How do you high pass your main speakers?

I am in agreement with @erik_squires 

Read this article

http://www.troelsgravesen.dk/High-Pass-Filter.htm

Thanks @perkri !

I paricularly think that audiophiles should focus on this sentence from Troels, which is in alignment with my previous statements:

But not having the midrange driver pumping deep bass has a positive impact on the midrange as well and it also relieves the power amplifier of some back-EMF coming from the speaker drivers. Pretty much a win-win situation.

While Troels is discussing a 3-way system with a dedicated midrange this is essentially the same as taking a 2-way and adding a subwoofer. High passing the satellite has enormous audible benefits that outweigh all of the puritanical nit picking by far.

Re: the OP and his sealed ATC SCM19 main speaker design with its huge magnet, large 3" and underhung voice coil SL-woofer, the distortion numbers here are already quite low up through the midrange, and my previous "leave it as it is"-answer (i.e.: don’t mind high-passing them) was partially in relation to this context. Granted, as a sealed design there’ll be excursion maxima at the tune, and thus there will be some influence into the mids at more elevated SPL’s with low frequency material exciting the cones into prodigious movement, not least if/when the voice coil exceeds the gap and its linear motion, but at more typical listening levels it’s a lesser issue.

Question remains: when will the efforts of high-passing them be worth it, and naturally this depends on the specific implementation of a HP-filter among other things. Given a fully active DSP-configuration steeper HP-slopes can be easily chosen, and it’ll make the HP-function and its sonic implications all the more effective. A mere 1. order slope here will still have some "bleeding" into LF-territory and is really only a half-baked solution - even with an 80Hz HP. Myself I’m implementing a HP over my mains at ~85Hz, 36dB/octave L-R slopes, and that’s with dual 15" woofers per channel w/100dB sensitivity and 800W continuous power handling - that is, tested with material into the bass region, so add a bunch of dB’s of effective headroom when high-passed as described. What’s interesting with such a powerful main speaker system is the difference a HP still provides for here; natively a ported design tuned at a relatively high 40-ish Hz, high-passing them removes the character of the ports, cleans up the mids even further with sharper leading edges, and seamlessly "delivers" them to a pair of very efficient 1/8 space loaded tapped horns that are quite "characterless" as well - not least when compared to the sonic imprinting of a variety of dual 18"-loaded direct radiating subs. All of this makes for a more seamless integration with the horn section from ~600Hz on up (111db sensitive). Indeed, here a HP over the mains makes a world of difference.

@erik_squires 

Your quote from Troels sounds as if he is discussing a 2-way speaker, where the midrange does double duty serving the bass too.  Why would the midrange be “pumping deep bass” on a 3-way speaker?

Not.all stand mounts are 2 or 2.5-way speakers but even with woofers dedicated to bass frequencies, there can be benefits of using a high-pass filter when using subs, such as keeping the LF drivers operating in the range where they are most linear and relieving the power amplifier of some back-EMF coming from the speaker drivers as presented in the quote from Troels that you shared.

@mitch2 I suggest you read the original article.