I received the following Quickstart Guide from Mike Hunter at DBX Harman International Technical Support
Start by setting all dials to the off position. And the output gain to 0 dB.
Gain-With the signal present, turn up the gain control until the 0 dB led lights, but the clip LED does not.
48V - This should only be pressed in if using a condenser mic that requires phantom power.
HighPass - Try pressing this button in. If the sound is too thin set it back out.
Bypass - This button should be in the out position.
Start with the density set to about 6
Drive - Turn up until you reach the desired amount of gain reduction.
Density - Adjust until the release of the gain reduction suits your taste. You really need to experiment with these settings to get the best results. You probably won’t want more than about 3-6 dB of gain reduction unless you are going for a certain effect or desire very heavy compression.
Frequency - Set to about 5K
Threshold - While making “ssss” sounds in the mic, turn up until you get the desired amount of control over the high frequencies. If no De-Essing is required, turn it off.
LF Detail - Slowly turn up until the lows sound good, but not overbearing.
HF Detail - Turn up until the high end sounds clear, but not harsh.
If no gate is needed, leave in the off position. If you want to set the gate, start by setting the ratio to 10:1.
Threshold - While talking or singing in the mic, bring up the threshold until the signal will no longer open the gate. Now back it off until the gate will open when the signal is present.
Ratio - Adjust this setting until the background noise once again becomes audible, then turn it back up slightly until the noise drops in level. Check the gate with the signal. What you are looking for here is the “happy medium”, where the noise is reduced but the gate sounds natural. You may not be able to fully remove the noise, but you should be able to lower it. If it doesn’t sound natural, try repeating this process.
Gain - Adjust this until you have the desired amount of level feeding the next device.