How important is a Subwoofer in a Home Theatre System ?

sub-woofer speakers

Your subwoofer is very important for your home theatre as it provides that impressive low bass rumble sound that dramatically enhances the sound of key sound effects - especially for crashes, explosions, and even background sound.   It is worth watching a movie and turning on and off the sub-woofer to experience the dramatic effect it has.  It really can enhance the total experience of a movie at home as it helps you achieve "audio immersion" and the "audio atmosphere" that the Surround Sound recordings were designed to deliver to you.

In fact you are materially letting down your multi-speaker system if you have not planned to install a sub-woofer. Your typical left and right primary may have an impressive bass response, but they won't be able to reproduce the very low frequencies of a good subwoofer.  Also, unlike most subwoofers, normal speakers do not have their own power source. Sub-woofers typically need to be plugged into power so they can really enhance the sound.

What is a Subwoofer?


A subwoofer is a speaker designed for very low bass frequencies.  These bass sounds are usually in the range between 20 Hz and 125 Hz.  At these levels sounds are often 'felt' as much they are heard - you will literally feel the couch vibrate and rumble!

Subwoofer speakers come in a variety shapes, sizes and enclosures and tend to be relatively large in size, between 20cm and 40cm in diameter (for the speaker).  A larger speaker helps achieve the lower bass sounds that other speakers cannot.  Therefore, once you include the casing for the speaker it is no surprise then that it can take up quite a bit of space in your listening environment.  And many enthusiasts complain of the low SAF (Spouse Acceptance Factor) of a large subwoofer box.  Well there are ways to hide your subwoofer with a bit of planning.

There are no fixed rules for placement of the subwoofer.  A free-standing subwoofer should be placed directly onto the floor to assist with the transmission of the sound from the subwoofer into a vibration that will be felt as well as heard.  Many claim that sub-woofers are non-directional - i.e. you can place them anywhere in the room.  This is not entirely true - the placement of your sub-woofer relative to where you sit can greatly enhance the sound you are trying to achieve.  The output can also depend on the shape and size of the room, and furniture placement.  You may also have to consider the SAF and the poor aesthetics of a big box with long cords in the centre of the room.

Poor subwoofer placement is a major cause of disappointment with Home Theatre performance. A little experimentation with subwoofer placement, and even with furniture placement, can often provide improved results.   Here are some tips that may prove helpful to improve the effect of your sub-woofer and also help hide it:

1. Place near a wall

By placing the subwoofer close to a wall, the low bass frequency sound waves coming from the rear and sides of the subwoofer case will be reflected from the wall. This will appear to magnify the overall bass level.

2. Place in a corner

Similar to the above, placing a subwoofer in a corner can also provide a perceivable improvement in bass.  The in-wall option as mentioned above can also be enhanced in this situation.

3. Mount it in the wall or ceiling 

Ceiling Speakers

There are now sub-woofer enclosures that are designed to be installed in the wall (or ceiling) so all you see is the front grill (which can even be painted to match the wall colour.  The internal casing is designed to reflect the sound waves out from the wall.  With a bit of planning to ensure you have the depth for installation, have power and a high quality subwoofer cable (RCA cable) to the installation point, you will have a truly minimalist yet powerful sound system.  Hey where did that sound come from?

4. Place within the front audio field

Try to avoid placing the subwoofer on the side or the back of your listening environment. This point will be more significant for larger and more powerful subwoofers (and obviously at higher audio levels).  Putting the subwoofer behind your couch may work for you, but at the output levels required to "make it work", your neighbours may be less impressed.


5. Hide it under the couch or coffee table

Where the Spouse Acceptance Factor is a major consideration, then hide it altogether!  I have seen (actually felt) a subwoofer under a couch and it truly puts you in the action of your blockbuster movie as the couch rumbles!  Many couches and coffee tables have cavities that can be easily exposed to accommodate a subwoofer.  In my recent renovation we poured a new polished concrete floor, but not before we ran power and a high quality subwoofer cable (RCA cable) to a discrete floor box where the couch and lamp table will be.  I have ordered a long flat style subwoofer that will be hidden under the couch (or table) - my wife will never know its there (but will feel the incredible sound).

6. Use two smaller subwoofers rather than one large

If one large central subwoofer is not practical, consider having two slightly smaller subwoofers enclosures placed on the left and right of your front audio field.  This can provide symmetry which is visually important and can help with the SAF too. Also, having two subwoofers will get rid of any directionality you might otherwise experience.

7. Use a dedicated subwoofer amplifier

Many Surround Sound amplifiers have a line level subwoofer output for precisely this purpose. You run a subwoofer cable from your main amp to the second dedicated mono or stereo amp for the subwoofer which drives your subwoofer speaker(s).  Once you have tweaked the level on this subwoofer amp, you can usually set and forget, since the actual volume level control will come from the main Surround Sound amplifier.