The DPL-15 is an IB specific designed Driver. A good amount of X-Max.
I forgot to include the specs:
Re: 6.1 Ohm
Le: 1.7 mH
Fs: 19.5 Hz
Qms: 3.27
Qes: 0.84
Qts: 0.67
Mms: 271g
Cms: 0.23 mm/N
Vas: 232L
Sd: 830 cm^2
Vd: 3.65L
BL: 15.67
SPL: 85.2 1W/1M
X-max: 22mm
X-mech 29mm
Photos are available here:
http://ibsubwoofers.proboards51.com/...lay&thread=406