If the Berber carpet is not tack-stripped to the floor, ie; area rug, I did a quick and cheap solution for my room with hardwood maple flooring. My Thiel 3.6's are 110 lbs with 3 spikes that penatrate just about anything.
For what it's worth, may not be an (AA)Audiophile Approved method but it worked in my situation which is almost identical to yours!
For a mere $10 at Lowes or Home Depot you can purchase a 4x8 sheet of 1/4" luan and have them cut it in half for you. With the 4x4 sheets I adhered low cost felt from a fabric store to the floor side and the placed the 4x4 sections under the speaker areas of the rug. Being that 1/4" is actually less than a 1/4" when it comes to wood it is not even visible from anywhere in the room. The Maple flooring is now safe from spikes and scratches from the felt backing. I've rocked and set my Thiels very hard to penatrate the carpet and it would take a 400 lb. Gorilla to push the spikes through the luan sheets.
For what it's worth, may not be an (AA)Audiophile Approved method but it worked in my situation which is almost identical to yours!
For a mere $10 at Lowes or Home Depot you can purchase a 4x8 sheet of 1/4" luan and have them cut it in half for you. With the 4x4 sheets I adhered low cost felt from a fabric store to the floor side and the placed the 4x4 sections under the speaker areas of the rug. Being that 1/4" is actually less than a 1/4" when it comes to wood it is not even visible from anywhere in the room. The Maple flooring is now safe from spikes and scratches from the felt backing. I've rocked and set my Thiels very hard to penatrate the carpet and it would take a 400 lb. Gorilla to push the spikes through the luan sheets.