Two subwoofers in smallish HT room?

My home theater system is set up in a 16x11x8 ft room. I currently have one line-level HT subwoofer in the front-right corner. It's a very good subwoofer (Vandersteen V2W), but it needs to play pretty loud to produce good LFE. When it plays loud, it seems to localize.

I've been thinking about getting a 2nd sub and locating it near, but not in, the back left corner of the room in an attempt to smooth out bass response and give me the opportunity to turn down the volume on the front sub.

Does this make sense, or will it make in-room bass response worse? Is the room too small for two subs?
Yes it makes sense, no its not too small. Although you may want to try it in other locations along the front wall.
Two small subs should load up the room very nicely and at the same time have the benefit of speed and adjustability. Definitely try different locations for best results. Good luck!
Definitely 2 subs. You can place them on opposite ends of the room and get some modes to cancel out. Much easier to get 2 working well as opposed to 1, particularly in a small room. Make sure they are the same sub.
Two of the same subs for sure. I try to match wave launch of subs with that of the two front mains.Measure out from back edge of dust cap to front edge of each respective speaker and sub. The difference will be the amount of offset..Typical sub will be 1 to 3 inches in front of mains..Acoustical phase match of subs to mains is critical in this type of alignment though more easily heard and measured. Recommend direct coupling of speakers to floor for even smoother bass much lower spurious cabinet noise and better hand off to mains.Tom
I don't know about Rives suggestion about canceling room modes by having one SW at the back, but, years ago when experimenting with matrix quadraphonic sound I found that bass from the front speaker could be greatly reenforced by the rear speaker playing the same signal, but with phase inverted. This would happen if the speakers were one half a wavelength apart.

I tend to think of subwoofers as just another driver of the speaker system, so that each speaker should have its own colocated SW. I have three for my front channels, and would have two for the rears if I thought that the rear LF response was a problem.

Phase inverted rear sub is being put to use by a few people these days...along with myself.

I read about this at Vmps's web site around 8 years ago so gave it a listen and loved it. There was also a long thread at the Audiocircle forum regarding this about a month ago. If I recall, the guy that posted on it had 4 subs.

Electrical phase reversal may actually be putting the sub in acoustical phase with the mains.You can also have a phase or timing issue with another sub plugged into a separate AC line other than that used for the main sub..Tom
Sogood51...I noted the bass reenforcement from an out-of-phase rear speaker as a BAD byproduct of matrix multisound. For me it seemed boomy. This is what you would expect because the reenforcement is peaked at a wavelength that corresponds to a room mode. I can't imagine why anyone would do it.

Sounds like you use a high X-over setting with your subs...boom should not be a problem.

Thanks for all the input! Looks like I will have to invest in a second sub for my room. More than two subs in the room isn't feasible purely from a space standpoint, unfortunately.

I'm quite curious as to why the there is a strong recommendation for two identical subs though. I guess I was kind of hoping I could get away with a smaller, less expensive sub as the second sub - a matching sub wouldn't be outrageously expensive, but it isn't cheap either, and these subs are LARGE. What would be the major disadvantages of non-identical subs?

"I tend to think of subwoofers as just another driver of the speaker system, so that each speaker should have its own colocated SW. I have three for my front channels, and would have two for the rears if I thought that the rear LF response was a problem."

It is my opinion that a truer sentence has never been spoken. Now if I could just find room to put a center channel sub...
Sogood51...My observation of bass boom when there was an out of phase speaker in the rear did not involve subwoofers or crossovers. Just plain vanilla speaker systems.

I bet that Rives mention of killing room modes with a rear subwoofer involved driving the two subwoofers in phase with each other.
Wy on earth would one drive stereo subs channels out of phase? They would cancel at some frequencies and add at others, surely...
Gregm...If the two out-of-phase SW are physically half a wavelength apart they will add at that frequency. I guess some people use this to boost the SW SPL. My point is that if this distance between SW is the length of the room that frequency is already boosted by the room, and cutting it by a rear located inphase SW makes more sense to me..
The out of phase hook-up method is used more for fun...has nothing to do with boosting SPL or trying to effect or not effect room modes.

Two subs in front and two subs in rear (out of phase) give deep bass sound effects in movies a roll-through wave effect that can add to the fun...thats it in a nut

For music only types...this may not be fun. It may also not be fun for those that use there subs in the freq ranges where Boom takes place...very deep bass can not Boom.

Sogood51...Fun and games for sure.

I don't think this has anything to do with SW X/O frequency. The sound wave doesn't care whether it is launched from a separate box or not. Very deep bass will boom nicely if your room is large enough to sustain the frequency, and the speaker/subwoofer is capable of the frequency. And, by the way, if your ears are sensitive to the frequency.

When almost 30 years ago I first observed the bass-boosting effect of out-of-phase rear speakers I didn't like it. However, for exploding car movies I can understand why people like it.

I guess I'll just agree to disagree findings are very different than yours. I would hate to be standing in the room when those 20hz booms take place though...should take no more than 100,000 watts or so to blow the windows and bring down the roof!!!

Sogood51...It was a surprise to me, but I measured about 4.5 watts rms into each of my three SW system, a total of less than 15 watts, to shake the windows in my listening room, using a warble test signal around 30 Hz. The assumption that LF takes a lot of power does not stand up to objective measurement. My CarverPro ZR1600 amps drive a woofer system with one side and a MG1.6 with the other, and if I crank up the volume I can make the MG1.6 side clip (LED indicator) while the SW side is still loafing. Hard to believe, but that's the fact.

You might want to check Rives website and study up on room resonance. (Maybe buy his gadget also).

I also run three subs, your measurements go right along with my findings. My Onkyo M-504 sub amp has large power meters and confirm that very little power is needed to shake my 4,800 cubic ft. room on it's cement slab floor.

I do indeed have all the tools to measure my room in 1db increments and am very lucky that it measures very smooth over-all with no large peaks/dips down to 17hz...I did build the room as a " room with-in a room"... with my sons help.

I guess where we differ is in how we define "Boom". I was born in 1950 so remember sonic boom before it was outlawed over our homes. You can get a 100hz freq to boom within a room...20hz?...naaah, it would take a huge amount of power.

I guess the other place we differ is on how X-over effects room modes. I have done hundreds of tests using many configurations...over-all measurements as a complete system (speakers+sub) can change drasticly with only a change of x-over settings.

At this time my front subs are 25 ft apart and located at around the ceiling/floor null-point, (Supertowers are upside down) and in the corners in other words. What do you think Rives would think of that!...gotta love those measurements and go with what works after all.

Sogood51...I am now set up with a crossover where I can alter the SW X/O frequency while music is playing by twisting a knob, and my ears and my spectrum analyser tells me what happens.

With a white noise test signal (flat 20-20KHz) I am able to vary the X/O frequency from 50 to almost 200 Hz with no audible or visible spectral change to the sound. This tells me that I have got the SW well matched to the mains. With music, I sometimes vary the X/O frequency.
With "heavy" sound, like organ, choral, or some orchestral, the six big cone drivers in the subs work better than the Maggies, and I crank it up to about 150.

My room resonates at about 60 hz. Always has with any speakers. Rives uses 70 Hz as his example on the web site. If you are lucky enough to have a larger room it will be lower.

Our systems are somewhat similar...planers, three subs with six large drivers. I suspect the difference that I measure and you don't are related to X-over and mains settings.

Sounds like you run the Maggies full-range thus always the same at their location with the only change being at the subs location.

I use fixed points which changes output freq levels at both locations having greater effect on least in my findings.

My Duetta Sig's have an in-room rise of 2db at 30hz and then a roll-off to 25hz...the lowest setting on my X-over is 35hz and the blend between the mains (run full-range) with 35hz X-over to the sub is a little much in my room...a new X-over {maybe one of the digitals) with more choice of filter would probably benefit.

At this point, I x-over at 50hz with 6db slope.

Well, I guess I have gone far off topic...sorry

Sogood51...My SW systems are built into the wall behind the Maggies, and "play through" the screens. So they are not moved around. I pull the Maggies out 4-6 feet when in use.

I do not run the Maggies full range. I think that getting the really LF signal out of the woofer is the main reason to have a SW. My X/O is 24dB slope.

The Behringer DEQ2496 analyser that I bought recently has really helped me understand a lot of things about my system that I previously could only guess at. I recommend it, and a crossover that you can diddle from the listening position. After the RTA shows you what your problems are, turn it loose in AutoEq mode, and be amazed!
A question was raised about using subs of different sizes, but seems to have been dropped.

I was looking for a second Velodyne HGS-10, when an opportunity to buy a local HGS-15 arose. The HGS-15 was delivered by a system integrator who is very familiar with high-end equipment. He recommended I set my pre-amp to send everything below 80 Hz to the sub. Relieving the smaller KEF 102/2s of handling these frequencies really opened them up; I was surprised that the effect was the same with the 104/2s. The sub sits on an Auralex SubDude. I set all speakers, including the sub, to equal SPL, using the C scale of my Radio Shack sound level meter with slow integration. The pre-amp generates white noise for this purpose. The result is seamless open sound without boom or heaviness, and a grand sound stage with precise imaging.

Now the question: Is it worth hooking up the HGS-10 next to the left 104/2, or should I move it downstairs to use with a pair of 102/2s, and someday look for another HGS-15. The room is 14' X 19', with an opening leading to a dressing area and bathroom. The existing setup seems quite free of peaks, and the single HGS-15 is quite able to deliver the goods for movies. Stereo music is about as good as I've heard.

db you now own both..Feel free to experiment, by doing so can only increase your experience and may be beneficial later on..I do feel your results will have you placing the hgs 10 in the lower level..Tom
I design rooms with multiple subs often. I agree with Rives about using two subs and room modes. They know what they're doing. This is one of the hardest things to get right in any home theater. I really dislike locating a sub that's near my seating area even if the bass is great. I strongly believe that the room's low frequency room behavior needs to be looked at first (test the room, our ears can easily deceive us) and a few questions answered:

1) Were you happy with the bass except for the low output? If you were happy except for the output I'd get another bigger sub and try it out using the processors crossover. The then play around with placement if needed.
2) The Vandersteen needs it's own crossover and your main L/R amplifier as per it's instructions unless you carefully changed it's hook up. It makes it hard to use it as an LFE.
3) If you still want to use two Vandersteens (or any two subs), although very good subs, their hook-up make them problematic to use. I'd probably try two identical of a different brand. I'd need to carefully set them up by taking measurements which can be done with a simple Radio shack meter, a free audio generators through your computer as a source or a very good CD that has very closely spaced frequency bands and a piece of graph paper. It's time consuming but very enlightening about bass performance.
Hi Soundprogression - thanks for the note. This particular Vandersteen subwoofer (V2W) is made specifically for HT applications. It does not have an external crossover like the Vandersteen 2Wq subs most audiophiles are familiar with. It's a line-level input only sub, and uses the processor's crossover, so in that respect it is just like any other HT sub on the market. My processor has two identical LFE outs, so adding a second line-level sub is a piece of cake from that standpoint.

My local dealer suggested I try the route you put forward in your first paragraph. I have been pleased with the bass of the Vandersteen, but not with its output. He thinks I ought to try a single Velodyne DD15 in the room before considering adding a second Vandersteen HT sub (or dual subs from other brands). He says the combination of higher output capability and the EQ functions of the Velodyne would probably make it an easy fit. It would also not create additional space constraints.

The only problem is that adding a second Vandersteen would cost approx $1300, whereas the Velodyne lists for like $4000. :-( I'd be able to sell my existing Vandersteen very quickly, but the Velodyne is still a big chunk of change.
That's good news. I saw Richard Vandersteen at CES and I failed to look up the newer sub. I mostly looked at his speakers.

What you could do in a pinch is stack Vandersteen subs. You get significantly more output with another sub (not double but say 3-5dB. 3dB officially but it depends on how they react in the room). That's often enough to satisfy people. Kevin Voecks used to do that at shows to make sure he had enough output to satisfy a crowd.

I think you still need to look at the room behavior to find out if your dealing with a big frequency hole next to a big peak to make sure that your not fighting another battle. Adding another sub in the smae location won't help you then. If you have some time and want to learn the subject, especially about multiple subs, try Dr. Floyd Toole's white papers on the subject,

I use a small and free tone generator named NCHTONE,, from of the headphone out of my laptop to my system when I don't wnat to setup my complete testing system. With that and a Radio Shack meter you can make a graph of your system's behavior and pretty much KNOW and not believe you know what the problem is.
Not knowing the power and capabilities of your sub, I will say that placing the sub in the corner is giving you some sonic challenges. However, it is boosting the bass output of the sub in the room. So, there's tradeoffs. You would get better quality bass if you put the sub where it is getting "flatter" response. This often means out in the room more, maybe nearer the front speakers. However, you may then have to try to overdrive the sub to make up for the lack of bass output.
A solution would, yes, be to add more sub(s), to add efficiency. Then, you simply will have to spend time finding good locations for both subs, and get phase right, etc.
If you find a good spot for one sub, where you're getting reasonablly flat bass response, you can then put another sub elsewhere in the room possibly. I would ONLY DO THAT, if I needed to counter a bass mode problem where the first sub is at. If, say, there's a peak from the first sub at a frequency, I'd try to place the second sub were it was in "the null" at that frequency, and vice versa. This would help smooth out bass mode problems, and provide smoother bass. HOWEVER, if you find a place where you're getting very flat response from the first sub, then I'd try placing the other sub right next to or on top of the second! That makes things easier, and you'll note have to worry about comb filtering phase problems, because all effected frequencies are longer than the distance between drivers.
In your case, sounds like, for best overall sound, you need, yes, another well placed sub possibly.
Still, spend time getting best sound from the first sub, then add another and experiment