Waveguide Bodies

A400G2 ⌀400 x 130 mm

A460G2 ⌀460 x 160 mm

A520G2 ⌀520 x 174 mm

E520G2 ⌀520 x 174 mm

Throat Adapters

1.4" / 36 mm
T520-36-STD-1	T520-36-EXT-1
1" / 25 mm
T520-25-STD-1	T520-25-STD-2	T520-25-STD-3	T520-25-EXT-1
Special
T520-ROSSO-STD	T520-DF10-171K

ATH Gen2 Waveguides

This set of kits offers a unique solution to the DIY audio hobbyists, especially to those who like to experiment in a long run. The main, big and the most demanding "mouth" parts need to be made only once, while the adapters for different throat sizes, exit angles, extensions and shapes are easily replaceable. The kits are provided as STL files for 3D printing, and for the axisymmetric waveguides also with the full Ath scripts allowing further custom modification and BEM simulation.

At the same time, these waveguides offer an excellent acoustic performance, basically free of diffractions and reflections - a truly remarkable feature. The A520G2 is a kind of "no-compromise", relatively large waveguide, while the A400G2 is basically just a smaller version, still performing extremely well though. Both waveguides can be used with a wide range of compression drivers. A460G2 is the latest iteration, maintaining virtually the same overall performace of the large A520G2 down to around 600 Hz, but in a noticeably smaller format (visually, even such reduction of size can make a big difference). It can be recommended for 1" drivers, where bigger devices offer typically only a negligible advantage. E520G2 is a segmented version (see [3]) of the A520G2. Performance wise, it is on par with the axisymmetric version, with possible practical advantages. (If in doubts which one to choose, pick the A460G2 - it doesn't lack anything of its bigger siblings, yet being smaller.)

The horn profile is a R-OSSE [1] variant for the common part, while the individual throat adapters are of more general, smoothly connected shapes. Those throat parts marked as 'STD' are the standard (shortest), non-resonant types. The parts marked as 'EXT' are extended-throat versions, improving on the low-frequency capabilities [2]. Each combination is optimized to provide smooth, well-controlled directivity with a mildly rising directivity index through the whole operating range. Figure 1 shows a (BEM-calculated [5]) benchmark of the performance (T520-25-STD-1 adapter shown).

The whole range of the T520 adapters can be used with all the waveguide bodies. The corresponding ANSI/CEA-2034-A [4] reports for some chosen combinations are shown in Figure 2. The data for these reports has been normalized for 5° off axis, meaning that they represent the performace of the device with the frequency response at 5° equalized to being perfectly flat.

It is to be noted that the directivity (and all the curves in Fig.2) stays virtually the same for all the throat adapters, irrespective of a compression driver used or its exit size. There may be small differences above ~15 kHz but overall the performance is very similar. This is possible because the waveguides were designed mainly with 1.4" drivers in mind, with a usable crossover frequency around 500 Hz and with the overall directivity adjusted accordingly. Smaller drivers with 1-inch exit can also be used, with the possible advantage that the top octave may be a bit cleaner. The extended-throat ("EXT") adapters still allow even some of the 1" drivers, if not most of them, to be used down to perhaps 600 Hz.

Figure 3 shows normalized throat acoustic impedance for both A520G2 and A400G2, simulated in free air, using the standard 1.4" adapter. Maybe not anticipated by common intuition, the throat impedances are basically the same - they are simply not dependent on mouth size in these kinds of waveguides. In fact, no matter how irrelevant, the low-frequency point⁽¹⁾ of the smaller waveguide is a tiny bit lower in this case.

Acoustic measurements with various drivers are available on the measurements page.

References