I'm working on a mix and I've got some female vocals that have a super sharp sibilance I'm only just now noticing. Even with stacked de-essers and some creative EQ I just cannot get it tamed. The take is otherwise pretty killer, so I'd love to rescue it. Are there any other tricks I can try so it doesn't sound like my singer is singing while wearing a retainer? :-)
 

I've had a vocal with that exact same issue. Initially I tried a couple of de essers but they destroyed the overall sound when I applied the settings required to eliminate the sibilance. I also tried various compressors, sidechained to bring down the volume of the sibilant frequencies but these also couldn't get rid of the nasties without taking away frequencies that the track needed.
In the end I took to surgically editing the waveform by hand. It took time and effort to get it right but it seemed the only way to get the results without destroying the good parts. If you really must keep the track, or can't record another take, then this may be an option for you.

I've always found automation combined with either a purpose built de-esser and/or a combination of a compressor and EQ fixes the extreme problems without touching the rest of the track simply because the extreme settings required are only "on" for a brief period.
 
//

Often when cutting a particular frequency, it can actually give the impression that the octave frequencies above and below have been given a boost (depending on the frquency content of the material).  Cutting these octave frequencies can help tame the sibilance, and I've often found that using a linear phase EQ for such tasks work best.
 
I've no doubt you're already well aware of this, but I thought it could be worth mentioning 

If it's just a single track (lead vocal) and you want it to sound amazing, do as stated above and edit the audio by selecting the esss and dropping the gain 3 or 6 db using process/audio/gain.
 
I have also made a template for deessing with the sonitus multiband by squeezing all the bands to the upper end and disabling the lowest band.  This acts according to the source, only squashing the offending frequencies.  It's a smarter deesser.  I also use the tape emulator on 7.5, and the Ca2a with the screw hard left.  These combined with console emulator LATER in the chain (and maybe the gloss too) restore a very sweet, analog-like upper end to vocals.  
 
Just remember, sometimes, it's actually faster! to edit each ess individually than to try countless plugins and settings.
 
I feel your pain, de essing has been a 15 year battle for me.  I hate loud ess and harsh consonants.  I have no tolerance for them in my mixes.  many songs on the radio have too much for my taste.

I usually use an eq. (pre-compressor) and play around between 8k-16k. If it's more of a shhh- then a little lower helps between 2-6k. Raise and drop the frequencies one by one and see where the Ms. S's Is's.

I then place a de-esser on that --and then add compression.
I have had to cut and remake many times though as rebel007 said. But with SonarX3 smart tool drawing fades along with the eq/de-esser usually is enough.
Sorry this is so long.
After its all done, I usually give it a nudge at 12k to bring it back to life.

Hand-edited automation envelopes are always the best place to start, but even that won't always solve the problem in extreme cases. For that, you have to go old-school and do it the way it was done before dedicated de-essers existed.
 
Here's how to do it. Clone the vocal track. Apply a sharp high-pass filter to the clone, rolling off around 4KHz. Next, put on a compressor and smash the sh*t out of it with a low threshold and very high ratio. The clone track should now sound absolutely awful, with ear-piercing sibilance.
 
Now route that track to the sidechain input of a compressor on the vocal bus. Start with a moderate ratio and gradually increase it until the essiness goes away.
 
It's also a good idea to isolate a particularly bad "S" and analyze its frequency content. If it looks like white noise, you're good to go and the above method is guaranteed to work. But there are two scenarios that can be especially problematic: when there's comb filtering and when there's a narrow spike in the frequency response. If you need help with that analysis, email or PM me.
 
 

I'm working on a mix and I've got some female vocals that have a super sharp sibilance I'm only just now noticing. Even with stacked de-essers and some creative EQ I just cannot get it tamed. 

 
If it's really essey you aren't going to get rid of it without hearing the tell tale signs of having gotten rid of it.
 
The best way to deal with esses is to accept them as being part of the singer's singing and choose a mic, mic placement, and pre amp that doesn't turn them into ice picking.
 
I've never heard a de-essing procedure that did anything and also sounded good.
 
 

Just as noise reduction is most effective with signals that don't have a lot of noise, de-essers are most effective with signals where the essing isn't too bad.
 
Another option if you're going to take the manual route is split the clip where the de-essing occurs, and use clip gain to reduce the level and/or insert EQ as a clip FX to take off some high end.

...wicked
I'm working on a mix and I've got some female vocals that have a super sharp sibilance I'm only just now noticing. Even with stacked de-essers and some creative EQ I just cannot get it tamed. The take is otherwise pretty killer, so I'd love to rescue it. Are there any other tricks I can try so it doesn't sound like my singer is singing while wearing a retainer? :-)
 

I usually use Melodyne for De-essing. It's manual labor, but easy to do.
 
Walt