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Cubo Sub / Cubo 21

The largest cabinet from the Cubo series stands upon the edge of portabilty; To big to be compact, to compact to be big.

Like it's predecessors Cubo 12, Cubo 15 and Cubo 18 it's a stand-alone bass bin. It will equal or out run an 18" reflex cabinet from 30 Hz and up in terms of sensitivty*. Like all Cubo-designs it excels on the KISS-principle, with a single angled cut and a cut list from 1 and a 1/2 sheets of 244 x 122 cm / 8' x 4'.

Development

Based on Cubo 15 and Cubo 18, Cubo Sub is the 3rd prototype in a series of cabinets aiming at good reproduction down to 30 Hz. Mount the driver with the magnet in the horn for best low frequency reproduction from 30 Hz up to 100 Hz. With the magnet in the chamber for maximum output from 35 Hz up to 110 Hz.

Versions

Cubo Sub is optimized for single 15"/ 18" drivers**, and single 21" drivers, nicknamed Cubo 21. 

All 21" drivers will fit in the standard Cubo Sub but in that case care must be taken when pre-drilling the bolt pattern. Plans for Cubo 21 are available through e-mail (questionsaboutcubo at gmail dot com).

*        Measurement against BR18a tuned to 37 Hz

**      Due to reproducing sub frequencies 18" drivers with an Xmax of 7 mm or more are favoured. On average a 15" needs 1.5 times the excursion capabilities to produce the same output as an 18" driver or 2 times that of a 21" driver.

Acknowledgements

The designer likes to thank Xoc1 for his aid in the development process.

 

 

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 Download highest quality: Picture below / right click / save as.

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Preliminary measurements can be found here: http://www.freespeakerplans.com/index.php?option=com_jfusion&Itemid=64&jfile=viewtopic.php&p=11555#p11555

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Cubo15 replied the topic:
8 months 13 hours ago
HI,

You can adjust the width to 660 mm, without any issues. I would set the high pass at 20 - 30 Hz (experiment a bit with frequency and slope untill it sounds just right), if you're going for maximum power/ output 30 Hz is better.
shem1 replied the topic:
8 months 1 week ago
HI Mr cubo could i make the cubo sub 660mm wide instead of 620?
Also what hpf would i need on the cubo sub running a pd186 mk1 in it?>
Cubo15 replied the topic:
1 year 3 weeks ago
There actually is, send me an e-mail at questionsaboutcubo at gmail dot com
Zambrotta replied the topic:
1 year 3 weeks ago
Hello cubo is there a plan for a dual cubo sub 18
Tetris replied the topic:
1 year 1 month ago
Over 6 years since I asked, I've FINALLY got round to starting my RCF LF18X401 powered Cubo Subs! Unfortunately due to the astronomical cost of birch ply now, I've gone for MDF, but one is nearly finished and am excited to see the results! Have incorporated handles into the bottom bracing which I hope won't affect things too much, but after years of negotiating stairs, I felt this was a necessary compromise! Will post updates when ready (don't hole your breath)  

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Cubo15 replied the topic:
1 year 8 months ago
A typical Cubo Sub driver has a Fs between 25 - 40 Hz, a Qts between 0.2 - 0.4 (lower is favourable) and a Vas between 150 - 300 Liter. Xmax 7 mm or more (more is better), a 4" voice coil (or larger) and Xmech preferably 20 mm or more (one way). A typical ferrite 18" will at least weigh in at 12 kilo (25 lbs).
Zambrotta replied the topic:
1 year 8 months ago
ok thanks so can you give me a guide on what to look at in the thiele parameters of a 18 inch driver that would do well in the cubo sub. Am sorry am still a novice in the diy speaker building

Zambrotta
Cubo15 replied the topic:
1 year 8 months ago
To be honest it's not the greatest loudspeaker, it might be meant for car audio originally (low Vas, high Qes) but it simulates surprisingly well in Cubo Sub. Without any alterations, going both low and loud with a rising response, wouldn't cross it too high though (preferably a steep 80 Hz-ish crossover).

Cubo
Zambrotta replied the topic:
1 year 8 months ago
Hello Cubo how are you the driver i can access for my cubo sub build has got the following parameters

Fs = 55Hz
Qms= 3.745
Vas=2.377 cu. ft
Cms=0.041mm/N
Mms=204.2g
Rms=18.85kg/s
Xmax=8mm
P-Diameter=370mm
Sd=1075sq.cm
P-Vd=0.86 liters
Qes=0.75
Re=5 ohms
Le=0.61mH
Z=5ohms
BL=21.69Tm
Pe=1000watts
Qts=0.625
no=1.439%
1-w Spl =93.73db
2.83-V SPL=95.77db


I would like to find out from you if its a good driver for the cubo sub and if there are any adjustments to be made on the cubo sub to get maximum output from it

Best regards

Zambrotta
Cubo15 replied the topic:
2 years 9 months ago
That does defeat part of the hybrid purpose, as the "tap" near the horn mouth does give it an ever so slight increase in output (near 60 Hz). It follows the concept of the 'tapped horn' in that regard instead of a 'rear loaded horn' a.k.a 'scoop' (driver placed on the front/ not in the horn mouth). The SBH is a 'front loaded horn' with a low frequency output nearer Cubo Sub IIRC.

Cubo 18 and Cubo Sub are two different designs.

 
blake8188 replied the topic:
2 years 9 months ago
Would it be possible to design some kind of hybrid between the Cubo 18" and the SBH in the sense that the driver in the Cubo would be in its own seperate space instead of the mouth of the horn/end of the throat? Or does that just defeat the purpose of it being a hybrid? I'm quite new to this so excuse the poor terminology please :)
Andrew4566 replied the topic:
3 years 1 month ago
Is the three layer buildup on the opposite side of the horn from the Driver for strength or needed for the horn tapper?

-Andy
Andrew4566 replied the topic:
3 years 1 month ago
Is the three layer buildup on the opposite side of the horn from the Driver for strength or needed for the horn tapper?

-Andy
Andrew4566 replied the topic:
3 years 1 month ago
Thanks Cubo!!
Cubo15 replied the topic:
3 years 1 month ago
The main benefit of a 21" driver over an 18" driver (in Cubo Sub) is either when you EQ it down low or when you have a lot of power available. I've send you the plans for Cubo 21 from questionsaboutcubo.

Cubo
Andrew4566 replied the topic:
3 years 1 month ago
18sound 21lw1400...I accidentally bought these.

Could you please assess how well this driver would work in the Cubo Sub?

-Andy
Cubo15 replied the topic:
3 years 5 months ago
I would rate them exactly in that order:

1. RCF LF18X401
2. Eighteensound 18LW1400
3. Fane Colossus Prime 18XS

Best regards Cubo
shashnatiq replied the topic:
3 years 5 months ago
Hi Cubo.
Which of these drivers wold be best suited for the Cubo Sub?
RCF LF18X401
Eighteensound 18LW1400
Fane Colossus Prime 18XS
Cubo15 replied the topic:
3 years 7 months ago

but it never sounded that great due to the heavy cone I think

It would be really nice if you new the T/S-parameters of the PD.

Now it's difficult to say whether you didn't like the driver, the cabinet or the incorporation into the rest of your system slash processing. If you know the T/S-parameters it's easy to compare them to the 21PW1400Fe and say if it's the same or completely different and if it attributed to your experience of the Cubo 21. To answer your question whether this is going to improve things for you without the T/S-parameters, we need to figure out what you didn't like about it exactly. What did (or didn't)  you do to it, processing, amplifier power, what tops did you use (any delay on those), magnet inside the chamber, magnet inside the horn, etc. To me the 18LW1400 in Cubo Sub with the magnet inside the horn or inside the chamber sounded like two different cabinets, one for 'rumble' and the other one rather tight and loud.

It would also help if you have heard the PD's in another enclosure, anything that tells us if it's the driver, Cubo or system settings, or a combination of those.

Typically a 21" driver doesn't perform that much better than an 18" driver, in the same sized enclosure, it just has more potential. You need either a lot of power or quite a bit of EQ to get that potential (air displacement) to fruition. Someone in the Netherlands is building a custom version of it and probably going for the RCF LF21N551 or Lavoce SAN215.30, I assume with a small nuclear reactor to power the amplifiers because they can handle it and need that kind of power to really shine (beyond the scope of an 18" driver).

Best regards Cubo
space141 replied the topic:
3 years 7 months ago
Hello Cubo and fellow community members.

I made a 21" version of the Cubo Sub a few years back now which was fitted with an old-shool Precision Devices driver that was rated 750W rms (ET211S) but it never sounded that great due to the heavy cone I think.

Can anyone shed any light on the following driver and whether it would be suitable for the CUBO SUB - I cannot find any recommeded TS parameters for drivers on the page, neither can I find a post of anyone else making the 21" version to my knowledge.

Any insight would be greatly appreciated - the driver is the Beyma 21PW1400Fe with the following specs:

Thiele-Small Parameters

Resonant Frequency (fs) 30 Hz
Impedance (Re) 5.2 ohms
Coil Inductance (Le) 3.7 mH
Mechanical Q (Qms) 7.44
Electrical Factor (Qes) .36
Total Q (Qts) .34
Comp. Equivalent Vol. (Vas) 14.18 ft3 / 401.5 Liters
Voice Coil Overhang (Xmax) 10.0 mm
Surface Area of Cone (Sd)m2 0.1734m2
Reference Efficiency 2.83%
Displacement Volume (Vd) 1729 cm3

Many thanks in advance,

TLC.
Cubo15 replied the topic:
3 years 10 months ago
I suppose you mean reducing the inner width to 30 cm, although I would make it as small as possible, so perhaps 28 cm inner width. Also, with a single driver that wouldn't work out all that great, I would fit two 10" drivers (one behind the other) on the baffle. It should just fit, with about 1 cm between the drivers. Only one 10" simply doesn't have the Sd to make it work but two have.
Now, although I'm a big fan of 12V PA systems that drop down low, it isn't the most energy efficient. If output is more important or how long the battery lasts, two Cubo 12 (with reduced inner width) will have more output between 50 - 80 Hz. This is where the most energy in bass is located, it won't sound as low but add a lot of thump.

Cubo
SubMeditation replied the topic:
3 years 10 months ago
Greetings Cubo,

do you think i could adjust the inner depth to about 30cm and put thi 10" driver in: www.lautsprechershop.de/pdf/mivoc/awm104.pdf ?
I've builded a tapped horn with this speaker and want to know if the extra wood & weight is really worth it, because i'm planing to build serveral of them for some 5ghz connected 12v bicycle systems.

Cheers
Cubo15 replied the topic:
3 years 11 months ago
I don't have any of the data anymore, I suggest making a (2D-)model in Sketchup and derive the Hornresp input parameters from there, if you need any pointers let me know.
Cubo
Stefist replied the topic:
3 years 11 months ago
Hello

I would be curious to see the simulationwith a rcf 18X451, A b&c 18DS115 and a bms 18n862.

Can anyone do this ?

cheers
Cubo15 replied the topic:
4 years 2 weeks ago
I have no data.