What makes a speaker perform well at low volume?

This is very important to classical music, as it is not usually very loud live. Next time you're at an orchestral performance, notice that you can easily hear someone's sniffling nose 5 seats away, or your own feet shuffling, on all but the loudest of crescendos. Most stereos have to be turned up much louder than the live orchestra to convey the same richness and excitement. If you can get involved with the music at low volume, you have a very special system indeed.
Excellent question, I wish I had the answer.

Well,

1st thing, study the Fletcher-Munson curve to help define how your hearing changes at varying dB's, then measure the average spl at which you listen to music. Look at the chart.

2nd realise that equalization is needed, whether the speaker has it subtley built in itself or something as coarse a loudness button on your amplifier.

All of the answers above to one small degree or another are correct but the true reality is a speaker that has boost in the highs and the bass will sound the best at low volumes period. Those speakers will achieve the nearest flat response to your ears relative to normal listening levels at lower listening levels.

A sensitive speaker and amplifier have little to do with the overall performance unless they address the F-M Curve in some fashion at the levels you are listening too. Address your hearing and background noise in the room and you will solve the problem of listening at low levels.

An decisive solution to your problem is the Accuphase DG-38. This will solve all your problems, at normal and low listening levels.

Honest1,

You are right about the volume difference in a concert hall vs. at home. I can easily whisper something to my wife at a concert, but she is always telling me to turn down the stereo because she can't talk to me.

This brings up an interesting question, of whether a stereo has the physical capability of conveying the type of dynamics of an orchestra. Of course, a stereo is a vastly simplified illusion, and is amazing the degree to which it approaches a real performace. However, consider that there are over 100 musicians on stage. Each musician has an instrument, often with multiple strings, each of which is vibrating independently. When you think about the 1000s of pieces of string, reed, skin, metal, and wood vibrating on the continuum of a stage, you realize that a stereo will always fall short. A full-range speaker will most often have only 8 points of vibration eminating from 2 points. Our mind is fooled even though the approximation can only be considered grotesque.

Also, a concert hall is very different than a living room. It is professionally designed and has space to allow the different vibrations to assimilate, reinforce one another, and disperse. How can one compete with that?

Rob

Second the good amp but add a very neutral cable

IME, the amp, the speaker and the cable all make a difference. Tube amps can sound excellent at low volumes, but I've heard a couple of SS amps that can too. Some speakers are better than others at low volume, more efficient speaker generally being better. My Tannoys were outstanding at low volumes maintaining life and presence, my AN E's less so which seem to lose life at very low volumes (and are actually efficient speakers at 94 db). But this last point I think could be related to the cable. I'm running 17 feet of speaker cable and something tells me that the long length of cable is not good for low volumes. I have not been able to try the E's on shorter cable.

Another good low volume pair was my JMR Trentes with the Resolution Audio s30 integrated amp. This amp is based on a DNM design which is noted for maintaining life at low volumes. Conversely, I had a Blue Circle amp that went dead at low volumes.