Cubo 18

I am in a position to buy 8 Cubo 18s and a very good price . They have been built with P.Audio P180/2242 drivers, which fall outside of the ranges recommended in the footnotes above. Could they still sound good? I haven’t had time to go do a listening test, but am curious how much difference it will make compared to more ideal drivers. Since I will have a lot of them, I probably won’t be driving them very hard.

Data sheet for the driver p-audio.co.uk/pdf/P180_2242.pdf

Hi Cubo15,

I am building three Cubo 18 Extended cabinets in 18 mm plywood and I plan to use B&C 18RS115-8 drivers.

The driver dimensions are:

* Overall diameter: 460 mm
* Baffle cut-out: 425 mm
* Bolt circle diameter: 443 mm
* Overall depth: 260.9 mm

Could you please confirm the correct mounting orientation for this driver?

1. Should it be mounted with the magnet visible inside the horn, or with the magnet inside the rear chamber?
2. Does the 18RS115 fit safely in both orientations without touching the rear panel or the lower internal brace?
3. You previously recommended an 18–30 mm spacer ring. Would an 18 mm birch plywood ring provide enough clearance for this driver, or would you recommend a thicker ring?
4. On which side of the baffle should the ring be installed?
5. Is the ring a suitable solution for the driver depth, or is it intended only to adapt the bolt pattern?

I would like to confirm the mounting before cutting the three baffles and ordering the spacer rings.

Thank you very much for your help.

Best regards,

Lelio

They have been built with P.Audio P180/2242 drivers, which fall outside of the ranges recommended in the footnotes above. Could they still sound good? I haven’t had time to go do a listening test, but am curious how much difference it will make compared to more ideal drivers.

Some people with high Qes drivers report a lot of output centered around 60 Hz, which means a lot of thumping bass at the expense of lower bass below it. Low to medium Qes drivers (0.2 - 0.3) offer a flatter, slowly climbing freq. response.

If you let me know your experience I can add it to 'the field of knowledge'.

Could you please confirm the correct mounting orientation for this driver?

Based on the preliminairy specs of the B&C 18RS115-8 and guessing the magnet diameter to be 15 cm. The driver won't fit with the magnet inside the chamber of Cubo 18 Extended, unless you use a 30 mm spacer ring on the outside of the baffle (to decrease the driver depth inside the chamber).

The B&C 18RS115-8 will fit with the magnet inside the horn (MIH), if you do not mount any bracing in the center. However, as that bracing becomes paramount with such a high power driver, it will be best to increase the height of Cubo 18 Extended from 62 cm to 65 - 66 cm. The increased height will be used to increase the space in front of the baffle. That way you can keep everything else the same, including the bracing. Mounting MIH makes sense as it better cools the driver (outside tips of the winding depth), it also offers the best low frequency response which ever so sligthly matches the B&C 18RS115-8 extended Xmax as well.

Cubo