EXAR 400 comes directly from the original extended throat experiment. It is a R-OSSE waveguide in its basis, utilizing the new segmentization technique, further improving upon the original EXAR 400-25 model.

The throat extension is using a cubic Bezier curve, instead of a straight cone of the original design, and the throat opening angle is now 0°. The waveguide is thus especially suited to be used with a 1.4" driver with an added custom reduction to a 1" exit (the so called ring plug). The extension allows the waveguide to be used safely from around 600 Hz with the directivity of a typical 1.4" controlled-directivity throat.

The STL kit has been simplified and now it uses the standard ATH mounting system. Some additional support under the mouth may be a good idea (not a part of the kit yet). The kit consists of a base, six identical petals and a mounting flange.

Note: The original 400-25 kit is still included in the package.