The filter used in older three-way four π and seven π speakers with piezo tweeters was actually a crossover, and raised the crossover point. I'd suggest that you might want to attenuate your tweeters by using a 0.1uF, 0.22uF or 0.33uF capacitor in series.About speaker plans, there have been several requests over the years for the older three-way models and also for updated plans using current production models. I make those available, but I don't post plans on the website because I want to keep track of their distribution. So I always make plans available only by request.