It appears that the -6 db down point of the LSA's is 35 Hz. I would start there and adjust upwards until you have enough bass or it starts to sound muddy. I would stick with the 24 db slope unless you have an option for a 48 db slope. The less frequency overlap between the sub and the mains the better.
Low-pass Setting of SVS SB-3000s subs with LSA Signature 80 speakers
One of my favorite things about the SVS SB-3000 subwoofers is that you can adjust so many of the parameters on their convenient app. I am using a pair of LSA Signature 80 speakers with a pair of SB-3000 subs, and I am trying to figure out what frequency and slope should I use to set the low-pass filters?
SVS recommended 50Hz and 24 db/octave, and while I tend to think that is accurate for the frequency, I’m not as sure about the slope setting. One thought is to buy a pair of in-line filters to use from the preamp to the amp of the LSA‘s to make certain, but I don’t know what the quality of those filters are (from Parts Express). I would appreciate any insights from users who have experience with set ups like this.
Also, I am using an dSpeaker anti-node with the subs, and that seems to really help a lot.