Smaller drivers can produce low bass IF the cone is of a high mass design and capable of long excursion. There are several problems here though. That is, why would you want to use a smaller woofer of higher mass? This reduces both transient response and high frequency bandwidth, negating much of the benefit of using a smaller driver. On top of that, a driver with more surface area reproducing the same note at the same amplitude of a smaller driver with longer excursion will produce lower distortion. The more "throw" that the driver makes, the more distortion that it produces. On top of that, longer throw woofers produce more reflected EMF, making them harder to control. On top of that, the smaller driver will have to move more air to produce the same spl, meaning that it will be producing more distortion at all times while running into Xmax ( linear excursion capabilities ) sooner than a larger driver. Obviously, there are a lot of "on top of's" in this equation : )
In plain English, this means that if you want deep bass out of a small driver, you'll have to make several compromises in other areas to get it. The only way to get low distortion and deep bass while retaining good linearity at high volumes is to use large woofers in a large cabinet or a multitude of smaller woofers in a large cabinet.
To quote speaker designer Bill Fitzmaurice: "The bottom line for speaker cabinets is that for the goals of a small box, a reasonably efficient system, and good bass extension, you may achieve any two of those goals at the same time, but not all three". Sean
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