Originally Posted by diy speaker guy
Originally Posted by Bigus
You mean, the type of stuff I might have picked up while earning a MS in mechanical engineering? Oh.
Look, your analogies are all misguided. I don't have the inclination to enter a lengthy back and forth over something that seems so obvious.
EDIT - Sd = diaphragm cross sectional area. It alwasy has and it always will. No matter what crazy inventions claim otherwise. Sd has NEVER been calculated by diaphragm surface area. I would hope that even the beginners among us know that. But I guess not.
Regardless of your education I don't appreciate being called misguided unless you can back up your claim with ANYTHING AT ALL and show me my error.
To save some hassle, let's describe Sd to be the cross section of air displaced per Xmax of the motor. This means Sd x Xmax = Vd .
A perfect comparison to this would be the consideration of 2 12" drivers in a face to face manifold. If the manifold had a 13" x 6" opening, is the Sd equal to that of 2 12" woofers or the 13" x 6" opening (close to a single 12")?
The rear side (facing motor) of the internal cone is open to the internal box volume, just as the rear of the 12" cone is through the openings on the front basket. The forward side of the internal cone is confine/funneled into the center hole of the 12" cone in the same location we might place a phase plug or coaxial tweeter. The hurdle is that the Vd of the internal cone has to exit through the center opening, but it does not communicate to the rear of the 12" driver.
The 2 cones do add for effective Sd at low frequencies, while internal reflections and directivity issues would cause the model to fall apart above some frequency related to the diameter of the inner cone.