Older Infinity subwoofers--what is a servo sub?

Servo subs are now more in the mainstream than they used to be and Infinity (Arnie Nudell, actually) was a pioneer in this. Basically, the servo sub has a device (accelerometer or sensing coil) that feeds info back to the amp/controller so that errors in performance are correctable. That's a simplification and there are many paradigms for this correction.

OTOH, I have no first hand experience with either of these models.

I've got an RS Subwoofer, 10" driver 100 watts and can find no info about it. If anybody has specs original price let me know. Thanks

I suggest you post this as a new thread with the model number if you hope to get a useful response.