How to Set Up and Calibrate a Subwoofer

This article is part of our Home Theater Design Series that goes over almost everything about designing a home theater.

Adding a subwoofer to your home stereo system or home theater system can make a huge improvement in your sound if you know how to properly position the subwoofer and adjust all of the settings. If you are willing to spend just a little bit of time learning how to set up a subwoofer the right way, the addition can transform your system. You might get lucky if you just plop it down, turn it on, and everything winds up perfect, but odds are you’ll need to play around with placement and adjustments to get ideal results.

The main reason people add a subwoofer is the obvious one: you will normally get deeper, and more, bass output.  What you may not realize, however, is that adding a subwoofer can also improve the midrange and treble definition of your main speakers. Although, there is a risk of a sub addition making your main speakers sound worse if you just drop one in without some tuning.

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Where you sit and where you place your subwoofer will have a tremendous impact on the ultimate sound.  If you have not read our article on subwoofer placement, please read that first before proceeding to the steps we describe next.  This article is all about how to properly set up and calibrate your subwoofer once you have it generally placed in your home theater.  

With home theaters becoming so popular, and great bass being an essential part of it, you will notice there are a large variety of subwoofers on the market to choose from.  At one extreme are basic models with simple connections and at the other are subwoofers with complete room correction built-in and even some have an app to help you fine-tune your subwoofer from your listening chair!  We will go over how the setup process applies to the different types of subwoofers out there.

First, there are some basic things about connecting up your subwoofer(s) you should do first before you start any listening tests.

home theater with bowers & wilkins 700 series speakers & wall sconce lighting

Connection & Setup Considerations

Wiring and Connecting

Every home theater receiver or processor has one or more subwoofer output jacks on the rear panel.  You want to use an RCA cable to run from the subwoofer out on your receiver to your subwoofer.  If you have two subwoofers, it is great if your receiver has two subwoofer outputs, but you can still get the benefit of two subs with just one sub out on your receiver. Simply use a high-quality “Y” connector to split the signal and run two cables from there.  Most subwoofers also have left and right input.  For home theater, you do not have to worry about this and can just connect to either one. The only exception would be if your sub has one of them labeled “LFE”, in which case you would use that connection.

A few subwoofers have both input and output connections.  Please confirm you are connecting to the ones labeled input.

While you are behind your subwoofer, you will probably see it has a knob for level control. For most subs, just set this at about 12 o'clock.  Also if your subwoofer has a phase switch or dial, set it to zero.

Avoid Double Crossovers

Another thing that is critical is to make sure you are not using two crossovers. The crossover is the electronic circuit that sends the low bass tones to the subwoofer and the rest of the sounds to your other speakers.

Almost all home theater receivers have subwoofer crossovers built-in and also most subwoofers have a crossover on the back of the subwoofer. These allow you to set the crossover frequency where the division between the subwoofer and your other speakers takes place. You do not want to accidentally cross things over twice. 

We find it best to use the crossover in your home theater receiver and bypass the crossover at the subwoofer. Make sure you connect to the bypass input on your subwoofer.  Some subwoofers will have two sets of inputs with one labeled bypass and the other labeled crossover.  Others will have just one set of inputs with a small toggle switch where you select bypass or crossover.

Home Theater Receiver or Processor Setup

Crossover Settings

Before you start listening, you will also want to make sure your settings are correct on your home theater receiver or processor.  Your receiver will have a section in the menu where you can tell the system if you have a subwoofer and where you want to cross it over.  Obviously, you want to tell your receiver you are using a subwoofer.  You then will normally have a choice of where to set the crossover on all of the speakers in your system.  Some receivers give you a choice of large or small, where others give you frequency settings.  It is best to start out with all of your speakers set to small or if you have frequency adjustments, set them all to 80 Hz.  

Distance Settings

The next step is to make sure your distances are entered into your home theater receiver.  Use a tape measure to find the distance each speaker is from your main listening spot and enter that into the settings.  We may change these later for the subwoofer, but for now, use what you measure.

Critical Tech Tip: If your subwoofer comes with a microphone and/or has an app or is wireless, it has digital processing inside that will delay the signal coming out of the subwoofer.  Most subwoofers like this have a delay of anywhere from 8 to 12 milliseconds.  A millisecond translates into about 1 foot of distance.  This means you will need to add, on average 10 feet, to your distance setting at this stage before you start listening to better align the signals reaching your ears from your subwoofer and main speakers. This only applies to subwoofers with room eq built-in, app control, or are wireless.  We will go over how to fine-tune this distance in the phase setup.

Level Settings

The last step is to do a rough level settings adjustment. There are a variety of decent apps on the market for smartphones that will let you measure SPL (sound pressure level). You can easily download one on your iOS or Android device.  We like SPL Meter from Studio 6. Turn the test tones on and match the levels up using the meter on your phone. In most cases, you will set the levels of all speakers to 75db. If you have multiple subs, for each additional sub, set your level about 3db lower since they will combine to about 75db (e.g. if you have two subs start by setting each at 72db).

Tech Tip: Remove the cover on your phone if you have one, flip your phone over and point it straight up when you are measuring levels.

Listening Adjustments for Subwoofer Placement

If you have not read our article on subwoofer placement please do so before proceeding with the next step.  You want to first place your subwoofer or subwoofers in the best spots possible in the room and then move on to sub EQ calibration below.

Subwoofer EQ Calibration

If you are lucky enough to have a subwoofer with auto-calibration, it is now time to do that step.  There will be instructions that come with your subwoofer on how to do this.  Normally there will be a calibrated microphone and stand you will connect up either to a computer or the subwoofer.  Just follow the steps and let the subwoofer calibration do its thing.  

Note: There are a few subwoofers on the market that have manual room eq on the rear of the subwoofer.  To use these, you will need some more advanced audio tools as you will need to know at what frequency the peaks are occurring in your room.  Room EQ Wizard is a good one, but you will also need to purchase a good USB microphone.  You will play some test tones through the subwoofer to visually see the peaks, then try to take them down by reducing the same or a close frequency on the back of the subwoofer.  We do not suggest you try to take out dips by boosting the EQ controls on the rear. Trying a different position in the room for the subwoofer is a better idea.

For those of you with subwoofers that have no calibration feature, you will skip the calibration step.

Subwoofer Phase Adjustment

For the best experience, we want the sound from our main speakers and subwoofer to arrive at our ears at the same time. This is what phase adjustments can do.  This adjustment is a bit geeky and you can skip it if you are more of a casual listener. However, when you do get the phase-matched between your subs and main speakers you get this sense of effortless sound that 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 handful of subwoofers on the market that give you the ability to adjust the phase from 0 to 180 with everything in between either with a knob on the rear of the sub or an app that allows you to do the adjustments.  

Changing the distance in your receiver will also adjust the phase, which is what will be more common for most home theaters.  Some subs have the phase knob (which adds delay) whereas others use an app--using a phone app allows you to change the phase from your seat which is generally easier.

We actually find it easiest to just change the distance in your home theater receiver or processor.

First, you will need to get a test tone to do this with. You can use this youtube link for a good long 80hz test tone that can play while you run your test. If you set your crossover with your main speakers to something other than 80hz, then use a YouTube test tone that matches your crossover frequency as our goal is to match the phase of our main speakers and subwoofers where they are both playing the same frequency.

Room With One Subwoofer

Set your home theater receiver or processor to play stereo.

Now sit in your primary chair and start up the test tones.  Make a note of the SPL you are getting. Then slowly increase the distance in 1ft increments and stop where you get the highest SPL measurement.  If your subwoofer does not have digital processing the maximum SPL will likely be at approximately the actual distance from the subwoofer. If your subwoofer has digital processing, the SPL will be highest somewhere between the actual distance and about 12 feet extra which would correlate with a 12-millisecond delay.

You are done.

Room With Two Subwoofers

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

There are a few possible combinations.

For those of you using a Y connector for two subs and neither sub has variable phase or an app, just follow the same steps as above if they are both on the front wall.  If one is in front and one in the rear and the rear has a 0-180 phase switch, try it in both spots to see which gives you the most output

If you have subs with an app or variable phase that are connected with a Y connector, do one sub first (preferably the one furthest away from you) using the distance control on your home theater receiver, then add the second sub and change its phase until you get the highest level reading.

If you have two subs with no adjustments, but your receiver or processor has independent distances, follow the same steps just using the distance instead of phase for each one.

Room With Four Subwoofers

For those of you with four subwoofers, you likely have a home theater receiver or processor that has Dirac or Anthem Room Correction and it will do all of the phase adjustments for you.   

At this point, it is a good idea to make a note of the distances you came to when you were doing phase as some receivers will get them wrong in the next step.

Final Receiver/Processor Calibration

Now that the subwoofers are all set up properly, if your home theater receiver or processor does not have any kind of room correction, simply go back through the test tones and balance all of your speakers out to 75db (with the combined level of all your subs at 75db).  

If your receiver or processor does have room correction, follow its steps now.  Unless your receiver/processor has phase alignment like Dirac or Anthem Room Correction, you will need to go back in after it is done and change the distance(s) for the subwoofer to the one(s) you noted after the phase calibration.  Our experience tells us the other systems get the phase part wrong.

We also suggest you look at our tips on calibrating your center channel speaker and running through them after these steps are finished. 

That concludes our tips on subwoofer setup.  We hope this article was helpful and brought your home theater up a notch or two!  If you have any questions or comments, feel free to reach out to us via chat, email, phone, or drop by one of our locations in Raleigh or Charlotte, NC.

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