Optimal Subwoofer Placement for Home Theater

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Today’s post is going to be dealing entirely with subwoofers and how they should be placed in a home theater. Subwoofers are the loudspeaker responsible for the low bass notes in any home cinema or even two channel system, a subwoofer can be categorized in one of two ways. Either powered or non powered. 

POWERED VS NON POWERED SUBWOOFERS

There really isn’t a difference between powered or non powered outside of a non powered sub getting its power from an outboard amplifier generally located in your equipment rack, whereas a powered sub has the amplifier built in. 

Powered subs are typically more common. However, it is possible and sometimes cost effective to find an unpowered sub for your system. The only difference then between an unpowered and a powered sub when connecting it to your system is an unpowered sub is connected to its outward amplifier much in the same way as your loudspeakers are via speaker cable, whereas a powered subwoofer with its amplifier built in connects to your AV receiver or AV preamp using either an RCA or balanced XLR style interconnect.

Now, there are many different styles, I should say, of subwoofers available. There are sealed, meaning there are no ports. There are ported subs using port, much like loudspeakers to augment their bottom end frequency response, maybe to give them a little bit more boom, when necessary. 

There are cylindrical subwoofers, there are multi driver subwoofers, but the basic premise behind any subwoofer, whether it’s powered on a single driver, multi drive,r ported, non ported, or what have you, is to recreate the lowest notes and or frequencies to better ground and enhance your home cinema experience.

HELP SETTING UP A SUBWOOFER

When it comes to setting up a subwoofer, there are many different theories. However I maintain like with any loudspeaker, a subwoofer does best when experimented with. So it really is important that you look at subwoofers no differently than you would any other loudspeaker. 

Meaning, their placement is just as critical as the time and energy spent placing your front channels, your centre channel or your surround channels. Now, you can put a subwoofer in a corner to reinforce its low frequency response. This is very common. And if you have a small subwoofer or a smaller space or maybe a subwoofer that doesn’t plunge in as low, placing it in the corner for something known as boundary reinforcement can help. 

If you have a subwoofer with, you know, great capability and you do that, it may prove to be too much of a good thing. So, again, critical experimentation and lengthy kind of playing around with what works best in your room is going to pay huge dividends down the line. If you have a subwoofer that can reach the lower depths, say 20 to 18 maybe even 15 hertz by itself, you’re not going to want a corner placement, but rather maybe placement two thirds into the room somewhere between your left and right speakers. 

If you want the cleanest possible bass than before, room reflections become an issue. Then you’re going to want to put this up pretty much as close to your listening position as possible. Again, experimentation is key, and no two rooms are alike. No two subwoofers are alike in this regard, so you really do owe it to yourself to experiment, play around and find what works best for you and your system. 

Another way to balance low end frequency response or bass response is to employ multiple subwoofers. Many subwoofers without getting too technical, allow for themselves to be daisy chained or connected together and treated as one. Now the benefits of having two subwoofers not only for more impact but it smoothens the bass response. Much like two speakers gives you a stereo image, two subs can create a more harmonious low frequency response.

In these instances, placing this up in the centre, front centre of your front wall and the centre of your back wall or maybe halfway along your right and left side walls creates this sort of stereo image, if you will. Again, whether you’re employing 1,2,3, or even four subwoofers , experimentation is key when setting up a sub in your system. 

SETTING UP A POWERED SUBWOOFER

Let’s say for instance a powered one. In this regard, you’re going to be connecting it to your AV receiver or preamp in one of two ways. Either through its subwoofer output or via its LFE output. Now, LFE is its own channel, meaning the sound designers who make movies for a living are putting information exclusively to that LFE channel. 

You need to go into your AV receiver, AV preamps settings menus and make sure that if there are two options , whichever you choose, you set the corresponding setting inside your AV preamp or receiver appropriately. This can mean setting it to LFE plus bass, or bass plus LFE, or both, or, you know, however it is dictated by your particular product. 

Once you have it set up properly, whether using 1,2,3 or four subwoofers, once you’ve connected them to your equipment properly, it’s important that you level match their output to the rest of your speakers, and this can be done in one of two ways. Many subs come with a volume dial or knob of some torque; typically located on the back of the subwoofer, adjusting this using the tone, or the test tone put out by your AV preamp or receiver to match your main centre and rear surrounds in terms of level is vital. 

You want your sub to play at the same level as the rest of your loudspeakers in order for everything to kind of blend in and play nicely together. So, you’re going to want to take an SPL meter, I use a radio shack SPL meter, and you’re going to want to play the test tone from your AV receiver and take a reading for your left or right main speaker; generally a test tone comes in anywhere between 72 and 75 db. 

Once you’ve established what your front speakers are outputting, send that same test tone to your subwoofer and match it using the volume dial either on the subwoofer or in your AV preamp or receiver; many of them have a level adjustment functionality to them in which case you can set the subwoofer to fixed or say unity gain, and then adjust in the AV preamp or receiver from there. 

Once you have everything level matched. It’s important to set your subwoofers crossover point; again you can do this at the subwoofer or in most cases you can do this at the AV receiver. I recommend doing it at the AV receiver which means you’re going to want to set your subs crossover point to fixed, or to outboard or whatever the setting may be where it’s telling the subwoofer that it’s crossover is going to be handled via another device.

From there, go into your AV preamp or receiver after setting the levels and set your subs crossover appropriately. The crossover basically is the frequency in which the sound is going to stop the low frequencies which are going to your main speakers, and then be routed to your subwoofer. In THX setups, this crossover point is customarily 80 hertz. 80 hertz is a great jumping off point but not necessarily a cure all. So you’re gonna want to play around a little bit. 

And that really is the basic overview of what a subwoofer does, how to get the most out of it, and how to properly set it up. Now there are more advanced methods of extracting the absolute pinnacle performance from a sub using outboard equalisation, or even automated equalisation systems like Odyssey that are built into many of your AV products. And we’re going to get into that in a future post I promise. But for now, I just wanted to cover the very basics to set you on your way and get you playing around with extracting the most performance from your sub.

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