I'm a Dummy, Tell Me About Turntable Mats

I knew there would eventually be the usual opinions here. I have one. 96.73% of the time they change the sound but don't improve it. I always wondered if HW was having a little fun at the expense of the rubes when he added a piece of very thin brown parchment paper as a platter mat with his decks. Platter mats, periphery rings and center weights all change the sound. Mats the most, periphery rings the least, center clamps/weights in the middle. Once your ears and brain become accustomed to the change they don't add anything to ultimate enjoyment. This is not what most vinyl enthusiasts want to believe, so they won't. 
The biggest benefit of platter mats is to enable those with VTA/SRA problems-those that can't go low enough-to achieve proper VTA/SRA. I think Herbie's caught onto this. 

Just why do you think mats change the sound? Could it be because they dampen the record in differing ways? If so would they be dampening some sort of resonance? Where would you guess that is coming from?

I knew I would get this type of response as I was typing what I typed. Substitute "deaden" for "dampen" and I can answer your question. Too heavy of a platter vis a vis the motor and bearing deadens the sound because of they-the motor and bearing-are over-loaded. Imagine a diesel tractor chugging up a hill with a heavy load. The same applies to adding too much weight and sound absorption with a cushioned mat and weights. 
You can insist in calling it "dampening" if you wish. Speaking of vehicles, imagine a Porsche 911 loaded up with four 350 lb occupants. Besides the grotesqueness of the mental image, would you call the driving quality-besides being blatantly dangerous-"damped" or "dead". 

I have the utmost respect for Ralph of Atma-Sphere on most topics, but I do tend to disagree with him on vinyl playback. IIRC, Ralph thinks a top version of a Technics 1200 with stock arm is pretty much as high as one needs to go with a turntable. Contrast that with Harry Weisfeld who's made some more ambitious decks (admittedly I am no longer much of a VPI fan) and he advocates for no mat at all on his massive aluminum alloy platters, even with his relatively unstable unipivots! I have tried a ton of mats with my Reed 3P's and various high-end cartridges. On my aluminum with copper top Steve Dobbs platter on my 301 I have found that no mat is just as good if not better than any mat. Copper has good qualities of it's own which explains why some platter mats are copper. On the massive platter being used on my TD124 I have a carbon fiber mat that I have kept on for no particular reason-the same deck sounds just as good with no mat. I bet I have five other mats that no longer see any use at all from Merrill, Herbies, and others. 
I think of Malachai-the on-again and off-again apprentice of Mike Fremer who with his humble Pro-Ject deck has repeatedly exclaimed the value of his various mats. https://www.analogplanet.com/content/malachis-mat-mishegas-felt-mats-rega-pro-ject-and-audio-technic...
For. those that don't know basic Yiddish, "mishegas" means craziness. 
The idea that a record resonates due to a tiny stylus modulating in a groove and that said resonant vibrations feed back into the stylus as the stylus continues to trace further into the groove-further than the creation of the inciting grooves/vibrations-is just that-an idea. An unproven mental pre-conception. 
As I said before, mats will change the sound. The issue is whether they improve the sound and that is subjective and system dependent. In general a mat is going to somewhat deaden the sound, but by only a very slight degree. I have found-and this is just my humble opinion-that when a platter gets incredibly massive and is coupled with a somewhat "cushy" mat, record weight or clamp, and periphery ring, all these things will slow down the sound, turning it from lively to anything but. For maximum liveliness/dynamics/propulsive punch, go naked. Record right on platter, no other mishegas. 

@fsonicsmith  You have mis-characterized my comments about the Technics, just so you know. I think its a very good deal. But I have a Triplanar on mine, as I feel the machine's weak points are the arm and the platter pad. Equipped with the Triplanar and a very different mat, it does an excellent job in comparison to my master tapes.

It was not intentional. I have already been corrected above by lewm. I do apologize. I have no doubt that a 1200 variant with a Triplanar arm can be a David amongst the Goliaths when it comes to price/performance. That is somewhat similar to my personal philosophy and yet paradoxically worlds apart. My hot rodded vintage idlers are night and day from a modern DD but I do focus on the arm and cartridge rather than the drive. 
And more to the point I continue to disagree that mats make a significant qualitative upgrade in SQ. 
Perhaps we should have a fun well-intentioned intellectual debate about the price/performance ratio of this https://www.audiogon.com/listings/turntables-shun-mook-audio-lp-clamp-legendary-record-weight-the-be...