I improve the HFT idea with homemade fishing cones lines... And with herkimer diamond inside some.... With various size for the cones.... And even connect grid of cones with copper tape and incredibly that work... I put also a bell of cones in my room center.....
I use also other less efficient resonator and 10 cheap modified Schumann generator with great succeess.... This is ACTIVE acoustic controls...
Most people use only passive materials for acoustic controls, but active methods help a lot especially in the high frequencies...
cost: peanuts
My motto is: Hi-Fi for the poor
My act is: Homemade work
The greatest myth in audio is the relation between quality and price, in fact the relation is non linear....
the second greatest myth is the idea that an audio system sound at his optimal level without needing to be embeds in the mechanical resonant dimension, in the electro-magnetic grid of the house, and in the acoustical fied of the room....