Relate sensitivity/impedance to speaker efficiency

Thanks for all the info. It's all good to know and I feel that I'm learning a lot.

To get into some specifics as Mmike84 suggested - A couple specific speakers I am considering are the Dali Helicon 800 and Acoustic Zen Adagio.

The Dali Helicon 800 is a 4 ohm speaker with a listed sensitivity of 89.5. I see the units shown on the Dali website are 2.83 V/1 m. According to what Almarg is saying this would correspond to a sensitivity of 86.5 for a 1w input - is that right?

The Adagio is a 6 ohm speaker and the website lists the sensitivity as simply 89 dB SPL @ 1 meter (doesnt indicate 1w or 2.83 volts). I noticed a couple of other websites reviewing the speaker list it as 89 dB / 1w / 1 meter. But I have sent an email directly to Acoustic Zen to ask them to clarify.

If the 1w / 1m unit is true for the Adagio, then according to what Almarg is saying, to directly compare these speakers you would have to say the sensitivity of the Dali is 86.5 vs 89 for the Adagio for a 1w input.

Also, the impedance curve of the Adagio is fairly flat as seen here in the 6moon review: Adagio curve

Unfortunately I cant find the same curves for the Helicon 800. The closest I can find is the Helicon 400 from the stereophile review and it drifts a bit more: Helicon 400 curve

Anyway, the ability to use tube amplification successfully is one important criteria for me in choosing the right speaker. Of course, there are several other things I am considering (room size, placement, price, etc). But if anyone has any opinions about how these speakers might perform with tubes relative to one another, I'd like to hear more. Thanks again.

Elevick-
I am mainly concerned with 2-channel stereo right now. And I am mainly looking for help in comparing speakers relative to one another with respect to how well they might perform with tube amplification.

Specifically, I would love to hear what anyone has to say about Dali Helcion 800 vs Acoustic Zen Adagio given the info on sensitivity and impedance charts I provided in my post previous to yours. Thanks again everyone.

Thanks for the additional info. Its all quite interesting I think.

And I'm still waiting for a response from Acoustic Zen to verify whether their sensitivity rating of 89 for the Adagio floorstanders is for an input of 1W or an input of 2.83 volts.

Nnck, First lets look at the two options as if they are both on the Power Paradigm (efficiency, 1 watt 1 meter).

Under this model the Acoustic Zen is 90/91db. The other speaker is 84/85db if it is also 4 ohms. If you want a tube amp the latter is going to be hard to live with unless you are near-field.

I lost you just a bit here. Seem like under the Power Paradigm, if the Adagio is listed as 89dB efficient, despite it being a 6ohm speaker, it's efficiency is still just 89dB, not 90/91 (that is, if the efficiency was measured in units of 1w / 1m, it wouldnt matter that the impedance is 6 ohms, and not 8).

Is still havent heard back from Acoustic Zen, but the Dali Helicon 800 is very clearly labeled on the manufacturers website with a sensitivity rating of 89.5dB at 2.83 V/1 m. Which means it must be 86.5dB at 1w / 1m (since it is a 4 ohm speaker).

Acoustic Zen lists the Adagio with an Avg. Efficiency (not 'Sensitivity' if that is at all meaningful) of 89dB SPL @ 1 meter. If that is a measurement at 2.83 volts / 1m, that would mean a sensitivity of 87.5dB (since it is a 6 ohm speaker). But if the measurement was at 1 w / 1 m (as some websites note), then the efficiency is simply 89dB, as stated.

Of course, I am new to this. So I dont know if I have it all right.

Still hoping for some explanation of the comments I made directly above.

But I did hear back from Acoustic Zen this afternoon and they verified that the efficiency of the Adagio floorstanding loudspeaker is about 89dB and the measurement is for 1w / 1m.

So it looks like I am comparing 2 speakers: the Adagio (6 ohm speaker) is 89 dB at 1w / 1m vs. the Dali Helicon (4 ohm speaker) which is 89.5dB but at 2.83 volts / 1m.