Hello,
Them crossover provides compensation for the time difference that results from drivers respective positions, for better time-alignment. The goal is imho acoustical phases in sync within the crossover zone.
Without crossover, the compression driver response is being late compared to the woofer's one : in my mind is time to travel from each driver to the ear (or microphone caspule). In my mind again is that this ideal point is rather located at PE than conventionnal distance for speaker measurement. This makes the "correct" design more complicated with passive crossover elements.
Even if the low-pass filter does provide baffle step compensation
Best regards,
n.
There are a few threads on the French audio site about the tn-2 filter. The above dwg is from one of them. There is the original diagram on the Lansing heritage forum which is originally referenced, then there are a few revisions. It looks like the phase ends up being inverted on the tad4001 to get the best alignment.
I've also compared the values that I can see on the sunship crossover.
https://www.sunshipaudio.com/p/crossovers-filtres.html?m=1
https://www.sunshipaudio.com/p/crossovers-filtres.html?m=1
If you have it in VituixCad environnement, both with impedance measurement and SPL/Phase of the horn driver mounted on the horn,
then you can fiddle around with the values. And eventually, adjust them for mounting of TD-4002 on A-290 horn (which I did).
But these days I prefer using the TD-4002 directly mounted on TH-4003 type horn, without the need for the 1.5 to 2p adaptor.
Regards,
n.