Our self are made in France by RAH Indel.
Our air self (ferrite cores increase the inductance but induce distortions) and copper. They come in four series depending on their section: TA, SA, LA and AD.
The larger the cross section, the less distortion the self will have on high intensities, and the less ohmic loss we will have.
The TA is reserved for tweeters cut on high frequencies.
The SA will be adapted to tweeters and mediums of small diameters.
With LA, we start to have more sections that will filter without distortion speakers requiring more energy.
Finally, ADs are the best option in high-end applications, where the reduction of ohmic losses in the filter is paramount. They will also be suitable for loud sound filters.