tomp wrote:
Then of course there is the delay within the feedback network and the response time of the sensor at the woofer, which typically may be an accelerometer, an additional voice coil winding, the combined woofers back EMF read off two parallel 0.1 ohm resistors, or a strain gauge, that adds to the errors. I am not sure any of those schemes can replace a really well designed driver and enclosure method.
Amen to the well designed driver and enclosure method. Personally I have never used a servo speaker because for the cost of the servo system I could get another driver and then have double the linear volume displacement which did more than the servo. Of course, if you don't want another box in your room the servo can help. BTW the time delay in the electronics is not a factor in modern op amps with gain bandwidth products of around 50 MHz and up.[/quote]
I wasn't talking about the electronics in the amplifier -- I was talking about the response time at the speaker through the transmission line and around the feedback loop. That has always been the argument for any feedback even within the confines of the amplifier. Does the name Matti Otala ring a bell?