Many listeners are learning about the sonic benefits of adding a subwoofer or two. The payback goes beyond the obvious added low frequency extension and power, to significant gains in soundstaging performance. To realize the full potential of your purchase, finding the optimum location for the subwoofer is critical. We’ll cover several topics to get you headed in the right direction.
The first suggestion would be to consult the manual provided with your subwoofer. Due to varying design philosophies, some manufacturers differ in regards to their ser up recommendations, so first and foremost, follow their lead. That said, I’ve learned the hard way that every room is different and every listener has a singular set of goals, so I encourage you to experiment with placement (this is also true with regard to placement of full range speakers as well).
There are some general rules of thumb and more than one scheme to follow for finding the ideal location for your subwoofer. Basic acoustical properties that affect sound reproduction in any given space will also influence your placement. First, know that midpoints in the room (along any wall or in the center of the room) are acoustical null points and should be avoided. For single subwoofer applications, it would seem obvious that centrally locating the subwoofer between the two speakers would be ideal. But that’s not the case. While a central location may seem ideal in terms of soundstage considerations, it is not be the optimal location with regards to reproducing low frequencies. Placement near an acoustical boundary (wall) will reinforce the output of the subwoofer by 3dB. Three boundary surfaces are engaged when the subwoofer is placed in a corner (the two walls and the floor) resulting in a net gain of 9dB. Free energy, so try to use it if possible.
If you have a single sub, one suggestion is to place it in the area behind the right speaker, using logic that the percussion section in an orchestra is typically located rear stage right. If you listen primarily to classical, this works, but not necessarily if you concentrate on other genres. In some single-subwoofer scenarios, the room itself (traffic patterns, furniture, personal preference, etc.) may dictate the general location. I suggest experimentation to see what works in your room, with the music you enjoy. Ideally, using two subwoofers is always best (see our article Way Down Deep – Adding A Subwoofer), and in that instance the locations are obvious, setting them up in the general vicinity of each main speaker.
Finding the right location –
The first step is selecting a piece of music, or low frequency sweep tones - sustained low frequencies that can be repeated are important.
I’ve seen several suggestions regarding the best way to find the ideal location for the subwoofer. Subwoofer manufacturer REL recommends starting in the corner, with the sub pointing along the diagonal axis of the room, and move it out bit by bit until the greatest amount of output is achieved, then fine tune from there.
Another suggestion is to place the subwoofer in the listening position then raising it up on supports to ear level. From there, crawl around on hands and knees (approximating the level of the subwoofer when placed on the floor) and listen for the location offering the strongest low frequency reinforcement and smoothest response. Be sure your wife or neighbors aren’t watching or you’re sure to be committed!
Fine Tuning –
Whichever method you choose, note that small movements – just an inch or two – can significantly impact performance, so a bit of careful tweaking is required to really dial in location.
Once you have the placement spot on, you’ll want to adjust any other parameters available to you on your particular subwoofer. Powered subs will always have additional controls for further fine tuning such as phase, crossover, level, etc. Getting these set just right may take some time, so don’t fret if you find yourself continuing to make subtle adjustments as you listen over days or weeks. Do listen to a wide range of material, and not concentrate only on music with bombastic bass. Simple recordings with very little bass may allow you to make more accurate subtle adjustments. The best sounding systems are ones in which the subwoofers never call attention to themselves, blending seamlessly with the main speakers. Music with very little low frequency information will tell you if the subs are artificially inflating what should be low-level information.
Another note regarding material choice is to include music with fast, expressive transients, fine tuning position or dialing in controls to maximize impact as well as extension. While you may have found the location and settings that realize subwoofer output potential, part of the ability required to blend seamlessly is articulation and speed, such that the subwoofer matches the main speakers in pace and time.
There you have it. Enjoy your new subwoofer experience!