Connecting a sub which way to go


I have a NAD165 Pre-amp and a Nad 365 amp I am connecting a SVS SB13 Ultra into the system. The 165 has a sub output,but is it better to use that or the signal between the pre amp and the amp stripping off the bottom end signals say 15HZ to 80 sending rest on to the amp?  The SVS has both a high pass and a low pass filter. The rest of my system is Paradigm S3 V2's and Triad Silver Monitor's
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In my experience, high passed small speakers/monitors with subwoofer setup is preferable, the speakers can play louder and cleaner, the power amps also don't have to work as hard as full range.
since you have everything on hand, why not try both way and let your ears make the decision, BTW, what is Paradigm S3 V2?
Paul McGowan (PS Audio) syas to use speaker cable from your amp to the sub. I scratched my head why speaker cables (main amp binding posts) to a powered sub, but it was a nice improvement 

However, I now have an Audio Alchemy DPA-1 (class D) AA says NOT to connect via binding posts, so.... check with the mfg
I prefer using the high pass option. I have tried both and I find that using the high pass give my mains a cleaner sound. Like the above post states,try both and let your ears you know which sounds better!
I am using both methods.
Main system has Vandy Treo's and 2wq subs using the Vandy Crossover.
Office has the VLR's and a pair of Hsu subs running off the speaker connections.
I like my Main system best, but the Office is no slouch. I might put in the HSU crossover, but I don't seem to need it right now.
Albeit, the Office has a bit more bass, but I kind of like the difference between the two systems.
As others posted, using the crossover relieves your amp from the heavy lifting of the bass frequencies, so if you are not using a very powerful amp, it might be the better of the two ways to go.
If you have a lot of headroom power-wise, it might not matter.
Bob
Ha! I came here to give you Paul McGowen’s answer: use a high level input for the sub. I appreciate the logic of it: whatever colorations or sonic signature your amp applies to the signal will also be applied to the sub and the speakers and sub will blend better. 
High level is the way to go, sub then takes on characteristics of the amp as well. As has already been stated. But I'm sure there are good sounding systems with both methods.
WRONG!

This underscores the MISINFORMATION that is often perpetuated on these threads. Paul McGowan DID NOT SAY TO RUN HIGH LEVEL FROM SPEAKER OUTS!

To directly quote Paul: "You want to let your main speakers go down as far as they can naturally. Don’t roll them off. The subwoofer should fill in whatever is missing in the main speaker."

You want to use line outs (optimally left and right line outs to two subs) of your preamp to your subs so that you can integrate them while utilizing the FULL RANGE of your mains.

The beauty of SVS subs is that they have a continuously adjustable crossover that you can fine tune so that they pick up where your mains leave off, maximizing integration. This way you are not constrained by the standard 80 Hz crossover typically used on a speaker level input on the sub, e.g., Velodyne. 

Please watch: https://www.psaudio.com/askpaul/why-dont-your-products-feature-a-subwoofer-output/
Wow chill out. What makes Paul McGowan such a god I wonder.
Some sub mfrs like REL recommend high level, I would trust them as one of the best sbwfr makers.
OP, whatever sounds right to you is best.

This is about the wilfull spreading of inaccurate information, not about Paul McGowan as an expert. REL doesn’t control the subwoofer market. I’ve tried their products and was unimpressed.
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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.



+1 for rlb61 , same here.
I agree with the last 3 posts.

Full range and cross the sub over low.  55 hz or lower.  Play around with sub placement.

Awesome speakers and sub btw.  I had a pair of S2 V3’s... don’t ever get rid of those; seriously

No audiophile runs the signal going to the main speakers and their power amp through the high-pass filter/crossover included in a sub. To remove the bass from the speakers and power amp (one of the main reasons for bi-amping, or adding a sub), you instead do one of the following two:

1- Install a high quality active crossover (Pass, First Watt, Bryston, Marchand) between the pre-amp and power amp. The design of these crossovers and the parts used in their implementation (the Pass and First watt are 100% discrete circuits---no ICes, OpAmps, or integrated circuits) are higher than that found in many pre-amps. For the low-pass signal, use the controls on the sub.

2- Install a capacitor and resistor of correct values (so to create a passive high-pass filter at the desired x/o frequency) on the input jacks of the power amp. Perfectionists have been doing this since the 1950’s. This method provides the purest/highest sound quality signal path, but creates only 6dB/octave filtering. Still, better than removing no bass from the speakers and their amp.

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.