Cubo 15

Ok, just for fun I made single Cubo15 extended because I had 4 x RCF L15P540 drivers laying around and waiting for something. Magnet is in a chamber, as it is much better this way (tested both ways).
Results:
Surprisingly good amount of SPL, 50Hz and up but plays down to 40Hz. Nice and punchy, when crossed at 80-90Hz.
For electronic dance music, psytrance, house etc.. very good design. 4 x similar cubo15's would be enough even for bigger parties!
For live music, well..propably not my first choice.
For comparsion, I do have many different subwoofer designs/boxes like standard reflex, miniscoop, hog scoops, 18" bandpass etc..

Oh, almost forgot to say, single man can lift and move cubo15 easily (18mm ply) which is also nice feature! Lots of fun from such a small design all in all.

Just wondering if I should try extra extended version.. I think L15P540 likes small chambers anyway.

Thanks for the review. The L15P540 is definitely most suited for Extra Extended.

As a rule of thumb, if:

Qts x Vas > 120, Cubo Standard
Qts x Vas = 100 - 120, Cubo Extended or Standard
Qts x Vas < 100, Cubo Extended

Only for Cubo 15:

Qts x Vas < 50; Cubo 15 Extra Extended

Best regards Cubo

Tested RCF L15P200A (cubo extended, magnet in horn), lows were totally missing, sound was one noted mid bass / no punch.  L15P540 is working much much better, even tho it's mid bass driver there was more 40-50Hz SPL compared to P200A.

P200A specs:
4 inch voice coil
Fs 29Hz
Qts 0.28
Qms 10
Qes 0.3
Xmax 9mm
Bl 17.2
Vas 280litres

Dont know what's wrong with this, specs are not too far off from recommended drivers.. maybe cubo standard would be better?

I've seen some different versions of the L15P200A on the internet, some of which have a Qes as high as 0.63, which would explain the lack of 40 -50 Hz. The version with a Qes of 0.3, claims a 4" voice coil, a Mms of 77 g, a Xmax of 9 mm and a BL of 17.2 N/A. That combination seems unlikely, if not completely wrong.

If you have the ability to measure the T/S-parameters, that would be a good thing to do, as the T/S-parameters as you posted do not indicate anything like you've reported. Unless it is a new driver (unused), if so that would be a likely cause.

Best regards Cubo

Yes there are three variations:  L15P200,  P200A and P200AK but there seems to be different parameters over internet as you said.  My versions are 200A indeed. 
I'll take some basic measurements like Fs out of these, let's see what is going on!

I've got two of these drivers, used but mint condition (looks like new!).

EDIT:  measured FS = 29...30Hz.
Re = 3.1ohms

Made some more outdoor test w/ P200A but it just wont work as I was hoping.  Lots of uncontrolled cone movement but not enough SPL and overall quite horrible honky/flappy sound quality.  
I think Cubo wants tighter driver having more BL or something to get it right!

Re = 3.1ohms

That indicates a 4 Ohm driver or an internal (semi) shortcut.

Normally it's an 8 Ohm driver, so that's not a good sign for any of the listed T/S-parameter to actually apply to this driver. At this point I would either conclude that the driver is not what it says on the label (even if it was the label is contradicting itself), or it's defective.

Best regards Cubo

Yes, its possible.  I have seen 4ohm versions tho.. Anyway I will put these two drivers to my dual 15" reflex to see how they perform there. 
Need to look for more drivers because I really would like to have two cubo15 enclosures with proper sound.  L15P540 is good when it comes to sound quality, but it lacks Xmax..and therefore cannot be pushed harder.

I'll keep informing about these odd RCF drivers, this thing has to be figured out! 

If you want similar performance to the L15P540 but louder, I would look at a driver that has a similar n0 (~3%) with a 4" voice coil and a Xmax between 7 - 9 mm.

Best regards Cubo

Cubo15 wrote: If you want similar performance to the L15P540 but louder, I would look at a driver that has a similar n0 (~3%) with a 4" voice coil and a Xmax between 7 - 9 mm.

Best regards Cubo

That would be ideal.  Sorry, but what is n0?