ATH Gen2 Waveguides

- All numerically optimized with a proprietary EAS algorithm, using R-OSSE[1] profile -
- Extremely low diffraction, no mouth reflection -
- Exemplary smooth directivity without pattern flips or midrange narrowing -
- Free of any near-cutoff issues of the historical designs -
- Available as DIY kits for 3D printing -



Measurements Page




A400G2
⌀400 x 130 mm
(⌀15.75 x 5.12")

A460G2 / E460G2
⌀460 x 160 mm
(⌀18.11 x 6.30")

A520G2
⌀520 x 174 mm
(⌀20.47 x 6.85")

E520G2
⌀520 x 174 mm
(⌀20.47 x 6.85")

Throat Adapters

Part No. / Link Input ⌀
[mm]
Low-frequency point (1) Input angle (2) Length
[mm]
Driver mounting (3)
[mm]
T520-25-STD-1 25.4 670 Hz 12° 61 4xM6/⌀76 + 3xM6/⌀57
T520-25-STD-2 25.4 740 Hz 31° 46 4xM6/⌀76 + 3xM6/⌀57
T520-25-STD-3 25.4 720 Hz 22° 52 4xM6/⌀76 + 3xM6/⌀57
T520-25-EXT-1 25.4 440 Hz 3.2° 135 4xM6/⌀76 + 3xM6/⌀57
T520-36-STD-1 36 580 Hz 8.8° 41 4xM6/⌀102
T520-36-EXT-1 36 360 Hz 150 4xM6/⌀102
T520-40-STD-1 40 530 Hz 46.5 4xM6/⌀102
T520-50-STD-1 50 500 Hz 12.5° 10 4xM6/⌀102
Part No. / Link Matching
Compression Driver
Input ⌀
[mm]
Low-frequency point (1) Length
[mm]
Driver mounting
[mm]
T520-ROSSO-STD SB ROSSO-65CDN-T 26.9 645 Hz 46 4xM6/⌀102
T520-DF10-171K Lavoce DF10.171K 25.0 680 Hz 60 4xM6/⌀76
T520-JBL2450 JBL 2450 38.1 530 Hz 40.7 4x6.6mm/⌀82.5
T520-ND3N 18Sound ND3N 36.0 540 Hz 47 4xM6/⌀102
(1) Frequency at which the throat acoustic resistance reaches 20% of its asymptotical value.
(2) Total angle value.
(3) Adapter-to-waveguide mounting is always 8xM6/⌀102mm (only 4 bolts are used in some of the adapters).

ATH Gen2 Waveguides

This set of kits offers a unique solution to the DIY audio hobbyists and audiophiles, 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.

Although being "universal" to a large degree, these waveguides offer excellent acoustic performance, basically free of diffractions and reflections. The frequency responses within the whole listening window are virtually identical - a truly remarkable feature and an evidence of the absence of any strong diffraction effects.

The A520G2 is a kind of "no-compromise", moderately large waveguide, while the A400G2 is basically just a smaller version, still performing extremely well though. 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. It can be recommended for 1" drivers in general, where a bigger device offers 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 used 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, short, 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).

Although it stems obviously from its axisymmetric nature, it's worthwhile noting that the data presented here describe the behaviour of the horn everywhere in the far field. In other words, a complete picture is shown. Don't get fooled by the so often presented cherry-picked data, where only a single selected plane is considered, even if the device itself is highly asymmetrical (and so is inevitably its acoustic performance). It's very rare that a complete picture is shown when there is good and not-so-good data to be choosed from :)

Moreover, these devices are round not because it's just easier (it is to a degree), but mainly because it actually turns out that the round shape simply provides the best acoustic results. They can be virtually perfect when optimized, and here's the evidence.


Fig.1 - Calculated polar map (A520G2)

The whole range of the adapters can be used with all the Gen2 waveguide bodies. The corresponding ANSI/CEA-2034-A [4] reports for some chosen combinations are shown in Figure 2. For convenience, the data for these reports has been normalized to 5° off axis, meaning that they represent the performace of the device with the frequency response at 5° equalized to being perfectly flat.



Fig.2 - ANSI/CEA-2034-A reports (BEM simulated)

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.


As a "spin off", the A460 horn has been designed, based on the A460G2, but already including a throat section and with the optimization boundaries loosen to not be limited by the existing Gen2 bodies. The result is a waveguide designed and optimized from throat to mouth as a single R-OSSE curve[1]. The opening angle of the 1" throat was set to 21.7°, matching Peerless DFM-2535R00-08, but of course other similar drivers can be used.

Fig.3 - Throat acoustic impedances


References

[1] R-OSSE Acoustic Waveguide (https://at-horns.eu/release/R-OSSE%20Waveguide%20rev7.pdf)
[2] Extended-Throat Waveguides (https://at-horns.eu/exar-story.html)
[3] Segmented Horns (http://www.at-horns.eu/seg-horn.html)
[4] ANSI/CEA-2034-A (https://webstore.ansi.org/standards/cea/cea20342015ansi)
[5] R&D Team - BEM simulation software (https://www.randteam.de/Index.html)


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Marcel Batík, Czechia, September 2024