Best Efficient versatile Speaker reaching 30Hz?

The Wilson Alexandria.

Nominal Impedance: 8 ohms
Woofer: One 15 inch - One 13 inch
Midrange: Two 7 inch (vented enclosures)
Tweeter: Ambience: One 3/4 inch Supertweeter
Tweeter: One Inverted Titanium Dome

95 Db @ 1 watt. Down to 18 Hz. Good luck with coming up with the coin for a pair. Pretty amazing that they are that efficent with the drivers they have.

Burton

I believe Soliloquy 6.3i and 6.5is would both fit the bill and not break the bank. Unfortunately I don't know the status of the company, but there are usually a few used ones at reasonable prices. I have their 5.3's that don't quite make your cut, but are outstanding speakers by any account and offer great bang for the buck. Underwood Wally sells them new and B-stock at reasonable prices and is an excellent dealer.

BTW, I don't think I'd agree that "efficiency is the key" when it comes to speakers. Perhaps you are not stating this well. I've certainly heard ineficcient speakers that sounded great, and efficient speakers that sounded bad within specific respective systems. I think "synergy" would be a better word. With that in mind it may be good to be more specific about what you'd be pairing these off with and what exactly are you after that you don't have now.

Marco

Silverline Sonata II or III (95db, 25Hz)
Soliloquy 6.3 (90db, 28Hz)
Coincident are also said to be quite good.
Reimer too has speakers to fit the bill.
Other option: add a sub. Our ACI Titan blends seamlessly with our 53Hz Klipsch La Scala horns. I've had three people ask me, "Do you only use the sub selectively?" when it was on.
I've owned both the Silverline's & Solilquy's, and find
them both to be highly musical, non-fatiguing speakers
that completely disappear in the room. On the used market, they are a steal!
Best of luck,
Howard

Well, I guess my speaker is close to what your looking for. My Hyperion 938s are supposed to be flat down to 30Hz (depending on room size), 90dB, 6 ohms nominal. I'm driving it with a cheap 20 watt solid state all-in-one Yamaha tuner/CDP/integrated to levels that would wake up my neighbors at night. And no it's not what I normally use with these speakers, just waiting for my new integrated amp to arrive. And it's probably the most affordable so far mentioned at $4500 retail.

On the used market:
Silverline Sonata II ~$2600
Soliloquy 6.3 ~$1500
Soliloquy 6.5 (22Hz) ~$3300
Bargains all, IMO. And they mate well with virtually any amp. That is, if you like the amp, you will like the sound. The speakers are that neutral sounding.

Howard