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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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rlb61
789 posts
 
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.



schubert
7,386 posts
 
+1 for rlb61 , same here.
b_limo's avatar
b_limo
2,277 posts
 
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

bdp24's avatar
bdp24
9,836 posts
 

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.

rlb61
789 posts
 
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.
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