Motor Force Vs. Cone Area 15/18/21s

[Th3pwn3r]

With all these 21'' subs out and about I'm wondering if we've reached a point of diminishing returns(I know things don't scale up equally even if size/power does). I was talking with a friend about what he thought of DDs 21'' sub and he mentioned that he felt there wasn't enough motor force. Aftering thinking about it I'm leaning toward agreeing, Reason being is that these 21'' subs use the same motors as 15'' and 18'' models. We all know that a 21'' sub should be louder than it's smaller counterpart using the same power BUT how much? Is it worth it? Do we need bigger motors for these bigger subs? I'd love to hear everyone's input.

[basskc]

yeah I feel you but cone area is the key factor here

[bbeljefe]

Depends on the motor. Is it a huge motor that, for a 15 is more than enough? If so then perhaps it's enough for the larger mass of an 18 or 21. If not then, obviously, no.

In my opinion, the more important concern with subs 18" and up is the volume they must have in order to function. For instance... generally speaking, a 10 needs one cube, a 12 two cubes, a 15 needs three and then when we jump to 18 we need 6 cubes. So even though the jump in volume isn't a larger percentage between 15 & 18 than it is between a 10 & 12, it's still a shit ton of real estate in a vehicle. And to my reckoning, that's the more negative aspect of running those subs. Especially when you consider that two 15s will fire in the space of one 18.

As for the 21 and up subs, I've never modeled one so I have no idea what sort of air space they require. But, I do remember the old EV and Cadence 30" & 34" subs and they were horribly inefficient novelties... which is why we no longer see them.

[TRON]

There's a shit load more than cone area and motor force to factor into this, and why would a 21'' driver is "louder" than a smaller one, whats the math on that one other than size? Both are important.

Just because a group of drivers all use the same motor, doesn't mean they all have the same t/s parameters.

Example:

I have a four 5'' drivers in my studio monitors...fills the room with incredible sound and accurate bass reference compared to a 12'' home theater subwoofer that uses triple the power.