Phase plugs stop "oil can resonance" which is caused by air trapped behind the dust cap. The high frequency dispersion is greatly improved as it reduces any beaming and broadens the sweet spot.

My highs are so much smoother than before I can hardly believe it's the same driver. I would think any driver with a whizzer/dust cap like the Beta's could benefit from phase plug implants.

The Betas have unseated the Tang Bands so into the closet they go.