Don't know the Velodyne model here, but many will place a "low cut" filter in the "to power amp" path. The recent SPLR series puts a 6db/octave filter at 80hz ahead of this jack so the main speakers see rolled off info below 80hz - while your "y" connector allows the main speakers to see a full range signal, unless you're using an outboard x-over.
Marty
Marty