There are countless posts on this subject in the thread over the years...
If you choose NOT to use an external sub with your towers, there are a couple of connection possibilities:
1. Run speaker wire only to your towers. In your AVR, set sub to "no" and speakers to "large" or "full". The full signal including LFE will be sent to your towers. The built in crossovers in your towers will send LFE plus appropriate low frequencies to the sub and bypass bass management on your avr. You will use the volume dial on the back of your tower to control the bass volume. All smaller speakers in your system that are crossed over will have the bass played through your left and right towers plus the LFE come from the towers. This is the simplest way to get a great result in most cases.
2. Run speaker wire to your towers plus rca (sub cable) to the LFE output on your towers. In your AVR, set sub to "yes" and speakers to "small". You can now use bass management on your AVR to control the LFE and crossover settings on your towers.
There is a lot of debate on what yields the best results. It's a hobby so experimentation is fun and the room may dictate what is ultimately the best solution.
I am currently between external subs having just sold my dual Seaton Submersive HP's so I currently am just running speaker wire to my BP7000's with Integra set to "NO" for sub and "Full Band". I get excellent results without the need to do an additional cable run. I personally see no reason to to run additional cable for bass management in this scenario.
Now, I do also have BP7000's for surround backs so I think it would be incredibly fun to run lfe to all four BP7000's so that I could have LFE coming from 4 separate locations. But my new subs should be here in the next few weeks so I don't want to go through the trouble. Just using speaker wire will only allow the LFE signal to come from the L/R speakers so if you have multiple full range speakers and you want LFE coming from more than the L/R speakers, then you would need to run RCA to all locations for LFE. This is personally the only scenario I would run extra cable for.---Most would probably just run the rest of the towers as large so they are playing full band, but LFE would still just come from L/R speakers with no additional RCA cable for LFE.
The final scenario that I highly advocate is:
3. Buy very capable external subs to use with your towers. Run speaker wire only to the towers and LFE cable to your external subs. On your AVR set sub to "Yes" and speakers to "small". Cross speakers between 60-80. Keep in mind a crossover is not a brick wall so lots of information below the crossover ultimately gets played via the tower. Benefits of your towers with built in subs but not using subs for LFE:
- very easy to integrate with external sub and much greater flexibility with crossover.
- lower crossover so you can avoid subwoofer localization
- many times, subwoofer location for the lowest frequencies is not ideally where your front left/right speaker locations are. Separate subs allow you to spread them around the room to reduce standing waves and have low frequencies sound better across many seating locations.
- although the built-in subs in the towers are adequate, they come no where near the high output, low frequency capability of very high quality stand-alone subs.
I have quad BP7000's with built in 1800 watt 14" sub drivers (essentially supercube reference in each tower). According to Definitive my four BP7000's have the output of 14 SuperCube One's but I still choose to use external subs.
Call me a bass nut, but I'm not the only one who does this. It's hard to match the bass performance of a high quality sealed sub.
I hope this is helpful and makes sense. You have many options. Enjoy your speakers!