August 29, 2012: This is an update of my subwoofer setup article from 2008.
Merely buying a great subwoofer is no guarantee that you'll wind up with great bass. There are too many ways to squander its performance potential, and that's why putting in the extra effort to achieve proper subwoofer setup is crucial. This two-part guide will help you get the best room-shaking bass from your subwoofer.
Part I: Placement and positioning
Part II: Connectivity and fine-tuning
Subwoofer Setup Part I:
Placement and positioning
While a subwoofer's deep bass is nondirectional, it would be unwise to just stick the sub anywhere that's convenient in your room.
That's why it's worth making an effort to find the best location for your sub; it can make a dramatic difference in the sound. Corner placement is the de facto strategy for most people, possibly because the sub will then be out of the way and almost always produces the most bass, but corner placement may not yield the most accurate bass, or smoothest transition to the speakers. The sub and speakers have to work together as a team, and ideally you should never hear the sub as a separate sound source. All of the bass should appear to come from the speakers.
With small speakers, it's best to keep the sub within 3 or 4 feet of the front left or right speakers. Once the sub is a lot farther away, it will be harder to maintain the illusion the bass is coming from the speakers. For really small speakers or skinny sound bars, keep the sub as close as possible to the speaker(s).
If you have larger speakers (with 4-inch or larger woofers), some placement experimentation may be useful; play a CD with lots of deep bass and keep repeating the track as you move the sub to all of the visually acceptable locations in your listening room. You'll be amazed just how different the bass sounds in different locations -- some will be muddy, some will sound louder, and some will reduce the bass volume. The goal is to get the best balance of deep bass from the sub and still have the mid and upper bass from the speakers in equal proportions (adjust the subwoofer volume control in each new position). In some rooms, smooth bass response won't be all that hard to achieve, but I've heard my share of "problem" rooms where the bass always sounds boomy or muddy.
If you're having problems finding the perfect spot, try this method: move your couch or chair out of the way, or into another room, and put the sub in the listening position. Yes, I know that sounds like a crazy idea, but it's just for test purposes. Now play music and movies with lots of bass, and take a little stroll around your room, stopping in the spots where you'd like to place the sub. As you move about you'll notice the bass' apparent loudness and definition changes from place to place. When you find the place that sounds the best, put the sub in that spot.
When all else fails, try placing the sub as close as possible to your couch or chair, with the sub in the "end table" position. That location can work wonders and really improve the sound of your subwoofer.
Larger speakers are generally easier to match with subs; small speakers or speakers with 4-inch or smaller woofers can require more fine-tuning to get right.
Subwoofer Setup Part II:
Connectivity and fine-tuning
If you have a wireless subwoofer, skip ahead two paragraphs. The Hsu Research subwoofer's rear panel pictured on the right is fairly typical. To non-audiophiles the maze of connectors can be intimidating, but in most instances the single-cable Sub In connection will be the easiest and best-sounding hookup method. Here you can see the Sub In connection on the Hsu's rear panel; on other subs the input may be labeled LFE, Direct, or Bypass. Next, turn the sub's (low-pass) crossover control knob to its maximum, highest numerical setting (you're going to rely on your AV receiver's internal crossover control to route the mid and high frequencies to the speakers and the bass to the sub). Turn the volume control halfway up.
If you need a long interconnect or RCA subwoofer cable, I recommend Blue Jeans Cable. How long is long enough? Measure the distance between your AV receiver and sub and remember to include the distances up and down over doorways and furniture. Buying a cable a foot or two too short is a drag, and after you've opened the package you may not be able to return it for a refund or exchange.
If your AV receiver has an auto speaker setup program, run the complete setup routine with the calibration microphone that came with the receiver. If you like what you hear, great, you're done! Then again, don't be surprised if the sub still doesn't sound as good as you think it should. I'm not always happy with the subwoofer's sound after I run these programs. So if you have any doubts, try turning the subwoofer's volume control up or down. That might be all you need to do. But if you don't like the change, return to the previous setting or rerun the auto setup to return to your original calibration settings.
If you're still not satisfied with the sound try using the receiver's manual speaker setup. If you're lucky enough to have large floor-standing speakers with 8-inch or larger woofers, you may wish to run them as "large" speakers. But your center and surround speakers will still likely work best run as "small" speakers. On some receivers you'll be presented with a wide range of subwoofer or crossover settings, from 40Hz up to as high as 250Hz. Your speakers' or subwoofer's user manual may offer specific guidance in this area; otherwise use the Audiophiliac's crossover recommendations: for small speakers with 2- or 3-inch woofers, try settings between 150 and 200Hz; for midsize speakers with 4- or 5-inch woofers, use 80 or 100Hz; and with large bookshelf speakers or skinny floor-standing speakers, try a 60 or 80Hz crossover. When in doubt about the speakers' sizes, always select "small" on the setup menu.
One of the other controls you may find on your subwoofer's rear panel is marked "phase." It's provided because the speakers and subwoofer sound best when they are in-phase -- meaning their woofers move in and out in sync with each other. To check your sub's phase, play music with lots of bass, listen for a minute or so, and have a friend sitting by the sub flip the sub's 0/180-degree phase switch slowly back and forth. The correct setting is the one that yields more bass. You may have to try a few different recordings before you hear any difference, and it might help to turn up the sub's volume level for this test. If you don't hear any difference between the 0 and 180-degree settings, leave the phase control in the 0 position.
Setting the subwoofer volume is next. Precisely matching the volume levels of the front left, center, right, and surround speakers is important, but subwoofer volume is more subjective. Some folks like to feel the sub working the room all the time -- and some prefer to only hear the sub's contributions with big special-effects-driven movies or dance music. A sound level meter can be a big help when setting speaker levels, but it's nearly useless for determining the sub's correct volume level. The "by ear" method works well enough. I can set the sub's volume level with DVDs in 10 minutes or less, but with CDs I might be fiddling around for days. Again, if you feel like this is all a little too complicated, relax, take a deep breath, run the auto setup program, and let the receiver sort things out.