After years of sustained development of the ATH design software (many features of which remain unpublished), it is now possible to design even the Opus 12 with replaceable throat sections. This primarily allows different throat diameters to be used while keeping the main body the same — manufactured only once — all while preserving the acoustic qualities of the original design. The results of this approach are presented as the 'V-ERS' version. The design utilizes OS-SE profiles combined with extended-throat techniques, improving acoustic loading beyond what is normally possible.

Two version of this horn are available — free-standing and baffle-mounted. Both use the same throat parts.

The mouth size chosen for this versatile version is 640 x 450 mm (W x H), noticeably smaller than the original Op.12 design. It should match well to a single 18" or a 15" woofer - probably much more affordable to many.

It should be noted that this horn (like the rest of the Op. 12 range) is not particularly well suited for multi-seat cinema use, as it actually doesn't give quite constant coverage over a large area to minimize seat-to-seat variations (especially the high-frequecy drop-off). Instead, it was designed rather with a single audiophile listener in mind. However, it's still not overly beaming, and within the listening window (±30° H, ±20° V) it provides a very smooth and clean response, as the high-resolution data in the figures below illustrate. Importantly, the overall radiated sound power rises only gradually toward the high frequencies, which helps the reflected and reverberant sound in the listening room remain neutral. There's virtually no diffraction apparent.

As for compression driver selection, drivers with low exit angles should be used. Although it is always possible to design a throat section with a wider opening angle (new adapters are available on special request), doing so will reduce the acoustic loading — one of the main design goals of this horn. Rather than using a wide-opening (high-expansion-rate) driver, it is much better to modify such a driver by inserting a slow-expansion ring into its (conical) exit section, effectively turning it into a smaller-throat driver that is well suited for the Op. 12 horns. For example, many 2" drivers can be modified this way and used essentially as slow-expansion 1.4" - 1.5" drivers, whatever the phase plug exit diameter happens to be. (Throat pinching is generally not recommended.)

Compression drivers with phase plugs terminating up to the exit aperture can be in general considered directly suitable to be used with the Op.12 horns.

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