Speakers that open up at low volume levels

They weren't my "cup of tea", but you might want to audition a pair of Harbeth's, if you like that "English sound".  If not, I'd recommend auditioning a pair from the Totem Element line as well.  Both are very smooth, very musical, great sound stage, don't need to be driven "hard" to sound their best, didn't seem to be picky about the electronics driving them, or the room they find themselves in.

Sky isn't limit in this case and there will be trade-offs and trade-off may be the dynamic range. I'm absolute freak on dynamic range and the larger one gets my choice.

Thiel, this is why I made it my reference.

Jeff---The ET LFT-8, an excellent loudspeaker with a for-some-reason very low profile. You're right, it's rather inefficient, yet imo sounds better at low volume (as well as high!) than Magneplanar's 1.7, a very similiar low-efficiency planar. A lot of Electrostatic speakers sound great at low volume as well, perhaps as a result of their unmatched transparency.

My Eminent Technology LFT-8a sound very balanced at low volumes and NOT efficient. Good for condo living!

My 2 cents.... I have some open baffles with audio nirvana 12" drivers in them and they sound better than any box design at low levels to me anyway. 96db

I'm too interested in this question. I'm no engineer so this information may be incorrect however what I've been able to piece together is that higher effeciency speakers are generally superior at lower levels due to thermal compression in lower effeciency speakers.

More specifically because said TC doesn't affect all frequencies equally lower-eff speakers are tuned for a range of power dissapation. If your speaker was tuned to play louder and you listen quietly your performance suffers as you're not suffering an effect compensated for in design. By this thought it seems rational there will be exceptions though without recommendations on use from the manufacturer finding them may prove difficult. Higher-eff speakers have little to no tuning for this factor and thus are consistent accross a wider range of volumes.

Well I do not think there is any speaker that can be said to "open up" better at lower volume than higher.  Things pretty much always open up with volume.

Some things to think about though.

Is your listening room quiet enough to hear clearly at low levels?

That matters a lot. If room is quiet many speakers with right amps do well at lower volumes I find.

Also at low volume the extreme high and low frequencies and some others that our ears do not hear as well need to be bumped up more than normal to hear everything correctly. Human ears do not have flat frequency response even if gear does at low volume. If gear doesn’t what sounds great at low volume may not sound as good at higher volume.

Preamps integrateds, receivers etc. used to provide loudness controls for this reason. Some were better than others but generally delivered better sound at low volume than otherwise. Unfortunately most audiophile gear forego any tone controls so you can’t have it all with many but not all products today.

If all is going well otherwise, there should be more difference in what speakers can do at higher volumes rather than low. That’s where a lot of work is involved and the men get separated from the boys.

Not all preamps nor amps necessarily retain flat output response at various levels. Some will argue that higher quality low power amps in general are designed to do better at lower volumes. SET amps are said to excel at low volumes when not stressed for example especially when used with high efficiency speakers.

Very hard for any one system to do it all best at all levels.

Just some food for thought.

I would think that most high efficiency speakers would qualify. I still have a pair of Tonian Labs TL-D1s and it didn't take much for them to come alive. Being a semi-open baffle design and being just a 2-way they didn't have that deep, full range sound you ask of but they are very satisfying to listen to at low levels.

All the best,
Nonoise