subwoofer to speaker connection

Lectron JH50(a 25 year old tube amp 50 w per channel) which is working well. 

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

I like to thank both yogiboy and gdnrbob for sharing their experiences. I especially like to thank      gdnrbob for taking time in looking up the Audio Physic sub manual. Although my sub is an older version, with cross over settings 32, 46, 61,80,105 Hz , the overall capability is the same as that in the manual, except the new manual is lot more clear in the directions. My sub has both a volume and roomgain function to adjust the instrument sound. After reading the responses, I like to further seek input and clarification for further understanding

1.       gdnrbob mentioned that you “like using the high pass filter…but it means the sub and main speaker aren’t overlapping frequencies, and thus muddying the sound”. If I set 61Hz above to amp to run speaker and 80Hz below for the sub using the Hsu high pass filter, wouldn’t I have 61-80 Hz overlap? Would you suggest such overlap  or just 80Hz (or another frequency such as 61Hz)above to speaker and below to sub? By the way, your experience on improving the sound with connection to sub (like that express by rcprince that I first read in Jan 17 audiogon forum)  is what prompted me to explore this possibility since I have a decent sub not being used. (I did try to sell once last year at Audiogon, but no takers)

2.       Yogiboy you mentioned that you have tried many subs and always preferred your system without them. What kind of subs and speakers have your tried? May be your speaker is an excellent one and thus no need for sub.(The other day I listened to the demo of Magico speakers with Chord equipment in a store and found such fantastic sound from the set up which further prompted me to explore the improvement on my speaker since I have the spare sub) My speaker, Focus Audio, is an old one about 20 years ago that listed about US$4000 and the sub(Audio Physic)  about US$2000.  My pre-amp is Transcendent , and amp is Lectron HJ50.  I am looking to see if I can improve the sound from the speaker by connecting it with sub properly,  so I can  truly test if there an improvement.

By the way, I am very thankful to the Forum and Audiogonians in sharing and advising inexperienced individuals like me. Really appreciate the help. Moses189

Thanks both  bdp24 and stringreen for providing the "scientific" reason in having bi-amp. I will for sure buy the Hsu high pass filter and will be looking forward to detect the difference. 
On a sonewhat separate but related question I wonder if you can help to advice. There  is another Lectron amp JH50 tube (50watt) amp available from a store possibly selling for $1500. Would there be any major advantage in having 2 rather than just one such amp to drive the 2 speakers I have? (With one such amp,  I normally turn the pre-amp volume control to half way to produce adequate volume to listen in my small room, 12 ft wide, 13ft long, 8 ft high). Moses189

Thanks for your comments, gdnrbob.  I wonder if anyone would like to further comment on future upgrades of my system since spending $1500 for  another Lectron JH50 amp will not provide any tangible gain in the sound (to be used as monoblocks) after adding my sub+high pass filter, what would be the next upgrade that you would recommend: change  my  Audio focus (Signature series model 78) speaker, or Transcendent Grounded Grid Preamp, or  Linn sondek LP12  turntable with Karma cartridge?

 I have tried the sound with and without  the Hsu bass optimizer.  I found that  combining my subwoofer with Hsu bass Optimizer with cross over at 60 Hz  to my amp,produced the music a fuller range.  The base part is especially better when listening to organ music  and a clearer voice when listening to Pavarotti singing. Any suggestion as to what would be a further worthwhile upgrade to explore with my system. 

I am glad to hear the improvement with the connection of my subwoofer +high pass filter. I am happy with the improvement and not in a hurry to further upgrade, assuming the next upgrade will be expensive. Will look forward to hear your experience with the high pass filter. Moses189

Thanks. What is the cost? The basic connection is similar to Hsu high pass filter.  I wonder if anyone has compared both and give an evaluation.Moses 189

Thanks for the suggestion. I am glad that it is not expensive. I already have tried the Hsu high pass filter which is working out well. I would be interested to compare this MiniDSP. I wonder if anyone has experience comparing these 2? Moses189

Thanks avanti1960 for your sharing of your experience

of achieving good base sound without purchasing a high filter. I wonder if using an inexpensive high filter would achieve similar effect as what you have used, except simpler and easier. In addition, by connecting the sub parallel with the speakers to the amp terminal, the advantage of the improving mids and upper base as per comment from bdp24 and filling in the “nulls” as per comment from  stingreen would be lost. Since I am a novice to this and do not have sound engineering or electronic engineering background, I hope all those with more experience and knowledge can help to understand better, so we know what would be the specific advantage of each. Moses189