Cubo 15

but the one loaded with the 2226 is the meanest of them all thank you for the design brother

Hello Cubo.
Can you judge which of these speakers is best for the cubo 15?
a) Kappa pro 15 lf2
b) Black Widow 1508-8 sps
c) STX W.38.1200.8.MC
Thank you in advance for your answer

Hello Oskar,
I have used two "W.38.800.8.MC" from two different series and I think they are quite weak speakers, so I don't know if the "W-38-1200-8-MC" will be much better.
Currently, I have loaded 15TBX100 and the difference is big.

Both the STX W.38.1200.8.MC and W.38.800.8.MC look good on paper, except one thing, the weight of the drivers doesn't correspond to such T/S-parameters: Normally you wouldn't use the physical weight of a driver to base it's performance on, but since all these drivers have ferrite magnets and from the looks of the photo's also have aluminium baskets, you would expect better overall performance with an increasing physical weight.

The 1508-8 SPS BWX for example, weighs 7.7 kg but it has a high-ish Qes (less magnet needed) and small Xmax (4.7 mm again less magnet needed), so those numbers add up.
The Kappa Pro 15LF, weighs 10 kg, has a medium Qes and Xmax, and a 3" voice coil instead of a 4" voice coil like the Black Widow has. Again those numbers add up.

The STX W.38.1200.8.MC, weighs 7.5 kg, (claims a large voice coil and Xmax, medium Qes) and the T/S-parameters suggest it would would be close in performance to the 15TBX100, however the 15TBX100 (also large voice coil and Xmax, medium Qes) weighs 12.3 kg.

So something is off, as I'm rather safe than sorry, I would exclude the STX drivers from the list.

1) Kappa Pro 15LF
2) Black Widow 1508-8 sps (or the Kappa 15LF, 9 kg but a steel chassis)

Cubo

hi cube, i'm savior from italy. i have a problem with 2 sub montarbo sw540. in practice they have the plastic cabinet and too small, so these subs sound the same way both front and back! I was thinking of building two new cabinets and came across the cube 15 project.
the features of my sw540 sub are:
MOSFET amplifier (class AB)
Max. Output power 550 watts continuous rms 850 max peak
Frequency Response 38Hz ÷ 120Hz ± 1dB
impedance 4ohms
Stereo electronic crossover 24dB / octave Crossover frequency 120hz

I think the woofer is from B&C but you don't know the model! however i found some specifications of this woofer in the manual.
Nominal diameter 15 "
Frequency range 37 ÷ 2000Hz
Sensitivity 99db
Rated impedance 4 ohms
Net weight 8 kg
FS 37hz
RE 3.04 Ohms
Qms 16.93
Qes 0.35
Qts 0.34
Vas 0.1m3
ηo 3.17%
B.l 16.62 T / m
SD 0.085m2
Xmax ± 5.25mm
 

Those are actually pretty good drivers, I would use them in Cubo 15 Extended or Extra Extended up to about 80 - 100 Hz. The only thing lacking is the Xmax, I would use a high pass at 40 Hz and use about 500 W of amplifier power per driver.

Cubo

thanks cube, my problem is that I would use his original amplifier which has the cuts already set and not settable!
you say they won't do?
the amp delivers 550watt, the cut is from 38hz to 120hz.
however in the diagram I may see that the cut is at 40hz 12db.
I'm ignorant of technical data! i have manufacturing experience with cnc machines, but i have always built cabinets and heads for guitar amps designed by others.
do you think maybe a bandpass like the turbosound tcx115b would be better, which as a frequency range is very similar to my sw540 sub? 

The high pass is good, I know that some Cuboteers cross Cubo 15 at 120 Hz or higher but I prefer 80 - 100 Hz myself, so I can't personally recommend it. The Turbosound tcx115b looks like a good choice, it won't be as loud as a Cubo 15 but it works better with the amplifier/ processing that you've got. So unless you're able to use additional EQ on the Cubo 15 (to suppress 100 - 150 Hz), I think the Turbosound tcx115 is a good choice. Best regards Cubo