The Five Cs of Subwoofer Setup | Wirecutter
A subwoofer is to sound what wasabi is to sushi. use it carelessly, and it will dominate everything else. but use it wisely, and it can make the whole experience that much more satisfying.
Subwoofers are much more complicated to connect and adjust than anything else in an audio system. the acoustics of your room have a much greater effect on the performance of the subwoofer than on your other speakers. Subwoofers often need to be plugged into different AC outlets than other system components, and most audio systems don’t include dedicated subwoofer connections. But millions of people have installed subwoofers to their satisfaction, and so can you.
We’ve streamlined the process into five steps, all of which conveniently start with a c: connect, control, trace, merge, and verify. In nearly 30 years of reviewing and measuring subwoofers, I’ve found that this method makes almost any subwoofer work well with almost any speaker system, no matter what other audio equipment you’re using. It will work with any of the picks in our best budget subwoofer guide, as well as any other conventional subwoofer.
1. connect
If you’re using your subwoofer with a home theater receiver, hooking up is simple: just run an audio interconnect cable like this one from the receiver’s subwoofer output to the home theater speaker’s line input. subwoofer (pictured above). if the subwoofer has an input labeled lfe, use that. if you only have left and right stereo inputs (line level), use either one.
If you’re using your subwoofer with a stereo receiver that lacks a subwoofer output (and many do), you can connect the subwoofer using an additional set of speaker cables, as shown above, as long as the subwoofer have speaker level. (speaker cable), as do the picks in our best budget subwoofer guide. typically you’ll run the left and right speaker wires from the receiver to the subwoofer, then from the subwoofer to the speakers. the subwoofer manual will probably include diagrams showing the connections clearly.
If you are using your subwoofer with a computer speaker system, your speaker system may have a subwoofer output or a set of line outputs that can be connected to a subwoofer. if neither is present, get an adapter in y like this. plug the adapter into and into your computer’s audio output, then plug one leg of the adapter into and into your computer’s speakers using a 3.5mm cable like this one (most computer speakers include this cable), and plug the other leg of the adapter in and adapter to the subwoofer’s line inputs using a 3.5mm to rca cable like this.
Humming problems are common with subwoofers because people often plug the subwoofer into a different outlet than the rest of the audio/video system; If the two outlets are on different breakers, a “ground loop” can result, causing a 60hz hum. sometimes a hum can even occur when the subwoofer is plugged into the same outlet or power strip.
To troubleshoot a hum problem, first check the audio connection between the subwoofer and the receiver. a damaged or partially disconnected cable can cause hum. If the cable is in good condition and the connections are solid, and if your subwoofer has a detachable AC cord that you can flip into its plug on the subwoofer, try flipping the connector. If your subwoofer’s AC cord is permanently attached or not designed to be flipped, and the subwoofer is plugged into a different outlet, try plugging the subwoofer into a power strip shared by the rest of the audio/video system. If this trick eliminates the hum, but keeping it connected this way permanently isn’t practical for you, try using an isolation transformer on the cable from the receiver to the subwoofer, or use a wireless subwoofer transmitter.
2. controls
Inexpensive subwoofers typically have only two knobs you need to adjust: volume and crossover.
The crossover frequency determines the highest notes the subwoofer will play. set the frequency too high and you could make ariana grande sound like vin diesel because part of her voice comes out of the subwoofer. set it too low and there will be a sonic “hole” between the subwoofer and the speakers, and vin diesel can start to sound a bit like ariana grande.
The idea is to have the subwoofer pick up right where the speakers left off. You can usually find the lowest frequency the speakers are rated to reproduce on the spec sheet on the manufacturer’s website or in the owner’s manual. For example, the spec sheet for the Acoustic Q 3020i, which we tested for our guide to the best bookshelf speakers for most stereos, shows that the speaker has a nominal frequency response of 64Hz to 30Khz. in this case, you should set the crossover frequency of the subwoofer to 64hz or a little more.
set the frequency too high and you could make ariana grande sound like vin diesel because part of her voice comes out of the subwoofer.
Be careful though: some manufacturers get a little optimistic about these specs. For example, the spec sheet for the AudioEngine HD3, which we tested for our best wireless bookshelf speakers and best computer speaker guides, rates its response up to 65hz, even though the HD3 is much smaller than the Q Acoustic 3020i and has a small 2.75-inch woofer. the best thing to do is set the crossover frequency of the subwoofer to match the speakers rating, then increase the frequency if you hear a “hole” between the subwoofer and the speakers, for example if vin diesel’s voice sounds weak and weak, or if the crashes and explosions in action movies don’t have the impact they probably should.
Please note that if you are using your subwoofer with a home theater receiver, you should set the subwoofer’s crossover frequency control to maximum and use the receiver’s subwoofer crossover setting. The standard crossover frequency in home theater systems is 80 Hz. If your speakers are small, with woofers that are 4 inches or less, you may want to set the frequency higher than 120hz; this will prevent your speakers from producing low frequencies, so they will be able to play a bit louder and the system will sound clearer. If you have larger speakers, like tower speakers, you may prefer the way a 60hz crossover frequency sounds. in this case, there is no hard and fast rule because the acoustics of your room will have a big effect on the results.
Now you need to set the level (or volume) of the subwoofer in relation to the other speakers. If you’re using a home theater receiver, it has a built-in test tone to help you set the subwoofer level. in this case, it is usually best to leave the subwoofer volume control at half and adjust the subwoofer volume using the controls on the receiver. If setting the subwoofer volume to half does not give you enough volume, try turning it up about three-quarters of the way, and then adjust the level with the receiver’s subwoofer level control. if you have to turn the subwoofer level up past halfway, don’t worry. Virtually all powered subwoofers have an internal limiter that will protect the driver and amplifier. unless you hear large amounts of distortion, no problem.
If you’re using the subwoofer in a stereo or computer system, simply set the volume of the subwoofer to sound best from the chair you normally sit in. the sound should be neither loud nor thin. You can also change the volume of the subwoofer on the fly to suit whatever music or movie you’re listening to. there are no rules here.
Most subwoofers also have a phase control: a switch or knob that slightly adjusts the timing of the bass so that the subwoofer is more in sync with the main speakers. in some cases this can help the subwoofer blend better with the main speakers, but the setting of this control is generally not critical. try different settings and see which one sounds best to you; if you can’t tell the difference, don’t worry.
Please note that most home theater receivers have automatic room correction technology which, in theory, should balance your subwoofer with your main speakers and adjust the sound of the subwoofer for the best performance in your room . there’s nothing wrong with trying this or sticking with the results if you like the sound. however, this technology is notoriously unreliable and can even make the sound worse. read our best av receiver guide to learn more.
3. crawl
The location of the subwoofer and listening chair in your room will likely have a greater effect on the sound than your choice of subwoofer. put it in the corner, and it will sound boomy. place it somewhere else, and some low notes will be boosted while others will be muted a bit. and the effects will differ depending on where you are sitting. Fortunately, your ears can’t detect where the deep bass is coming from, which means you have a lot of flexibility when it comes to placing your subwoofer.
If you want to get the best sound out of your subwoofer, there is a time-honored technique you can use to find the optimal spot for it. Place the subwoofer in the chair you sit in most often when listening (no, seriously), and play a tune with a melodic bass line, like “Aha” by Steely Dan. now crawl around the room with your head close to the floor (yes, we’re still serious) and find the place where the bass line sounds the smoothest. that’s where you want to place the subwoofer.
Unfortunately, this location will provide the smoothest bass for that seat alone. for many audio enthusiasts, that’s fine, because other people in the room with them may not be as picky. if you care about giving everyone the best sound, go ahead and do the crawl, then listen to the bass line again from your main listening seat and then from the other seats. then move the subwoofer around until you find the best compromise. or better yet, skip to the next section of this article.
If sound isn’t as important as looks, simply place the subwoofer where it’s convenient. should still sound pretty good, regardless of placement, if tuned correctly.
4. combine
If you’re worried about even bass from every seat in your room, there’s an easy, though often more expensive, solution: buy two subwoofers instead of one. Placing a subwoofer in the front left corner of your room and a matching subwoofer in the front right corner will provide smoother, more consistent bass response as you move from seat to seat. In a widely publicized research project (pdf), scientists at harman international (parent company of jbl, infinity, revel, mark levinson and a host of pro audio brands) determined that placing four subwoofers in a room (one in each corner or one in the middle of each wall) produced the most consistently smooth bass in the entire room. they also found that two subwoofers (in the corners or in the middle of opposite walls) did not give as good a result, but they were still much better than a single subwoofer and obviously a much more realistic solution for most people. Considering the low prices of our top picks in our guide to the best budget subwoofer, buying two subwoofers can be a practical alternative for serious listeners.
That’s not to say that two substitutes are the best solution for everyone. on a considerably less advertised research project I did for sound & vision magazine, my listeners and i (including wirecutter’s lauren dragan and geoffrey morrison) confirmed harman international’s results when various sitting positions were considered, but found that for a single listener (or a listener who doesn’t care what they do others in the room listen), it’s generally smarter to spend your money on one large subwoofer than two smaller ones. this way, you get more rock-’em/sock-’em bass for your money.
Hardcore enthusiasts tend to use a subwoofer equalizer to adjust the sound of one of the two subwoofers in a way that corrects faulty response from the other, but at that point you’re getting into a much more expensive system and (much more complicated setup) than we’re talking about here.
5. check
When I was working at Dolby Laboratories, the company that has done the most to set the technologies and standards for home theater sound, an audio journalist asked me how to achieve the most precise balance between a subwoofer and the main speakers. Within Dolby’s huge and well-funded research department, I found an engineer who was considered the company’s foremost subwoofer expert. So what should I tell them? I asked after he had described from memory the results of eight studies on the subject, some dating back decades. “Just tell them to adjust it by ear,” he replied.
as the dolby engineer hinted, the myriad of variables in subwoofer setup (volume level, crossover frequency, the characteristics of the main speakers, room acoustics, and the subwoofer’s own idiosyncrasies) mean that achieving a “perfect” setup is virtually impossible. Many home theater enthusiasts get a little closer to perfection by using a measurement microphone and USB interface (or USB measurement microphone) in conjunction with the free Room EQ Wizard computer application to tune subwoofer performance, and that’s what i do when testing subwoofers for wire cutters. but that’s much more serious than most casual listeners will probably want to understand.
A simpler, though much less accurate, alternative is to use the real-time analyzer (rta) feature in a smartphone app like audiotool (for android) or db rta audio spectrum analyzer (for ios) . If you’re playing pink noise (available from many sources, including YouTube) through your system, these apps will show you how smooth the bass response is in your room and how well the subwoofer blends with your main speakers. Two caveats: choose an application with at least ⅙ octave resolution and measure from your main listening chair (or couch).
Even if you have measurement equipment and the knowledge and patience to use it, the ultimate test of a subwoofer setup is whether you like the sound. so when you’re done, just sit back and listen to some of the movies and music you love. the goal is to get your system to the point where female voices don’t sound puffy and male voices don’t sound thin. you should also be able to feel the impact of the couch during explosions in action movies without the bass sounding boomy in lighter music like most pop and jazz. Even after everything sounds good, you may need to adjust the subwoofer’s volume frequently to best suit the movie or music you’re listening to.
And if all this sounds like too much trouble, unplug the subwoofer for a minute or two and you’ll quickly see why it was worth the effort.
