STF-1 / NAD C320BEE Setup

[pickles]

I have the STF-1 sub and I am looking to use it with my Nad C320BEE integrated amp. I have read through some of the earlier posts regarding setup options, but I am still not clear which is the best way to hookup the sub. Mind you I am quite a newbie, having just got my STF-1 sub and Nad amp within the last few weeks. I have only had an A/V receiver in the past, and the setup with the sub was easy; just use a sub cable to connect to the sub-out from the receiver.

From what I gather, there is more than one way to setup my Nad amp and sub. You can use the high level inputs or you can use the dedicated sub-in. Basically what I want is to have the amp control the bass volume, and have the bass integrate well with the sound from the speakers.

I have diagramed two ways that I think might work. In diagram 1, there is a Y-adapter to split the signal from the left Pre-Out. In diagram 2, I am running speaker cables from the amp to the sub high level inputs, and running cables out to the speakers from the sub speaker outputs.

Diagram 1

http://i34.photobucket.com/albums/d119/lkv11/diag1.jpg

Diagram 2
http://i34.photobucket.com/albums/d119/lkv11/diag2.jpg

I have been using the sub with my receiver so far, and have been very satisfied with the sound. The STF-1 rocks!

[Lwang]

You can't use option 1 as drawn because the pre-out that is joined together at the sub's line in will short each other out and cause significant level drop. It might look like you have 2 pre-out communicating with the sub's line in, but in reality, each pre-out will see the other pre-out, and each pre-out having the same output impedence would mean each is trying to feed into something that has an input impedence that is the same as its output impedence. This would require siginificant current capability which is not available in a preamp. It's like connecting 2 amp's output to each other, or an amp with an output impedence of 0.1 ohm trying to drive a 0.1 ohm speaker

In your drawing, it looks like you are feeding 2 left channel line outs to the sub, I presume you mean 1 left and 1 right line out. Either way, it can't be done. You would have to either feed only the left or right, or have an intermediary buffer stage that will accept 2 line level, and output 1 summed pre-out to the sub.

[pickles]

I guess I have to try my designs out to see what works best. At the moment I still need to buy speaker wires, interconnects, and the y-adapter. I will wait for the weekend since I don't have time at the moment to shop and also do the setup.

Basically with diagram 1, I will be using the y-adapter (http://www.thesourcecc.com/estore/Product.aspx?language=en-CA&catalog=Online&category=Audio+Plugs+%26+Jacks+Adapters&product=2740501) to plug into the left preout, and have one interconnect attached to the adapter go to the left main-in, while the other interconnect go to the sub. Will that work?

Here's the back of my Nad amp just so you have an idea what the diagram is referring to. The pre-outs are connected to the main-ins by a jumper. I have removed a jumper from the left pre-out.

http://i34.photobucket.com/albums/d119/lkv11/PB290684.jpg

So far I am loving my Nad amp. It has a very sweet musical quality, and tons of power to boot.

[Lwang]

That would work, but you are getting the bass from only 1 channel. You would need a stereo-mono contraption in order for both channel's bass to be reproduced. You are probably better off with diagram 2. The only issue with that method is if the bass signal clips the NAD amp, that signal will be fed to the sub and it will try to reproduce any of the harmonics within its signal range.

The STF1's line in was basically made for LFE outputs, that is why it never made accomondations for L and R input.

[pickles]

You are probably better off with diagram 2. The only issue with that method is if the bass signal clips the NAD amp, that signal will be fed to the sub and it will try to reproduce any of the harmonics within its signal range.


Not sure I fully understand. Does the sound become too bass heavy then? Also will the clipping likely occur? Looks like I will go with option 2, because I want the stereo two channel effect of the bass.

[Lwang]

If you use speaker level input on your sub, that means you will be feeding your it via the amp's speaker output. Even though you won't be pushing any current from the amp to the subwoofer, you will still be pushing all the voltage swing from the bass signal in your music source (or how else will the sub's amp recognize the signal?). So if you have music with heavy low freq passage compared with other freq range, the signal output required might be beyond what's available on your amp's voltage rails. Granted, if you didn't have the sub in the first place, that distorted signal would be pushed to your speakers and it would sound much worse, but with the addition of a subwoofer, you don't want that to be the limiting factor.

This is in a sense what REL means when they say the sub's bass would take on the characteristics of the amplifier that is powering your main speakers. If your amp sputters, the sub will sputter.

[pickles]

Thanks for the explanation. Just another question... will the sound be any different, better or worse, when the speakers are driven from the sub (like in diag 2) as opposed to being driven directly from the amp? I just hope that there is no sound degradation having it hooked up this way.

[Lwang]

Companies like Rel wants people to hook up their system like diagram 2 because your bass would take on the characteristics of your amp, so if you have a tube amp that when hooked to a dynamic speaker sounds dry, that dry sound characteristics coming out of the amp will be fed into the subwoofer amp, causing the sub to sound dry-ish. Now hook up a planar and the bass blooms, the amp's output characteristics that in part made the planar bloom will be fed into your sub amp, causing that type of bass characteristics to be produced.

Anyway, YMMV. This is called bass augmentation, which basically mean your speakers are driven full range and the sub augments what the speaker can't produce.

Another method is called active bi-amplification, which utilizes dedicated high and low pass crossover at the line level, therefore the signal going to your 2ch amp would only contain the higher freq signal that is intended for your speaker to reproduce, and the sub produces anything below that. This way, the burdensome power sucking bass signal never even goes into your main amp, and your speakers are not huffing and puffing trying to try to recreate signals that it can't even produce anyway. Hsu's higher end amps has this feature, but they also have a crossover box that cuts the low freq signal in which you hook in your line-out/main-in section. You would still need Y adaptors and some 2 ch signal summer so as to feed your 1 channel line level input.