Ok... I'll do my best to explain my "plan" as best as I can lol. The enclosure is 1/2 vented and 1/2 6th order bandpass. Basically a box with 3 compartments. The top compartment houses a visible 18" speaker, the middle has the magnet side of a hidden 18" speaker, and the bottom compartment is the face of said hidden speaker. All 3 sections are ported. The 'vented' portion is tuned to 64Hz, and the bandpass is tuned to 24Hz (rear) and 58Hz (front). This (through WINisd) shows a near 10dB gain @ 59Hz for the bandpass, and near 10dB gain @ 66Hz for the vented.
To make things complicated, this box is for a mobile DJ setup, and needs to be... uh... mobile lol. total box dimentions are 48.5"W x 44"H x 30"D. So with the use of some simple hydrolics and some fabricated plexi-glass dividers, the box is shrunk to only 27"W. (when not in use)
Now for some specs:
Vented Portion of Box: 17.749 ft^3 tuned to 64Hz (when expanded)
BandPass Rear: 9.002 ft^3 tuned to 24Hz (when expanded)
BandPass Front: 6.251 ft^3 tuned to 58Hz (when expanded)
The Drivers that I originally intended for this hybrid enclosure were Faital Pro 18XL1500 (18" drivers)
*details found @ usspeaker.com
Thiele / Small Specs of said driver:
Impedance 8 ohms
AES Power Rating 1,500 Watts
Program Power 3,000 Watts
Frequency Response 30Hz - 1.5kHz
Sensitivity (1W/1m) 98dB SPL
Voice Coil Diameter 4" / 100mm
Voice Coil Length 31 mm
Air Gap Height 15.5 mm
X Damage (peak to peak) 56 mm
BL Factor 28.1 N/A
Resonant Frequency (fs) 31 Hz
Impedance (Re) 5.4 ohms
Coil Inductance (Le) 1.45 mH
Mechanical Q (Qms) 7.4
Electrical Factor (Qes) .33
Total Q (Qts) .31
Comp. Equivelant Vol. (Vas) 7.24 ft3 / 205 Liters
Voice Coil Overhang (Xmax) 12.9 mm
Surface Area of Cone (Sd)m2 0.1174m2
Reference Efficiency 2.0%
Diaphragm Mass (Mms) 236 Grams
Mechanical Compliance (Cms) .01 mm/N
Mechanical Resistance (Rms) 6.5 Kg/s
*Originally* I was planning on pushing each driver independently with it's own Behringer EP4000 (Behringer's new 4000w amp @ 4ohm Bridged Mono)
... at which point it dawned on me that the Faital Pro 18XL1500s are 8 ohm speakers, and i would only be getting about 1/2-2/3 of each amps potential output. These speakers are rated @ 3000w Program, and @ 8 ohms, i would only be sending each speaker aproximately 2800w at clip (using 1 4000w amp for each speaker independently). If I bridge the speakers together in parrallel, then I drop the ohm rating of the cabinet to 4 ohms, but would only be able to feed it 1 amp @ 4000w (so still only 2000w to each speaker) The other "viable" option it to blow a few grand on a 6000+ watt amp to push both speakers @ the 4ohm load.... and my pocket book says that ain't gonna happen any time soon lol.
So I started looking for speakers with similar specs as the Faital Pro 18XL1500's but that come in a 4ohm version... no luck. Closest I can find is the B & C 21SW150 (21") which would work well, but is $250.00 more per driver.
Basic Goal of this whole sha-bang: be able to have the -3dB drop-off at or below 25Hz and be able to push 140dB+ @ 1m (@ the 63Hz mark)
Using 2 Faital Pro 18XL1500's and 2 Behringer EP4000 Amps @ 8 ohms, this cabinet configuration has a -3dB drop-off @ 23.41Hz and hits approximately 144dB @ 2800w/1m @ 63Hz (taking into account the +3dB Boost for x2 drivers) Really the only problem I have with this is knowing that out of a possible 8000w (with the 2 amps) I'm only effectively able to use 5600w @ clip.
If anyone has any suggestions / comments, please feel free to post. This is my first venture into building my own cabinets, and I couldn't have told you what Thiele-Small specs were two weeks ago
