Build your own DIY Horn speakers.
Detailed description and how to from start to finish.
These are a folded Horn speaker or back loaded horn speakers with full range Tang band w81772

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To get the plans pause the video at around the 2 min mark on a computer screen (not a small phone) you will see all the measurements you will need.
All the internal dividers are 37cm as indicated in the middle of that screen cut those at once as it is critical so when you close the side they all lineup. The schematics of the Crossover are in the video at 7:15.