Try SPITFISH, Im not 100% sure of what a low-frequency ess is but SPITFISH is one of the best de'essers out and it's free! You can also use an EQ that will key in on exact frequencies and filter the noise out by cutting the frequency it's on.
I'll drop a tip... I'm using a de-esser in an eq-esque fashion. For the sake of clearing 'muddiness' on individual tracks, it works like a tamed EQ in this sense, so you're not cutting lows when they're useful, but cutting them when they aren't. Picked this tip up from some top guy.
Personally, I would create 2 basslines...one with the lows as is (when useful), the other (using processing) to cut it when they're not useful. Thats just what I would do if I ran into a situation like that. I'm not saying that your tip wouldn't work, I'd just handle it differently. =)
try hp filter with a high slope, though i still gotta say that still should be done through eq/compression. The muddyness is probably due to hitting max headroom which implies you should tune down some channels so you have breathing room on the master bus.
I learnt this off a top guy, he explained it in more depth/detail than I did. I'm liking the results it has. Gonna prove useful on my pianos. On most things I'll just cut, but on pianos I'm going to find it most useful, and perhaps acoustic guitars.
Thanks for the responses. I tried using waves de-esser but it only goes down to 2000hz
I have about 95% of the presets in Waves Mercury Bundle saved as a zip. If anyone wants or needs them, PM me your email address and I'll send it to you...here's a screen shot of how I organized them. This is just a few...there's a lot more.