How can they not effect the sound

From my experience, dents may be in the dustcap in the middle of the bass driver in which case, unless the damage is extensive, it is likely no effect on the sound.

My first task in my first hifi job at a Tech Hifi that specialized in refurb gear, was testing used speakers prior to attempting sale. Those with voice coil issues, usually due to being driven by amp that was clipping, had to have drivers replaced prior to sale.

In many cases, the issue was merely a pushed in paper dustcap. Ugly and a defect for sure but no impact to sound. Solution: replace the dustcap, or the easy fix: use a safet pin to punch a small hole in teh dustcap and push it back out to normal from behind.

THese speakers were then sold at a discount determined by magnitude of defects, if any. Common practice to this day.

Dented soft dome or other material tweeters: different story. Any physical defect there is likely to have an effect on the high frequency sound. Could range from minor/not a significant issue to major. Devil will be in teh details.

From experience I learned never buy expensive speakers with exposed soft dome tweeters unless there is a grill or some other way to insure no accidents. If you have young children in the house: doubly true.

Additional not often mentioned advantage of Ohm Walsh CLS speakers: all driver components are safely sealed in a metal mesh can. You would have to knock one over or drop it accidentally to cause physical damage.  This helps account for their famed  longevity..

To anyone who wants to reclaim the feeling of late 60s/early 70s free-form FM radio, or are interested in what it was like, there is a music podcast called Radio Free Gunslinger that perfectly captures it. There were 120 episodes and they are archived at the website below. Each episode is between an hour and an hour and a half, composed of four sets of music, and the only common thread is being off the beaten path. Rather than having a DJ between the sets, the program is "hosted" by excerpts of interviews with luminaries such as Vladimir Nabokov, Moms Mabley, Bing Crosby, Laurence Olivier, Larry Fine, Elvis Presley and Lee Harvey Oswald. The website includes playlists for each episode so you can see what sort of music is on offer. Here's the main link: 

https://radiofreegunslinger.blogspot.com/

Here is an episode I particularly like, hosted by Der Bingle, and ends with a long excerpt from "The Cradle Will Rock":

https://radiofreegunslinger.blogspot.com/search/label/Bing%20Crosby

The effect of the speakers is to make the sound but the dents affect the sound!

Using a vacuum is a very good idea.  If all else fails, try grabbing some Gorilla tape and ease the sticky side into the indention.  Then a gentle (or not so gentle) tug.