What is a Cox Box?
A cox box is the electronic device a coxswain uses to amplify their voice through speakers in the boat, show live stroke rate, time pieces and (in modern models) display GPS speed and distance. The Nielsen Kellerman CoxBox has been the international standard since the late 1980s.
What's in a cox box
A cox box is a small handheld unit (about the size of a paperback book) with a battery, an amplifier, a microcontroller and a display screen. It connects to:
- A headset microphone the cox wears, plugged into the box.
- Speakers mounted along the spine of the boat - usually 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 triggers each time the seat reaches the catch.
- A power button, mode selector and timer controls on the front of the unit.
GPS-enabled units add a GPS antenna inside the case and connect to satellite for boat speed, distance and split data.
Models and pricing
Nielsen Kellerman (NK) is the dominant manufacturer. The current product line:
- CoxBox Mini: entry-level voice amplifier with stroke rate and timer. Smaller and lighter than the Pro. Around \xC2\xA3500.
- CoxBox Pro: the standard senior club model. Larger display, storable presets, longer battery life. Around \xC2\xA3650.
- CoxBox GPS: Pro features plus GPS-derived boat speed, 500m split, distance covered, and session logging. Around \xC2\xA3700-750.
Competing brands include Coxmate GPS (Australian-made, popular in Australia and New Zealand), SpeedCoach GPS 2 (NK's smaller GPS-only unit, used by sculling crews and as a backup display), and various Empacher and StrokeCoach amplifier units. Most British clubs run NK CoxBoxes.
How crews use a cox box
In training, the cox uses the box to call drills, manage rate during rate-ladder pieces, and time intervals. The display shows live stroke rate so the cox can verify that the crew is at the prescribed rate during steady-state work.
In racing, the cox box is the cox's tactical instrument - they call rate changes, pressure shifts and race plan calls through the microphone, and verify on the display that the crew has executed each call. Coach tools let the coach review session data after the row when GPS-enabled units are used.
Maintenance and care
Cox boxes live in a wet, dirty environment - rivers, salt water, mud and weather. Maintenance basics:
- Rinse connectors with fresh water after every session.
- Charge on a regular cycle - most modern cox boxes are lithium-ion with 8-10 hour run time.
- Replace headset microphones when they crackle, cut out or pick up wind badly.
- Store dry - never leave a cox box in a wet kit bag overnight.
Many clubs maintain cox boxes alongside the boat fleet, with a tracking system for which unit is in which boat, charge status, and known faults. Boat booking software can extend to cox box assignment so coxes know 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 battery-powered amplifiers coxes had used since the 1960s. The original CoxBox combined voice amplification with the first electronic stroke rate display, and it transformed coxing - rate calls became precise rather than estimated, and the entire crew could hear the cox clearly even in wind. The CoxBox brand has dominated international rowing ever since.
Cox box FAQs
What does a cox box do?
A cox box does three jobs at once: it amplifies the cox's voice through speakers placed along the boat so every rower can hear, it counts and displays stroke rate live during the row, and it acts as a piece timer. Newer GPS-enabled cox boxes (CoxBox GPS, Coxmate GPS, Nielsen Kellerman SpeedCoach) also display boat speed, 500m split and distance covered.
How much does a cox box cost?
New Nielsen Kellerman CoxBox units cost around \xC2\xA3500-700 in the UK depending on model. The CoxBox Mini is the entry-level unit, the CoxBox Pro is the standard club model, and the CoxBox GPS adds boat speed and distance via GPS. Coxmate and Empacher units are competing options at similar price points. Most clubs maintain a fleet of cox boxes assigned to specific boats and managed alongside boat maintenance.
How do you connect a cox box?
Cox boxes plug into a wiring harness installed in the boat. The harness runs from speakers down the spine of the boat back to a connector near the cox's seat. The cox box clips into that connector via a multi-pin plug. The cox wears a headset microphone (or holds a handheld mic in older setups) that plugs into the box. The unit also reads stroke rate from a small magnetic sensor on the stroke seat's slide.
What is the difference between CoxBox Mini, Pro and GPS?
The Nielsen Kellerman CoxBox Mini is the basic unit - voice amplifier, stroke rate and timer, smaller and lighter than the Pro. The CoxBox Pro adds a larger display and storable presets. The CoxBox GPS adds GPS-derived boat speed, 500m split and distance, plus the ability to log full session data for review on a computer afterwards. Most senior clubs use Pro or GPS units; school and learn-to-row programmes often run Minis.
How do you maintain a cox box?
Rinse the connectors with fresh water after every session - salt and silt corrode contacts. Charge the battery on a regular cycle (most modern cox boxes are lithium-ion with 8-10 hour run time). Store dry. Replace headset microphones when they crackle or cut out. Many clubs assign cox boxes to specific boats with a maintenance log so it's clear which units are out of service.
Related
Read more in our rowing glossary: what is a coxswain, what is an ergometer, what is stroke rate, what is the stroke seat, rowing boat types, browse all terms. Also useful: coach tools for crew lineups and boat booking and equipment tracking.
Tracking the cox box fleet shouldn't take a spreadsheet.
Row HQ tracks boats, equipment, faults and assignments across the club. Built by rowers, used at Oundle Town Rowing Club.