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Old 21st March 2013, 03:58 PM   #1
rafaro is offline rafaro  Guatemala
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Join Date: Feb 2006
Location: Guatemala

I am in the process of designing subs cabs for pro sound use and need the optimal balance between cab size, spl output, quality of sound and ease of construction. The final choice is between a Vented QB5 filtered alignment vs a TH. Aiming at an F3 of around 35Hz and driver choices are yet open.

Which do you think will provide the best balance most benefits......Opinions suggestions discussions are welcomed

Last edited by rafaro; 21st March 2013 at 04:00 PM. Reason: mistake in title
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Old 22nd March 2013, 10:53 AM   #2
djk is offline djk
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Join Date: Feb 2001
Location: USA
The optimum trade-off between bass extension, box size and efficiency is with a Qts=0.312 and a 6th order vented design with Fs=Fb=Faux with a Q=2 filter for Faux.

A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).

Eminence Kappa Pro 15LF-2 (or similar):

A small PA:

A compact high output PA:

The Kappa Pro 15LF-2 is -3dB at 35hz in the design shown, and four cabinets can be built from five sheets of 4x8. The design is 104dB/2.83V/1M mid-band (and a 4Ω load). The PPSL has about 20dB less 2nd harmonic distortion that a normal reflex box. Will handle 1200W (sine) at 4Ω without exceeding x-max, more on actual program material.

Driver Properties
Name: Kappa Pro-15LF-2
Type: Standard one-way driver
Company: Eminence Speaker LLC
No. of Drivers = 2
Mounting = Standard
Wiring = Parallel
Fs = 35 Hz
Qms = 7.3
Vas = 198.8 liters
Cms = 0.191 mm/N
Mms = 108.3 g
Rms = 3.263 kg/s
Xmax = 6.7 mm
Xmech = 18 mm
P-Dia = 330.2 mm
Sd = 856.3
P-Vd = 0.574 liters
Qes = 0.32
Re = 6.5 ohms
Le = 1.4 mH
Z = 8 ohms
BL = 22 Tm
Pe = 600 watts
Qts = 0.307
No = 2.568 % (one driver)
2.83V (2W at 4Ω) SPL = 104dB (150hz)
Box Properties
Type: Vented Box w/ Active HP Filter
Shape: Prism, square (optimum)
Vb = 6 cu.ft
Fb = 35 Hz
QL = 6.087
F3 = 35.19 Hz
Fill = none
No. of Vents = 2
Vent shape = rectangle
Vent ends = one flush
Hv = 10.87 in
Wv = 2.5 in
Lv = 16.71 in
Active 12 dB/oct. HP Filter
Fx = 35 Hz
Qx = 2
Candidates for the Darwin Award should not read this author.

Last edited by djk; 22nd March 2013 at 11:23 AM.
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