Good Materials for Curtains

I would suggest buying the heaviest natural material offered in the width and length you require. In back of them on the same or on an additional rod have a slightly smaller pair of wool blankets with with slits cut into the top that will go on the rod as a backing panel. You can conceal any appropriate material behind the chosen curtains so that it is inconspicuous to everyone but you and your significant other. The heavier the materials the more bass absorption you will experience. As always your mileage may vary. It may take some tweaking. Isn’t audio FUN!🤡

I think a lot of it depends on whether you’re naked or not whilst listening to your HiFi.

These curtains are meant to block outside noise more than provide a sound treatment for a room. Probably will do both, however.

I've never needed to use ... but if I did, I would try the "Block out" curtains. They are for blocking out the light... and so they have a rubber backing. I think that would do wonders over just  fabric alone.

Vinyl is very good for sound absorption - I have used a vinyl roller blind behind the listening position and in front of a window with great success.

The blind only had to be extended about 18-24 inches for optimum  benefit/effect.

I have also tried a strip of vinyl 8 ft x 2ft in an open plan concrete condo again at ceiling height (12ft high) behind the listening position and at one side between the open plan kitchen and the listening area.

My new basement listening room has several dropped portions of ceiling to accommodate heating ducts, which seems to trap unwanted reflections at ceiling height. The room is also irregularly shaped, which also helps a lot

I have seen a couple of acoustic specialists which incorporate vinyl into their products

It would appear that the vinyl does not have to be very thick, which helps with the weight problem

Hope That helps - Steve