General Advice

LMS stands for Loudspeaker Management System (LMS) and is essentially a active digital crossover.

An active crossover is needed when using different cabinets. For instance, a system using Piglet 212 cabinets with Zeus 4 cabinets. The active crossover splits the frequency and assures that each loudspeaker is just playing in its optimum frequency range.

The LMS also gives you digital control over the equalization, delay and peak limiting. The equalizer or EQ allows the soundsystem to have a flat frequency response in any venue. The delays ensure that all the loudspeakers are working in time and phase with each other even if they are in different positions. Finally the peak limiters help protect your soundsystem by stopping the amplifiers from clipping.

Here are the correct LMS settings for use with Traction Sound loudspeakers.

Crossover Filters

The crossover slope ranges from 1st Order (6dB/Octive) to 8th Order (48dB/Octive). The higher the order the more effective the crossover is at blocking frequencies.

There are main types of filters commonly used in crossovers. These are Bessel, Butterworth and Linkwitz-Riley. Different filters affect the audio signal in different ways.

Bessel filters are designed to have linear phase response at the crossover frequency. This means they keep the wave shape over the crossover filter. There is also a slight dip in amplitude at the crossover frequency when the high pass output is summed with the low pass output.

Butterworth filters have flat frequency responce over the passband. This results in a small peak in amplitude at the crossover frequency when high pass output is summed with the low pass output.

Linkwitz-Riley filters are designed to have a smooth amplitude when summing the low pass and high pass outputs. The gain at the crossover frequency will be 0 dB with a smoothly changing phase response.

We would recomend using 4th Order (24dB/ Octive) crossover slopes with Butterworth filters for bass and Linkwitz-Riley filters for mid-range and treble.

LMS Choice

There are different LMS more suitable for different applications, such as touring and install. Touring LMS tend to have access to settings on the front panel. Install units often don't have front panel controls and instead are controlled from a computer or remote control to stop unqualified people tampering with settings. Most LMS will have presets for common soundsystem configurations for you to use as a starting point. You should also be able to save your own preset so you do not need to set everything up again at the beginning of each gig.