I’m replying out of courtesy to explain with rationality and fact, rather than try and convince. I think a lot of people would also make the same assumption so please don’t take offence but I think youre missing the point of a DC filter and what it actually (not supposedly) does.
You don’t ‘hear’ DC - there is no audible noise, like static or white noise. Maybe you’ll hear the transform hum a little bit that’s a vibration that you’re hearing, caused by DC.
However, DC on the mains will definitely affect a transformers performance and it will, in many cases cause a transformer to hum or vibrate. A real phenomenon and a real factor in the ability of a transformer to operate to optimum capability - which is important in audio systems.
DC doesn’t make your cone hum. It doesn’t hiss and it doesn’t whistle, so no matter how close you get, you won’t hear it.
However, remove DC from your mains and your transformer will performer better.
Will it audibly affect your particular speakers? I am not saying, so at all. But it’s easy to test.
Would such a circuit affect ambient noise in your room? - absolutely not, unless your transformer is humming and you can hear it! A DC filter would stop that, for sure.
The science absolutely guarantees that removing DC improves a transformers ability to do its job, and therefore it is very likely to make an audible difference in audio equipment. I bet your speakers were designed on a clean mains supply, for sure.
Will it sound ‘Better’? That’s subjective and in your head, I agree.
But will it make a difference? - Yes.
And is that actually measurable? - Yes.
And is that good for the whole electronic’s design, function and purpose? - Yes.
Not to worry though, I’m not selling it and it’s probably not for tabletop speakers. But proven principle of physics isn’t snake oil and the principle of removing DC from an AC power supply is known to affect audio equipment and I suppose that’s all I’m trying to clarify.
And in even shorter summary - that’s why I’ll be inclined to try one in my system to see if it can help improve performance.