Choice of crossover filters

 

 

Choosing corssover filters is a very delicate thing - even if we use the best driver in the world it will sound poor if the correct crossover filter is not used too. Developing filters is an art of comrpomising. The challange is to make all parameters work perfectly - at the same time. The parameters usually looked at are:

 

• Phase linearity
• Transient response
• Frequency response

1. A first order filter provides the best impuls response and small phase errors, but the frequency response is usually difficult to optimize perfectly. An advantage is the low price.

 

2. For a long time, the 4:th order Linkwitz-Riley filter has been considered the best option. The advantage is the good frequency response and good phase behaviour. The drawback is the lack of good transient response, and also the higher price.

 

Transient/Impuls response = The signals way through the filter to the driver is affected in terms of amplitude

 

An example of a good compromise might be a hybrid between an active filter in the bass region, and a passive filter for the midrange and top end.

 

An active amplifier offers better filtering in terms of precision and slope, besides adjustable and at a low cost. Another good thing about power amplifiers connected directly to the drivers is that the filtering takes place before the amp. More adjustment options can be offered that are not possible with passive filters, such as phase, crossover frequency and level. The use of active bass drivers reduce the load of the main amplifier, causing less distorsion.

 

This kind of hybrid concept is for example what we have chosen for the 99 2.2 system.

 

Crossover frequency = the point where a driver is supposed to operate below or above. You can vary the crossover frequency of a subwoofer to determine how much of the bass region it should cover.