Can I use a custom ported SPL enclosure for playing music?
Probably not. You need to know more about the enclosure before attempting this. If the SPL enclosure is tuned above 50Hz, it should not be used for music. Music can go significantly lower than 40Hz. If you play music below the port tuning of the enclosure, the woofer can (and probably will) be damaged. Below the port tuning frequency, the woofer becomes “unloaded” resulting in loss of control and physical damage.