I got the siren to make a 3 port undertone on the 6 port side with some triangles cut from a dishwashing sponge to reduce airflow to half of the ports on the 6 port side. With smaller sirens the air physics are much different to full size ones & I took that into account to get the required undertone. Then using a plastic cup with a hole cut in the bottom then sat it ontop of the cardboard tube from a large paper towel is how I get the 500s 10/12 sound in the video. I also placed sticky tape inside of the stator to reduce the large gap between the rotor & stator. I then fabricated then extended stator trumpets using a compass to draw out the circles required for the cutouts & strips of cardboard for each of the stator openings, Hot glue was used to hold the extended stator trumpets in place.