Cubo 15

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

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

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

Cheers, this is super helpful!

I might wait till I can afford a more appropriate then, do things properly. 

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!

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

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.

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

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!

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.