The acid test would be if the sorbothane/springs/ podiums etc were switched in and out (with speaker height maintained) without the listener being aware.In the last 2 years some of my changes were subtle and subjected to some doubts even by me... In this sense a "placebo effect" is possible for a specific change...
But for an incremental number of not so subtle changes like moving an acoustic absorber or reflective surface or diffusor, the changing experiments are the key.... No need to blind test for acoustic treatments.... Listening is mandatory,...
An Helmholtz array of tubes and pipes with variable necks are the same thing.... You listen, you try varied lenght of necks with different pipes volumes, no need to a blind test....
Most of my experiments, but not all for sure, never need a blind test to assure me of their existence positive effects....
Then this placebo mantra and blind test urgency convinced me that MOST people here have never conducted listening experiments nor even devise experiments in their own in the mechanical, electrical and acoustical dimension....They want to buy miracle solution and they are afraid to do it....But there is NO miracle solution, only an incremental sets of controls we are obliged to work with and with many , many low cost devices in my case... I needed plenty of time, listening time for the experiments, i never need money for tweaks or upgrades...
I bought nothing, used my own homemade devices which perhaps explain my fearless endeavour... I dont buy snake oil or costly tweaks then i was fearing no fraud...At worst i bought some S.G. i modified 10 bucks each for verifying some audio claims by people who tried this or by company who sell them like Acoustic Revive....No need of a blind test for a 10 bucks experiment...
All those afraid to experiment with peanuts costs devices are lazy or dont have the time, because it takes me 2 years many hours each day during my retirement, or are in the situation where in a beautiful living room experiments is out of the equation....These are the main reasons for fear: lazyness, lack of time, fear of snake oil costly miracle product, the wife factor and no room to play with....Thats all....None of these factors interfered in my case...
To answer your post specfifically , using sorbothane give very audible effects, but way less positive than my rightful, dyssemetric or without dyssemetric compression, use of springs ...i used a sandwich of varied materials under my springs....This sandwich was already useful before my sandwich at peanuts costs...(bamboo plate,cork plate.granite plate, quartz feet, sorbothane pieces)
No need of blind test.... 😁😊 No blind test will reveal the limit of sorbothane effect.... You must go on experimenting to learn that....
Also like i already said, listening is not an innate ability, it is some HABIT someone learn to use in a specific environment, with specific gear, specific musical files.... It is not an automatically transferable superpower in any environment, with any gear, and any musical files...Like some may suggest... Like some pretend it is wanting to debug the alleged claim ....I never claim that for myself.... I only claim what i learn experimenting....
Your listening is not an absolute power and never will be, it is the origin point for an audio journey, no more no less....
Blind test is useful to experiment with by companies for scientific or market reasons and fun with audio groups of audiophiles yes, but it is of NO USE in any personal audio journey... Believing otherwise reveal a fear of doing anything, buying or experimenting alike....
We already know only too well what happens when cables, DACs, CD players, 192kHz+ bitrates etc are all tested in this manner.
NONE of these changes in your list are powerful like acoustic treatment or acoustic controls, or electrical grid controls, or mechanical vibrations and resonance controls....They are way more debatable changes and they are precisely the ONLY changes people consider generally because it is" buying and ready to plug" solutions, no need to experiment at all, no listening experiments time is need... It is not surprizing that many people ask for blind test to prove the real existence of these subtle claimed change or not so drastically audible changes...
More imporetantly all these changes in your list are gear dependent... they dont work the same positive or negatively with all gear...
But acoustical treatment and controls, electrical grid controls, and mechanical vibrations or resonances controls work with ANY gear the same..... They are what i called controls on the working embeddings dimensions of ANY sustem....They are NOT upgrades they are not "tweaks".... They are no cost devices created in listenings experiments.... I sell creativity, a method, a concept at no cost.... I dont sell anything else...