Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

How I made a PA System

Discussion in 'Miscellaneous [BG]' started by Mud Flaps, Dec 1, 2003.


  1. Mud Flaps

    Mud Flaps

    Feb 3, 2003
    Norton, MA
    To understand this story, you must first understand my setup. My bass goes directly to my head which has a patch bay for my DigiTech BP200 Multi-FX pedal.

    With that said, it was really late Saturday night and I wanted to play a little while without waking up my family. I tried hooking up my headphones into the headphones slot in the pedal. I dropped the headphones on the floor and I heard a "THUMP!". This was odd because the floor of my room is carpeted; thus, inhibiting loud THUMPS!. I put the headphones on my head, and I heard scratching noises. By now you must be thinking that I'm real stupid to not know that something is going on. The idea finally struck me. So I tried yelling into my headphones, my cab yelled back at me. I thought this was terribly funny and I woke up my family in my hysteria. How the headphones were amplifying my voice through the amp and stuff was beyond me.

    Can anyone explain how I made a PA system out of my bass rig? How do the headphones act as a microphone?
     
  2. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    It's quite simple really.... microphones and speakers operate on the same principles but opposite from one another.

    A speaker takes an electrical signal and causes a coil of wire (the speaker's voice coil) to move in the magnetic field creating vibration of the cone. A microphone senses vibration of the diaphram (like a cone) and causes the coil to move in the magnetic field causing an electric signal to be generated.

    Make any sense?
     
  3. Skorzen

    Skorzen

    Mar 15, 2002
    Springfield MA
    Hence some studios using a woofer as a mic on the kik.
     
  4. Mud Flaps

    Mud Flaps

    Feb 3, 2003
    Norton, MA
    Sort of. The only problem is that I am not a robot, and my diaphram does not produce an electrical signal. So I'm still confused. And even if my voice was being broadcasted through the headphones, why would it be sent back to the amp?
     
  5. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    I'm not sure how to make a technical explanation, non-technical...

    Microphones and speakers have three components in common...a diaphram (cone) type device which is connected to a coil of wire that surrounds a magnet (and immersed in a magnetic field.

    When your voice vibrates the cone of the speaker in the headphones, it moves the coil of wire in the magnet's field. This motion causes an electrical signal to be imposed on the coil, which is connected to the headphone cable, which you had plugged into the input of the amp (not the headphone jack).
     
  6. Mud Flaps

    Mud Flaps

    Feb 3, 2003
    Norton, MA
    OOOOH! I think I get it.

    First of all, I thought you meant my diaphram, as in the one sitting beneath my silly head. That's why I thought that you thought that I am a robot! Wow! The power of words!

    So you are saying that instead of being vibrated by a magnetic field, the cone is simply being vibrated by the sound waves from my throat. I think I get it now!