subwoofer to speaker connection


I am a novice and would like to seek advice from fellow Audiogonians. In  reading the forum 128025-84361 (Jan this year) on speaker and sub connection, I am intrigued  by the comment   from rcprince “Virtually every review I have read remarks on how the mids and upper bass from the main speakers are improved when you add a subwoofer…”. I have a pair of Focus Audio Signature Series (Model 78) speaker and one Audio Physic Luna sub. Would connecting these 2 produce improvement in the sound of music? If so , how  can I  best connect my sub and speaker ? I don’t mind buying the high pass filter and inline cross over as mentioned in the above forum, if needed. Moses


moses189
Thanks a lot yogiboy.  The information really helps me to understand the connection better. I have now connected one pre-amp output to my amp, the second pre-amp output to my sub. I like to seek opinion of
1.whether it will be better to use the Hsu Research high pass filter so high music tone can be send to my amp when connecting the sound source from the pre-amp. This will allow my sub to provide the base sound, with assumption that the quality of base is better from the sub than my speaker.
2.sub placement: The manual you recommended stated that " If the A/V receiver (AVR) equalizes the subwoofer channel during auto-set-up, corner placement will often provide the best overall performance". For  stereo set up, my amp will unlikely equalize the sub channel. So would it better to place sub on right corner where most base instruments are played from right in an orchestra (I mostly listen to classical music).

Thank you very much

@moses189
I like when using one sub to place it in the center of the speakers. You can move it around to see which is best for you You should start with changing the adjustments on the low pass filter on the sub until it blends with the mains. If you use a high pass filter you will cut off the low bass on your speakers.You won’t know how it will sound until you try it. BTW, I’ve tried many subs and always preferred my system without them. Give it a go,since you have the sub you have nothing to lose !
I prefer high pass filters as they allow your amp and main speakers work more efficiently while allowing the sub to do what it does best.
I, too, am considering the HSU highpass filter for my HSU subs.
I can't find much info on your amp, but it looks to be a nice one. 
I assume your preamp doesn't have low frequency output, so you are going to need a crossover.
For $100 the HSU is a reasonably priced unit. For my main system I use the Vandersteen M5-HP filters which do the same thing but at a higher fidelity point. 
I will politely disagree with yogiboy regarding the benefit of subs. Every system I have added them was improved. 
Audio Physic has a nice tutorial on placement on its' website, too.

Looking at the Luna manual:
https://www.manualslib.com/manual/1141221/Audio-Physic-Luna.html?page=10#manual
I see you can connect the sub with speaker cables (in parallel with your speakers), and use the subs controls to adjust crossover frequencies.
Though using it this way will mean your main speakers are running full frequency. I am doing this currently in my office, but I prefer using the high pass filter as it lightens some of the work for the amp, but it means the sub and main speakers aren't overlapping frequencies, and thus muddying the sound.
B