Woofers:

Normally stored energy is not an issue for woofers when used under 100 hz.  Since I seldom use low frequency drivers much above this I normally don't measure stored energy.  

Generally I like to connect the driver and input tones starting at 20 hz and just listen.  You can tell a lot just from this.   Given a low distortion tone source you would be amazed at how different one woofer can sound vs. another.   Some begin to sound like a square wave especially at higher frequencies near 100 hz.   Also, at very low frequency some become very noisy with lots of wind noise coming from the back of the driver.  Having too small a pole vent is a common source of such noise.   Recently I have done some measurements of this noise by placing the microphone near the edge of the driver mounted on an open baffle.  The idea being to place the microphone in the dipole null to cancel the 20 hz tone and just listen to the wind noise.

DATA:

Blueprint Series I  12"

DPL-12

Peerless XLS  12"

Shiva

Titanic (Original)

Titanic MKII

Titanic MK III 15"  vs Bully 15"  plus more data on the XLS 12"

TC2+ vs XLS

Dayton RS 12" Hi-Fi High Excursion Woofer