Here’s the problem: Because of the enormous power required to generate bass, the bass amplifier on stage will often be three to 6 times greater than the power employed by the electric guitar. For example, the Ampeg SVT is 300 watts while a Marshal 50 watt half stack can easily keep up. Once the bass is generated, it travels further and of course sends out a wider dispersion pattern, particularly at low frequencies.

In a typical club, the bass from the bass amp coming off the stage is often so loud, that it mixes with the bass signal from the PA. Because the two sound sources are positioned differently with respect to the front of house (FOH) mix position, they arrive at a different time and therefore become out of phase. This not only happens at the fundamentals, but also at the harmonics which of course send information to the brain such as slap, tone and localization. As the bass level coming off the stage increases, the resulting effect (called comb-filtering) makes mixing the sound al the more difficult. Unfortunately, when the stage volume exceeds the sound engineer’s ability to control the signal, the bass is often turned off (muted) in the front of house mix and the definition from the bass is lost for most listeners.

As it is impossible to solve all of the phase problems in a room, (due to reflections off walls and ceilings and seating position) the intent is to at least provide the mix position with the best sound possible so that the end mix is balanced. This is where the Phazer comes in.

A typical stage set up is as follows: The bass connects to a direct box which feeds the PA. The bass signal then goes to the stage amp. As the electrical signal from the bass is traveling from the DI box to the front of house travels at almost light speed, it will arrive, be mixed and sent to the PA virtually instantaneously. The sound from the PA system reach the engineer’s mixing position based on how far he is stationed away from the PA system. Sound travels through the air at 1130 feet per second. Let’s assume the mix position is 50 feet away fro the PA. This means that the sound will arrive in 56 milliseconds.

The sound from the bass amp will also be generated almost instantaneously but since the bass amp is positioned at the back of the stage, say, 15 feet behind the PA speakers, the bass signal will arrive at the same place some 17 milliseconds later. By slightly delaying the signal going into the PA system, we can time-align the two signals so that together, they sound better.