Never used it on speakers but I had a black BMW. In certain lighting conditions I could see very faint swirl marks. Most people probably didn't notice but I did. On the recommendation from a friend (professional auto painter) I used the 3M Imperial Hand Glaze prior to waxing. The glaze is not an abrasive. After, I could not see the swirl marks on the car.
You may try the glaze on a small area of a speaker to see if it helps. I don't think you need to apply a wax after like you would on a car. A little difference in how to remove the excess glaze as compared to auto polishes and waxes....no need to wait for drying time. If there is any glaze left on the surface after using the microfiber, just apply more glaze to that area and wipe off before drying. Never tried the stuff on anything but cars but it really did a great job on them.
You may try the glaze on a small area of a speaker to see if it helps. I don't think you need to apply a wax after like you would on a car. A little difference in how to remove the excess glaze as compared to auto polishes and waxes....no need to wait for drying time. If there is any glaze left on the surface after using the microfiber, just apply more glaze to that area and wipe off before drying. Never tried the stuff on anything but cars but it really did a great job on them.