Your subwoofer is a critical element in your home theater system. The low frequency from the subwoofer is what puts the boom in an explosion, the rumble in a spaceship and the thud in a gunshot. However, even the biggest and baddest subs may not meet your expectations if they aren’t placed and set up properly.
“It’s a classic story amongst Home Theater Professionals – the client spends all this money getting a giant subwoofer to complement the rest of their system. But, when they sit down to watch a movie, the person next to them complains about too much bass, while others feel the bass is too weak.
– John Dahl, Director of Education at THX Ltd.
It could simply be a difference in personal preference, but more than likely it’s the room itself that is the root of the problem.
In layman’s terms, a Room Mode is how a room’s dimensions change the bass coming from a subwoofer. The frequency at which a room resonates directly correlates to its dimensions, acting much like a giant pipe organ. The result can be a change in both bass volume and tone as you shift your listening position from seat to seat.
To identify Room Modes, begin by placing the subwoofer in the corner of the room and play either music or a movie with lot of bass. As you move from seat to seat, listen for volume and tone changes. A rectangular room made of heavy rigid construction like concrete or cinder block materials will exhibit fairly obvious effects – you may even see a pattern, where the volume dips and peaks throughout the room. If lighter weight, more flexible construction materials such as dry wall are used, or the room is large and open, the effects will be less obvious.
If you’re looking to identify and correct bass mode problems, THX recommends you consult a THX Certified Professional.
Note that equalization is the last item on the list. Equalization works best if all the other solutions are applied first.