Connecting a sub which way to go

I have tried it both ways. As I see it, running the sub from the preamp out while running the mains full range is the way to go. Why? Just think about this ... the internal crossover in a sub probably uses fairly mundane capacitors. The crossovers in your speakers are likely far superior, such as in my case, where my JA Pulsars use the Modafferi crossover. By using the sub’s crossover, you are taking the signal from superior capacitors in your expensive preamp and forcing it through a mid-grade capacitor in the crossover before it is sent to your amp. That creates a sonic bottleneck, and actually degrades the sound. While there is some truth to the idea that running high pass through the sub alleviates some of the load on the amp and speakers, I think that placing the sub in the signal path really diminishes the sound overall and prevents you from hearing what your components can really do in synchronicity.

One other thing of which to be cognizant ... many subs have an input impedance of about 10K Ohms, yet many pre-amps have capacitors that cannot drive such a low impedance. So, depending on circumstances, you may want to replace the capacitors assigned to a second pair of preamp outputs with capacitors capable of driving a sub’s low impedance. Currently, Don Sachs is building one of his Model 2 preamps for me and is doing exactly that in my build.