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The loudest and best sounding 21" sub for under 0!!
The loudest and best sounding 21" sub for under 0!!
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Old 8th September 2011, 06:20 AM   #1
Bart Oetken is offline Bart Oetken  United States
diyAudio Member
Join Date: Feb 2009
Default The loudest and best sounding 21" sub for under $400!!

Today have for sale is a P.Audio SD-21 el 21" subwoofer. This sub is basically like 2-15" subwoofers put together. The voice coil is 6" in diameter and is 2" tall. Its 40% bigger than a 18" subwoofer. I bought this thing for a dj service. Just to big for what I needed. Its in new condition, its been screwed into a enclosure, but is in very good condition.


There is a 8" coxail speaker beside it to give you an idea of the size of this sub. This is a hell of a bumping machine for the money!!!

This would be great for a big home theater system, club, bar, etc!!

This subwoofer is no JOKE!! It weighs 77 pounds.

Nominal Diameter 533 mm, 21 Inch
Rated Impedance 8Ω
Operating Bandwidth 20 Hz- 300 Hz
Power Handling Capacity 1200 W rms R.M.S.
Sensitivity 2.83 V, 1M 96 dB
Effective Piston Diameter 460 mm, 18.1 Inch
Voice Coil Diameter 152.40 mm, 6 Inch

Thiele - Small Parameters
Resonance Frequency Fs 32.8 Hz
DC Resistance Re 5.8Ω
Mechanical Q Factor Qms 9.526
Electrical Q Factor Qes 0.378
Total Q Factor Qts 0.364
BL Factor BL 31.55 T x m
Effective Moving Mass Mms 315.02 gr
Equivalent Cas air load Vas 292.92 liters
Effettive piston area Sd 0.1662 m2
Voice - coil inductance @ 1KHz Le1K 0.81 mH
Half-space efficiency Eff 2.64 %
Airgap Height Hag 15.0 mm
Voice coil Height Hvc 30.0 mm
Voice Coil Over-Hung Xmax 7.5 mm

Physical Information
Basket Die Cast Aluminium
Magnet type,size ODxIDxH (mm.) 300 X 170 X 18 Ferrite X 2 | 152.3 oz
Voice coil Former Glass Fiber Bobbin | High Temp 200-250 oc
Voice coil Material Aluminum Flat Wire / In- Out | High Temp 185-230 oc
Cone Material Pulp Paper
Surround Cloth
Unit Weight /piece 35.0 Kgs., 77.0 lbs

Paid $850 for it. Asking $375 plus shipping and a 3% pay pal fee. There are alot of subs out there for $375, but they dont come anywhere to this Big Fella.

I accept paypal

email address and pay pal address
Attached Images
File Type: jpg SDC11531.JPG (838.2 KB, 152 views)
File Type: jpg SDC11535.JPG (843.8 KB, 140 views)
File Type: jpg SDC11536.JPG (845.8 KB, 133 views)

Last edited by Bart Oetken; 8th September 2011 at 06:31 AM.
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