How to Set Up and Calibrate a Subwoofer?

                                How to Set Up and Calibrate a Subwoofer

Adding a subwoofer to your home stereo or home theater system can greatly improve your sound if you know how to place the subwoofer properly and adjust all the settings. Adding a subwoofer can transform your system if you're willing to spend a little time learning how to set it up the right way. If you just add the subwoofer, turn it on, and everything works perfectly, then you're in luck, but chances are you'll need to tweak the placement a bit to get the desired effect.

The main reason people add subwoofers is obvious: to generally get deeper, more bass output. What you may not realize, however, is that adding a subwoofer can also improve the midrange and treble clarity of your main speakers. However, if you drop in a subwoofer without making some adjustments, you risk making your main speakers sound worse.

Where you sit and where you place your subwoofer will have a huge impact on the final sound. This article is all about how to properly set up and calibrate your subwoofer when you place it in your home theater.

As home theater has become popular, bass has become an integral part of it, and you'll find a wide variety of subwoofers to choose from. One is a basic model with simple connections, another has a subwoofer with full room correction built in, and some even have apps to help you fine-tune the subwoofer from your listening chair. We'll cover how to set up different types of subwoofers.

First, you should do some basic work on hooking up your subwoofer before starting any listening tests.

Connection and Setup Notes

Wiring and Connections

Every home theater receiver or processor has one or more subwoofer output jacks on the rear panel. You'll run an RCA cable from the subwoofer output on the receiver to your subwoofer. It's great if you have two subwoofers and your receiver has two subwoofer outputs, but you can still connect to two subwoofers through one subwoofer output on the receiver. Just use a high quality "Y" connector to split the signal and connect the two cables there. Most subwoofers also have left and right inputs. For a home theater, you don't have to worry about this, just connect any of them. The only exception is if your subwoofer has a connection labeled "LFE", in which case you'll use that connection.

Some subwoofers have both input and output jacks. Make sure you are connecting to the jack marked IN.

When you're behind the subwoofer, you'll probably see that it has a knob to control the volume. For most subwoofers, just set it around 12 o'clock. Also, if your subwoofer has a phase switch or dial, set it to zero.

Avoid using two crossover points

Another crucial thing is to make sure you are not using two crossover points. The crossover is the electronic circuit that sends the bass to the subwoofer and the rest to the other speakers.

Almost all home theater receivers have built-in subwoofer crossover points, and most subwoofers have crossovers on the back. These allow you to set the crossover frequency between the subwoofer and the other speakers. You definitely don't want to divide by two.

We find it best to use the crossover point in the home theater receiver and carry over to the subwoofer. Make sure to connect to the subwoofer's thru input. Some subwoofers have two sets of inputs, one labeled bypass and the other labeled crossover. Other subwoofers have only one input, with a small switch that lets you choose direct or crossover.

Setting Up a Home Theater Receiver or Processor

Set crossover point

You'll also want to make sure the settings on your home theater receiver or processor are correct before you start listening. There will be a section in your receiver's menu where you can set whether or not you have a subwoofer in your system, and what crossover frequency you want. Obviously, you want to tell your receiver that you are using a subwoofer. Then, you can usually choose to set the crossover points on all the speakers in the system. Some receivers offer a choice of large or small, while others let you choose the frequency setting. It's best to start with all speakers set to small, or if you're tuning frequencies, set them all to 80Hz.

set distance

The next step is to make sure the distance is entered into your home theater receiver. Use a tape measure to measure the distance between each speaker and your main listening point, and enter this into the setup. We may change these settings for the subwoofer later, but for now, use your measured values.

Key Tech Tip: If your subwoofer has a microphone and/or has an app, or is wireless, it has digital processing inside it that delays the signal coming out of the subwoofer. Most subwoofers like this have 8 to 12 milliseconds of latency. 1 millisecond corresponds to a distance of about 1 foot. That means, before you start listening, you'll need to add an average of 10 feet to the distance setting at this stage to better adjust the signal from the subwoofer and main speakers to your ears. This only applies to subwoofers with built-in room EQ, app control, or wireless. We'll detail how to fine-tune this distance in Phase Settings.

set volume

The final step is to roughly adjust the volume settings. There are many good smartphone apps out there that allow you to measure SPL (Sound Pressure Level). You can easily download one on your iOS or Android device. We love Studio 6's SPL Meter. Turn on the test tone and use the SPL Meter on your phone to match the level. In most cases, you will set the volume of all speakers to 75dB. If you have multiple subwoofers, set your level about 3dB lower for each additional subwoofer, as they will combine to be around 75dB (for example, if you have two subwoofers, start with each set to 72dB).

Adjust the position of the subwoofer

If you haven't read the article on subwoofer placement, please do so before proceeding to the next step. First, you'll want to place your subwoofer or subwoofers in the best position in the room, and then perform the subwoofer EQ calibration below.

Calibrating the Subwoofer EQ

If you're lucky enough to have a subwoofer with an auto-calibration feature, now is the time to start this step. Your subwoofer provides instructions on how to do this. Typically, there will be a calibrated microphone and stand that you can hook up to your computer or subwoofer. Just follow the steps and let subwoofer calibration do its job.

Note: Some subwoofers on the market have a manual EQ behind them. To use these, you'll need some more advanced audio tools, because you need to know the frequencies at which peaks occur in your room. The Room EQ Wizard is a good option, but you'll also need to invest in a good USB microphone. You will play some test tones through the subwoofer to visually see the peaks, then try to reduce the peaks by lowering the same or a similar frequency on the back of the subwoofer. We don't recommend that you smooth out the lows by beefing up the EQ controls on the rear. Trying to place the subwoofer in different places in the room is a better approach.

For those using subwoofers without calibration, skip this calibration step.

Adjust subwoofer phase

For the best experience, we want sound from the main speakers and subwoofer to reach our ears at the same time. That's what phasing can do. This adjustment is a bit tedious, and you can skip it if you prefer casual listening. Still, when phase matching is achieved between the subwoofer and main speakers, the sound quality you get is pretty amazing.

Tech tip: If your home theater receiver or processor has Dirac or Anthem room correction, it will do this step for you. Lucky you!

There are a small number of subs on the market that allow you to adjust the phase between 0 and 180, either via a knob on the rear of the sub or an app that allows you to make the adjustment.

Changing the distance setting in the receiver will also adjust the phase, which is more common in most home theaters. Some subwoofers have phase knobs (which add latency), while others use an app—it's usually easier to use a phone app that lets you adjust the phase from your seat.

We've actually found the easiest way to do this is to change the distance in your home theater receiver or processor.

First, you need to get a test tone to do this. You can use a long 80Hz test tone that plays while you are testing. If you set the crossover point of your main speakers to something other than 80Hz then use a test tone that matches your crossover frequency as our goal is to match the phase of the main speakers and subwoofer as they both play the same Frequency of.

There is a subwoofer in the room

Set up your home theater receiver or processor to play stereo.

Now sit in your master chair and start testing. Make a note of the sound pressure level you get. Then slowly increase the distance in 1-foot increments and stop when the highest sound pressure level is measured. If your subwoofer doesn't have digital processing, then the maximum SPL is probably about the same as the actual distance from the subwoofer. If your subwoofer has digital processing, the SPL peak will be somewhere between the actual distance and about 12 feet away, which correlates to a 12ms delay.

There are two subwoofers in the room

For two subwoofers, the process will depend on your home theater receiver or processor.

There are several possible combinations.

For those using Y-connectors to connect two subwoofers (neither with variable phase or app), just follow the same steps as above if both subwoofers are placed near the front wall. If one is in the front and one in the rear, and the rear subwoofer has a 0-180 phase switch, try it in both positions and see which gives you the most output.

If your subwoofers have an app or variable phase and are connected via a Y connector, use the distance control on your home theater receiver to adjust the phase of one subwoofer (preferably the one furthest from you) first, then Add a second subwoofer and change its phase until you get the highest level reading.

If you have two unadjusted subwoofers, but your receiver or processor has separate distances, follow the same steps, but only use the distance instead of the phase of each.

There are four subwoofers in the room

For those of you with four subwoofers, you probably have a home theater receiver or processor with Dirac or Anthem room correction that will adjust all the phasing for you.

At this point, it's a good idea to note down the distances you came up with when doing the phasing, as some receivers will get them wrong in the next step.

Final Calibration Receiver/Processor

Now that all the subwoofers are set up, if your home theater receiver or processor doesn't have room correction of any kind, just go back to the test tone and balance the output of all the speakers to 75dB (combined volume of all subwoofers is 75db).

If your receiver or processor has room correction, follow its steps now. Unless your receiver/processor has phase correction like Dirac or Anthem room correction, you'll need to go back when you're done and change the subwoofer distance to what you recorded after phase calibration. Experience tells us that the phasing part of other systems is wrong.