Best Subwoofer Connection for Music

@oldrooney   "I haven’t gotten that far yet on this go-round. I’ve placed the sub in the listening position and gone around the room to find the spot the bass was strongest.'' 

Determining your rooms actual standing wave bass modes using a sub placed at the listening position playing low frequency cadences. THEN locating the loudest bass modes is actually the very first step in setting up a -3dB subwoofer system.

There the subwoofer/s use the rooms modes requiring the least amount of their power and processing needed for their best performance, integration and the musicality designed during post production.

The room rules, not the system. Good luck with it.

@m-db Thanks. I feel that I will to develop some skills along the way because despite several attempts at integrating subs, I haven’t been able to get lucky yet. And you’re right about the room ruling. I’ve got two completely different systems set up in the same room, and guess what? They sound virtually identical. The average living room is indeed a limiting factor that even acoustical treatments can only mitigate, but not remove entirely. The Sound Doctor makes that point before all others, I believe. Thanks for the response. 

@panzrwagn and others, I think I’ve figured out why some people are recommending the high level connectors, provided that the sub has high-level out, as well. If the full range, high level, signal goes to the sub first, the sub applies a low pass filter to the signal for the purpose of selecting the frequencies for its low frequency driver; but it sends the remaining frequencies (low cut = high pass) out the high level speaker out terminals to the main speakers. So the effect is the same, separating low frequencies from the main speaker and sending them to the sub; it’s just that the means are different. I’m sure that filtering is best done at the low level, but would suffice for testing out the theory. 

@oldrooney Yeah, but that's not how it works. Opening up any subwoofer with high level inputs and primary speaker outputs and you'll see they are just passthroughs tapped to feed the subwoofer amp. Hi level inputs typically have a high impedance value tap across which the signal voltage is measured, then padded down to line level which feeds the subwoofer amp and it's LP crossover. The high impedance presents no meaningful load on the main amp, and the full range signal continues on to feed the primary speakers. 

Doing what you suggest would require some very large value and thus very expensive capacitors and coils just for a single fixed frequency and would likely impact overall sound quality of the primary speakers.

@panzrwagn Thank you for educating me. Then I don’t know why anyone recommends using high level I/O for integrating subs in a music system, but I swear I have read/heard the advice more than once, and it always caused me to scratch my head. I couldn’t figure out why they would recommend the practice. I thought I must have missed something. And, No, I wasn’t recommending building a crossover at high level voltages, even I’m not that crazy. I thought there might be one in the sub circuitry that could be used. 
 

As an aside, in other contexts [like power transmission] ‘Low Voltage’ is about 2.3 kilovolts (at the power plant); ‘High Voltage’ ⚡️ is over 4 kilovolts (on the transmission line to the substation near your house). The size of of the capacitors on crossovers for a network that size would be truly prodigious!