There also test tones in Spotify. I am also interested in the Ryan Audio underseat subs but wonder how does it perform vs the JBL BassPro SL.

Regarding the JBL BassPro, I have inquired in one JBL store and available naman sa kanila kaso wala daw harness. Ano yun? Paano gagana yung underseat subs pag ganun? Lol.