D
David Grant
- Jan 1, 1970
- 0
I was reading back on rec.audio.pro about the feasibility of a
motion-controlled loudspeaker and found this cited as the main drawback:
"The biggest problem with this approach is that, above self resonance
(where most of the energy is pumped into a speaker) it is an force or
velocity device, not a position device. That is, the force applied to
the mass of the speaker (and the considerable mass of the air in front
of it) is proportional to the current delivered to the speaker. So
there is a considerable phase shift between the speaker current and
the position of the cone, as well as an integrator type frequency
response (reduced excursion at higher frequencies for similar
current)."
(John Popelish)
But wouldn't a PID controller address this? I seem to recall in robotics
lab a similar dilemna: We had a 16" flexible ruler mounted
cantilever-style to a servo shaft. Our input control signal was a square
wave which was supposed to cause the tip of the ruler to move suddenly
from position 1 to position 2 (some number of degrees away). Without the
PID controller (open loop control) the response was out of phase and had
horrible ringing, overshoot, etc... with it, it was vastly improved.
motion-controlled loudspeaker and found this cited as the main drawback:
"The biggest problem with this approach is that, above self resonance
(where most of the energy is pumped into a speaker) it is an force or
velocity device, not a position device. That is, the force applied to
the mass of the speaker (and the considerable mass of the air in front
of it) is proportional to the current delivered to the speaker. So
there is a considerable phase shift between the speaker current and
the position of the cone, as well as an integrator type frequency
response (reduced excursion at higher frequencies for similar
current)."
(John Popelish)
But wouldn't a PID controller address this? I seem to recall in robotics
lab a similar dilemna: We had a 16" flexible ruler mounted
cantilever-style to a servo shaft. Our input control signal was a square
wave which was supposed to cause the tip of the ruler to move suddenly
from position 1 to position 2 (some number of degrees away). Without the
PID controller (open loop control) the response was out of phase and had
horrible ringing, overshoot, etc... with it, it was vastly improved.