Speaker Dimple

Use a guard of some type or rest your arm against the face of the speaker, hold the vacuum nozzle firmly in both hands and gently move the nozzle toward the dome. Don't get too close or you are going to have difficulty controlling the nozzle

I read about that method in Dr Comfort's "Joy of Audio" - never tried it though ;-)

With the vacuum use the bypass opening usually on the wand to regulate a lower amount of force.

The biggest problem with the dimples is that they affect dispersion and subsequently imaging.

If you listen to a single speaker at once, you may not be able to detect any difference- as the actual driver is behind the dome. However, if you listen in stereo you will find things to sound erratic and imaging to suffer.

Good luck

The purpose of the dome is dispersion.

It is very possible that your defect is inaudible.