A well-tuned subwoofer can make even a modest music or theater system sound spectacular. On the other hand, a poorly integrated subwoofer becomes nothing more than a distraction. Even the biggest bassheads out there will admit that a properly setup subwoofer makes the music and movie experience better. If your subwoofer is setup properly, you will not necessarily hear the bass coming from the subwoofer itself but will instead sense the bass in the room rather than hearing it come from a specific point (the actual subwoofer). Nothing is more distracting than a subwoofer that isn't integrated properly.
With all of that in mind, here are a few suggestions on how to set your subwoofer up to get the most out of your system – regardless of size and cost.
Use Your AVR’s auto-setup routine
Most modern AVR (audio-video receivers) have a built-in room setup app that will do most of the math and hard calculations for you. To get the best response from your AVR’s setup program, set the included microphone up on a stand or tripod in your main listening position with no obstructions around it – then leave the room while the program runs. Sophisticated programs will have you do this several times for each listening position.
If you have to enter them manually, be as accurate as possible when entering the distances of each speaker into the setup program. With accurately set distances, sounds that are supposed to come from different places at different times will be processed to arrive at your ears when they are supposed to. For example, a helicopter flying from the rear to the front of your room will sound more cohesive if the distances between the rear and front speakers are accurately set. If the distances are not accurate the sound may become disjointed or disconnected from the video material.
Of course, once you’ve run the setup program, feel free to experiment to get things dialed in to your taste. You can always run the program again to recover the system-calculated settings if you get too far into the weeds.
Set the Volume Properly
We all love massive amounts of bass. But too much bass is, well, too much! Play a song or a bit from a movie you are familiar with (and that has lots of bass) with the subwoofer gain set all the way down (infinity). Slowly adjust the subwoofer gain to the point where you can hear the bass begin to fill in the bottom end. THEN STOP! That’s it, that’s all the bass you need. It may not be all the bass you want but that’s a personal choice. Keep in mind, when a song or soundtrack to a film is mastered the engineers and directors put in the amount of bass they feel is necessary – in relation to all of the other frequencies – to convey the message or emotion of the passage. If you’ve set the subwoofer volume properly it will be loud and subtle as designed and it will integrate with the entire program or passage as intended.
Set the Crossover Properly
George Lucas and his merry band of geniuses over at THX set the standard crossover frequencies for movies and theater at 80Hz. In almost every case, that frequency will work just fine. However, if you want to tweak a bit to suit your tastes, or get the most out of your speakers, here are a few simple rules to follow:
If you look at the specs for our LS50 you’ll see two different low frequency specifications, -3dB and -6dB. The -6dB frequency is the point at which the speaker loses its useable low frequency response. There will still be frequencies present below this frequency but they will be diminished to the point they are no longer actually heard by most listeners. The -3dB frequency is the point at which frequencies begin to gradually diminish – they’ll still be there but just not as loud as frequencies above that point. As you move lower from the frequency the greater the diminishment. The -3dB frequency is the frequency you want to use when setting your subwoofer crossover – in the case of the LS50 that would be 79Hz. Some will say that you should set the crossover point 10% above that -3dB frequency, but with decent quality components it’s really a matter of taste rather than a hard and fast rule. Again, find the suggested crossover setting and experiment from there.
NOTE: The "Crossover frequency" specification in the above picture gives the frequency for the internal crossover between the midrange driver and tweeter and is not related to this discussion.
If you hear an unnatural bump at frequencies around the crossover setting, try lowering the crossover point. Conversely if you notice a definite loss of frequencies around the crossover point try raising the crossover point. In either case a few Hz either way should do the trick.
Set the Phase
Without getting into a whole bit about phase relationships (see KEF Blog: How To Get the Most Out Of Your Subwoofer: Phase and Positioning for more detail) simply experiment with the phase control on your subwoofer and go with the one that sounds best to you.
As with everything else in the audio world, it’s all really a matter of taste. You may just want to bask in the glory of rafter shaking bass and nothing else but if you want a seamless integration of all of your speakers these tips may help you get even more enjoyment from your system.