Need design help for sub..

[sounder]

I have a Radio Shack 40-13001A 15" woofer with the following specs:


Nominal Impedance:................................................8 ohms RMS
Frequency Response:...........................................25 Hz-2000 Hz
Free Air Resonance (Fs):.....................................................25 Hz
Infinite Baffle Resonance Frequency:..................................24 Hz
Piston Area (SD):...........................................................0.0855 m
Rated Power Input - Nominal:...........................................100 W
RMS Thermal Power Limit (PMAX):......................................200 W
Flux Density (BL):................................................................10.29
DC Voice Coil Resistance (RE, ohms):...............................5.5 ohm
Voice Coil Inductance (LVC at 1 kHz):..............................0.77 mH
Equivalent Air Volume (VAS):...................20.8 CU. ft. (587.5 liters)
SPL:.....................................................................91 2 db/1W/1m
Moving Mass (Mms):...............................................................91g
Electrical Q Factor (QES):.......................................................0.71
Mechanical Q Factor (QMS):...................................................3.22
Total Q Factor:.......................................................................0:58
Equivalent Acoustic Volume (VAS):.......................................523.9
Mechanical Suspension Compliance (CMS, M/N):........487.41 UM/N
Mechanical Mass of Cone Assembly and Free Air ..............90.95 C
Mechanical Mass of Cone Assembly Only:..........................76.17 9
Peak-to-Peak (Maximum) Linear Excursion:........................3.8 mm

Power Handling:....................................................100 watts RMS
Magnet Weight:................................................................29.9 oz.
Speaker Weight:..............................................................118.4 oz.


I modeled a 100l non vented enclosure on Winisd and get a hump at approx 60hz and a falloff of low frequencies. The graph is flat w/ a 400l enclosure but ...save the trees. That's too BIG!

Anyway, what is the best way to proceed. I have a 50 W rms gainclone and am intending to build a 3rd gainclone monoblock for the sub. Should I use a passive xover or is there a simple active surface that will help the linearity?

This is the response in 100l non vented enclosure:

 

[sounder]

Oh the orange graph is the vented 100l example. almost not wort the trouble IMHO.

 

[Vikash]

I've modeled it using Unibox and the response is not good. A 15" with an xmax of 1.9mm and an f3 of 45Hz (peak at 73Hz, max excursion with 7w input) in 100litres is not worth the effort IMO.