Size: 62x62x62cm

Frequency: From 40 Hz up to 110 Hz

Enclosure Type: Hybrid

Recommended DriverKappalite-3015lfKappapro-15lf-2kappa-15lf or  drivers with EBP of 100 or higher; Fs (27-50 Hz), Qts (0.21 - 0.41), Vas (150 - 300 L) / (7.4 - 11.1 ft^3). Where EBP = Fs / Qts (strictly speaking it's Fs / Qes)


Cubo 15: Cubo is a multi purpose, stand alone bass bin that will equal or out run a single 18" BR*, of similar size, from ~ 40 Hz and up in terms of sensitivity. Utilising a non-expensive driver such as the Eminence 3015LF, Kappa 15LF and Kappa 15LF Pro** and a cut list from a single 18 mm*** sheet (244 x 122 cm) / (8' x 4') with a single angled cut, Cubo 15" realizes a cost effective, small and light weight enclosure following the KISS-principle.

Development: In 2007 the first prototype was build and tested. Cubo 15" is the 4th prototype in a line of hybrids aiming at the achievements as stated above.  The measurement below shows the gain over the stated bass reflex (see * for details). Cubo 15 plans are also available in an Imperial version, plan available on request.

Versions: As a rule of thumb:

Qts x Vas > 120, Cubo Standard
Qts x Vas = 100 - 120, Cubo Extended or Standard
Qts x Vas < 100, Cubo Extended
Qts x Vas < 50; Cubo 15 Extra Extended

Magnet orientation:

The driver mounted with the magnet visible (the magnet in the horn) typicall gives the lowest bass response and slightly better cooling of the voice coil. Mount the driver with the magnet inside the chamber for most output around 60 - 80 Hz or the highest possible crossover frequency.

Footnotes:* 18Sound 18LW1400 in a 175 liter bass reflex tuned to 37 Hz. (6,6 ft^3) vs. Cubo 15 ; Eminence Kappa 15LF.          ** Apart from these drivers Cubo will work with a wide variëty of 15" drivers preferably with an EBP of 100 or higher; Fs (27-50 Hz), Qts (0.21 - 0.41), Vas (150 - 300 L) / (5.5 - 11.1 ft^3). Where EBP = Fs / Qts.  If you're uncertain if a driver is suited, PM or mail me at This email address is being protected from spambots. You need JavaScript enabled to view it.         *** If you want to use 15 mm material use 11-ply Baltic birch, nothing less. Plans available on request.

Designer: Cubo15 [view profile]alt

 

Cubo 15 Standard Plan:

Cutsheet (clearly visible after download):

Cubo 15 Extended Plan:

Cubo 15 Extra Extended Plan:

Only the 2 inner horn panels are different from Cubo 15 Extended, all else equal.

 

 



Cubo15's Avatar
Cubo15 replied the topic: #24905 1 day 21 hours ago
Your gut feeling is important but you seem to have difficulty substantiating your claim in measurable terms. What exactly is the benefit of the optimization of the flare rate and how would one measure that? I think the reflectors are small compared to the wavelengths involved and thus do not have a significant influence on the frequencies involved.

There's a few things to consider as designing a (bass) cabinet is about compromises, any 'optimization' of the design will lead to at least one 'downgrade' in another field of performance. What you call an optimization of A, someone else will just call B performing worse.

An expanding horn with length X will not tune as low as a non-expanding horn of the same length, based on excursion minima, although this might not necessarily show as such in the frequency response. In other words, increasing the flare rate of the horn will decrease the tuning frequency. Secondly any increase in horn volume, be it by length or horn circumference increase, will lower the volume of the rear chamber which will further increase the tuning frequency, unless the increase in horn length offsets the decrease in rear chamber volume. You could opt to decrease the horn throat but this will increase the compression ratio, which can lead to unpredictable behavior (beyond simulation) and possible damage to the driver on high power levels. To keep the design favorable to a wide range of drivers, with unknown quality within the Qts x Vas range, the compression ratio is best sparingly increased if at all.
Regardless of how you combine these factors, unless you keep the horn volume from increasing, your optimization of the horn flare will decrease the low bass output and increase the peakyness of the lower response. Resulting in worse time behavior below 100 Hz and less low bass output, in return for better time behavior above 100 Hz and a slightly higher allowable crossover frequency.  

If you're interested in the time domain, look at the group delay, phase and impulse response in Hornresp. They're however not always straightforward in their practical meaning and as your suggested changes are small, so are the differences in these graphs, it might be impossible to call one better then the other. For me it's the combination of simulating, building and hearing multiple designs that gives me a feel for how to interpret the combination of these graphs and what is desired, I'm positive I do not understand as much of it as I could or would like to. 

If you're not really sure how this flare rate optimization does improve characteristics to what extend and in what way, I suggest opening a topic about it on diyaudio.com, not only will you find more like-minded souls but also the wealth in knowledge currently lacking either of us
TommyBear's Avatar
TommyBear replied the topic: #24903 5 days 16 hours ago

Knowing the above frees the ability to look at the segments from a different perspective, the Extra Extended segments approximate a hyperbolic horn contour, giving a lower tuning at the expense of output near the 50 - 60 Hz mark. If you keep the horn mouth the same, a smoother horn flare rate will decrease low frequency extension, while increasing output near that same mark.
Extended stands to lose the KISS-principle, 3 angled cuts instead of 1, no backward compatibility between Standard and Extended because of cut sheet differences and construction. All the while I don't think you'll simulate a significant difference let alone measure something. Feel free to try though.

 

If the Extra Extended abandons the KISS principle to some extent, why not optimise this first segment further? The first 'channel' segment serves - if I have understood the explanations correctly - to extend the horn. Here, too, I have the feeling that the design creates an avoidable resonance that is reflected in the in/out vibration behaviour - but perhaps my gut feeling is simply deceiving me here...

Would it be an approach to improve the approximation on the one hand and the stability on the other hand by using two conically arranged boards in this first segment? Or, with less material input - and less gain in stability - to make the segment boundary not parallel to the lid? In any case, the desired extension of the horn would be achieved.


Curious Sunday greetings
TommyBear's Avatar
TommyBear replied the topic: #24902 6 days 9 hours ago

Consider the size and behaviour of the frequencies involved here. A wavelength at 100 Hz is 3.4 meters, at 10.000 Hz it's 3.4 centimeters, so at 10 kHz your thumb is a considerable obstacle but at 100 Hz your entire arm isn't. Likewise, at 10 kHz this horn is a complete mess but at 100 Hz and below it isn't noteworthy. You might find a stepped segment response to have the same order of performance.

It is clear that due to the wavelengths in the frequency range under consideration, the approximation of a horn contour is easier/less problematic than in the mid-range or high-frequency range. In my opinion, however, this only applies to the consideration of the amplitude curve over the frequency. The discontinuities definitely lead to reflections and these should be reflected in the transient and decay behaviour. I don't have the experience here to know how strong this is and whether the effort is worthwhile through - still discrete - but more continuous transitions between the segments.
How do you assess this from your wealth of experience? Efficiency losses/reduced sound pressure due to overall volume reduction but better behaviour in the time dimension?

Greetings
TommyBear's Avatar
TommyBear replied the topic: #24901 6 days 10 hours ago

I'm not sure why there's a lack of reports on the 15LB100, I know it has been used a few times. I'm expecting it to work as intended.

 

Unfortunately, I can only find German-language contributions that are all without 'depth' and therefore do not help me. I had assumed that the loudspeaker could be found in other countries under a different designation, hence the question.

At Thomann there are two more budget speakers presumably from the same Chinese source: 18-500/8-A and 15-300/8-A. Is there any experience regarding the use of the 18" in the Cubo Sub? And the other 15" should be usable in the Cubo Kick 15 - its low maximum excursion should allow a safe operation with a 4th order high pass filter in the range of 100.125 Hz...

Cheers
julius111's Avatar
julius111 replied the topic: #24900 6 days 13 hours ago
the top for this rig was built after this plan: celestion.com/blog/build-this-compact-10...y-pa-speaker-design/

i have used a different horn, though. they suggest x-over 2.1khz, but that sounded too honky for me.
kept increasing until i was happy with the result, listening to jazz albums i know well. the limiting factor in any case is the amplifier board, great set of features but lack of engineering finesse.

best, J.
Cubo15's Avatar
Cubo15 replied the topic: #24899 1 week 9 hours ago
Why do you not like the constant cross-section of Extra Extended? What would a continuous transition between segments in Extended achieve? I really would appreciate an answer because I just don't see it. 

Consider the size and behaviour of the frequencies involved here. A wavelength at 100 Hz is 3.4 meters, at 10.000 Hz it's 3.4 centimeters, so at 10 kHz your thumb is a considerable obstacle but at 100 Hz your entire arm isn't. Likewise, at 10 kHz this horn is a complete mess but at 100 Hz and below it isn't noteworthy. You might find a stepped segment response to have the same order of performance.
An additional board in the corner however would take away air volume from the horn and thus it actually takes away performance, which can be measured if the air volume is significant. It will also help to improve the frequency response somewhere near 1 kHz and above but considering the intended range... 

Knowing the above frees the ability to look at the segments from a different perspective, the Extra Extended segments approximate a hyperbolic horn contour, giving a lower tuning at the expense of output near the 50 - 60 Hz mark. If you keep the horn mouth the same, a smoother horn flare rate will decrease low frequency extension, while increasing output near that same mark.
Extended stands to lose the KISS-principle, 3 angled cuts instead of 1, no backward compatibility between Standard and Extended because of cut sheet differences and construction. All the while I don't think you'll simulate a significant difference let alone measure something. Feel free to try though.

I'm not sure why there's a lack of reports on the 15LB100, I know it has been used a few times. I'm expecting it to work as intended.

@Julius: 4 kHz sounds a bit high, although without any driver information it's hard to be sure. Nice picture!
TommyBear's Avatar
TommyBear replied the topic: #24898 1 week 12 hours ago
Hi Cubo,

i am planning to create a Cubo 15 based on an inexpensive loudspeaker of Chinese origin (~€130). The speaker is offered in Germany by Thomann as a replacement speaker for their budget PA speakers 'the box'. Its designation is 15LB100-8W ( 166844_specification.pdf & 166844.pdf ). According to the paper values (Qts 0,34, Vas 113,5, rated power 500W, 4" VC, Xmax 22mm - 11mm) the speaker should work well in an Extended Cubo 15, and with a 4th order high pass at 350-400 Watt it should still have enough reserves for a safe operation. If more power is needed, the speaker should be stacked with a second Cubo 15 and driven with 800 Watt (~1kW for headroom) at 4 Ohm.

Unfortunately, I have not been able to find any reports on this speaker in a Cubo 15 - is this perhaps because the speaker is available outside Germany under a different name?

Yes, based on the paper values, the Extra Extended Cubo 15 variant would be a possibility. However, I don't like the constant cross-section of the first 28.5 cm of the EE variant, so I would use the 'normal' Extended variant.
Apropos: is there a Cubo 15 EE parameter set for this one for Hornresp? The transition from the first segment to the second is a mystery to me. The cross-section at the end of the first segment is much larger than the entrance cross-section of the second segment, isn't it? Why was this discontinuous transition chosen? Wouldn't an additional board in the corner achieve a better transition? I have something similar in mind for the transition from the second to the third segment. That's why I would like to 'play' a little with a simulation in order to realise a prototype in a more targeted way...

THX & Greetings
julius111's Avatar
julius111 replied the topic: #24896 3 weeks 9 hours ago
Hi Cubo,

thanks for sharing your plan! i‘ve recently built what i would call a „light“ version of the cubo15.

to put it on a tricycle, i‘ve used 12mm birch multiplex and left out any piece that was (in my view) not necessary to the mouth of the horn. also, i had to make it only 59,9cm wide, so it would fit the frame. i chose the cubo15 design since i am a big fan of the KISS rule, and the designs support of many different drivers- i thought if it can handle different drivers, it could handle my messing around with it, as well.
my cabinet is driven by a eminence kappa 15A, which i already had on hand. i was concerned if the lack of braces would result in resonance from the body. but since the speaker is powered by a tiny class D amp board, there is less than 100 watts going in, so there is no problem before the amp starts to clip audibly.

in case anyone is curious, the amp is a tinysine 50+50+100W with bluetooth and dsp, which i am running active 3 way. the top is built after a plan from celestion, again using drivers i had. currently, the dsp is only doing crossover at 90 and 4k hertz, but i plan to do some measuring and correct phase and frequency response. crossover points and gain reduction (something like -10db for mid and -17db for hf) were chosen by listening to different music which i use regulary to set up sound. i am happy for any suggestions on how to improve ;)

the (almost) finished cabinet can be seen in my profile pic- i just need to add a speakon connector in the back, so the cable won’t come out the mouth, and glue & screw the top plate. so far, i am pretty happy with the result!

cheers! J.
Cubo15's Avatar
Cubo15 replied the topic: #24889 1 month 1 week ago
Hi,

Typically Fs will lower over time, while Vas will increase, also excursion will increase (= better bass) over time due to the suspension loosing up. I would use them in Cubo 15 Extended.

Best regards
Papay's Avatar
Papay replied the topic: #24886 1 month 1 week ago
Hello Cubo! I have speakers "BIG syp 1506" I measured their parameters Fs = 47 Qms = 10.111
Qes = 0.551
Qts = 0.522
Vas = 90
The thing is, the speakers are new. And the parameters may change after a while. Tell me, can I use them in Cubo 15 and in which version?
Sorry for my english, google translate!
Drew282's Avatar
Drew282 replied the topic: #24869 2 months 3 weeks ago
Cheers, this is super helpful!

I might wait till I can afford a more appropriate then, do things properly. 
Cubo15's Avatar
Cubo15 replied the topic: #24868 2 months 3 weeks ago
Hi Drew,

I advise you to use the Qts x Vas rule to decide which Cubo 15 version you should build, I put extended research into developing it

Qts x Vas > 120, Cubo Standard
Qts x Vas = 100 - 120, Cubo Extended or Standard
Qts x Vas < 100, Cubo Extended
Qts x Vas < 50; Cubo 15 Extra Extended

However, the Xmax on this driver is small, even with a 40 Hz high pass I wouldn't put more then 200 - 300 Watts into it. Due to its Xmax it's best suited for use in a top/ full range cabinet.

Cubo
Drew282's Avatar
Drew282 replied the topic: #24867 2 months 3 weeks ago
Hiya Cubo15,

I'm planning to build one of these cabinets you decided and am getting pretty excited about it. I wanted to get your advice about which version to build before I get started though. I'll be using a monacor sp-15-300pa driver (link below) because I was gifted one and it'll match my amp.

Let me know what you think would be best,

Cheers!

www.loudspeakerdatabase.com/MONACOR/SP-15-300PA
Cubo15's Avatar
Cubo15 replied the topic: #24866 3 months 1 day ago
The p. Audio p150/2226 is a good driver (also Extended), not seeing any pictures though :( You can also send it to questionsaboutcubo at gmail dot com

Cubo
Zambrotta's Avatar
Zambrotta replied the topic: #24865 3 months 1 day ago
......
Zambrotta's Avatar
Zambrotta replied the topic: #24864 3 months 3 days ago
hello guys the bass coming out of my cubo 15 extended is amazing am planning to build two more n load them with p. Audio p150/2226 15inch speakers
Zambrotta's Avatar
Zambrotta replied the topic: #24862 3 months 1 week ago
Thanks Cubo will start my build today using 16mm mdf.... cannot afford to buy birch plywood it's expensive.Wil send pics soon.
Cubo15's Avatar
Cubo15 replied the topic: #24860 3 months 1 week ago
The T/S-parameters you send me are of the BM-15LF, whereas you mention the BM-15W here. As far as I can tell those are two different drivers, the BM-15W has substantial lower Xmax, Qts and power handling, however both are best suited for Cubo 15 Extended.

Best regards Cubo
Zambrotta's Avatar
Zambrotta replied the topic: #24856 3 months 2 weeks ago
Greetings from Zimbabwe. I want to build a pair of Cubo 15 standard version and load them with p. audio blue monster bm-15w 400w speakers. I would like to find out if those speakers are suitable for those cabinets.Plizz assist
Cubo15's Avatar
Cubo15 replied the topic: #24851 3 months 4 weeks ago
@ Simon H: Last time I checked they were on the 'plans-page' freespeakerplans.com/plans/14-plans/basscab/44-cubo15

@ Buje: It will be difficult to place an 18" driver on a 17" baffle (it can be done though). I usually make a 2 part plywood ring (two rings of at least 18 mm thickness), with t-nuts embedded within it. The first ring fits the 15" bolt pattern and is large enough to fit the 18" driver, the second ring allows the 18" to make at least 18 mm of excursion (at least Xmax but preferably Xmech). The rings are glued together but the structure as a whole is removable, so you can still mount 15" drivers later.

Alternatively you can glue an 18" + diameter plywood spacer ring to the baffle directly (with t-nuts embedded within it), front mount the 18" driver on the spacer ring.

Cubo
Buje's Avatar
Buje replied the topic: #24846 4 months 15 hours ago
18sws1000, how should I place them, using the 15 hole or enlarging to 18? Thank you
simon hesthaven's Avatar
simon hesthaven replied the topic: #24845 4 months 15 hours ago
Hej Cubo.
Greetings from Denmark! and great work by the way : )

Is it still possible to acquire the plans for the standard cubo15?

Simon H
Cubo15's Avatar
Cubo15 replied the topic: #24843 4 months 1 day ago
The jbl 18sws1000 or jbl 15sws1000? Technically both but I favor the 15".

Cubo
Buje's Avatar
Buje replied the topic: #24842 4 months 2 days ago
Hi, i have a couple of cube 15 extended, can i use them with jbl 18sws1000? thank you, sorry google translator.
dajnaton's Avatar
dajnaton replied the topic: #24815 6 months 3 days ago
Hello Cubo15, greetings from Venezuela. I would like to know where to download the plans for the 15 cube version using 15mm wood sheets.

Would you recommend MDF?

I have been using Mini Scoop 18 for years and would like to change them for greater portability.

Excuse my english, use google translator.
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