How to add a Subwoofer to 2 channel stereo setup?

I hope this doesn't sound stupid, but I am looking to add a subwoofer to my system, but am somewhat unsure about how to do so. I have both a stereo preamp(Classe CP-50) and amplifier(actually a couple of stereo/mono amps- Monarchy Audio SM-70 Pros) which I use to drive my front speakers. However, as they are small bookshelf speakers, they have rather limited frequency response only going down to about 70 Hz or so. I am looking to add a subwoofer to extend the bass response, but don't know how to connect my sub. To what output?

I have tried outputting the signal through a line-level sub/LFE interconnect directly from my DVD player's Digital Coaxial out, and the 5.1 channel analog audio output to my subwoofer's(Sony SW-M 500 or something like that) line-level input while of course outputting the front speakers from the Left and Right channel outputs to my preamp, but this doesn't seem to work as there is no sound coming from my sub although the front speakers apparently sound fine. My preamp being only stereo does not have an "extra" line-level input/output for a subwoofer, so I don't know what to do.

I don't know if it means anything, but I believe I have an "active" powered subwoofer, as I must plug in a separate AC cord into the wall. It also has a volume control, frequency response, phase control and everything.

I am hoping to upgrade my speakers to a more full-range model to match my recent amplifier upgrades(in both sound quality and frequency range), but until then is there anything I can do to add my sub?

Also, does anybody have any good speaker recommendations to go with my above mentioned equipment?

I am seriously considering Totem Arros, but they only reach about 40 Hz according to Totem's specs. I have given thought to some others, but given both aesthetic, space and budget constraints(maybe $ 1K for a pair of speakers used), it has been a difficult search.

Anyway guys, thanks for your help, and take it easy.

The Audio Novice in training ;-)

Typically an active/powered subwoofer will have both line-level and speaker level inputs, speaker level outputs and sometimes even a line-out.

If the sub has a line-out, you can connect the subwoofer in a "loop" between the pre-amp and power amp by running a pair of interconnects from the pre-amp outputs to the sub line-level inputs, then another pair of interconnects from the sub line-outs to the power amps. In this configuration the low frequencies played by the sub are typically "stripped off" and the output to the power-amp/main speakers no longer contains this low frequency information.

If your sub does not have the line-outs, you can connect it using speaker level inputs. In this setup you may have the opportunity to put the sub in a speaker level "loop" by running speaker cables to the sub, then back out to the main speakers (low frequency information stripped off) or you can simply run speaker cables to the sub and main speakers from the same binding post on your amp.

I would highly recommend you check the manual for the sub to see what options they recommend. If you don't have the manual, you can usually find them on the Sony site for download. If none of their recommendations make sense, post back to the thread and I'll try to provide some more specific instructions....


I have a set of Tetra rebels, which are sublime low bass speakers. I remedy this with a Rel sub. The Rel has a line with 3 connections: positive, negative, and ground. I simply wind the positive and ground wire around the amp's right speaker terminal and wind the negative wire around the amp's left speaker terminal. That's it! People dislike subs because there often is a 'hole' in the lower mid section. The Rel has a variable rolloff which adjust quite high, and the Tetras have good lower mid-bass, so it works. Hope this was helpful.
doesn't look like you have a sub. if you don't, look at the rel's. i used a rel strata III with my totem model 1's. to hook up a rel, you actually hook them up straight from your amp along with your speaker cables to your speakers. in this setup, you run your speakers full range, and you tune the subwoofer to you speakers so there is no hole in your sound. rel is an excellent choice and 1 of the best crossover systems.
as for totem arros, lisen to them before you use a sub. i used a pair in my den without a sub and i was impressed. the room was 11x13 and i put the arros in the corners. wonderful sounding. if you are going to play the arros load or for home theater, than i would use a sub and crossover to the sub around 60 - 80 hz. if you like the arros, a little more $$$ and i would recommend the totem hawks. more full range and will play loud. no need for a subwoofer here.
Thanks for your help guys. I guess I know what all that other "stuff" is for on the back of my sub now. I thought I could just use the speaker-level outputs to hook up some speakers. I tried to set up some rear surrounds from the subwoofer's speaker out terminals and nothing happened. It didn't work very well, needless to say. Also, I do have the manual for my sub and guess I should probably read it before setting everything up next time.

After reading your explanations though, I think I can take from here. Well, hopefully.

Reubent, I think I will try both ways just to practice and see if I can hear a difference. And, I'll probably have some fun with it. Hmmm... running speaker wires to both the speakers and the sub from the same binding post is something I would've never thought of, very interesting and ingenious.

Chashmal, I guess your pretty ingenious too. ;-) As for that sub "hole"... yes, it is a problem posing a noticable and rather pesky disturbance in some of my music. It's also bloated and boomy at times with SUBstantial overhang on many an occasion. At least on my sub, and forgive the pun, LOL!

Rbstehno, your half right. I don't have a good sub for music, but it does work fairly well for movies with the deep tone, boom and rumble. And this setup is half, half now for movies and music. I was running everything on a receiver before, then I upgraded my amp and preamp to separates and just need to upgrade the speakers to full-range to finsh a decent mid-fi/hi-fi audio system. And as for the Totem's, I hear you on the Arros, I was thinking the same thing about maybe not needing the sub. I have a fairly small room and will probably position the Arros close to the walls and corners, thus reinforcing the bass. I have heard the Hawks, and they're a very nice and sensual little speaker, but unfortunately I just missed out on a sale of them here for $1,000 or so, listed mabye only a couple of weeks ago or less, if I remember right. I was getting ready to write my email to the seller, when it showed up sold on the classifieds list... after I had looked at the ad about three times, darn.

Anyway guys, thanks again for all your help.

As always,
the Audio Obsessed Novice - in training. ;-)
Guys, you may be forgetting one thing: To add a mono sub woofer to a 2 channel system be that as it may that with modern recordings most all low frequency content is dead center which means that there are identical signals on both left and right channels, when these 2 channel signals are summed together they will phase cancel. Bag End has an "integrator" which claims to solve this problem. The only other way is to derive the sub from only 1 channel (left or right) but this is less than perfect. Otherwise it is 2 subs, one for left the other for right.
Wrongo bongo...I use a single channel summing REL and there is no phase cancellation at all. None. Zero. Also, I listen to modern recordings all the time (especially acoustic jazz trios lately) and the bass is usually NOT dead center...often it's panned by the engineer more to the left or right of center although it varies (and the lowest notes are not directional but may seem so from aural cues from overtones). Brad Mehldau's stuff is a good example...bass middle to one side, drums middle to the other, piano across the middle.
I would first check your DVD manual to see if there is a configuration setting that downmixes audio tracks to 2.1, with .1 being for the subwoofer output.

If a music dvd or cd has no dedicated .1 track (as most normal cds do NOT), then there is no signal coming out of the subwoofer connection.

There may be a setting on your DVD player that does mix 2 channel audio discs to synthesize the .1 output.

If it doesn't then you would need to ensure that the DVD player is sending downmixed full range audio to the left & right outputs which are then connected to your Class Pre-amp.

From there, if it were me, I'd simply buy some rca splitters so that you can run a set of rca cables to both the sub L/R line level inputs and L/R inputs to your power amp.

Your speakers would get full range audio - so no 'bass management' - but it seems you run them this way now anyway.

I don't think there is any phase cancellation - if there were then your main speakers would see the same effect.

This is how I have my sub set up - get plenty of bass.
I've just started using a sub with full range speakers. Although my ML Summits go down to 24 Hz, I have a deep (-10dB) null at ~60Hz, and couldn't really change their position in my family/listening room to address it. I just got the new ML BalancedForce 210 sub, and, at first blush, looks like it will really smooth out that null, while further "energizing" the low bass region.

However, I believe the need for adding sub(s) to a full range speaker is very room/system dependent. I have two audiophile friends running ML Summits in smaller rooms, and both sound exquisite as-is, so sometimes it could be overkill.
Actually, modern recording have "stereo" bass, and is not summed to the middle. Older recordings are ther ones that have the bass summed, and this is done on purpose because with record Lp's, if you have out of phase bass, it could actually cause the needle to vibrate so much and pop out of the groove.

REL subwoofer is the easiest to integrate into any system.
Otherwise, check the Sony site for correctly setting up your sub.

Keep me posted & Happy Listening !
Wolf -
Do you need to place your single channel summing REL subwoofer directly in-between your speakers, or can you place it to the side of one of the speakers and still have normal imaging?  I'm thinking of adding one subwoofer and it would need to be placed to the left of my left speaker, close to, but not in, the left corner of the room.  My understanding has always been that low frequencies are not directional, so there should be no audible clue as to their point source.  Would this be true in my proposed set up???

One sub (the larger one) is placed behind the left main, and the other against a side wall only because I stick it in a window above it sometimes for outdoor deck enjoyment. Same signal to both (summing the signal, not stereo). When I was using the one (left side) sub you really could not tell where it was particularly, and since bass hugs flat surfaces it was all over the room although it was specifically tweaked for my middle "sweet spot." Since I have the subs set at where my mains naturally start losing their low end ability (mid 50s maybe) they blend well and imaging is unaffected. REL recommends trying the sub in various spots (manuals are easy to find online)…corners, etc., until it feels right, and I agree…you can put a sub over in the corner and it can sound great! 
I have a 2.2 monitor sub set up and use a Dspeaker Antimode Dual Core 2.0 with fantastic results. My subs are next to the monitor stands equidistant apart. It took about an hour to tweak the bass and now the mids and highs sound better. YMMV
My preamp (Odyssey Candela) has an extra set of outputs, so I run two subs from each.  They are crossovered at around ~27hz.  I'm using dual Rythmik F12G with Magnepan 1.7i's.  The blending is seamless as the speakers run full-range, and the subs provide sub-bass.