Know of a "Dirt Cheap" tweak?


I am looking for tweaks to improve the overall sound quality of my audio system. I recently purchased some TPC contact cleaner and it made a believer out of me. I noticed a signicant improvement, as if a veil was lifted my system sounded more clear and transparent. Bass got tighter too. Do you know of any cheap tweaks that have made a SIGNIFICANT improvement to the sound quality of your Hifi system...let us know... :-) Comments welcomed!
kasboot
Sabai,

I got the cones from Joann's a local craft shop, the end caps from a plumbing  supply shop. For placement I followed  Synergistic Research suggestions. I will look into Franck Tchang too. Thanx for the tip
lexphin,

You were lucky to find them. Are they copper? Franck Tchang's placement is mandatory here. Google Franck Tchang acoustic resonators placement. This will take you to the page on his site with the diagrams. He is the master. Everyone else followed him.
Any extras you can put on other components and tweaks. I have them on DAC, transport and other devices.
Hi Sabai
    Yes, they're copper. I followed Franck's placement as close as I could, my room is a bit asymmetrical. Have not listened with this position, will report back with "perceived" changes. 
lexphin,

Copper is good. There are also silver cones but they are not easy to find. Franck Tchang's placement is perfect in my system. I would be interested in knowing your impressions. SR uses crystals under the screen. Audio-Magic copied this in their bells, but with no screen.