Why Cubo subs work so well ?

As I read it: First he links a driver with a large Xmax to a heavey, strong cone and increased power handling. Then he links the tapped horn
driver to a heavey, strong cone with high power handling. There are other ways to get a larger heavey cone (large voice coil diameter and added mass/low Fs)
but in this case a significant portion is supplied by the large Xmax.

As you might know a large Xmax requirers more winding length (everything else the same). More wire length means that the electrical power (ie heat)
is spread over an larger surface area and mass, thus a driver with a larger Xmax often has high electrical power handling due to more wire length.
Larger mass cones are often desired for horn loaded systems and/or other systems (ie BP) where an extra mass/load is placed upon the driver due to the large
volume of air in the cabinet being moved accordingly. In reflex cabinets and also Cubo designs a large part of the air act as spring (the chamber) whereas the horn acts as mass.
A tapped horn is largely mass and minimized chambers.

Always good to be prepared.

Best regards

Cubo

That is what he says in the last two paragraphs of page 2. BTW you described it in a way which was certainly clearer to me, thank you! However it is still a contradiction to what he says on page one regarding excursion. Nonetheless I have found I feel I understand the design a bit better,and at some point I probably will build some Cubo subs. I really like the work you have done with the whole series!

The driver (a relatively inexpensive 21" driver) I have just about settled on isn't suited for a Cubo sub unfortunately (which was why I was trying to understand this better ,to see if I could use it with this design). It has sufficient Xmax,but to low of an EBP. It was really designed for use in a bandpass box. Although its very efficient in the range I want it to be, some of that efficiency was obtained by using more compliant suspension and surround than would be acceptable in this design. I do have some really good and relatively inexpensive 12s that would be suitable for a pair of Cubo 12s,but they are in use currently.

This discussion has been VERY helpfull to me. I may not have decided for sure what route I want to go,but I have better perspective now and can make a more informed decision!

A tapped horn needs the sort of driver that's capable of high excursion but it doesn't need the excursion itself.
Tom Danley is a bit like my mathematics teacher, if she (the latter) seems to contradict herself, I'm usually the one making the mistake.

If you post the T/S-parameters of this 21" driver I will simulate if it's suitable for Cubo Sub/21.

Best regards

Cubo

Cubo15 wrote: A tapped horn needs the sort of driver that's capable of high excursion but it doesn't need the excursion itself.
Tom Danley is a bit like my mathematics teacher, if she (the latter) seems to contradict herself, I'm usually the one making the mistake.Cubo

Thats a lot more clearly explained !!!! Thank you very much !

Cubo15 wrote: If you post the T/S-parameters of this 21" driver I will simulate if it's suitable for Cubo Sub/21.

Best regards

Cubo

That would be WONDERFUL!!!!

General parameters:
Nominal diameter: 21 inches
Impedance: 8 Ohms
Operating bandwidth: 45 hz - 1.7 khz
Power handling: 1,000 watts program / 2,000 watts peak
Sensitivity: 100db 1w/m (-3db)

Ts parameters

Fs: 22.4 HZ
Re: 6.3 Ohms
Qms: 2.5961
Qes: 0.3801
Qts: 0.3315
Vas: 703.8 liters
Sd: 0.1706 square meters
EBP: 58.8
Xmax: 9mm

Hi, I just joined in to this site. Just looking through and saw this sub enclosure. All I can say is wow.
I just ordered 2 - 18" IXL-18.2.2 Mach 5 from www.istonline.ca and was wondering if these subs would be a good candidate for this CUBO box.
I was going to build the boxes as per their site suggest but if your box would do the trick, I would save 2 sheets of 2X8 in the process.
Please let me know if they would do the trick.
Thanks,
Lucky1

Hi Lucky1,

Are you talking about Cubo 18 or Cubo Sub? In both cases it will not be as efficient as is common for regular PA-drivers in those cabinets.

About 96 dB/W/m in the working range as opposed to 93 dB/W/m in a large reflex cabinet tuned to 40 Hz (it's designed to be tuned near Fs).
In Cubo 18 it will be usable down to 35 Hz (set a high pass there), without ever getting close to it's rated Xmax (22 mm, one way I pressume).
In Cubo Sub it will be usable down to 27 Hz with a 25 - 30 Hz high pass.

Best regards

Cubo

Thanks for the response. I was looking to build 2 box like your CUBO 18 using the 18" drivers (IXL-18-2-2) from a firm in Canada that builds subwoofer at a good cost.
Their box is quite huge
The 18" can move 22mm / linear Xmax. Here's the site list for this sub;
Fs (Hz)18, Re (Ohms)3.4, Qes 0.39, Qms 5.59, Qts 0.37, Cms (mm/N) 0.184
Rms (kg/s) 8.69, Mms (grams) 434, BL (Tm) 20.5, VAS (L) 274, Sd (cm^2) 1029, Lp (2.83v/1m) 91.6
Also their site suggest either bass reflex box of 150/200 L or EBS 250/350 L but their site has only one box design for their 18" at 285L net volume at 17hz tuning port.
So the big question is... would the CUBO 18 box work for this type theoraticaly?
I would install the sub with magnets outwards. These new subs i'm building are to complement the Servo 15V1 and Servo 15V2 from Paradigm in my home theater room.
I know some might think that it will be too much but there is never too much!
Thanks again for the reply.
also, i'm new to any posting site, this is my firt one, how do i send the pictures once done?

Theoretically it will work (better with those T/S-parameters as the ones I used). What frequency band do you want to use them for?

You can post pictures by uploading them to a site like imageshack.us/ and link to there.

Best regards

Cubo

Thanks for the info
I would like to have them run as low as they can go......17hz would be nice and lower would be better. I am using a phase coupled activator from Audio Control (which they dont produce anymore) on the Servo15V2 and it is amazing how the activator actuaty gets a sub to go very low. I would propably move the activator on the new subs. If you can find a used one (phase coupled activator), I would recommed it to anyone to buy it, you wont be disapointed!
Forgot, on the high side of frequency, I set the processor at 80hz for all the subs.
Thanks again for the promt reply.

Hi,
been reading through this thread and have a question regarding the suitability of the Beyma 21L45 21" driver for the Cubo Sub.

Firstly the TS Parameters from the Beyma info sheet:
Nom Dia 540mm, 21"
Overall diameter 550mm
Volume displaced by driver 20 l, 0.7 ft³
Power 800W RMS
Program Power 1600W RMS
Sensitivity 99dB/1W/1m
Frequency Range 20-1200Hz
Voice coil length 25mm
BL factor 30.5 N/A
Moving mass 0.250kgm

fs 30Hz
Re 6.5 ohms (3.25 ohms for 4 ohm version?)
Qms 9.91
Qes 0.33
Qts 0.32
Vas 500 l
Cms 112 µm/N
Rms 4.7 kgm/s
Efficiency % 3.9
Sd (m²) 0.1764
Xmax 9.0mm
Xdamage 35mm
Le @ 1khz 1.8mH
Vd 1600cm³

Now the versions I have are 4 ohms; but all the other relevant TS Parameters should apply (trust I've copied them correctly from the sheet).

Any info would be much appreciated regarding suitability for the Cubo Sub please, plus plans?

thanks in advance
Mik