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Furuno DFF1 Review

The Furuno DFF1 black box sounder is an add-on network sonar designed to provide data to any of the Furuno NavNet multifunction display units.

We used a Furuno NavNet 3D 12-inch MFD coupled to an Airmar B44V thru-hull transducer to test the DFF1 black box sounder.

furuno dff1 black box sounder

Furuno DFF1 Black Box Sounder

This unit is capable of producing 600- or 1000-watts RMS of output power depending on the transducer used with the unit. The Furuno manual lists a number of optional transducers including dual frequency units, single frequency units, transom mounts and thru-hulls in plastic or bronze rated for either 600- or 1000-watts of power.

The DFF1 black box is built on an aluminum chassis and encased in a protective plastic box that measures 8.5-inches square and 3.5-inches deep. On a boat the DFF1 needs to be mounted in a protected area since it is not rated waterproof, but only splash resistant.

The box uses a standard 10-pin Furuno transducer port and a network cable connection to move data from the transducer to the MFD. Power (12- to 24-volts DC) is supplied through a three-pin twist lock connector. Dip switches are accessible under a rubber cover and are set from the factory to work with a direct connection to an MFD.

If you connect the DFF1 to a network hub you’ll need to rearrange the external dip switches. The default output power of the DFF1 is set at 600-watts. Changing to 1000-watts requires repositioning an internal dip switch. We tested the unit with a 600-watt power rating set.

I reviewed the Furuno DFF1 using the full screen sounder display mode using high, low, and dual frequency display modes. This sounder has A-scope, zoom, bottom lock, variable range marker and shift functions.

Functions like gain and depth range can be quickly adjusted to optimal settings with dedicated pushbuttons. I used the up/down arrow range buttons to set the depth for the area where our test target had been placed.


furuno dff1 black box sounder on furuno navnet 3d 12 mfd

The big screen of the NavNet 3D MFD we used for testing let the DFF1 shine. Here you can see the unit picked up and displayed all three of our test targets. The left side of the screen is the 50 kHz display with gain set to about 80%. Three clearly visible fish arches show up onscreen at the depths of our test targets. The narrow beam width of the 200 kHz display had no trouble finding all three of our test targets. We achieved our best results using the manual settings for gain and depth. Overall on the water performance of the DFF1 was very good.

Gain can be manually adjusted separately for both the high and low frequencies. A single press of the button brings a bar graph onscreen for the displayed frequency. Gain is then adjusted as needed with the RotoKey. RotoKey is a rotary control knob with a pushbutton enter function built-in.

If you are using a dual frequency display a second press of the gain button switches you to the other frequency. I liked this design feature and found it easy to use.

Common sounder function selections like frequency to be displayed and turning A-scope on or off can be accomplished using the RotoKey to both view and choose options. More obscure functions like picture advance speed and clutter as well as a host of other adjustments are made using the sounder menu.


Maximum Power (Watts RMS)600 / 1000
Frequency (kHz)50 / 200
Transducer Used for TestAirmar B44V
Auto Depth RangingYes
Manual Depth RangingYes
GainAuto / Manual
Bottom LockYes
Warranty Period (Years)2


On our first few passes over our test range I noted this unit painted the sample targets well. Fine-tuning with manual gain did provide more definition to the target balls. I rated presentation of the DFF1 black box sounder data as very good.

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