Jeff Flowerday said:
No putting it in a bag won't help a ho hum reverb.
Not sure the exact reason behind it but I assume it has something to do with dampening the vibrations from the cab and sound waves.
Hey, your guess was the closest!:tongue:
A reverb tank works "thusly", in the immortal words of Slip Mahoney. A signal is fed to a transducer working much like a speaker, only instead of moving a voice coil and speaker cone to push air it moves some long springs. At the other end the springs are mechanically coupled to another transducer to change the spring vibration back into an electrical signal, like a crude microphone. Since sound waves travel much slower mechanically along a spring than as an electrical signal in a wire and since the springs will change their length as they vibrate (that's what springs do, after all) you get lots of delays and phase shifts added to the signal that add up in the end to an echo or reverberation effect.
Unfortunately, vibrations can be picked up at the "mike" transducer that came from unwanted areas. Particularly in a loud combo amp where the speaker is close to everything the sound vibrations from the speaker can travel through the wood of the cabinet and the air in the back, into the metal can of the reverb tank and into the "mike" or "pickup" transducer.
This can cause feedback through the reverb tank, just like with a mike too close to a speaker. Crank the reverb up and you start to get a high pitched scream or howling noise.
The idea of the bag is to muffle the sound from the speaker from getting into the reverb tank. A bag looks much nicer than stuffing an old blanket over the tank.
It even works...sorta and sometimes. :tongue:
