[dwk]

I'm still not entirely sure how the FR89EX differs from the FR88EX. I know that the FR88 was made by the unfortunately named Hustler Audio (they have their own upgraded and more expensive version of the driver called the 'trinity' I think), and my impression is that the FR89 is now made by someone else. Whether anything else important changed isn't clear.
 The FR88EX certainly did remarkably well in zaphs testing - hopefully the FR89 maintains that performance. 

It appears that I'm actually going to cobble together my FR88's into simple enclosures to test. I'd be looking to cross them around 200-400 in a 'FAST' style enclosure.  We'll see how it goes.

[Teflon]

These two drivers do appear very similar. To make it more confusing there is a 4R and 8R version of the FR89 and they are slightly different in appearance from each other as well as compared with the FR88 - just look at the shape of the dust caps, linear excursion, coated / non-coated Al cones and 'dimpled' cone on the FR89 8R version. The main item of interest might be the claimed higher sensitivity of the FR89 - if it's real.