High Frequency Drivers Announced
Our products will soon be autographed with our own high frequency drivers!

Since 1992 Lange Loudspeakers manufactures loudspeakers for professional applications. Differentiation from other manufacturers became in recent years more and more difficult. Many customers today ask for original manufacturer of components (drivers) mounted into loudspeakers, model of driver, impedance... High frequency drivers are in fact the heart of a loudspeaker. Despite the fact that there are several valuable selections that can be made between driver manufacturers, we have been always trying to give our signature to the products we design. After a careful evaluation of the inherent technical issues involved in high frequency driver design and manufacturing we decided to invest during the last years the necessary resources in order to realize some reliable components that in the future will equip our products. We faced design issues related to magnetic structure design, phase plug design, sample production test and evaluation, diaphragm material selection as well as voice coil type to implement. A new production process had to be considered into the design phase in order to realize reliable components that are at least in line with the drivers we have been using successfully till date. Regarding an innovation grade we have done our best in order to design products that should offer some advantages, at least when used in our products...

We decided to start in January 2011 from neodymium magnetic structures designing them from scratch and, after having performed tests we have been encouraged by the results. A dedicated CNC controlled ultra-thin magnetic probe has been used to acquire data along magnetic gaps. Those test instruments are not simply available on web-stores, we had to realize them for our specific needs in order to acquire data with up to 10 micron resolution. We selected the most useful materials available for diaphragm domes and suspensions, designed them with the voice coil types that among our experiences best suit our targets. To be noted is the fact that the most reliable high frequency Diaphragm & Voice Coil makers are located in Asia. We do not claim to manufacture high frequency diaphragms. We rely on manufacturers that made them for most international brands during the past 30 years and that can be considered the best ones in the field. Forming process of a metal dome is not easy, it involves machinery skills, specific tooling and experience. Asian manufacturers offer such a broad selection of materials, adhesives, voice coil types and versatility that it would be non-sense and time waste to start producing those parts in house. Some manufacturers do so but the results are by far not comparable with Asian standards. Also production stability and repeatability must be evaluated when designing precision transducers...

The selection of aluminum as material for the 1475-8A diaphragm is the result of different considerations. We could choose between titanium, Mylar (or other exotic polymers), aluminum, beryllium, combinations of any of those metals with polymeric suspensions, different diaphragm suspension geometries. Titanium has some advantages, but most of them go in the direction of reliability; it is very robust, can sustain more power and is extremely resistant to corrosion, but 1,65 times heavier if compared to aluminum. Mylar (or polymer made diaphragms) are tricky. They impress at first but tend to cause listening fatigue with time due to a often too stiff diaphragm suspension. Aluminum is extremely light and robust. It is easy to work with and is a cost effective material. It offers excellent frequency extension thanks to his reasonable low mass. Beryllium is among the stiffest materials available and needs great care in the manufacturing process. However high frequency driver performance depends on the interaction of different aspects. Phase plug, magnet type, compression ratio, voice coil, diaphragm type, diaphragm weight, material and suspension. It is not true that Beryllium domes offer per se a better performance. Also there are not impressive performance specs that give indication of significant advantages, especially if compared to aluminum. Beryllium has 1,46 less mass if compared to aluminum, it is stiffer and sound travels at twice the speed into it. Speed of sound into beryllium is basically the main advantage as longitudinal speed of sound into the dome pushes resonant frequencies (bending modes) to higher frequencies. However anodized aluminum makes a very good figure as well and, if considering also price, aluminum remains an excellent alternative for HF driver diaphragms that are tailored on qualitative and faithful reproduction. What we have been considering into design phase is to stay away from resonant areas with phase plug slots in order to avoid excessive ringing imposed by diaphragm bending modes. We mapped the entire diaphragm locating the most stable sections and designed phase plug slots just below them. This approach resluted in a coherent frequency response with some remaining, well damped resonances.

The first functioning and reliable driver we made, maybe the first ever designed in Switzerland, is the 1475-8A. The number refers to the date of introduction 2014 (14), the voice coil size of the driver in millimeters (75), the nominal impedance of the driver in Ohms (8) and the material of the diaphragm, (A) that stands for aluminum. This driver is in fact different if compared to all other 75mm drivers on the market, starting form the 1" throat. Usually 75 mm domes have 1,4" or even 2" throats. The 1475-8A is the first 75 mm dome driver on the market that can be mounted on all horns available, from 1", to 1,4" up to 2". A smaller throat involves a higher compression ratio and enables a better high frequency extension. The 1475-8A has a remarkable frequency extension that ranges from 800 Hz up to 18'500 Hz. The phase plug has been designed in house. It is an annular type device that synchronizes the energy entering from different dome areas. The voice coil consists of aluminum flat wire. The weight reduction if compared to copper coils allows the moving parts of the 1475-8A to be almost as light as beryllium domes mounted on copper coils. The oxidation process of the entire diaphragm increases stiffness up to a level found in exotic ceramic diaphragms or magnesium alloy domes. The magnetic structure presents 15'500 Gauss to the coil, completely surrounding all wires with the same flux density (+/- 2,5% flux variation in the gap). We tested many magnets in our laboratory that present higher induction figures (20'000 Gauss or more) but the maximum field only encloses part of the coil. Also high flux magnetic structures are more unstable (+/- 15% or more flux variation presented to the coil). The 1475-8A is a true under-hang design with more modest induction but higher wire turns into the gap. This means that second harmonic distortion is reduced and better performance at frequencies below 1 KHz can be achieved. Also a very light moving assembly has already a natural high frequency extension capability; a more modest magnetic induction increases mid-range output by up to 3 dB.

The 44 mm voice coil driver family includes 3 types of diaphragm materials with dedicated phase plug. Clearly there is a broader selection in the 44 range since bending modes into diaphragm material as well as stiffness are not dominant design factors. Material type among our perspective is a more decisive factor in terms of application, efficiency and stability. All our 44 mm drivers have 0,68" outlets or throats. This means that we must inevitably realize new, dedicated horns for our drivers. And this is one important aspect that makes those drivers different. First of all they are relatively short. This means that acoustic energy travels trough a short phase plug that faces directly the horn instead of an adapter or a tube. This allows better directivity control of frequencies higher than 10 KHz because higher pressure is presented at the horn throat. The first section of the horn is in fact responsible for very high frequency directivity. A second advantage of a short phase plug resides in better distortion figures if compared to longer devices. A broad diaphragm material choice allows to select the best performance for each application. For example, a loudspeaker intended for external use at very high sound pressure levels is better fitted with a titanium diaphragm. Small mid-ranges may are better paired with a Mylar dome driver that has some advantages in the cross-over region. Aluminum diaphragms offer better quality, better frequency extension and very high efficiency as well. The 1444-8A/T/M drivers will soon equip a new series of loudspeakers with dedicated high frequency horn.

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