In this article I would like to share some measurement results for my new WN300ALO plywood horn. Based on the PLA prototype described here
some initial measurements were already done and a preliminary passive crossover network was designed for use in my existing speaker system. This way it was possible to immediately have a listening session when the horns arrived at my home. The measurement results for the PLA horn have not been published because of my concerns about using PLA for such a large horn mainly because of inherent self resonances. And indeed some pronounced and distinct resonances were present in all the measurement data. This has been also verified by spectral analysis when knocking on the horn at different regions. But the results were still good enough for designing a crossover network knowing the problematic resonance frequencies. Maybe it is possible to change the the outer shape of the PLA horn providing better damping. In total contrast to the PLA version the full block plywood version has exceptional good internal damping properties which was one of the main reasons to choose this material and the overall shape of the horn.
Basically it was planned to have a reference setup to compare to so we first listened to the my existing speaker system with 18sound ND3SN@TH4001 fin horn which was my primary choice since a longer time. The TH4001 was a big improvement compared to round Tractrix or any CD horn I tested in my system except for some missing depth of the 3D soundstage. After some songs with the TH4001 in place we mounted the WN300ALO and also changed the readily prepared HF part for the crossover network. What happened with the sound reproduction by switching to the new WN300ALO horn surpassed my highest expectations.
Some time ago I presented the first article about my development of the ALO William Neile horn type and the underlying construction method. Although, most of my previous worksheets use a super ellipse for each 3D layer / spline along the horn axis. To have an alternative option for William Neile horns I have implemented the the necessary math together with evenly distributed Neile parabolas used in this context to build up the horizontal construction wave front. All William Neile (WN) horns based on the super ellipse algorithm will get the extension “SE” in their name.
By varying the Lamé exponent of the super ellipse formula many different shapes from elliptical to almost rectangular are possible. At throat everything always starts with a Lamé exponent of 2 which indicates an ideal ellipse. Of course, if major and minor axis of the ellipse are equal there will results a perfect circle at throat. If major and minor axis differ an ellipse will result. Generally, the major axis is the horizontal plane because it is intended to radiate more broad compared to the vertical plane (minor axis). For higher Lamé exponents of the super ellipse formula the resulting shape will be an almost rectangular spline but a transition function is needed to provide a smooth transition from exponent 2 to higher values along the horn axis. A very similar procedure was already used for my spherical wave horn (SWH) and JMLC worksheets.
This article is about the first making of such a horn by DonVK who much preferred the native elliptical shape and asked for my assistance to optimize a horn for his setup. Finally, we ended by with two horn of different cut-off. This article describes the making of the first smaller version.
The second part of this article series deals with 1in4 (1.4 inch) William Neile ALO horn. This is the next logical step on my agenda. Also because the new 1in4 William Neile ALO horn is supposed to replace my current TH4001 which is a good sounding horn so the expectations are set quite high. The category of the so-called fin horns seems to me to be quite popular and their good sound properties are usually reported. However, I am of the opinion that the known underlying assumption for the construction of fin horns, especially the fin shape and arrangement, does not lead to a coherent wavefront over all frequencies at the exit of the individual channels. I have developed an improved version of different curved fin arrangement which implements equal path lengths of each channel together with the right and exact opening angle for proper exponential acoustic loading, but this is another story. So to speak the TH4001 is a good performer but has some serious design issues. The William Neile ALO horns use what I call natural dispersion instead but with it’s own limits one has to accept. What I want to say is that it is not possible to achieve such wide radiation for a very low-loading horn similar to a fin horn. In my opinion, this is not necessary at all for use in normal listening rooms. But many are somehow still of the opinion that some kind of cinema horns with extremely wide dispersion should be set up at home but these were intended to reach hundreds of people in a large cinema hall with evenly distributed sound impressions at every single seat. A slightly narrower dispersion can definitely be an advantage, especially in smaller listening rooms and when only a few listening positions in the room have to be considered. The intrinsic problems of fin horns, which are related to the the individual channels (shape, length, arrangement), such as cavity resonances or excitations or the suboptimal addition to a coherent wave front, cannot occur with a natural dispersion horn. For example, anyone who doubts that e.g. 30 degrees of even radiation can be sufficient should mark this angle with two strings on the floor from each loudspeaker to the listening position and preferably with the loudspeakers angled slightly inwards and then look at the area of even radiation delimited by the strings on the floor. My 1in4 William Neile ALO horn will achieve about twice as wide dispersion in the horizontal plane.