Low-sensitivity speakers — What's special about them?

In the case of dynamic (box-type) speakers, as a general rule of thumb small physical size, deep bass extension, and efficiency trade off against one another. So among the kind of small "bookshelf" speakers you are interested in more efficient speakers will tend to have less deep bass extension than less efficient speakers. There are many exceptions, of course, but as I say that set of tradeoffs can be considered to be a general rule of thumb.

And regarding deep bass extension, especially in the case of smaller speakers, some users will prefer to augment that with powered subwoofers, while some will not due to space or other considerations.

Other tradeoffs are also involved, of course. Larger cabinets tend to cost more than smaller cabinets, everything else being equal. The impedance characteristics of a speaker can affect drive difficulty as much or more than efficiency or sensitivity. (If Stereophile has reviewed a speaker that is under consideration the measurements section of the review will be very informative in that regard). Amplifiers tend to sound better when driving high impedances than when driving low impedances. For a given level of amplifier quality, and within a given class of operation (A, AB, or D) higher powered amplifiers tend to cost more than lower powered amplifiers. So within a given class of operation a greater percentage of the dollars one chooses to invest in an amplifier will tend to go toward quality rather than toward watts if high efficiency speakers are used.

And of course how all of these factors are addressed comes down to individual preference and budget. Personally I prefer relatively large floor-standing speakers having relatively high efficiency and benign impedance characteristics, which therefore are very versatile with respect to amplification. But the opposite approach works well for many others.

Good luck. Regards,
-- Al

Are you building a system for this room from scratch or do you have an amplifier you wish to use?  It is the AMP/speaker combination that will determine suitability for your room. As Al stated the impedance issue is also a factor. I you have an amp which one? 

From my experience it is hard to find a small bookshelf type speaker that has reasonable bass level (50hz) and sensitivity rating above 87dB at the budget level of the Dynaudio Evokes (below $1000 I believe). Also finding ones that have do not drop below 4ohms somewhere below 200hz is difficult. 

If you don't have an amp purchase the speakers you like and find one that will drive them to the required level. The small room works in your favor. Also if you won't be trying to drive yourself out of the room with volume.  

Generally speaking if you do have to play the speakers at volume, lower efficiency speakers have something called 'thermal compression' where the voice coils can heat up, significantly curtailing musical peaks.


But if size is an issue and your room is not large (and so not requiring a lot of power), a lower efficiency speaker can offer better bass as Al pointed out.


But a nice sub option if space is an issue is the Swarm by Audiokinesis. It is 1 foot square by 2 feet high so its not the smallest sub around and there are 4 of them to be used to kill standing waves in the room. But they are unlike other subs in that they are designed to be placed directly against the walls, and work best if asymmetrically placed. So they can work very nicely in a small room. This allows you a smaller or more efficient main speaker, since that speaker only need to down to 80Hz.