A Detailed Explanation Of The Aux-Fed Subwoofer Technique: Summary

Aux-fed Subwoofers were commonly used as an effect to enhance a live audio experience, the article titled A Detailed Explanation Of The Aux-Fed Subwoofer Technique, explains the benefits of how having an aux-fed subwoofer system can help eliminate low rumble noise and improve the sound of the overall live audio mix.

Setting up of an aux-fed subwoofer is a little different from a usual PA system setup. A typical PA system has a stereo mix sent from the FOH console through a crossover system, also know as a loudspeaker processor, where the signal is then divided into three different sections with the use of filters and is then delivered to it’s appropriate speaker. The crossover points for the speakers depend on the frequency response of each individual speaker. There is usually an overlap from one speaker to the next, so there aren’t any frequencies that are lower in level from the others. When the crossover points are set, the level for each section of frequencies shouldn’t be changed, because it will change the crossover points and the phase of the system.

An aux-fed subwoofer system is set with two loudspeaker processors. One loudspeaker processor is receiving signal from the stereo bus and the other one receiving signal from an aux send that has the low frequency dependent channels sent to it. The input channels sent to the independent subwoofer processor are post-fader and post-EQ, so any change made to those channels will be seen by both the mid, high and sub speakers. The channels that are typically sent to the aux-fed sub are the low frequency instruments such as the kick drum, floor tom, and bass guitars. Most of the important elements of those instruments are in the lower sub frequencies. This technique helps improve the overall sound of the mix.

The technical benefits of using an aux-fed subwoofer, is that low frequencies from other microphones do not go to the subwoofers at all. By creating a signal path where only assigned input channels can go to, removes the unnecessary low rumble noise that doesn’t belong in a mix. This technique removes the low frequency effects of male vocals using dynamic cardioid microphones, Plosive consonants from speech, and microphones that might pick up sounds of wind and air conditioning rumble. A high pass filter can be used to diminish the low frequencies from input channels, but multiple microphones on the same stage will only reinforce each other and increase the low frequency content of the overall signal.

The aux-fed subwoofer technique can be used for many different music genres and applications such as, rock, R&B, ethnic music, and outdoor events. There are some applications that shouldn’t use the aux-fed subwoofer technique because it disturbs the natural emotion and content of the music. An example is an acoustic jazz band. The low frequencies from the piano and drums are less dense and the sub frequencies boost the musical content.

The aux-fed Subwoofer technique can be a wonderful musical effect but it also has it benefits in improving the technical side of live productions and prevents damaging of the speakers.