open baffle: matching bass driver and U frame side wings

I made a U baffle 12in wide with 8in deep wings and was able to get about 43Hz -3dB with 8x slot loaded 6.5in drivers. A lot of it depends on your driver Fs, Qts, and surface area. More info in this thread.

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Here is raw response of the woofer.
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I ended up crossing to 6FE100 mid at 500Hz and the mid to a planar tweeter at 4.5kHz. Your AMT would work well in a similar way. Here is my crossover:
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