Bass management--high/low pass filtering

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.

@cooper52 I actually did it myself. I built two high pass filters, one for each channel as I’m running my Audio Research Ref 5SE to two separate ARC Ref 250SE mono blocks. The monoblocks feed a pair of Revel Performa F328Be speakers.

I got some help designing the second order high pass filters from GR Research (they were happy to help me without charging me a dime, which was very appreciated) and I will be happy to share the circuit diagram with you. What made it a little bit more complicated for me was that I’m using balanced connections between the line stage and the monoblocks, but it’s only a few more components.

This does indeed relieve the main speakers from, in my case, anything below 80 Hz, and of course my two subwoofers have low pass filters and with REW I can make sure everything melds really well.

Comments here saying that "main speakers should always be run full range," in my humble opinion, don’t know what they’re talking about. I believe there’s absolutely no basis for that statement, as then in its extension you would say that you don’t believe in crossover filters, as high passing the upper part of the frequency range to the main speakers and let the subwoofers take care of the lowest frequency duty is exactly the same thing as what a crossover filter does inside the main speakers.

@gdaddy1 per my comment above, in my opinion your comment is simply not true

@bimmerlover   Your speakers have triple 8" drivers for excellent bass resonse.

 24Hz (-10dB); 26Hz (-6dB); 35Hz (-3dB)

By crossing at 80hz. you cut them off at the knees. Why buy a speaker this capable and then put a choke on them? I'd bet the triple 8" drivers produce BETTER, tighter mid-bass in the 35 to 80hz range than your subwoofer.

It's called a "subwoofer" for a reason. To lift the line in the sub region. For you the sub would come in around 40hz. It's NOT a woofer. You have triple 8's for woofers but instead your asking the subwoofer to handle this mid-bass range and hobbling the very capable triple 8" drivers. Why buy them if you don't use them?