Full measurements of the HTM-12+ upgrade crossover for the DIY Sound Group HTM-12v1 speaker kit

This crossover was developed when I was recently asked if there was any changes or upgrades that could be made to the original HTM-12 design. I was already planning on setting up to test another speaker outdoors the same weekend so I installed the original drivers back in the HTM-12 cabinet and took a set of new measurements to determine what changes could be made to improve the performance and sound quality of this design.

I ended up dropping the crossover point a little so the directivity transition between the woofer and waveguide was smoother (similar to the HTM-12v2). The lossy air core inductors used on the woofer in the original crossover design were changed out for lower DCR I-Core inductors which improved the bass response and output bringing it more inline with the rest of the response. I also tried to make some general adjustments to further even out the frequency response but was at the limit of what could be reasonably accomplished with the fairly straightforward passive crossover. I certainly did not want the crossover to become overly complex in order to smooth out the remaining small peaks and dips.

The on axis comparison to the stock crossover can be seen on the first graph below.

The following measurements were performed on my 10' tall outdoor turntable. Measurements were taken at 2.83v / 2M just below the tweeter axis and scaled up 6dB to approximate 2.83v/1M level.

Measurements are gated at 14ms and blended to the diffraction adjusted nearfield woofer response below 200hz. Smoothing applied is 1/48th octave.

HT-12+ polar data exported from VituixCAD