Townshend Maximum Super Tweeters Ribbons, Amazing Results Definite Keepers

1. Make sure you take time to get them time and phase aligned, for a long period I had mine set up skewed in relative to the speakers, I thought the additional treble energy sounded best that way but what I subsequently discovered was that I was actually compensating for excess reflected energy around my seat, once I addressed that aligning the supertweeters exactly with the speakers made a great difference in dimensionality and a much more realistic performance all round. You can also purchase tiny spikes to make sure they point at ear level (something like this https://www.ebay.com/itm/10pcs-Threaded-Spikes-Replacement-Body-Jewelry-Parts-Steel-14g-16g-3x3-4x12...) Net net adding STs may throw up some room acoustic issues you need to address
2. Invest in good quality cables to connect them -- going from a $100 pair to Audience AU24SE was a good step -- look out for cheap short pairs used on the 'Gon
3. After you've lived with them for a while dial back the level -- drop 3dB and maybe up the cross over -- likely you'll find you had then too hot at first and that the majority of benefit is from having as little from the ST as possible (especially after you address #1 above)
4. Look into tweaks -- wrapping tiny bits of foQ damping material around the speaker cables where they connect to the ST is very audible -- given STs will pick up and radiate any HF hash in your system it behooves you to work to eliminate this and the foQ material is very helpful in this regard

Somehow the super tweeters seem to improve the PRAT (pace, rhythm, and timing...not sure how this is possible) and add to the realism of the sound and add slightly more air.