adding a sub

i recently purchased paradigm studio 40 v4's. I feel i'll need a sub, possibly 2 small ones. My question is this: my amp has only binding post for right and left channels. My pre only has 1 pre-out. Where do I hook up a sub? If I hook it to 1 channel on either side how does that affect the speakers?amp? I may get 2 small subs just because all of my stuuf has to be symmetrical or I freak out a bit.
You should try Rel subs. They have 2 positive connections (right and left) and 1 negative (goes to either black). I think they are absolutely stunning pieces of equipment, highly adjustable and versatile. I also think 2 small ones is better than 1 big one.
Get a sub that will take the L/R RCA outputs and provide L/R high-passed outputs for the input to your amp. There are many.

What you will find is there are many ways to connect a sub (or a pair of subs). My perfered way is different than Kal's.

I prefer to use subs with speaker level connections - you connect the subs to the same binding posts on the back of your amps (or even the binding posts on the back of the speakers). Just double up the connections.

I prefer subs with variable crossovers that give you crossover frequency options of 30 Hz at a minimum. You'll probably get advice to cross your subs over around 80 Hz. IMHO, that's the best way to hate the sound of subs. For a starting point, multiply that -3 dB down point on your speakers by 0.70 to establish your base crossover frequency of your subs. As always, YMMV.

Also, I prefer subs that give you 0-degrees, 90-degrees and 180-degrees of phase control. IMHO, 2 subs are better than one.
Parts-Express:Dayton Reference drivers and the 240W plate amp.Allows high and low level input and adjustable crossover,level and phase.The 1K ohm/high level input will not effect the impedance that your amp will see.
My sub sounds much better using the speaker-level connections. the input impedance of the amp for th sub has such high impedance that it will not affect you ramp or full-range speakers at all.
Go with Kal's recommendation. It''s more general and practical than the others. Also, 80 Hz is likely to your best bet for crossover. There's rationale behind that choice, not mysticism. If you require symmetry for psychological reasons, go with two, but a single larger sub may be more satisfactory.

There's rationale behind that choice, not mysticism.

You are right, there is's called THX specifications.

If I may quote:

It is the product of much development, and, when used in concert with THX speakers (or others which exhibit the correct roll-off), represents the best overall compromise of minimizing localization, extending dynamic range, and as it turns out, minimizing LFE truncation. When Dolby Digital was coming to the consumer marketplace, THX looked at an inordinate number of modern 5.1 soundtracks and guess what they found in the LFE channel: not much at all in the region of 80 Hz - 120 Hz, making their original choice of 80Hz rather fortuitous. Dolby Digital's LFE channel has a digital brick wall at 120 Hz, not a roll-off, so content creators almost always roll-off their stuff, usually somewhere around 80 Hz. Therefore, chucking the top band of the LFE is no big deal but the argument here is that a standard SSP crossover set much lower than 80Hz or so may actually be costing you bass content.

However, if you are getting great 2-channel sound with a sub crossed over at 80 Hz, the more power to you.
I also agree with Kal's suggestion. I would consider the SVS SB12-Plus It has the necessary line level high-pass outputs. You run the left & right preamp outputs to the sub; run the high-passed left & right sub outputs to your amp. You'll also need an SPL meter and test tones to properly level match the sub to the main speakers.
Okay men, let me get this straight. The sub I bought, which hasn't arrived yet, has a "low level" input/output that are rca. Then there is a set of jacks, which look like speaker jacks, that say high level. However there are 4 of those jacks for each side. I will take rca cables from my pre to the low level on the sub. I will then use a y splitter and run my cables from the high level outlet to my amp. Does this sound correct? If not I will contact SVS an see whats going on. I'm sure there will be directions with the sub.
If your sub provides both RCA inputs and outputs, then you'll run a pair of ICs from your preamp's output to the sub's RCA inputs and then a pair of ICs from the sub's RCA outputs to your amp's RCA inputs. Sometimes the sub's RCA outputs are filtered and sometimes not. There should be no reason to use speaker (high) level connections.

Had you provided the model of the sub, we could possibly provide more help. But, yes, there should be hookup directions with the sub.
Thanks for all the info. I have found the information on this site extremely valuable.It is a fantasic resource.

Bob, I bought a SVS PBS12 NSD.

I apologize for my tendency to be redundant on some subjects, like this subwoofer, but I just want to get the right thing and hook it up correctly.
Great choice. I was able to find the manual for that sub. Here's a section:
Line In/Out. Use either of the sub’s “Line In” jacks to connect the subwoofer to the output jack of your receiver/processor. Feeding just one input is enough. If you are using a conventional amp and/or a stereo setup you can use the “Line Out” jacks to send sound (filtered of deep bass information) back to your system amp. A simple RCA to RCA cable is all you need for either type configuration.

The important point is the "filtered of deep bass information"; in other words the line outputs are high-passed. That's exactly what you need for your main speakers. They don't provide a diagram showing a 2-channel hookup, but it's as you'd expect -- preamp outputs (both left and right) to the sub's RCA inputs; sub's RCA outputs to the amp's inputs.

If you don't have cables yet, I highly recommend Blue Jeans Cable There's probably no better cable than their LC-1, but I use the Belden 1505F because it's almost as good but smaller diameter and more flexible.
Thanks for your info Bob. I was wondering about that. It says only one cable, but I figured I'd need 2. I am expecting it Wed. I will get everything going and hopefully figure out the meter, I bought one of those also. Thanks again for your information.
It's good you picked up an SPL meter. You can find calibration info with test tones here:

Good luck and let us know how it turns out.