View attachment 178908
Here's the amp hooked up to a test woofer with the speaker - terminal floating.
View attachment 178907
Here is the amp playing into the same woofer at the same level but with a clip lead connecting speaker - to the shell of an RCA jack.
So there is a difference that's not substantial and very much frequency dependent. While I can measure this here pretty easily, it inspired me to look at some tests into an actual woofer (a little 3" Hivi).
At 1% THD/40Hz, I can get about 600mV (not going to talk about power since the impedance curve is all over the place) with the speaker - floating. If I put a clip lead from speaker - to the shell of an RCA jack, that number goes up to around 720mV.
If I try this again at 1% THD/250Hz, I can get 2.9V with speaker - floating and 3V with the speaker - grounded.
These
are different, but I will leave it to others to properly quantify this in ways maybe I shouldn't