Best Subwoofer Connection for Music

I have struggled to integrate subwoofers into my two channel systems in a way that enhances the system’s musicality. The best system so far is an old, cheap, dual coil subwoofer, but it has limited capability. I have two subs I want to add, one each, to each of my current systems. (Profile still under construction, which I’ll detail below.) I’ve heard PS Audio’s recommendation of the use of high level connections for music (versus low level connection for Home Theater LFE [Low Frequency Effects]), and I caught a comment on one audio YouTube post to be sure your subwoofer had both hi-level IN and Hi-Level OUT. This, to me, means that the subwoofer connection for music being recommended is Amp [Left & Right] —> Subwoofer Input [Left + Right] —> Subwoofer Output [Left & Right, again] —> Main Speakers [Left & Right]. Is this right? Just like the old dual coil subwoofer, but this time, the Subwoofer plate amp is adding Left + Right.

One Sub has both low level and high level inputs [an 90’s RCA 10” 100 Watt unit marketed by RadioShack. The other Sub, 15” 250 Watt from Dayton Audio, has three different options for audio I/O, to include two sets of low level I/O: (1) RCA and Speak-On connectors for low level input, and (2) RCA and XLRs for low level output. Meanwhile, it also has (3) high level spring clip speaker connectors for both input and output.

(1) I would like to integrate the smaller sub into my tube setup which consists of a Rogue Audio RP-9 + Rogue Audio ST-100 Dark 100 wpc feeding a full-range vintage acoustic suspension Warfedale W70E 3-Way which features a wonderful 15” driver, that I sometimes wish had a bit more ‘punch. (2) I would like to integrate the larger sub into my solid state system which features a McIntosh C100 preamp [I’m still learing how to parse McIntosh model numbers] which allows one to connect to three separate amps [Main (unswitched) + Speaker 1 & Speaker 2 (switched)] currently feeding dual McIntosh MC252 power amps bridged to mono, powering 90’s era full range B&W 801M Series 2 speakers with front ports and upgraded crossovers. The B&W speakers could benefit, I feel, from the ‘wrap around’ room-filling bass sound a 15” driver can provide.

The Dayton plate amp is the most recent addition, and if I need to upgrade the plate amp in the old RCA sub, I’m open to that, maybe by Christmas. [I had forgotten it had only ‘one-way’ connections.]

I’m mostly concerned with what connections would allow me most effectively integrate each sub into my two ‘music only’ systems. Thanks for any help you can offer.


@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!

@oldrooney "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."

It's cheap for manufacturers to add and it allows you to bolt on a subwoofer to any system, thus extending the potential market for that subwoofer. It also does nothing to extend the dynamic range of the system or protect a small satellite speaker's woofer from LF over-excursion.