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I was looking at my old Dynaco A25 speakers and noted that they had taken a bass-reflex box, and by stuffing the port judiciously with fibreglass, had what they considered an improvement, "Aperiodic loading", which rather than plugging the port, adds some resistance to the back wave. At that time, the speaker was considered a breakthrough design. No one else seems to have picked up on this. Can anyone comment? Is it worth trying with a Pi4?
I've made a lot of measurements with damping material placed in different positions within the cabinet. My goal was to find what effects placement had on damping various frequency ranges; Specifically, I hoped to reduce internal standing waves. What I found was that placement away from the cabinet walls helped reduce upper bass and lower midrange but had almost no effect on lower bass frequencies. I use this to good effect by placing a sheet that spans the cross-section between the midwoofer and tweeter, which also separates the woofer and the Helmholtz port.