Bass management--high/low pass filtering

+1 @avanti1960 !

I agree with running your speakers full range.  I have the option of setting both the low and high pass filters in my main system.  I find I like the sound better running the speakers full range and now full range out to my subs using the preouts.  I even switched off the low pass filter on my subs.  You need to have a room that is well setup acoustically and I dial in the volume on the bass but it works for me.  I’m a bass guy which is a good thing because only my dog can hear the high end anymore.  Suggest experimenting with your settings and find what you like best.  It’s a fun part of this hobby for this old guy.  

While some choose to use a high pass filter to the main speakers with sub(s), I think there are many reasons to not.  A lot of popularity with high pass filters comes from AVR surround sound, where there are Dolby settings in the AVR processor for this.  the theory is that it cleans up signal going to small main and certainly small surround speakers.

But for great stereo imaging, and disappearing subs, getting the most bass cues possible to your left and right speakers helps immensely. Your ear can localize tones quite low, so using the low pass filter on the sub prevents you from localizing these sounds. Think plucking of the bass string vs the deepest tone it creates.

As @avanti1960 said, you have respectable bass output with your speakers, use it.  This allows the lowest possible cut off for your sub. 
 

Additionally, adding  any filter, processor etc in line with your speakers potentially inserts distortion.  I work very hard to avoid this.  No room correction, Roon processing, graphic equalizer etc. 

I am not knocking quality high pass filters.  But at best they add complexity.  I have enough wires!

the only reason I would consider not sending full signal to my mains is if the woofers were flopping or distorting.  And most quality speakers with good amplification do not do this.

KISS

I'm one to try and keep things simple.  There have been lots of thoughtful comments and I agree that it's usually best to play the speakers full range and then have the sub reach up to that point and fill in.  

Outboard DSP or anything else added to the signal chain will raise the noise floor and is always a tradeoff.  

Start in the shallow end of the pool.  Get your sub and do you best to integrate it.  Unless your room is particularly problematic you should have some great sound.  Only if the sound is unsatisfactory move to the deep end of the pool and add something else in the signal chain.  Good luck and cheers. 

@avanti1960   +1

Adding complexity and restricting the speakers won't help anything. They are design to be full range.