Line Arrays

For line arrays we offer a broad family of proAMT drivers – from the classic lengths of 6, 8, 10, 11.5 and 12 inches to a 4-inch variant that can be cascaded and thus joined together to form radiators of any length. This makes it possible to cover different sizes and application profiles – from compact installations to large arrays with long throw.

Chamber volume

In principle, three designs are available in each driver length, differing mainly in the volume of the rear damping chamber. This volume determines the relationship between usable frequency range, crossover frequency and reserves:

The smaller the rear volume, the more restricted the frequency range towards the bottom – at the same time, the maximum possible sound pressure in the working range increases.

The larger the volume, the lower the driver can be integrated and the lower the crossover frequency can be chosen – however, the reserves in the lower part of the transmission range decrease accordingly.

In practice, therefore: the lower the desired crossover frequency, the more likely the variant with the larger chamber volume will be preferred – depending on the midrange drivers used. Conversely, the very flat variants show a pronounced rise in the frequency response in the lower part of the transmission range. If this rise is corrected digitally, additional reserves can be made usable precisely in this range.

For quick orientation, we use the following designations for the rear housing shapes:

• R = largest chamber (largest volume)
• 2F = medium chamber
• 1F = very flat design, closed at the rear, without an additional chamber

Magnet volume

In addition, two magnet systems are generally available for each variant, differing mainly in magnet volume and thus in sensitivity. Here it is worth evaluating the behavior not only from datasheets but in practical terms – because experience with compression drivers cannot be transferred 1:1 to AMTs.

At first glance, AMT drivers appear less sensitive than classic compression drivers. In practice, however, this is more than compensated for by the better acoustic coupling of the cylindrical wave. As a result, the energy required for comparable results is often considerably lower with the AMT than expected – although the raw sensitivity figures would suggest otherwise.

Measurement reports are available for most variants, produced by Four Audio in Herzogenrath. We are happy to support the design process with advice and – where appropriate – with samples, so that the right variant for crossover frequency, coverage and reserves can be found quickly.