Geithans are the only good speaker because they have full range cardioid? Nope. There are othersFFS I didn't write they are not very useful just co-axial is not crucial at longer distances.
One could argue that the Geithans are the only good speaker because they are available cardioid over a wider frequency range than all but a tiny number of others. In the far field that probably makes more difference than co-axial.
This is all a bit stupid though.