We had a thread on pretty much this topic not too long ago...
My favorite speakers are the equivalent or the actual speakers that you might have found in any typical 50's and early 60's console hi-fi or "stereo". That would be a lightweight paper cone, usually paper surround, and high sensitivity. The key is both the high sensitivity, meaning that it has limited power handling and is designed to run off a low power amplifier.
These older speakers usually have small diameter voice coil which usually means that the driver will run higher in frequency than a large diameter voice coil...
I have used everything from 8" to 15" drivers of this type. They tend to sound warm, clear and rich... like you remember AM radio being!
The earlier comment on not using tweeters is good, imo...
The old sealed back Jensen midrange drivers, with a cap in series to block the lows is all that is needed if you want or need a bit of "presence rise" in the speaker. Or a more modern small speaker or midrange will do as well.
If you see old console radios being chucked, grab the speaker boards!
I got some Magnavox "Golden Voice" drivers that are quite nice that way.
The cabinet for these older drivers is not terribly critical... they'll work open baffle.
_-_-