Single vs. Dual Subs

For two channel stereo the best to the worse is: A pair of woofer towers, a pair of front firing subs, a pair of down firing subs, a single front facing sub, one down firing sub.

I agree with @mijostyn - my experience is that adding a second sub resulted in significantly better sound compared to using a single sub.  The designer of my speakers (Michael Kelly with Aerial) has commented about the benefit of multiple subs in the Aerial literature, in addition to saying more than two subs is even better.  As full disclosure, at the time I added the second sub I also switched from larger, (almost) full-range, bass reflex floor standing speakers to moderate sized, acoustic suspension, stand-mounted speakers.  The stand-mounted speakers are solid to about 40Hz and the subs roll in at that frequency.  The result is a vastly superior ability to tune the bass to the room, lessening of nodes, absence of boominess, more power/drive in the low frequencies, and greater clarity up through the midrange.  Both sets of main speakers utilize the same midrange and high frequency drivers so the only difference is in how they handle the bass.  It is a bonus that the subs have their own remote control, making it easy to dial the bass volume up or down to sound best with specific musical content.

The technical theory behind multiple subs stacks up and there’s a lot of support for it.

People I respect a lot like Toole propose this, but they often are talking about large rooms.

Conceptually this practice makes perfect sense to me. However in simulation, I just can’t get it to do much. So I’m unable to recommend it as much as I used to. If only I had the time energy and money to buy another 15" sub and shlepp it around my room. :)

I defer to those with more hands on experience than I.

Of course, you all know, the middle course here is bass traps plus EQ. The traps reduce the nulls and peaks, and the EQ takes care of what’s left.  Unlike multiple subs in a room, this is an approach which I have enough experience personally to recommend.  Of course, I'd never deny anyone the right to spend money, and I acknowledge my limitations in experience.

The technical theory behind multiple subs stacks up and there’s a lot of support for it. The only caveat I can see is that to make the most of it you need to be pretty flexible about where those subs go, if they just go right behind the L/R speakers then it may be an imperceptible improvement. Also it’s worth remembering that your room is a 3d space so different height placements should be considered as well. Basically symmetry is most pleasing to the eye but probably the worst way to lay out your two subs. If you have the freedom to put them wherever you want then there’s a good chance you’ll hear the benefits.
You’ll also want to do a bit of research into how to systematically set them up either by ear or using a mic.

What do two subs add to the music presentation that a single dialed in sub is missing provided that single sub is dialed in perfectly for the listening position?

<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>

You answered your own question. If ONE sub was dialed in perfectly, the second sub will add ZERO.

The first one is dialed in PERFECT. STOP!! :-)

Second who said the first sub can’t have 6 active drivers and 12 passive radiators, BUT all in the same SINGLE 50 cubic foot box. :-)

One box fits all in some cases.. At one time I built 500 lb enclosures that were 22 cubic feet. You only needs two in a 50 x 100 x 12 room.
2 18" 2 15" and 4 passive 15" radiators.. 500 watts was plenty..
BTW they were Bins not subs, they were CUT on purpose at 28 hz and below.. 28-80 hz. The room still had 4 72" Narrow baffle bass columns 80-280hz. 6 8" MB drivers per enclosure

It’s about pressure in a room for BASS. 60-80hz and below not so much. WRONG kind of pressure.. High sub pressure can wear you out.. I don’t like it when I have to open my mouth to EQ the pressure fast enough to get clarity in the mids...

I've built single driver slot loaded bass bins.. ONE would fill a hole two car unfinished garage to 110+ db.. with 200 watts MAX. Boom Boom in the room room.. Modified Jensen Imperial Subs.. I've seen them look like an upright pianos, they were so big..

When you see SUBs working well into the BASS region, that’s when it get messy and bloated..

Regards

One sub can be fine with your head in a vice. It depends how important a smooth room is to you.

twoleftears

Grow another one?

It's all about nodes. With one sub in a room smaller than a wavelength no two locations are going to have the same pressure, i.e.bass response.

I have a small dedicated listening room with a single chair in it. I had a single REL sub and thought my setup sounded pretty darn good (Anthem STR, Merlin TSM’s), I decided to try adding a second subwoofer, the improvement was well worth the investment.

You may have a single, fixed listening position, but the sound that you are hearing is coming from the whole room.  And a single sub, no matter how well placed, will tackle all the acoustic anomalies that the room has.  

Actually not a lot....

Take a look at the Room EQ Wizard room simulator.

I've run a few simulations and honestly with an untreated room the benefits of filling in nulls aren't something I can replicate.

If anyone puts together an REQ simulation that shows 2 subs vastly better please point me to it online, I'd love to learn that this is better than I think it is.

Best,

Erik

@lalitk,
+2

I have two JL audio E112s both are high-passed at 60hz but no dsp. 
Over the last few months both broke (bad volume pots) and needed repaired so I had one sub at a time as I rotated then out for repair. 
During this time I optimized the placement with one sub (large dedicated room). After a lot of messing around I got one sub to sound fine but the volume level adjustment was picky and it never felt just right. I assumed this is because there were some lumps in the bass. Some songs seemed light and some seemed heavy. 
After a few months I got both subs fixed. Dropped them into their normal spot and boom everything locked into place and sounds much better. No more chasing sub volume adjustments. With two subs placement is much more flexible too. 

A single sub can do the job but you MUST find that "perfect spot" in your room. Incorrect placement will sound horrible.

OP, I appreciated your question because my room cannot accommodate a SWARM. When I move into a new room, I will be able to try it. Your question is a logical one for someone like me, and there's no reason you should be berated for limiting the question. After all, you said "at the moment" and "caveat" to try to forestall the kind of denigration you (alas, inevitably) received. 

I like the answer from @lalitk  for it's directness and simplicity.

I found a some good information, here: http://www.avrant.com/av-rant-737-interview-with-todd-welti-on-subwoofers/

“What do two subs add to the music presentation that a single dialed in sub is missing provided that single sub is dialed in perfectly for the listening position?”

When you add a second subwoofer, most of the peaks and dips get canceled out by the second sub. Two or more subwoofers also help in reducing low-frequency distortion and offer improved dynamics over a single subwoofer. This is a simple function of having more radiating area, plus more power on tap.

The realism and imaging you experience from two subs over one is unmistakable.

One Sub does not have the power to load most rooms down to 20 Hz at least up to 15 inches. An single 18" sub might get you there. Two 12's is the minimum. Two 15's even better.

Speaker frequency response is taken near field usually at one meter from the speaker. 4 meters back in a 16 X 30 foot room is a much different story. In order to get the right "feel" you need a rising response from 100 Hz down to 18 Hz. That takes big drivers and a lot of power. Two subs will also smooth out the nodal behavior in the room. Without proper low end you will never feel as if you are at a live performance.

You can obtain satisfactory results with one sub, but to achieve really great integration you also you need; lots of time, and a way to equalize and tailor the bass frequency response to correlate to your listening position. I have found great results by using an old Velodyne SMS 1 Sub equalizer. It allows you to hook up a monitor and has a long enough microphone cable to setup at your listening position to achieve exceptional results. By adjusting EQ parameters on the Velodyne EQ, you can see in real time what effect  your settings will have at the listening position displayed on the monitor. It is easy to use if you under stand crossover settings, slope, phase, -+20db settings for frequencies of 20-120hz, and a few other settings that I forget. It does allow up to two subs to be hooked up. 

Strictly interested in confining the discussion to your pre-determined conclusion. Wonderful. But you get the answer you weren't looking for anyway. Each additional sub, by being in a different location adds to the number and location of bass modes. The result is that for each additional sub the bass becomes smoother, and smoother bass is faster cleaner more articulate bass. It also improves extension, slam, and dynamic headroom. The man who wrote the paper discovering the distributed bass array approach you are so intent on not talking about even reduced it to a mathematical formula expressing the improvement of each addition sub.

The single greatest development in high end audio in a generation, but you don't want to talk about it. What a shame. Oh well too late now.

Your single sub by the way never can be "dialed in perfectly" but in order to understand why you will have to first permit talking about that to which your mind is currently closed to considering.

Wouldn't it be wonderful if we could just dictate to the world how things are? Maybe. But it would not be the world we live in now, would it?