I also have a small room and found that when I went to two subs sound was much improved.
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Two subs are an improvement over one in just about any room, even at low levels. The advantage of multiple bass sources is that it breaks up standing waves that may be present in the bass, smooths the bass by "filling in" dips that may occur due to room interactions, and adds a spaciousness to the whole soundstage presentation. It also adds at least 3 dB more gain in the bass frequencies with 2 subs working together, which can allow you to reduce bass levels and enjoy lower distortion. Two subs also gives you a lot more flexibility in room placement, as you learn to "work" the room for best sound (corner placement vs wall placement, even stacked subs.) With recordings that are not typically multi-tracked studio productions ("multiple-mono"), you will discover stereo bass effects, typically in orchestral recordings with minimal mics used. This preserves phase information, and allows it to be reproduced in your listening room as recorded, with real space and dimension,(an argument against stacked subs, which will not do the space thing.) You don't need monster subs to get all of these benefits; this is a case where 2 smaller and more agile subwoofers can potentially outperform a single large one. Good luck and have fun with it!
No, there is no "need" for two subs in a moderately sized room. You can get very good results with just one if properly done. However, once you hear the difference between two properly set-up subs and one doing the best that it can, you will "want" two subs. There is a difference between what we "want" and what we "need" BIGTIME in this hobby : ) Sean
Well, as always, we have achieved complete unanimity of thought on the topic under discussion... (grin). Sean's comments are valid: there is no "need" to have two subs, unless your personal criteria include getting the best performance from your system (sorry, Sean, no attack meant). Gasman has identified some of the reasons favoring two subs in a system, to which I would add that using only one sub requires that you sum the left and right channel inputs, thereby losing phase and channel-related information that can be important in creating a cohesive sonic picture. (This may not be a major concern if you only want to reproduce low frequency sound effects from DVD's, but will definitely be an important consideration if you want good music fidelity.)
When I began playing seriously with subwoofers in my system about two years ago, I started with a single sub of modest quality. When I added the second sub to make a stereo pair, I was surprised how much the overall sound improved for music as well as HT. Last fall, I sold the two subs I had and replaced them with Vandersteen 2Wq subs, and the overall musicality of the system went up dramatically.
Richard Vandersteen has made the comment in several interviews that subwoofers do more than just juice up the deep bass. If the sub and crossover are properly designed to integrate well with the main speakers, the main speakers will have less -- often significantly less -- harmonic and intermodulation distortion because they are not trying to reproduce the low frequency range. The result is clearer, better focused upper bass and lower midrange reproduction, which yields more transparent, detailed sound. My own experience with the two Vandy subs certainly proved this to be true.
Hence, if you are looking for the best musical performance from your system, I urge you to think about eventually having two subs. If money is tight, start with one sub now, and add another later. However, don't get cheap subs that are intended mainly for HT LFE reproduction. There are a number of subs that do a fine job with music that aren't terribly expensive -- see the Audiogon archives for the numerous threads of recommended subwoofers for ideas.
First off, it is not true that "subs are nondirectional." It is true that low bass is "nondirectional," which is to say that we cannot tell where it's coming from. But it's quite likely that a sub will be producing energy up into the range where we can begin to pick up locational information. (And don't forget that wherever you set your crossover, your sub will be producing sound above that point.)
This doesn't mean that a single sub can't work. It can. Remember, if you didn't have the sub, you wouldn't hear the low bass at all. Which is worse: Not being able to place the bass? Or missing it entirely?
I pretty much agree with Sdcampbell.
But if I were on a budget (for which I am) I would take one good musical sub over two mediocre subs everytime.
The quality of the sub means everything. And this is one region where it's better to do without than to do with poorly. But it can be done.
And don't settle for a sub that stops reproducing at 30Hz or even 25Hz. Any decent full range speaker can pretty much handle that region. Ensure that the sub will reproduce faithfully to below 20Hz. That's what a sub is really for.
For sake of clarity and so that some of you may better understand where i'm coming from, i have two subs in my HT system, two subs in my main 2 ch system and two subs in my bedroom system. The two systems that do not have subs consist of large modified horns / tubes in one and full range drivers / mono-blocks in the other. I could probably use some subs with the horns ( -3 @ appr 30 Hz ) but finding something that can keep up with 104 db sensitivity is not that easy. The "full range" drivers actually have quite measurable output down to 5 Hz ( believe it or not ). I found this out when playing the Cardas sweep tones on the Ayre Acoustics disc.
As such, i'm surely a believer in running dual subs, but would agree that one "good" sub is better than two budget models. Obviously, placement becomes more critical with one sub but you can get good results if you put forth the effort. Sean
I don't agree stereo subs are harder to blend. They are each playing separate stereo channels. No different than two speakers (just the lows). If you have problems with stereo subs, you will have the same problem with the bass response of your two main speakers. It is not the subs.
Now using double subs (two subs playing the same signal) might pose a blend problem.
Wave launch, and phase intergration of stereo subs is a major part of the blending process. This is mostly a time consuming problem. The process can take much longer when your main speakers have 2 woofers in each cabinet. These woofers, one loading near the floor and the other loading near the ceiling do effect the arrival time of the first bass wave. Placement becomes even more critical when your room is of irregular shape. Bass loading in odd shaped rooms can be an ordeal. With much time and care the payoff of two 15in. servo subs loading with their four 10in. brothers makes for a grand and accurate sounstage.
I've had a single Titan II LE for over a year and absolutely love it. It is seamless. I've wanted to try a second unit but didn't have the extra funds. A couple of monhts ago a friend got one of ACI's new Force subs. We spent a couple of weeks playing around with it and concluded that it sounded a LOT like the big brother. So I started experimenting with stereo subs. At first the results were not an improvement. However, after changing room placement and tweeking the settings, well let's just say I now know that I'll be getting a second Titan II when I can afford it. We've found improvements in soundstaging and bass detail. I will add that I would definitely rather have one "great" sub than two "good" subs.