Subwoofer Placement—Crawling Around for Bass?
Early on in my audio career I began to hear more and more about acoustics and, in particular, how difficult it was to get good bass or subwoofer response in a room. Subwoofers can go anywhere in a room because they aren’t directional. Frequencies below 80Hz, like those emanating from a subwoofer, aren’t localizable—or shouldn’t be if it’s configured properly. But just because you can place a subwoofer anywhere in a room doesn’t mean that will yield the best sound. Complicate this by the fact that subwoofers are large and are often the target of speaker-hiding spouses, and you’ve got a potential issue for getting good bass response.
But how do you find the right spot for a subwoofer? It’s simpler than you might think.
How Subwoofers Differ from Smaller Speakers
Subwoofers only handle low frequencies, so they don’t need tweeters and they don’t need the mid-sized drivers that your main speakers have. They just need to pump out astronomical amounts of bass—typically at frequencies at or below 80Hz. At those frequencies, waveforms are very long. While the wavelength of a 1kHz tone may only be around 13 inches in length, the wavelength at 40Hz is roughly 28 feet! Those larger waves cause a lot more issues with peaks in the room, and they quickly “gang up” when they hit obstacles like block walls and bounce back into the space. The goal when placing a subwoofer is to eliminate as many of those peaks as possible at the listening position. That means moving the sub around.
If you’re like me, moving a subwoofer is something you aren’t going to want to do a lot of. It’s a heavy speaker and the thought of taking it on a 12-inches-at-a-time journey around my living room isn’t my idea of fun.
But there is another way.
There is actually no difference between how a sub sounds from its position to the user, and how it sounds from the user to the sub’s position. Let me clarify that if you didn’t understand. If I put the subwoofer on the ground and sit on the sofa, the sound is exactly what I would hear if I were to place my ear where the subwoofer is and sit the subwoofer on the couch.
Sound weird? We call this “crawling for bass”. It may seem weird, but it’s a brilliant solution to placing a subwoofer in a new room—or when placing a new subwoofer in an existing room.
Crawling Around for Bass
Here are the basic steps to do this:
- Unpack the subwoofer and place it on your couch. If you can set it on a box to get it to listening level, even better.
- Use a long enough RCA cable to connect it to the line level subwoofer output of your AV receiver.
- Download a low-end sweep from someplace like AudioCheck.net. Play the sweep on repeat.
- Turn the volume up until you can really hear the subwoofer at a decent enough level (if you have an SPL meter this would be around 75-80 dB SPL).
- Crawl around in places where you are able to place the subwoofer, and find the location where the sound has no audible volume boosts or dips. It doesn’t do any good to crawl around in the middle of the room because even if you had located the perfect spot, you’re not going to place the sub where you can trip over it (unless you’re VERY committed to good audio!)
- When you find the location that produces bass that isn’t “peaky” (where certain frequencies are way louder than others) and (more importantly) where the volume doesn’t dip too low, your work is done.
- The last step is to verify your findings by placing the subwoofer and re-setting the levels for all speakers. This would be the perfect time to re-run your room correction on your receiver. Now it is time to enjoy the bass!
One final thing to note is that you probably don’t want to achieve perfect bass in just one spot. If you have perfect bass, but there is a “suckout” or a huge peak to your right and left, you’re not going to win any awards for best host at your next movie night. You may have to adjust a bit to get a good compromise. We have other articles on Getting the Correct Subwoofer Settings so venture over there if you want additional help on making sure you have the bass management and crossover settings set up correctly for your speakers.
Do you have two subs, and/or would you consider buying another if it made your movies sound better? Let us know on Facebook or comment below and join in the discussion.