Formaldehyde-free. What? Yes. Now that we know that nearly all the lumber used to make loudspeakers contain formaldehyde, a carcinogen banned from loudspeakers sold in California after December 31, 2010, do you want to be in a small room with a pair of loudspeakers off-gassing formaldehyde fumes or inches away from loudspeakers on your desk off-gassing formaldehyde?
Small. For practical reasons, including ease of placement and scarcity of space, especially on a desk, near-field loudspeakers should be small. Moreover, if they are not formaldehyde-free to begin with, small loudspeakers will limit your exposure to formaldehyde. In addition, all being equal, small loudspeakers image better because usually the drivers have to be placed closer together to fit on the baffle which brings them close to the ideal of being a point source.
Acoustic suspension design. Although they are not as popular as they were in their heyday of the late 1950s through the 1970s, acoustic suspension (sealed box) loudspeakers that are the same size as ported loudspeakers will usually produce better and more accurate low bass response. Not more bass output, but better bass extension. They will also have better transient response which will contribute to better imaging and better resolution of low level detail. Moreover, if the loudspeakers are not formaldehyde-free, they will off-gass less formaldehyde than ported loudspeakers which expose you to off-gassing from the outside surfaces as well as the internal surfaces of the loudspeakers and to any toxic glues or substances used inside the loudspeakers through the ports. Why are ported loudspeakers more popular? They are more efficient and produce more voluminous bass. But they don't work as well on a desktop or bookshelf because usually the ports are on the rear and that muddies-up the bass when they are placed near to rear walls. If you are a purest and value accurate reproduction, all other factors being equal, acoustic suspension loudspeakers have less distortion than ported loudspeakers. Small folded transmission line loudspeakers such as our Sampan FTL are an alternative to acoustic suspension design. The FTL has similar transient response characteristics and even better bass extension than acoustic suspension designs of similar size. But I don't know of any other TL loudspeakers that are anywhere as small as our Sampan FTL.
A point source or close to one. A point source loudspeaker is either a single driver loudspeaker or one where the tweeter and woofer are placed very close together so that their response simulate the response of single driver loudspeakers. Why is this important? If the loudspeakers don't use a single driver or a close-coupled two driver arrangement, then as you move up and down or side to side the distance between two or more drivers and your ears will change causing sound from the drivers in each loudspeaker to arrive at your ears at slightly different times which in turn cause slurring and the loss of low level information. A single driver or a two-way “point source” loudspeaker will provide more coherent, integrated and accurate sound because all the sound emanates from the same spot. In a multi-way loudspeaker the sound becomes integrated further away from the loudspeaker because of the different distances between the drivers on the baffle and the listener. That does not bode well for listening in a desktop environment where you are a foot or two from the loudspeakers.
Crossover-less or first order (6 dB per octave) design. With regard to crossover design,less is more. The more complex the crossover, the more current it soak's up, the more coloration it adds to music, and the more phase distortion it produces. Most of the really magical loudspeakers use only a few or no crossover components. In the ideal loudspeaker, a single drive full-range loudspeaker, the sound is continuous and integrated. A first order crossover allows considerable overlap of the output of the drivers which simulates the continuous output of a full-range single driver loudspeaker. There are no phase or discontinuity problems. In a multi-way loudspeaker the crossover or dividing network partitions the frequency spectrum to the different drivers. That is great for power handling but not so great for accuracy. Some discerning listeners can hear the separation or discontinuity that results from use of complex crossovers in loudspeakers, especially when they are seated near to the loudspeakers.
So what about sensitivity?Well, it is less of an issue than you think. How many watts do you need to drive your loudspeakers to reasonable volume when you are sitting very close to the loudspeakers, especially in a small room? Not too many! But more important is the issue of accuracy and sound quality. As Dr. Floyd E. Toole, formally of Canada's National Research Council has observed, "Sadly, there is an approximately inverse relationship between sensitivity and sound quality... more often than not, the most sensitive speakers are slightly less refined in their sound quality and for a given box size, they will have poorer bass." The sensitivity issue is often a concern for those who want to build a music system around a particular low wattage amplifier. However, since the loudspeaker is the greatest determinant of the sound of music systems, my advise is to start with the loudspeakers and and build the music system around them.
Small Loudspeakers sound, well, small.
Not necessarily. It all depends on how the loudspeakers are voiced. Voicing is an art. Done well, it makes small loudspeakers sound like large loudspeakers. In a one to one comparison between a well voiced small loudspeaker and a larger loudspeaker the difference in size will be obvious. But as you listen to a well voiced small loudspeaker you will forget about its size. To illustrate this point: In a recent review of our Sampan, the reviewer set up the pair of Sampans next to the a pair of Triangle Cellos, which are roughly 18 times the size of the Sampans. Everyone thought the sound they were listening to was coming from the Cellos.