kit bag overnight.
Many NZ clubs maintain a cox box register alongside the boat fleet, tracking which unit is in which shell, charge status and any known faults. Boat booking software can extend to cox box assignment so coxes arrive at the boatshed knowing exactly which unit they have and whether it is charged before they push off.
Origin and history
The first cox box was developed by Nielsen Kellerman in 1985, replacing the megaphones and basic battery-powered amplifiers coxswains had used since the 1960s. The original CoxBox combined voice amplification with the first electronic stroke rate display in a single unit, and it changed coxing fundamentally - rate calls became precise rather than estimated, and the whole crew could hear the cox regardless of wind, rain or boat traffic. The CoxBox name has been synonymous with the category internationally ever since, and it remains the most widely seen brand at NZ club boatsheds today.
Cox box FAQs
What does a cox box actually do on the water?
Three jobs at once. It projects the coxswain's voice through speakers along the hull so the whole crew hears the calls regardless of wind, rain or boat traffic. It tracks and displays stroke rate live, fed by a magnetic sensor on the stroke seat's slide. And it times pieces and intervals - the timer is what anchors the race plan. GPS-enabled units (NK CoxBox GPS, Coxmate GPS, NK Speedcoach GPS) add live boat speed, 500m split and session distance.
How much does a cox box cost in NZD?
New cox box units in New Zealand typically cost NZD 1,100 to 1,700 depending on model and current exchange rate. The NK CoxBox Pro - around NZD 1,400 - is the standard at most senior club and university shells. The CoxBox GPS sits around NZD 1,600-1,700 for the added speed and logging features. The Coxmate GPS is comparable in price and widely used in NZ thanks to its GPS accuracy and the simpler trans-Tasman supply path from Australia. Clubs typically maintain a fleet of cox boxes assigned to specific coxed shells.
How is a cox box wired into the shell?
Through a fixed wiring loom installed inside the hull. The loom runs speaker cables from the bow end of the boat back to a multi-pin connector mounted near the cox seat. The cox box plugs into that connector. The coxswain wears a headset microphone (older shells still use a handheld mic) that plugs into the unit. A small magnetic sensor mounted on the stroke seat's slide feeds the stroke rate signal into the unit.
What is the difference between the CoxBox Mini, Pro and GPS?
The CoxBox Mini is the entry-level unit - voice amplification, stroke rate and a timer, in a lighter and more compact body. The CoxBox Pro is the standard for senior NZ club, university and school programmes: larger display, programmable presets, longer battery life. The CoxBox GPS adds all the Pro features plus GPS-derived boat speed, 500m split, cumulative distance and the ability to log a complete session for post-row review on a laptop.
How do you keep a cox box working in NZ conditions?
Flush all connectors with fresh water after every outing, especially after sessions on salt-water harbours like the Waitemata in Auckland or the Otago Harbour in Dunedin - salt corrodes the multi-pin contacts faster than any other failure mode. Keep the lithium-ion battery on a regular charge schedule; modern units run 8-10 hours per charge. Store the unit dry between sessions. Replace headset microphones at the first sign of crackle or intermittent signal. Log faults against each individual unit so it is clear which boxes are out of service before the morning briefing.
Related
Continue in our rowing glossary: what is a coxswain (the human in the seat), what is an ergometer, what is stroke rate (the cadence the cox box measures), what is the stroke seat, rowing boat types, or browse all terms. Also useful: coach tools for crew lineups and boat booking and equipment tracking.
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