Cubo Sub

I'd personally go for two seperate cubo's, this gives you a lot more flexibility and a sturdier box. I've built both and the double one if often left behind since the singles are a lot easier to handle (one man lift).

I have no problem with the size and carrying of the box. I would like to build that in figure B without compromising the sound

Well, in that case I would go for option C.



Option B will also work but if, for whatever reason one driver will stop working, (damage, overpowered, etc.) the output of other driver will be partially absorbed by the one that stopped working. Meaning it might quickly follow the firsts fate.

Having a panel in-between, ensures enough separation between the drivers/ cabinets, so that the single left driver will keep it's full output and health. It also serves as a brace for the horn mouth.

Option A will work just as well but option C, will work good enough,plus it has a cut sheet :woohoo:
(e-mail at questionsaboutcubo at gmail dot com)

Best regards Cubo

Thank you very much Mr CUBO, very kind

Hi Cubo.

If using cubos as singles indoor and stacks of 2 per side outside (Maybe just one big stack). And using cornor or wall-loading indoor, what do you reckon I'll get the best result from? A cubo18 or Cubo Sub loaded with a Fane 18XS. People that I've heard talk about the Cubo15 say that their main problem is they don't go high enough to be a kick, nor low enough to be a sub, so I reckoned that building the biggest cab with an 18" would give me a lot more low, thus putting it in the sub category.

What do you think?

I would prefer a single stack, one or two cabinets high in the middle, against a solid wall most of the times. However multiple stacks divided over the corners can sometimes also do the trick. Most important is to experiment with placement, sometimes one or two meter to the right or left can do wonders.

Cubo 15 was designed as an all round bass cabinet and in my opinion it's just that for 90% of music out there. I prefer to get the kick from the tops or separate kicks. If you truly need sub there's no substitute for Cubo Sub. Cubo 18 is basically a Cubo 15 on steroids but Cubo Sub is a different animal.

The Fane 18XS will work in both but as per design it was aimed at Cubo Sub.

Best regards

Cubo

Hello Cubo,

Interestingly I can find very little info on this page with regards to building the 21" version of this sub which is what the plans are for on this page (mostly it's 18" & 15".)

Anyhow, I am very pleased to inform you that we have now just finished building the second of two of these monsters and are quite pleased with the results but think that they could be improved somewhat.

We are using two identical (vintage) Precision Devices drivers (ET211S) which are rated 750W RMS, 1500W peak - I have tried getting the T/S parameters for these but PD have changed hands since these were made and they can't help me out in that regard. My feeling is that these are more suited to Scoops and don't seem to be suited for this sort of combo chamber/ horn enclosure - the magnet is huge and the cone is probably quite heavy in comparison to most drivers these days with a relatively slow response....?

Anyhow, maybe this is also an issue to do with our compressors limiters as we were kind of expecting a bit more db before the cone starts popping...

So we were maybe thinking about looking to replace them with some more modern drivers - haven't come across any recommendations so far on this thread for 21" drivers...

Have been scouring ebay for ions and have someone who is offering some RCF LF21X451 for around £300 a pop but they are based down in Yorkshire (We are up in Glasgow) and think they have now been sold.

I have just come across this new listing on ebay for a 21" driver which links to a reputable retailer called bishopsound. Their driver looks almost identical to the B&C 21SW152 but at a fraction on the cost...currently on sale for £199....!!!

This is the jargon from the ebay listing:

"I have made and sold over 1000 of these drivers on my website Amazon and eBay and to date, only 2 have needed a re-cone. I keep my quality high and my prices low because I remove all unnecessary overheads. Read all about Bishopsound on my website and visit uk.trustpilot.com/review/bishopsound.com to read what my customers say."

bishopsound.com/shop/21-replacement-neod...oofer-4%CF%89-bwn21/

What do you reckon...?

Sorry this is turning out to be a rather long post... We were looking to drive these with a CREST CA12 AMP which is 1200W into 4Ω Stereo or 2800W into 4Ω Bridged Mono Power.

Would we need one amp per driver if they are rated at 2000W RMS - surely we don't need to crank it that much but then maybe 1200W isn't quite enough...?

Many many thanks for all the help,

Will post up some of the pics from our build soon,

Thomas (TLC Sound-System)

Also,

One other thing before I forget. I am aware that the best way to stack them would be to have the two horn mouths next to each other (as hopefully shown in the below image)

However, this then creates a divide in the middle which is 108mm wide... We were considering making horn extensions for the two cubos (as shown in Tempest's post) but how would we integreate this around such a large divide...? (Hopefully it's not really an issue considering the size of the wavelengths that we are dealing with here...)

Would it be worth considering removing some of this material so it would only be two panels of 18mm instead of 6 at the throat exit which it is currently...

Horn Extension:

i.) Continuing the mouth of the horn out directly in a straight line

ii.) or having two more angles (allowing it to be slightly shorter) like a Martin Audio WSX bin...

Thanks again.

To get the maximum out of your current drivers, your best bet would be to get the T/S-parameters for the ET211S drivers and/or get the biggest horn cabinet you can find for them. To get the T/S-parameters you could perhaps measure them?

As for Cubo Sub, have you tried the ET211S with the magnet in the chamber (so front of the cone visible)? There's quite a difference to be noted between mounting the magnet inside the chamber and inside the horn, both in how it sounds and output-wise.

As for putting the cabinets with the mouths together, in theory you could leave the divider out entirely. Originally the panel is so thick, because it's the primary panel the driver pushes against. Personally I would leave them as is, you could even use them to bold the extension to it, using t-nuts or threaded inserts.
As for the extension itself, I would keep the same angle as the baffle or larger. If the extension is 77 cm deep, you could have the horn expand at such a rate that the mouth is the entire front area.

Bisshopsounds gets most of it's gear from China, so even if it does look alike, it's no guaranty whatsoever that it is alike.Three key factors in it specs that I miss are:
- Voice coil size
- Gap depth
- Winding depth

Looking at the magnet size, I don't think we're dealing with a 6" voice coil here but rather a 4". So if it doesn't even look the same and has a VC that's 1.5 times smaller, I doubt it is the same. Regardless, it could be a quality unit or it might not be, that's impossible to tell at this point but I would be very hesitant to put a bridged CA12 at a 4 Ohm BWN21.

If you're going to use an other 21" driver, even though the T/S-parameters of the ET211S aren't known at this point, it's safe to assume that to get substantial more output, you're going to need that extra bit of power. So that would amount to a single CA12 per driver. Most of these high power 21" drivers will likely be with a rather heavy cone and generally are not used for the frequency range that attributes to a fast response, typically crossing over between 60 - 80 Hz.

Alternatively, mounting the driver with the magnet inside the chamber and/ or using an extension will also achieve this. You could even do it all.

Best regards Cubo

Hello again & thanks for your in-depth reply.

I hear what you are saying about the Bishopsounds driver - I might call them later to see if I can get these figures. What sort of figures should I be looking for in a decent quality driver?

We have had the magnets in the horn for a fair while now and have tried the drivers the other way around a while back but might go back to that configuration now that we have two of them. Only thing I was thinking might also be a possibility is that these cones are just a little tired (not as rigid as they once were) and struggle to obtain the output that they would have been capable of when new - I have occasionally heard the drivers pop (I assume this is when the voice coil jumps out of the magnet gap...?) at levels which don't seem that loud.

Is there more compression acting on the cone when pumping air into the chamber than if it were with the magnet inside...

So, I have drawn up another sketch of what it might look like with two 21" cubos with 1m horn extensions when put together (They will definitely need more bracing but again, this is just a sketch.)