Simplistically, a subwoofer is a speaker designed to reproduce bass sounds at 80hz or less.  It is a critical component of your home theater system, and when setup correctly, adds fullness and depth to your music, as well as a sense of realism to your videos.  Incorrectly setup, your home theater system subwoofer can sound like the subwoofer in your neighbor’s son’s Honda, i.e., a special effects device with rumbling bass creating an absence of clarity, that simply vibrates the pavement, and pretty much drowns out most sound within ten feet of the car.

Setting up your subwoofer, and for that matter, your entire surround sound system is not something that in most cases can be totally accomplished in a single afternoon.  The subwoofer itself will take a week or two to “break in”.  The process of setting up your surround sound system involves connecting all speakers, making some minor adjustments on the subwoofer and in you AV receiver’s configuration program, running an automated setup program (if your AV receiver has one built-in), and placement of your subwoofer.  So far, all of this can be done easily in an afternoon.  The step that takes the most time is the final “tweaking”.  In this process, you take the results from your automated setup, and make adjustments that sound best to you.

How Should A Well Configured Home Theater System Sound?

Some might say like a movie theater, and I would say that outcome would be a stretch.  For most of us, home theater systems are set up in rooms designed to be living spaces, whereas the theater was designed to be, well…………, a theater.  What variables affect sound quality?  Besides the type, caliber, and power of the hardware you have purchased, there are plenty of variables that will affect the sound quality of your system:  the type and quality of media you are using to reproduce sound; the size of the room; height of its ceiling; composite of the walls, floor and ceiling; the number and size of the room’s windows and doors, the amount and placement of the room’s furniture, and this list can go on, and on from here.   Won’t THX certified equipment give me the best sound possible?  It certainly won’t hurt, but there are still a good number of acoustical variables to deal with.   Alas, the outcome of all your purchases, and configuration on your home theater system is subjective, and it boils down to what you like.

You can determine how well your system is sounding by using two very sensitive tools that are able to capture frequency responses from 20hz to 20,000hz, are omnidirectional, and both are connected to one of the most powerfully designed computers on the planet.  If you guessed I am talking about your ears and your brain, you are correct.  Ask yourself these questions:

1. From where I am sitting (assuming you are sitting in your normal listening/viewing location), can I hear both distinct and discrete sound from my Left Front, Center, and Right Front speakers?  Does sound transition seamlessly from one speaker to another (an example would be watch a movie with jet plane flying from right to left.  You should hear the plane travel from right to left progressively from your front speakers)?
2. Do my Rear Right and Left surround speakers produce clear and audible ambient sounds, and can I still hear my front speakers when the surround sound speakers are operational (some exceptions from your media might be car wrecks, explosions, etc, as the nature of the sound might be designed to emanate from the rear surround speakers)?
3. Can I hear speech clearly from my front center speaker (unless there is some action in the movie that would normally prohibit hearing sound, as in real life, i.e. a loud explosion)?  Do I have to keep adjusting the loudness of my center channel speaker so I can hear it?
4. Can I hear clear bass response, without unnecessary “rumble”, and is it unidirectional (you can’t point to where the base is coming from)?
5. Are mid-range sounds clear?
6. Do my speakers provide an immersive theatrical experience (Violins sound like violins?  Rumbling volcanoes sound real?  Diesel trucks?  etc.)

If your answers to all the above is yes, then your system is correctly set up.  Let’s get the process going:

Connecting Your Subwoofer.

Subwoofers connect to your receiver in two different ways:  Line Level and Speaker Level.  With your subwoofer and AV receiver turned “off”, do one of the following:

Line Level.  This is the preferred way to connect your subwoofer to your receiver.  Typically, this is a monaural signal. You will find a single female Sub “out” jack at the rear of your AV receiver, using a subwoofer audio cable, connect to this jack and to the female RCA jack on the rear of your subwoofer labled:  LFE, Direct, or Bypass.

Speaker Level.  This type of connection is rarely used anymore.  Should this be your only option, connect you left front speaker wire from your AV receiver to the left front speaker “IN” connector on the rear of the subwoofer.  The right front speaker wire follows the same process from your AV receiver to the subwoofer’s right front “IN” connector.  (Note: Each speaker wire consists of two separate cables, one Positive, and one Negative.  Match the Positive cables to their respective Positive connectors, and the Negative cables to their respective Negative connectors. A mismatch here could damage your speakers and/or your system.) Now run speaker wire from the sub’s left and right “Out” connectors to their respective Left and Right speakers.

Verify.  Check your owner’s manual for both your subwoofer and AV receiver and verify all connections are properly made before your turn on any power.

Initial Configuration

Subwoofer

1. You will want your AV receiver to control configuration of your subwoofer.  To do this, on the rear of the subwoofer, disable the sub’s Crossover Network by turning the control knob all the way to its maximum setting.
2. Again, at the rear of the subwoofer, set the Volume Knob to medium setting.

AV Receiver Setup Menu

1. Most AV receivers with a MSRP over $300 have a built in surround sound configuration program.  A provided microphone is placed at designated locations in your room.  The AV receiver transmits a sound, speaker by speaker.  During this process, the AV receiver determines the size of your speakers, number of speakers, if a subwoofer is attached, distance speakers are from your normal listening area, and calculates a decibel setting for each speaker.   One popular built-in program is Audessey.  If your receiver has such a program, run it now.  UPDATE:  (02/27/2015) If you use Audessey, set Sub Woofer  crossover all the “up” at 120hz, volume at 50% (the 12 o’clock position), and if there is a low pass or LFE filter, set it to off.
   
2. If your receiver does not have such a program, go to Components, below.

Components

1. If your TV is setup to a satellite or you get your television through a cable, you probably have some sort of set top box or PVR.  If you are connecting any of these devices through your AV receiver, then you need enter the devices setup menu, and set sound to bitstream, or digital output.
2. If you have a DVD player, Apple TV, etc. be sure to set them for digital output as well.

Subwoofer Placement

A very inclusive article about subwoofer placement can be found at Online Audioholics Online Magazine,  (by Alan Lofft — last modified August 25, 2010) http://www.audioholics.com/tweaks/speaker-setup-guidelines/subwoofer-placement-guidelines  

This is a portion of the article:

• “The worst place for a subwoofer is in the middle of a room.
• The most difficult room shape is square, so if you have the flexibility to choose which room you’ll use for home theater or you are building a new home and designating a space for home theater, avoid rooms with equal dimensions.
• As you move the subwoofer closer to a wall, the bass output will become stronger.
• Bass output will be maximized as you push the subwoofer into a corner.
• The closer you sit to a wall, the more pressure your ear will pick up and the greater the bass intensity will be, but it may become uneven– alternately boomy or anemic as you move in either direction.
• Adjusting the distance of the couch or chairs relative to the walls and/or the subwoofer relative to the corner will almost always be beneficial in helping smooth out the deep bass heard at several listening locations in the room.
• Adding a second subwoofer won’t cure the problem of standing waves or uneven bass, but it will result in a greater number of listeners hearing smoother overall bass in more locations. Try placing the second subwoofer in a location near the wall opposite the first subwoofer.
• Avoid rooms with concrete floors and walls. Walls where the wallboard flexes are more absorptive and produce fewer problems with “bass boom.” If you can’ t avoid concrete walls, add studs and one layer of wallboard to the walls of the room to further aid absorption.”

You may want to test several locations for your subwoofer.  Before you decide on media for your test, consider these facts for your media selection:

• Your selection should have full rich bass sound.
• You want to select media for your test with the highest quality of sound reproduction.  Do not use MP3’s, “ripped” DVD’s, or streaming video, as all of these formats have been compressed from an original source and as a result, there is a high probability that some elements of the sound tracks have been removed.
• If you are using a turntable and a record (yes, there are still those, me included, that love the sound reproduction from vinyl records), you will have an analog signal output.  You can set your receiver to a “Stereo” listening mode.  This should activate your Left and Right Front speakers, and your subwoofer. If you subwoofer is inaudible, try a PCM based listening mode, like Dolby Digital Pro Logic II, or DTS Neo:6.  Either of these two selections will activate your entire surround sound system.

Final Tweaking To Your System.

In this section, you will test some different variables against the automated setup you completed earlier (If you were unable to perform the automated setup, this section will provide some base line settings for you to “zero” in your speakers).  In your AV receiver’s speaker configuration settings menu:

1. Write down on a piece of paper the current settings for:  Speaker Size, Cross Over Network, and the decibel setting for each speaker.  As we are now going to test some different settings, your notes will allow to return back to the “automated” settings if you so desire.
2. Be sure the subwoofer setting is set to “ON”
3. Regardless of their size, set all speakers to “SMALL”.
4. Set the crossover network to 80hz (“sub” to 120hz).
5. Set Dolby Dynamic Range Compression or “Midnight Mode” to “OFF”.
6. Using the same media you used to test your subwoofer placement, listen to your surround sound system now.  Start asking yourself the  six questions listed above in “How Should A Well Configured Home Theater System Sound?”.  Again, mark down the new settings.
7. Check that your subwoofer is in Phase with the rest of your speakers (basically, the woofers on all speakers are going “in” and “out” at the same time.  You will find a Phase switch on the rear of your subwoofer.  Using your test media, play a few songs, flip the Phase switch to the alternate position. Now replay the same music. If you can’t tell any difference, the return the switch to its original position.  If you hear more base in one position of the switch over the other, keep the switch in the position with increased base sound.  I have found in most cases, there is no difference between the two Phase switch settings, but still, you don’t know if you don’t try.
8. Think of the crossover network’s function as kind of a traffic cop, sending high sounds one direction, and lower sounds another.  The you raise the settings in the crossover network, the more lower tones go to the subwoofer, and conversely, the lower settings, the more lower tones the front, center, and rear speakers will reproduce.  Typically, speakers of 2″ to 3″ have crossover networks set to 150hz to 200hz; speakers of 4″ to 5″ are set at 80hz to 120hz; and large speakers, 6″ or more, are set to 60hz to 80hz.  Also, subwoofers reproduce sound up to 120hz.  Armed with this information, what you want to do is find the best balance of sound coming from your speakers. Keep the subwoofer at 120hz.  A good place to start is to check the manuals for your speaker, as they often recommend a crossover setting, and may state as well any limitations on their speakers to settings that are too high.  In my case, I have Bose speakers, and the recommended crossover setting is 150hz, and after trying settings from 80hz to 200hz, 150hz was indeed the “sweet spot” I was looking for.  Play your test media, and choose a suitable crossover setting.  Note:  While you are testing the crossover network, leave your Speaker Size setting to “Small”.
9. The final test is the volume of your speakers.  For your subwoofer, play some action sequences from movies, and some of your “test” music media.  At this point, adjust the volume of the subwoofer from you AV receiver’s configuration menu.  There is no right or wrong level here.  The correct volume is personal taste, but be careful, as it is easy to get the bass too overpowering.  For the volume of the front, rear, and center speakers, go back to our original  questions at the beginning of this article.  A common mistake is that the rear speakers are either totally inaudible, or to the extreme they are too loud and over power the front speakers.  The proper balance is for each speaker to be clear and distinct.  My test for this (I’m not kidding) is watching a episode of NCIS.  The audio from this TV show has a lot of emphasis on the rear surround speakers, making sound reproduction from these speakers much louder than most TV media.  I adjust the rear speakers to a point where I can clearly hear the front speakers.  I know it’s not scientific, but it just works.

Summary

When properly configured, your surround sound system should provide an immersive listening experience.  There are a lot of different ways to get to that level of listening experience, but in the end, it boils down to personal taste.  Putting it all together is a fun and very satisfying process.  I hope this article has been helpful.