I bought the combo from PE, the BE10 ia recommended by Magnetar and yes it made from Mylar, I am very happy with it, very smooth even when new. I cross over at the minimun freq.,ie 2.5Khz min freq. recommended by the manufacturer. It sounds fine to me.I have not measured the combo, remember this combo is very cheap and when compared to the expensive brother, BE250(if you have the money buy this unit), I strongly suspect it will dip at higher frequencies, probably above 10-12Khz. I use an active x-over I can easily equalise it.
The combo is well worth a try, less than $60 per side.