Free Speaker Plans

Cubo 18:
Cubo 18 is a multi purpose, stand alone bass bin that, like Cubo 15, will equal or out run a single 18" BR*, of similar size, from ~ 40 Hz and up in terms of sensitivity. Cubo 18 works with a wide variety of 18” drivers. It has a cut list from just over a single 18 mm*** sheet (244 x 122 cm) / (8' x 4') with a single angled cut. Cubo 18" realizes a cost effective, small and light weight enclosure following the KISS-principle.
In 2007 the first prototype was build and tested. Cubo 18" is the 5th prototype in a line of hybrids aiming at the achievements as stated above.  Cubo 18 Standard and Cubo 18 Extended will both work with a wide variety of drivers, if uncertain which one will be most suited, build Cubo 18 Extended or mail me at This email address is being protected from spambots. You need JavaScript enabled to view it.
Size: 62x62x65cm (HxWxD)    
Frequency: From 40 Hz up to 110 Hz    
Enclosure Type: Hybrid

3D Model (by K-M-Sound-System):

Cubo 18 Rebated 6mm:


Cubo 18 Extended Rebated 6mm:

Footnotes: 18” drivers preferably with an EBP of 100 or higher; Fs (22-42 Hz), Qts (0.25 - 0.58), Vas (200 - 450 L) / (7.4 – 16.7 ft^3). Where EBP = Fs / Qts . Measurements will follow.
Cubo 18/15 (difference): Cubo 18 is 3 cm (/ 1 1/6th inch) deeper then Cubo 15. Due to phase similarities Cubo 18 and Cubo 15 can be  used together without noticeable issues. Cubo 18 has on average slightly more output for a given input in comparison with Cubo 15 (based upon electro-mechanical relatively similar drivers), especially between Fc high and Fc low,whilst Fc high and Fc low, remain similar (= cut-off frequency).
 Cubo 18: Front view
Cubo 18: Side view without side panel
Cubo 18: Driver for comparison
Cubo 18: Detail magnet and bracing
Cubo 18: Magnet facing out
Cubo 18: Magnet in chamber

Posted: 5 days 13 hours ago by Knobs100 #21596
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I built 5 cubo 15 a couple of years ago and put eminence cappa pros and they sound pretty good especially inside. I can get 4 JBL 18" neo speakers that came out of vertec boxes for $100 each. I was thinking of building 4 cubo 18 to go along with the 15. I can run them on different Crown XTi amps and cross them a little different if I need to. My question is will 4 of the 18 give me the thump I am looking for live music outside or do I need to look at a horn loaded W cab
Posted: 2 weeks 2 days ago by hazzbo #21580
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Hello, does anybody have CNC plans for cubo 18's extended? we have a machine and would like to make X8 cubos for personal use down in Cape Town.

Made two Cubo 18's with fane 18xb's thrilled.

my email - This email address is being protected from spambots. You need JavaScript enabled to view it.
Posted: 2 weeks 3 days ago by Cubo15 #21578
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@Weloveit: Magnet in or out

@Tgeessounds: That looks good, so I hear it's another one for the list of builder-approved-drivers?

@Gfoster: I consider pretty much all drivers with a stamped steel frame as budget-drivers. In this a case a 4" VC budget driver that will work best in Cubo 18 Extended. I always wonder about the class of drivers that has everything a good driver needs but than doesn't seem to have the flux left to get the Qts down to European standards. Seemingly as a counterbalance the Vas is relatively low. Both Qts and Vas negatively influencing sensitivity, apart from that it will work.

@Weloveit again: This goes for pretty much any group of cabinets you build that will play the same frequency range: All the same, looks best, works best.

Best regards

Posted: 3 weeks 2 days ago by weloveit #21555
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Would you recommend 4 cubo 18's or 2 15's and 2 18's
Posted: 3 weeks 3 days ago by gfoster #21550
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So looking at this thread the following driver will be ok? P-Audio IMF-HP18B any ideas yet what tops will work better with them?

Posted: 3 weeks 4 days ago by t.geessounds #21545
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these boxes are really speaker friendly i run these 2 cubo with budget speakers on a 2400 crown bridge 40 to 90hz lr24 an these thing beat
thanks :woohoo:
Sir Cubo..
Posted: 3 weeks 4 days ago by weloveit #21543
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Also what difference does it make with the magnet facing inwards, or outwards?
Posted: 3 weeks 4 days ago by Cubo15 #21539
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@T.geessounds: A textbook example of how I would like to see every Cubo build, how does it fare?

@Welovit: Please, no. I mean, yes it would work but please don't. It all looked good till I saw the Qes and the physical weight. How about the Thomann 18 500? On paper it almost looks to good to be true.

Best regards

Posted: 3 weeks 5 days ago by weloveit #21536
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Hi would the Fane Sovereign 18-500's work in it? if not is there a cheapish driver that we could use?
Posted: 4 weeks 1 hour ago by t.geessounds #21521
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am building 2 cubo 18Ex for some speakermax WF18THOR speakers let hope these speakers perform well as i know these box can ;)
Posted: 4 weeks 13 hours ago by Cubo15 #21516
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The RCF LF18X451 has a good balance between efficiency and excursion, meaning it will work in both Cubo 18 and Cubo Sub. I've used a similar driver in Cubo 18 recently and with 1800 Watts it was definately unlike other Cubo 15 and 18 experiences. In fact it came closer to the vibrations felt with Cubo Sub, so putting it in Cubo Sub in the first place would be a good choice.

Best regards

Posted: 1 month 2 days ago by Tweeter_Box #21503
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anybody tried the RCF LF18X451 in a cubo yet?

would it work? specs are as below:

Resonance frequency: 30 Hz
DC resistance: 5.4 Ohms
Mechanical factor: 6.7
Electrical factor: 0.29
Total factor: 0.28
BL Factor: 30.5 T · m
Effective Moving Mass: 260 g
Equivalent Cas air load: 220 liters
Effective piston area: 0.122 m²
Max. linear excursion (mathematical): 13.5 mm
Voice - coil inductance @ 1kHz: 1.4 mH
Half-space efficiency: 1.90%
Power handling capacity: 1800 W AES
Sensitivity: 97 dB
Frequency Range: 30 Hz - 1000 Hz
Effective Piston Diameter: 395 / 15.6 mm/inch
Max Excursion Before Damage (peak to peak): 54mm
Minimum Impedance: 6.8 Ohms
Voice Coil Diameter: 115 / 4.5 mm/inch
Voice Coil Material: Copper
Voice Coil Winding Depth: 34 / 1.33 mm/inch
Number of layers: 2
Kind of layer: inside / outside
Top Plate Thickness: 15 / 0.6 mm/inch
Cone Material: No presed pulp
Cone Design: Straight
Surround Material: Polycotton
Surround Design: Triple roll
Posted: 1 month 5 days ago by Cubo15 #21494
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@Rotebass: Cubo 18 and Cubo Sub are roughly in the same sensitivty ballpark, this is also a bit driver dependant of course. Cubo Sub drops considerably lower though (for those interested in heavy bass).

@Thohaug: Rubber feed are cool ;)

Always good to see more measurements too.

Best regards

Posted: 1 month 1 week ago by thohaug #21473
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Yes i will be using rubber feet. Approx 15-20mm high that will sink about 1,5-2mms under the weight of the subs. This will ensure (mathematically) optimal decoupling and any resonances will be moved out of the audible range down to about 5-10hz.

Will be doing some free air measurements soon to check on the frequency response and more. Just from a little testing these small boxes have remarkably high output and have a nice clean sound. I like them a lot from the little testing i've been doing.
Posted: 1 month 1 week ago by rotebass #21471
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Is the difference between Cubo 18E and Cubo Sub a few dB of sensitivity and a few Hz of extension, or is there anything drastic difference?

If there isn't a huge dip in sensitivity I'd like the extra 5 or 10 Hz that Cubo Sub provides, and a nicer form factor (for my application at least).
Posted: 1 month 1 week ago by Cubo15 #21470
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@Rotebass: The 18TBW100 is best used in Cubo 18 Extended, with the magnet inside the horn. Parameter-wise it's a true subwoofer driver though, so it would have it's place in Cubo Sub as well.

@Thohaug: Daring colour, looks good. Are you gonna use rubber feet?

Best regards

Posted: 1 month 2 weeks ago by bee #21463
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good effort.
Posted: 1 month 3 weeks ago by sn95 #21450
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Nice looking
Posted: 1 month 3 weeks ago by thohaug #21448
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Building is now finished!

Here is the end result.

Posted: 1 month 3 weeks ago by rotebass #21443
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Hey Cubo,
Plans have changed since I last posted, Fane turned out to be a dead end in my area. I currently have a B&C 18TBW100 sitting in a box, I know that some of the other B&C 18's have been modelled but I can't find anything on this driver.

Any thoughts?

Posted: 1 month 3 weeks ago by Cubo15 #21439
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There is subtile differences between different stacking configurations, some might pronounce the ~100 -120 Hz 'kick'-region, others have slightly more 40-50 Hz output.. Stacking flattens response but can also create peaks. Personally I prefer to place these differences under the heading 'personal preferences'. Placing the horn mouth's together is always a good idea though.

Best regards

Posted: 1 month 3 weeks ago by thohaug #21436
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Thanks for the reply!
Also one more thing. How is it by stacking these 2 and 2? or even 4 by 4. Is there anything to gain?
In the case which it is something to gain then how is the best way to stack them in order to get the most advantage of it?
Posted: 1 month 4 weeks ago by Cubo15 #21433
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Those are goood drivers (third o intended). They will also work in Cubo Sub for that lowest oemmpph. In Cubo 18 Extended they'll offer maximum SPL, whilst still being a one-man-lift.

Best regards

Posted: 2 months 15 hours ago by thohaug #21426
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Hello Cubo. My friend and I are having a project and the plan is building 4x of the Cubo 18. High Spl in the lower range and good sound quality is why we have chosen this build. We Browsed through some drivers and we landed on the RCF LF18G401. How do you think these drivers will fare in this build?
On paper they look like a pretty good match, but I'd like your opinion on our choice.

Here is the T/S Parameters:

Resonance frequency

Fs 33 Hz

Re 4.8 Ohm

Qms 7.6

Qes 0.30

Qts 0.29

BL 24.6 T · m

Mms 182 gr

Vas 268 liters

Sd 0.122 m2

Xmax 8.5 mm

Le1K 2.4 mH

Eff 3.09 %

I laid the spec sheet file here in addition if you need to see something else about the driver
Posted: 2 months 1 week ago by Cubo15 #21396
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The MT130 or MT121 become suitable i.m.o. if you're ending up with building at least 4 x Cubo 18 (total). If you're using 1 or 2 Cubo's, a simple reflex cabinet is a better choice, as it offers wider dispersion and will easily drop down to 80 Hz.

Best regards