https://diy.midwestaudio.club/discussion/2997/1-5-way-sealed-bass-top-box-interchangeable
Now working on the third iteration for the top box, revisiting my beyma 5CX200Nd from a previous build. Looking at an open baffle L structure to sit on top of my 1.5 way dual 8 in sealed woofer box. Latest iteration was with the ESS Heils crossing ~850- 910Hz, and I had recently moved the inductor for the rear firing .5 woofer from ~ baffle step frequency down to just support where a single sealed 8in would start rolling off on its own, so I doubled the inductor value. The idea was to provide double the Sd and therefore have reduce excursion / distortion at lower end eq’d levels, and limit mid-upper bass frequency interactions. A bit more complicated than a PR, but more controlled low-end response, and providing a smoother roll-off down below fs than PR/ported designs.
I’m always looking for the ‘simple’ implementation but haven’t yet been comfortable with a 1st order mid / tweeter crossover, due to limits of the tweeter. I’ve been intrigued with the Classic Seas A25 with its woofer running full range with a simple 1st order HP on a tweeter and am a fan of dipoles (Maggie’s). With this beyma at the outset I wanted to run it open/baffle format for a far as it would go both directions as it had a measured decent smoothish roll-off going from 4kHz out thru 12kHz+ (the tweeter is a sealed compression driver with its own horn / not playing off of a moving waveguide as with many coaxial designs). Additionally, running bi-amped with a minDSP for Xover between the 1.5 way woofer and the top (passive btwn the mid and tweeter of the coaxial) it provides an advantage of placing any modifying filters before the coaxial as a unit, and as such not messing with relative phase of the drivers. Fortunately, the beyma measured well enough to not need a notch filter by itself. I built a simple 2nd order passive HP with a Lpad circuit for the tweeter, running the midrange without a filter (initially selecting reversed connection for the tweeter showing additive at crossover).
Additionally, running the coaxial with the modified Amp Camp Amp (thanks again Tom) by placing an active HP filter ~400Hz it saves the amp from producing/ amplifying ~45% of the low-end audio power signal just to be subsequently scrubbed off as heat with a post-amp passive filter, as the Pass Amp Camp Amp is an ~ 5W 4ohm / 9W 8ohms ‘beast’. The coaxial, on its open baffle, starts rolling due to baffle width and height, ~ 600 to 400ish Hz so adding an active 1storder HP at 400Hz (before the amp) seemed to make sense, netting something looking like a 2nd order HP. I just quickly set up a 2nd order LR LP at 400hz for the 1.5way woofer box to get some initial readings.
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