changer, you need to work on limiting the ctc distance, something like this. but even that is on its limits for near field listening
Hi peanuts,
my previous provisional cabinet was oriented towards a close c-to-c distance with the same asymmetric waveguide. This approach is the legacy of a set of assumptions that the people who popularized the constant directivity horn speaker with DIY-ers put up as their approach, but they themselves were following some rule of thumb. This assumptions where 1) guided by the assumed relevance of asymmetric waveguides to control flour and ceiling bounce and 2) controlling the lobe tilt and the phase coherence of a passive speaker. The first design criteria is wrong, my use of an asymmetric waveguide nothing but a legacy of this false assumption. Not only is the tight driver spacing uneccessary, but also, the early loss of pattern control due to too small vertical dimensions of the waveguide lead to pattern flip below and above the crossover which show up in the early reflections as unwanted energy. It is much more important to control the vertical pattern to the same degree as the horizontal pattern, giving you real constant directivity. The second consideration is not of concern to me, as I use an active crossover with delay.
Further, the creator of the simulating software VituixCAD, Kimmo Saunisto, persuasively showed that a close c-to-c approach with two way speakers has other problems, when 1/4 wavelength cannot be achieved, and this is the case most times in a two way system: If both radiators are too close to each other in a two way system, due to the energy sum of both radiators on the vertical axis, the DI and sound power curves feature a stark and high Q curve, discontinuous and not desirable for an optimized in-room response. The current driver spacing of this speaker cabinet is optimized for an even DI throughout the crossover region, it is 1.2 lambda, which is ~ 33 cm at the 1250 Hz crossover frequency. In combination with a waveguide which is i. e. axisymmetric or rectangular, but with a vertical pattern the same as the horizontal, like a M2-style waveguide, sound power and DI will be optimal. As both radiators, woofer and the waveguide, feature a big surface area, the problem of driver spacing is further reduced.