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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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  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's Avatar
Cubo15 replied the topic: #25016 2 weeks 4 days 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's Avatar
Zambrotta replied the topic: #25015 3 weeks 1 day 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's Avatar
Cubo15 replied the topic: #25013 3 weeks 1 day 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's Avatar
Zambrotta replied the topic: #25012 3 weeks 3 days 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's Avatar
Cubo15 replied the topic: #24890 1 year 1 month 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's Avatar
blake8188 replied the topic: #24887 1 year 1 month 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's Avatar
Andrew4566 replied the topic: #24835 1 year 5 months 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's Avatar
Andrew4566 replied the topic: #24833 1 year 5 months 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's Avatar
Andrew4566 replied the topic: #24827 1 year 5 months ago
Thanks Cubo!!
Cubo15's Avatar
Cubo15 replied the topic: #24826 1 year 5 months 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's Avatar
Andrew4566 replied the topic: #24825 1 year 5 months ago
18sound 21lw1400...I accidentally bought these.

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

-Andy
Cubo15's Avatar
Cubo15 replied the topic: #24763 1 year 9 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's Avatar
shashnatiq replied the topic: #24762 1 year 9 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's Avatar
Cubo15 replied the topic: #24715 1 year 11 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's Avatar
space141 replied the topic: #24714 1 year 11 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's Avatar
Cubo15 replied the topic: #24650 2 years 1 month 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's Avatar
SubMeditation replied the topic: #24648 2 years 1 month 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's Avatar
Cubo15 replied the topic: #24635 2 years 3 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's Avatar
Stefist replied the topic: #24630 2 years 3 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's Avatar
Cubo15 replied the topic: #24601 2 years 4 months ago
I have no data.
oksana's Avatar
oksana replied the topic: #24600 2 years 4 months ago
I want to get data for hornresp
Cab calloway's Avatar
Cab calloway replied the topic: #24586 2 years 4 months ago
Amazing thanks very much for the info!
Cubo15's Avatar
Cubo15 replied the topic: #24585 2 years 4 months ago
The Celestion is a very decent 15" driver and although I would normally recommend Cubo 15 Extra Extended as the best match, I've seen lesser 15" drivers used successfully in Cubo Sub. So if those drivers survived, these definitely will. The attachment shows Future Pussy Sound System, 8 x Cubo Sub loaded with the Eminence 3015LF (if I recall correctly).

Cubo
Cab calloway's Avatar
Cab calloway replied the topic: #24580 2 years 4 months ago
Hey Cubo,

Sorry if this has been asked before (couldn't find anything on it) but what do you think of the Celestion FTR15-4080HDX being used in a cubo sub? I can get a pair for reasonably cheap and was thinking of building the subs with these and then upgrading later on to 18s when I can afford them. The subs would be used for mostly house and disco at open airs.

Thanks!
Cubo15's Avatar
Cubo15 replied the topic: #24420 3 years 1 month ago

you're saying a 4 ohm version sub rated 1200watts will sound different as compared to the same model 8 ohm version sub
rated 1200watts

Ideally it does not but power handling is simply a measure of how much (thermal) energy the driver can handle before it burns up. If Qes, Le, etc. are different enough, it can affect the sound, although these differences are least noticeable in bass and sub enclosures.

ss the RCF LF15G400 a good driver for the cubo sub?

As far as 15" drivers go, it's actually a pretty good Cubo Sub driver. For a 15" driver that's a very respectable Mms.

Best regards Cubo