thanks for yall advices. i kind of get it that to get the boomy ones, the setup needs to be ported type and rotary fan for da extrme. im not sure about the connection between the low frequency, wattage, dB, amplifier. as i read, double the wattage increases 3dB. but dB is overall loudness of the sound, and dB alone can not measure loudness of low frequency sound? amplifier provides extra electrical power and controls the volume of high/low frequency sounds? do u need additional amp to get the mile effect? so if i would like the low frequency soundz to travel 1km, what kind of spec would you recommend? awful sound quality is ok as i do not consider about treble high frequency sound quality. like this under 10K baht from homepro, will it travel da distance? https://www.homepro.co.th/p/888108800093?lang=th&gad_source=1&gad_campaignid=17611471329&gbraid=0AAAAADDk-KXtFQOKco47TTpt9R9eRTJoB&gclid=CjwKCAjwvNfSBhBiEiwAyaGMCXpQkE0gwp5Xv9NBwv3NHTyIMLgAtOI_B_M5cCx7HOfjHDKIumE9tBoCHn8QAvD_BwE