Speaker driver sizes - pros and cons

@br3098 
In general, you are correct that a smaller driver is normally faster than a larger, but as I stated, A Properly designed driver: 
Mass is not always an issue,  understand that adding mass increases qms/qts,  adding mass decreases sensitivity... If you add a softer material, you'll find a more rolled off frequency,  if you add a hard material, you'll find extended frequency response,  The material added matters as well as if you coat the entire cone or add to the dust cap or even the rear of the cone.  
I'm really not stating an opinion. I've proven many times that a properly designed larger driver can be as fast as a smaller driver. 
I'm not sure what you mean by "over-driving a cone"  but proper cone, voice coil, excursion limits and even dust cap can produce a larger driver that extends well into the midrange, no doubt, depending on the final speaker design, you can certainly have beaming or lobing effects. but I have built and know where a set of speakers are right now that are a 15 inch 2 way that do a great job,  all drivers are custom modified for a natural rolloff at 1800 hz and when set up correctly,  they are excellent. 
Your overall premise that a smaller cone extends frequency smoother than a larger cone is correct. 

timlub, with all due respect I do not agree for several reasons:
1- Mass is always an issue.  Larger motors do help, but the reaction time also increases; larger motor or not.
2- Mass vs motor: over-driving the cone is typically only a concern with larger speakers.
3- Larger speakers have more issues with wave propagation timing and scattering effect.

I have owned and heard lots of great 12"-15" speakers.  But in the same family, for example, I have never heard a 15" cone driver resolve more midrange and top end information than an 8' version of the same driver.  All things being equal and in the same family.  More bass, yes.  Better response across the entire bandwidth, sometimes yes but no more often than not.

My assertions above assume we are limiting our discussion to dynamic drivers and not compression drivers, correct?

I don’t think you’ll find a 12” driver that is actually considered full range. Those larger drivers are normally used for PA applications and their frequency response is within the midrange band. Anything larger than an 8” driver will require a crossover to a tweeter. That’s been my experience when trying to build my own single driver (audiophile) speakers. YMMV. 

@br3098 
Hi br3098.... I didn't forget to mention that at all.... I don't believe it.  I've heard 15 inch woofers that are very fast and dynamic.  Mass vs Motor tell the story.  As long as you have enough motor structure to push the mass speed is not an issue.  The problem lies when you start having too much motor. Yet another subject. 

timlub, you forgot to mention that smaller drivers are usually faster than larger drivers - less mass to push and pull back and forth.

Also, I disagree that small speakers can't reproduce a large orchestral experience.  You just need more than one; active and range limited or passive.

After years of owning, testing and listening to all types and sized of speakers and main drivers from 2"-15", I prefer a single driver (or dual as mentioned above) no larger than 8' and coupled via high level output to a pair of very good subs.  This combo seems to work best for me, but I should also mention that I am driving tube amps ranging from 1Wpc SETS to 50Wpc push-pull.
 

Here are typical differences. These are not cast in stone.
Advantage of small driver:
better frequency extension in the treble region
smoother midrange response
tighter focus in imaging & soundstage
Easier to use in any size room (smaller)

Advantages of larger driver:
Moves more air for more impact in midrange and bottom frequencies, large rich images.
Better excursion limits for better power handling
Normally produces large rich soundstage
Normally higher sensitivity

Disadvantages of small driver:
Less power handling
Cannot portray the large orchestral experience as well
Limited Frequency response in bass
Normally less sensitivity

Disadvantages of larger driver:
Normally not near the treble frequency extension
Normally not as clean in the midrange
Normally requires a much larger cabinet
Beaming is often a problem

I've had a pair of Silverline Prelude small towers for years, and they're punchy, coherent, sweet sounding things. 2 3.75" (!) woofers and a 1" tweeter in each rear ported cab, all drivers are magnesium/aluminum including the tweeter...I recently replaced these (haven't sold 'em yet...hard to part with them) with Klipsch Heresy IIIs that sound remarkably similar in the sense that they're clean and coherent, a squat and fat 3 way with 2 titanium driven horns and 12" woofer. They don't play as low as the Preludes, but I've used 2 REL subs with both designs so no problemo, and I bought the Heresy IIIs simply to have more efficiency available. Utterly different designs, both do music amazingly well. Note that paper cones show up in some form or other in many high end designs (Wilson for example) as do soft dome tweeters, and they respond to what the designer wants to hear...my metal dome Preludes were never harsh or metalic sounding, and neither are the titanium drivers in the Heresys. 12" paper woofers...who knew?

Depends on what brand and composition of the drivers used as well as the xover and cabinet design.So size of the drivers are a very small part of a total design.

Thanks Erik, have posted the question there too.

To start with, the (3) 4 inch drivers will have about 1/3 of the surface area of a 12 inch driver. If you want surface area to be approximately the same, it will take (9) 4 inch drivers to be equivalent to a single 12 inch.

Hi OP,

The forum at DIYAudio.com is a MUCH better place for this type of question. You'll find experts there on a range of subjects related to speaker and driver design and construction. 

Best,

Erik