Velodyne DB-12


Sep 15, 2021
On the DB-12, this is 250mm, which puts the effective cone area (Sd) at 490cm².

Sd is an important specification because it means the Velodyne DB-12’s cone can ‘drive’ nearly half a square metre of air! By way of contrast, a typical 254mm (10-inch) diameter cone has a cone area of around 230cm², which means that two DB-10s won’t move as much air as a single DB-12. So sometimes, size is more important than quantity!
* half a square meter is 5000cm² (50 * 100) and not 500cm²!
* a typical 10 inch speaker actually has a Sd of around 350cm². Maybe you were thinking of 8 inch woofers, which still have an Sd of around 250cm². As you go up in diameter, the surface ratio between consecutive sizes gradually decreases, so it's pretty wild to say 1 x 12 > 2 x 10
* the amount of air a speaker can move is calculated as Sd * Xmax and is a volume, not a surface. Subwoofers with a lower diameter can definitely move as much, or even more air than higher diameter woofers, if they have a higher Xmax to compensate. Seeing the size of the magnet and cheap construction on that woofer, it doesn't seem to offer anything spectacular in excursion (Xmax).

Didn't bother to read the rest of the article.