Do these speakers exist?

I'm really not sure about this, but, Meadowlarks might. First order cross-overs while usually offering fairly flat impedances still have the reputation for being a bit challenging for amplifiers. SET's might not be the first choice for such speaker designs.

I have a K.C.S. 96db hi-eff ribbon, 2 way with fostex 12in woofers, 1st order with hovland caps alpha core copper foil inductors.Baltic birch cabinet 1 1/2in T ,Solid cherry ribbon mounts,28hz-40khz $1900 shipped.I have used on 300b set 9 watts with great results,built 6 pair this is the 1st prototype and uses better crossover than production model.Price incs frieght system is lightly used.

Ummm, I believe the Gallo Reference 3s match your criteria. Avaialable for WAY under $10k...

-RW-

I'm sure you've looked at Green Mountain. Impedance does dip a bit below at some frequencies, but you can definitely drive them with your 20 watt SET. I would not rule them out (or others mentioned here) just because the spec sheet doesn't line up perfectly with your rigid criteria.

Thanks for the replies.

1) The Green Mountain speakers are absolutely killer. The C3 is quite a stretch for me at $17K and the Calypso is 88dB sensitive and 4ohms. Likely marginal with SET.

2) I used to have Gallo Ref 3s. They are 88dB and just don't cut it with 20W SETs in my experience.

3) I should have said no ribbons. Dynamic speakers only. No ribbons, no horns. I'd never heard an example of either that sounds SOTA for me.

Thanks again.