Trying to use expander to replace Scheps expander

[jatech1]

I use a Scheps expander to push down the noise floor. Threshold set to -45db, floor=-18, close=0, attack=1.0, release=100. This is used to slightly tamp down my noise floor and breaths in voice... it does not touch anything louder than -45, and only downward expands a max of -18 (floor) from there. I have been trying to duplicate this with ZLCompressor in expander mode, but I cannot find the right combination of settings to mirror this behavior. I have Threshold set to -45, ratio=2:1, expander mode. This alone, from what I can understand, should show in the input/output graph ONLY levels quieter than -45 being attenuated, but I see everything being reduced. Am I misunderstanding how to set the expander to reduce only levels below -45 by up to -18 and leave everything above -45 untouched?

[zsliu98]

The level is a quite vague concept. The default mode in ZL Compressor is sample-based dynamic control. Perhaps you could use press the R button to enable RMS compression and set RMS Mix to 100% (or something close to 100% to combine RMS/sample control)? Does it work better now?

[jatech1]

That actually does seem to make it work better. So, it is all about what it "detects" as the current level as compared to the threshold you set? Enabling R and setting mix to 100 make it a lot better. I still see levels in the graph that are above the Threshold setting being attenuated slightly... mainly within 12db of the threshold. Then I adjusted Length up to 160 and it seems to do exactly what I want now. Is there any drawback to length at 160? What Speed setting is best to keep it as audibly invisible as possible to the levels above the threshold? Oversampling and lookahead do not seem to help. Any benefit to using them? Thank for your help!

With RMS and Mix:

[jatech1]

After length set to 160:

[zsliu98]

That's correct. However, it is impossible to tell what are correct parameters :) I could also tell you the meaning of parameters:

RMS Length: Controls the RMS window length (in millisecond).

RMS Speed: Controls the relative attack/release speed of RMS compression.

RMS Mix: Controls the mix percent of RMS compression.

Besdies these, if you want to reduce noise level, you may want to lower the Floor value.