I haven't tried these IQSE, but I first bought one of his small filters and placed in in my amp signal in and I liked the improvement. Later I bought two of his larger golden filters (can't remember the names, sorry) and placed them inside my speakers, between crossover and drivers for midrange and trebble and again liked the improvement. And I purchased two more. These filters are the same as used in his Bybee Bullets. What I have now are the big golden attached to the positive lead of the speaker driver. Next step would be adding the smaller black filters (less expensive) to the negative legs of midrange and tweeter. For the bass I didn't perceive any benefit so not using them there.
For what is worth, Jack Bybee does answer emails and with me was a straight shooter. He said the best use of his filters is as close to the speaker drivers as posible. At no point he was trying to sell me his products.
I liked the improvement these filters made and will buy the black ones in the near future, when I finish building my new speakers and can try them with new SET amps.