• Kiss flat FR good-bye. The horn and driver WILL create a comb effect in the response for the bass and lower mids. It will be interesting to see if surgical EQ can correct this. I am not hopeful.
• I was afraid this would have a slightly rising response like the Voxactiv's. It does not. In fact, I would describe this speaker has having a somewhat reverse TH-900 response. Bass extends surprisingly low to 50-60Hz, but then drops like a rock. Upper mids on up through high treble are recessed. Strong emphasis on low to mid-midrange.
• Rolled off up top. Personally, I WILL need a supertweeter to augment the Fostex. A joke among speaker designers is that these kinds of full range horns are for old people who have lost their high frequency hearing. I think there's some truth to that. As an FYI, old audiophiles hate it when you even hint that their high frequency hearing is shot. They get all testy, defensive, and shit.
• It's very fast sounding. Evident on string plucks, percussion, voices, etc. Very punchy. Throws sound at you. I almost jumped off my seat to the bass Jennifer Warnes' Rock You Gently. Funny considering that only the harmonics of the bass notes were being produced - the fundamental bass notes being well below what this speaker could reproduce.
• Amazingly resolving in the midrange.
• Congested on passages where there was a lot was going on. But this could be because I was using only one speaker, and hence driving it louder than I would if there were two speakers.
• I suspect the solid-state electronics used are holding this speaker back. A well executed tube amp may be the ticket for this speaker to reach its potential in terms of dynamics and resolution.

So would you call the frequency a reverse V? How would you compare performance to say, a Klipsch RF-42 II, or would that be apples and oranges?