I think you need more powerful transformer such as 25-025 or more ,as increasing volume distorting sub woofer base, or if you want to use same transformer use 22k preset so volume increase smoothly.
I have not completely tested but when I will complete my 8" Subwoofer band pass box then I will test it. If it will not working properly then I will change to 25-0-25. Thank you for your support and suggestions 🙏
