Bezzola's optimized bass reflex loudspeaker port

thingiverse

I'm currently following DIY speaker design plans calling for straigh reflex ports. Looking for print files, I came across new findings on how to do it better. The gist is: flare both ends so that particle velocity contours at port exit have minimal curvature.Here is the parametric file to that end:Diameter center: this is the thinnest part of the portLength port: according to bezzola, this should be thrice the smallest diameterDiameter end: according to bezzola, this should be roughly twice the smallest diameterBend radius: bezzola seems to have had good results with 8.4mmVolume cabinet: bezzola's reference design was roughly 30 liters, their port tuned that to 40 Hz. I'll try three ports for a speaker thrice the volume.Splineratio: 0.7 looks nice? I don't find it in the literature. Probably, we should optimize so that particle velocity contours at port exit have minimal curvature but freecad isn't comsol. If I know nature it'll be roughly golden ratio anyway. In their other work on waveguides [3], Bezzola found something in the neighborhood of 70% to work well in some cases. According to [4], THD should be better than straight, either way.Wall Thickness: I don't think the port wall gets mechanically stressed but this is where we could counter anything like that.Resonance Frequency assuming straight port (just the ballpark, it probably computes low by some 5 Hz judging by [1,2].) =(2.35625 10 ^ 4 (D_c / 10) ^ 2 N_ports / (V_box (Len / 10 + 0.732 * D_c / 10))) ^ 0.5Port count: this only affects the frequency calculation above.[1] https://www.researchgate.net/publication/339726207_Loudspeaker_Port_Design_for_Optimal_Performance_and_Listening_Experience[2] https://www.comsol.com/paper/optimal-design-of-bass-reflex-loudspeaker-ports-81561[3] https://www.researchgate.net/publication/339726427_Numerical_Optimization_Strategies_for_Acoustic_Elements_in_Loudspeaker_Design[4] https://stars.library.ucf.edu/cgi/viewcontent.cgi?article=1956&context=honorsthesesEDIT 17.11.24: Fixed three missing constraints