@lewm, it is not an echo. It sounds like a very high frequency copy of the music. What is vibrating can not emit anything from maybe 6 kHz down. I'm just guessing. With the vacuum engaged I can just barely make out cymbals. With the record loose it is 2X louder and I can make out a little more. It is still very quiet. You have to put your ear next the rim of the record to hear it. I remember my old Zenith which I got when I was 4 years old. I use to marvel how I could hear the music with the volume turned down. It was pretty loud. You could hear it across the room.
Remember the old Victrolas? They had a sowing needle in a shank fixed by a grub screw. The shank was attached to a diaphragm in the throat of a horn. Same thing but no diaphragm or horn. You are hearing whatever is vibrating. The less you hear the better is the control over distributed resonance from the stylus and cantilever vibrating. The cavity around the stylus can act as a horn which is why many manufacturers stick the cantilever out in thin air. That resonance is reflected back at the cantilever to be heard. You really only want to listen to the record. Nothing else.
The best record playing set ups hardly make any noise at all. There may be a few out there that make no noise at all. I have never heard one make absolutely no noise but I have heard a few get very close.
Just don't laugh when you see a guy with a tonearm stuck in his ear.
The point of all this is, the job of a turntable mat is to help control resonance. It is to help keep the record from vibrating under the stylus.
Because records are not flat a mat can not do it alone. People figured that out and started using record weights, then record clamps, then taking a lesson from record lathes, vacuum clamping. I am comfortable with saying that vacuum clamping is overall the best. I do not know if it sounds better than reflex clamping but it does results in the best control over the record with the least effort and stress on the record.
