I find these responses to the Less Loss Speaker Firewall less than enthusiastic and certainly not convincing.
This product is not cheap. about $1600.00 per set, and most people will probably require two sets.
Putting a simple capacitor across your speaker terminals will yield immediate and vivid results. That's why in the future I may give the Stein version a try, they also make an inline version too. However I doubt the efficacy of inline.
https://www.steinmusicstore.com/collections/zubehor-speaker-match