The 1 ohm resistor should be a reasonably precise 5W or
better type. The other resistors can be 1/2w or 1/8 watt 1% types.
The diodes are for protection.
When using this in PRAXIS, make sure to select
"Current Sense " for the impedance measurement types, and set the
probe resistors properly (there is a menu for that in the Levels Form, under
"Setup->General"). You can also measure frequency
response of loudspeakers when they are connected via this network, as the
Probe2 is properly connected across the speaker terminals.
(The probes of PRAXIS aren't used with this, of course, the
cables connect direct from the network below to the Audpod).