My Hornings circumcised the Lowther drivers they used, removing the whizzer cone, and implementing a cone tweeter. You may want to contact Tommy Horning for advice on doing so
Whizzer cone removal
I've got a pair single driver speakers I've supplemented with a ribbon supertweeter and single cap crossover at 3khz. I'm just wondering about very carefully removing the whizzer and if anybody has tried this and if it worked to positive effect. Thanks!