How to set up your subwoofer (properly)
A good subwoofer can improve not just the bass, but the entire experience of music listening. Unfortunately, lots of people who buy subwoofers are left unsatisfied. Not because there's anything wrong with the subwoofer they bought, but simply because they didn't have the time or knowledge to set it up properly. This article aims to help you dial in the sound of your system by making sure the basic settings of both your subwoofer and receiver is configured correctly.
Most of the article is written with the assumption that you have an amplifier / receiver / processor with a dedicated subwoofer output and crossover capabilities, but there's a small section towards the end for those who don't - so scroll down if that's you! It also assumes you have a decent subwoofer that has the capability to keep up with the rest of your system.
Also, the first thing to do is to try to find a good place for your subwoofer, this article gives some guidance on that subject.
Note: This is all general recommendations. It's always a good idea to experiment, and of course choose what you think sound the best. If you have the equipment and knowledge to measure the results, even better.
Initial setup of your subwoofer
Before running the room setup procedure on your receiver, let's check the settings on your subwoofer. We'll go through the most common controls likely to be present on your subwoofer.
Volume / Gain: Set this straight up or half-way to max (12 O'clock).
Crossover: Set this to max (typically 160 or 200hz). Your receiver will control crossover.
Phase: Leave this at 0 degrees for now. This will also be handled by your receiver.
If you have any other controls or settings on your subwoofer, leave them at their default setting.
Running room setup / calibration software
All modern surround receivers have pretty advanced room calibration systems that will automatically set distance and levels to all your speakers, including the subwoofer. Most also do a decent job at applying EQ to correct for standing waves in the room. This makes the life of your subwoofer a little easier. Follow the instructions on-screen and/or refer to the manual of your amplifier / receiver for this point.
Note: Whenever you move any speakers, your subwoofer, or move the entire system to a different room - this procedure needs to be run again.
Checking the configuration after room setup
There are a few things that surround receivers often get "wrong". Let's walk through them and adjust as necessary. Please refer to the manual if you are unsure how to find these settings.
Crossover: Crossover is the frequency at which the receiver starts to roll off the bass, and hand it over to the subwoofer. This can typically be configured as one setting for all speakers, or individually for each speaker category (front, center, back, etc). Your receiver measures what your speakers are capable of, and configures the crossover accordingly. That's not necessarily the best choice of crossover. Typically, you will get a much better bass response if you relieve your speakers of the deepest bass, even if you have pretty large speakers.
You should never choose a crossover that is LOWER than what your receiver selected, but often it's a good idea to go higher. Even if you have large speakers and your receiver set the crossover to 60 or even 40hz, the THX recommendation of 80hz is a good choice most of the time, even with large speakers. You can even try 100hz.
Speaker settings: You typically have this setting for each speaker category, and it can be set to either "small" or "large". What this really means, is whether the crossover you configured in the previous point is active or not. If you set it to "large", the speaker will play the full range of frequencies, and not send anything to the subwoofer. As a general rule, this should be set to "small" regardless of how large your speakers are.
Note: When watching movies, the soundtrack typically have a dedicated subwoofer or LFE channel. If all your speakers are set to large, this channel is the only thing that will be sent to the subwoofer. When listening to music, your subwoofer will be quiet. A workaround for this is selecting a subwoofer setting called "LFE+Main" if you can find that in your settings. This will have the subwoofer and main speakers both play bass during music. Typically this gives poor integration, and is not advisable. So set all them speakers to small.
Volume: You may need to adjust the subwoofer volume after room setup. Many find the need to turn the volume up by 3-6dB. Here you just have to try what sounds best. This can be done either with the volume control on the subwoofer, or in your receiver settings.
But what if I only have a stereo amplifier?
If you don't have an amplifier with crossover capabilities or room correction software, you can still benefit from adding a subwoofer to your system. It may however be a bit more difficult to integrate with the main system.
Since you will be unable to cut any bass from your main speakers, you will need to select a lower crossover frequency than you'd otherwise would. You also need to set the crossover on the subwoofer. You need to experiment to find the right crossover frequency, and having a look a the specifications of your speakers might be helpful. Slightly above or below the lowest they are specified to reproduce, might be a good starting point for the crossover. Let's say you have monitors rated at 69-20,000hz. Then a crossover of 60hz might work. But 80hz may work too. Your room affects the response, so you just need to test what works.
You also need to dial in the volume manually. Try to increase the volume until you can clearly hear the sub, and then dial it back again a little bit.
If your subwoofer has a phase control, you can experiment with this too. Have a friend test different settings, and choose the one that sounds best (not necessarily the one with the most bass).
There are other settings to look into, but those are different depending on your receiver brand, so that's beyond the scope of this article. Hope this was helpful!