DRC

[Linn_agnostik]

I would not allow any DRC to touch anything > 400 Hz at all. The TacT might be all or nothing proposition there.

First of all I would experiment with speaker placement. The JansZens are hybrids first and foremost (would not think you'd have that problem with pure electrostats). Google Get Better Sound - a ton of great tips on placement and others. Small changes matter - I can totally destroy the sound of my Sasha's by moving them an inch closer to the side walls. Generally speaking, if dynamic, ported speakers are less than 0,5m from boundary walls (measured from the port side) you'll have problems

If that doesn't help try the DS range from Linn, as uk75 suggest. Have had it, one of the neatest solutions to removing bass peaks on the market, very transparent. The Behringer option suggested above is nowhere near to it, sound quality wise (as anything in the audio chain that uses the TOSLINK inputs/outputs).

You don't mention anything about your source - if it is a computer then google for Dirac - might be a better option, although if I recall correctly it performs some magic on 400Hz+, which is anatema to me...