DCAudioDIY.com :: View topic - New driver servo system

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.

tomp wrote:

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.

I still have a problem with this
it looks like the correction is made after the problem occurs

I know there are lots of servo subs out there and people love them. I am sure I have heard them with out knowing it, but I remain skeptical
sounds like one could really mess up coherency

Author:	tomp [ April 29th, 2020, 3:19 pm ]
Post subject:	Re: New driver servo system
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.[/quote] 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.

Author:	SoundMods [ April 29th, 2020, 3:25 pm ]
Post subject:	Re: New driver servo system
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?

Author:	tomp [ April 29th, 2020, 3:58 pm ]
Post subject:	Re: New driver servo system
SoundMods wrote: 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. 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?[/quote] Of course. And most of his work was done back when most devices were slow with lousy gain bandwidth product. Not so much an issue today.

Author:	Pelliott321 [ April 29th, 2020, 4:27 pm ]
Post subject:	Re: New driver servo system
I still have a problem with this it looks like the correction is made after the problem occurs

Author:	Roscoe Primrose [ April 29th, 2020, 4:58 pm ]
Post subject:	Re: New driver servo system
Pelliott321 wrote: I still have a problem with this it looks like the correction is made after the problem occurs It always is. Only variable is how long after.... Roscoe

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Author:	Pelliott321 [ April 29th, 2020, 5:03 pm ]
Post subject:	Re: New driver servo system
I know there are lots of servo subs out there and people love them. I am sure I have heard them with out knowing it, but I remain skeptical sounds like one could really mess up coherency

Author:	SoundMods [ April 29th, 2020, 6:27 pm ]
Post subject:	Re: New driver servo system
Pelliott321 wrote: I know there are lots of servo subs out there and people love them. I am sure I have heard them with out knowing it, but I remain skeptical sounds like one could really mess up coherency You hit the nail on the head! That's why the major players don't do motional feedback.

Author:	tomp [ April 29th, 2020, 7:09 pm ]
Post subject:	Re: New driver servo system
If the correction occurs in a time frame that is shorter than the brain can recognize and the deviance from the "perfect" signal is very small it is not a problem. The faster the response of the feedback circuit and the higher the gain, the less the error that will be allowed to get through. Having the uncorrected signal can be a bigger problem. To repeat, feedback is a good thing unless it is not done properly and then it is a bad thing.

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