Bass! Low, deep, thundering bass! With the ready availability of high quality sources and well recorded software, much of today’s music demands much more power and impact than many otherwise competent music and Home Theatre systems can handle. As a result of this, sub-woofers have become the answer to a question which simply was not considered in the past – should I look at getting a sub-woofer?
A sub-woofer is a single speaker enclosure housing a bass driver, designed to reproduce only low frequency information. They are designed to augment the bass of an existing pair of loudspeakers, which, when mated to a sub-woofer, are called satellites. Some manufacturers make specific sub/sat systems, while others make sub-woofers which can be tailored to function with any pair of speakers. The lower the frequency, the greater the amount of power required to reproduce it. The result is that most high quality sub-woofers require additional amplification. This may result in additional expense for you if the purchase of an extra power amplifier is necessary. However in most cases when purchasing an add on sub-woofer, the amplification is built in to the enclosure, saving cost and ensuring a proper match between the demands of the speaker and the power output of the amplifier. The sub-woofer must know when to cut in and out, which requires a piece of electronics called a cross-over. Your home speakers have a cross-over built in to each of them to distribute the sound, as required, to the tweeter, midrange or woofer. A cross-over in an add-on sub-woofer will be one of two types – active or passive. Active means that the frequency at which the sub-woofer starts to work can be adjusted, allowing us to tailor the sub to any set of satellite speakers. In matching a sub-woofer to a set of speakers the cross-over point should be set to reproduce the missing information, namely the low frequencies that the speakers are incapable of producing. Passive cross-overs are pre-set and work well in some situations, but they are inflexible and consequently cannot always attain “seamless” results (not being able to hear when the satellites leave off and the sub takes over). Since bass is monaural and because the lower the frequency the more omni-directional it becomes, (you can’t detect the origin of the source) placement is very easy. It is therefore not necessary that the sub be placed between the satellite speakers, unless that is where you would like it to be. Some set-up rules of thumb do apply however. The amount of volume we get from a sub-woofer can be controlled by its placement within the room. When the sub is placed within the length of its cabinet of a standing surface (walls, floor ceiling etc.) the sound pressure will increase by 3 dB (a noticeable amount). Therefore a sub placed in a corner, next to two walls and on the floor, will have a lot more volume than the same sub placed in the middle of the room. Most amplified subs have a volume control to provide compensation for room positioning. When this control has been set for the position you have chosen in the room, the volume knob on your main amplifier will now operate the volume on your sub-woofer and satellites together. Hook-up to an existing system can be achieved by using the variable or sub out connector on your amplifier, or the regular speaker line connectors. An RCA patch cord is used for hook-up to the variable or sub out connection, which will now automatically control and vary the volume of the sub-woofer. The tape output or fixed pre-amp out will not allow you to control the volume of the sub-woofer from the main amplifier. The easiest hook-up is with the speaker line connections. Simply run your existing speaker wires which now go to the main speakers, into the sub-woofer. Then run a second pair of wires from the sub to the speakers, which then places the sub between the amp and the speakers. Be warned! Once you have tried a sub-woofer it will be difficult to listen to your system the way it was before, because not only will you get much deeper and richer sound from any tape, CD or home theatre movie, but the addition of the sub-woofer will lessen considerably the load on your amplifier, providing additional surplus power for your main satellite speakers. In addition, since the satellites are not now required to work at reproducing deep bass, they are free to concentrate on providing midrange. This is one of the benefits people do not expect from a sub-woofer and are pleasantly surprised when they hear a much clearer midrange, most noticeable when reproducing the human voice. The addition of a sub-woofer to a stereo or home theatre system, can provide one of the best values available in add-on electronics today.