I want to count and log the BPM of a rather large bass speaker (250-400W RMS range i assume).

BUT there is a mostly wooden/stone wall (~40cm) between me and the speaker + a 50cm air gap.

I managed to detect the speaker with a normal microphone, but that gets confused once there are other noises like talking or foot steps in the room.

So my idea was to build a large coil around some graphite rod to build a sensor for electromagnetism. Then connect that to a audio amp and feed the result into a audio card microphone input.

Would that maybe work? Any guesses how far the magnetic field of a bass speaker is detectable? How much wire should i use for the coil?

Edit:

So i found this video https://www.youtube.com/watch?v=83edokt3K5c of someone using a giant coil to pick up a very small speaker from a few feet away, so i assume its 100% possible, and the speaker i am trying to pick up has like 200-300x the power of what he is picking up in the video.

    • einfach_orangensaft@sh.itjust.worksOPEnglish
      5·
      15 days ago

      Yeah very very much so, for years, they only shut up when i bang the sealing, they love loud EDM at 3am in the morning and i kinda wana automate the sealing banging part now.

      • prenatal_confusion@feddit.orgEnglish
        2·
        15 days ago

        Warum brauchst du den bpm part? Reicht das nicht ein accelerometer an einem esp um das zu erfassen? Oder Mikro oder vergleichbares

        Das klopfen dann über was separates mit Motor und Relais

        • einfach_orangensaft@sh.itjust.worksOPEnglish
          2·
          15 days ago

          Mit dem BPM part will ich sicherstellen das es sich wirklich um musik handelt, und dachte daran das klopfen jedesmal im selbem BPM wie die musik zu machen aber mit phasenversatz, quasi wie ein echo

          • prenatal_confusion@feddit.orgEnglish
            2·
            15 days ago

            Haha gute Idee. Aber auch das geht mit einem accelerometer ohne den grossen Aufwand. Dann Signal Filtern und du hast was du brauchst. Hort sich komplex an aber gibt’s garantiert schon Bibliotheken für einschlägige maker boards.