Connecting dual subwoofers to a stereo preamp

There is bass output in both left and right channels, so you want to use both left and right channels to the sub.

Also, you do not want to use the tape out as it is unattenuated. You want the volume sent to your subwoofer to vary with the volume set on your preamp. If there are not two sets of output on your preamp. You can get a splitter that connects directly to the back of the preamp.

LFE is for Home theater. A different animal.

Thank you for your response.

Yep. I know what LFE is.

I was mistaken. My preamp has main1 and main2 out. I use Main2 out for my subwoofer. There are not two sets out outputs that I can use. It’s exactly as I show in my drawing except its not tape, it’s main2.

Using both left and right from the preamp to EACH sub defeats the idea of stereo subs. Other than the "tape" error in my drawing, should my schematic work okay? I have the little splitters you’re talking about. I’ve used them for other setups. But again, that would null the stereo idea to the subs.

Do you follow me?

Send L output to left input of left sub.

Send R output to right input of right sub

Only need a y splitter if your preamp has only one sub output.

The documentation for the SVS SB3000 implies that if you connect a cable to only the LFE (right) RCA jack then the sub assumes you are using an LFE output from a processor. I could be wrong about that. Their documentation is not great.

Although in one spot it says this: "- Push repeatedly [the "+" button] or long press to increase volume, raise the low pass frequency cut-off or to set to LFE, or to increase Phase degree" so I’m not 100% sure.

@udo I own two SVS SB-4000s. You do not need the Y-splitter. Just have the left out going into one input on the left sub and the right out going to another input in the right sub. The only time you need a splitter going direct into sub is if you only have a single sub and your preamp only has a mono out to connect to it. 

Thanks @blisshifi. That helps. I had a feeling that would work.

I'm still hemming and hawing about whether to hook up 2 in stereo or not and even whether or not to get 2. I've had one nice sub for a long time and I've never been unhappy with it (my M&K V125).

I'm considering just getting one SB16-ULTRA for now and running it just the way I've been for years. When I have a more flexible budget, if I feel the need, I'll get another SB16-ULTRA.

My 20 year old Nautilus 805's are still amazing along with the rest of my gear (Rotel amp and Adcom preamp) even without a sub but they really do need it and when you're used to it it's a bit of a drag when you have to go without!

@udo If you have the room and budget, dual subs are worth it. Having a single sub will not deliver the clarity and imaging across the whole width of the sound stage. For bass, a single sub may just ever so slightly manipulate where a bass player may be standing on the stage. Not drastically, but sometimes every last measure counts. But my biggest affinity for subs is to only use them for their lowest frequencies, almost inaudible, such that their waves clean up the rest of the frequency spectrum, and having two or more enables this to be done evenly across the room. When I sometimes had one sub in the past, I felt that there was more openness on the side where my sub was placed. My room is 19’x23’ with a sloped ceiling that goes up to 18’, and two SB-4000 work very well. Prior I tried two SB-3000 and they didn't go low enough to make a huge difference. 

@udo 

Have you done any research into implementing a "distributed bass array"? Sometimes it is referred to as a "swarm".

It uses 4 subs, not 2. Pre-out left and right are sent to a crossover unit like the MiniDsp 2x4, where a crossover frequency is applied prior to the distribution to each sub.

With 4 subs most of the peaks and nulls created by your room are mitigated.

The improvement is amazing.

Go dual, you will never regret it as long as you place them correctly. In my experience, do not place them by the mains just because you want stereo. Place them on different walls. One behind the right speaker and one a third of the way down the left wall is my setup. They still play perfect stereo and give you clean bass at any position in the room. Placing them by the speakers results in heavy boomy bass along the back wall, at least in my house of stereo and it is heavily acoustically treated. That was one of the best tip I got on this site. Wish I remember who it was to thank them.

What you’re doing isn’t clear to me, but it looks like you’re combining the left and right channels together at the amplifier output to create a mono signal for your sub. Is that correct? If so, the problem I see is that most amplifier and preamplifier outputs are wired in parallel. So if you tie the L and R outputs together at an amp output, you’re likely to have mono signals at the amp's other outputs, too.

Thanks for all the input everyone. I think I'm going to go with 1 sub for now. I'd like to use 2 but I want to spend some decent money on them and right now, while renovating my new house (well, old house, new to me) my budget is too tight and I'd rather spend more than a grand per sub. I think I'll one the SVS SB16-ULTRA for now like I mentioned above and then in several months when things have settled down I can get another. 

@cleeds - no, that's not correct. My schematic doesn't show that. I'm not combining the L/R at the preamp. I'm sending L to one sub and R to the other. But I'm not going to do that now. I'll revisit all this later. With just one sub for now, the connections are a no brainer. Just what I've been doing for the last 25 years with my M&K.

@hifibliss - my room isn't as big as yours. It's only 14' x 17'. It's an okay size but I think 4 subs would be too much and like I said above, it's not in my budget. Ideally after I have 2 nice subs I'll upgrade my mains to a full range pair. I used to have a pair of Nautilus 803's but had to sell them 20 years ago for financial reasons. I really miss them. I have to do some research when I get new mains but I've wanted pair of B&W 802D's lately or maybe 803D's. We'll see when I get to that point.

Thanks again everyone!