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CN212 Details

ScottTunes

ScottTunes

Gear-A-Holic
Feb 7, 2011
1,117
662
Left Coast
#1
I am building (because I cannot afford to purchase) my own version of the Berg CN212. I would greatly appreciate some help!

I have approximated the external dimensions. But more importantly, I need the port dimensions. I will "tweak" for DeltaLite II drivers. But I need a starting point.

If you don't mind:

What are the (triangular) port dimensions?

And;

Why the "off-set" drivers?

Thanks for any assistance in this project!
 
#2
Making a cab for Deltalite 2512's with cab volume and tuning the same as a CN212 will not produce the tone and performance of the CN212. Your cab is going to be a DIY 212 with Deltalite 2512 II's. You should abandon the CN212 copy. It will be a copy only in size, not in tone or performance (even if the CN212 drivers are 2512 derivatives). Very likely, the cab size and tuning for the CN212 drivers will not optimum for the 2512's. Such a cab would certainly 'work' and likely even sound pleasant. However, you could do better for the 2512's.
 
#5
Astro sonic means that you're using the wrong approach - different speakers act differently in different boxes, at least in terms of the low end. So if you want to build a cn212, you're going to need those drivers, if you're using deltalites, there's already going to be a difference in performance that is going to be different from the berg - so you really might as week start from scratch.
 
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#7
Again, specifics, please!

Thank you Astrosonic and pie_man_25, for your attention. But, neither of your posts answer my questions.

I already have all of the Eminence driver specs. And, I am quite familiar with cab design, and using Eminence cab design software, and have built many cabinets for my own use.

I realize Jim B custom designs his Eminence made drivers. They aren't going to be substantially different from the KappaLite or DeltaLite drivers. And I prefer the tone of the DeltaLites in the TL cabinets I have (and built). Therefore, enlarging the cabinets (as JB has done) will get me 90% of the way there. And I am already fairly certain how the cab will sound, sans tweeter/horn.

I would greatly appreciate the CN212 port dimensions to compare with mine.

Also, is there a design goal for the off-set drivers? I can find none (other than port placement), and am of the opinion that vertically aligned drivers would be better for clarity and dispersion.
 
#9
Biggest difference will be a cab without the tweeter/crossover. I prefer old school anyway, so that suits my design goals.

The triangle ports have a lower vent velocity than round ports (also less inherent ring), and slightly lower than shelf ports.

Another alteration I'm considering is a 10* baffle angle. But that complicates the front to back "sound post."
 
#10
I don't know about bergantino, but my cabinet has b&c woofers, if you like lots of bottom and low mids those drivers are great, but not too clear on the high mids I don't think. I know there's a thread about a guy who made a 112 with a b&c woofer, and his results seemed promising, and apparently more midrange content than my cabinet - the link is right here: Another DIY cab thread. Loud, Small, and Cheap. 22 pounds that pounds. | TalkBass.com

It seems like a good cabinet, and you could easily just build one 212 by building two 112s as a vertical stack.

Edit: I didn't see the earlier posts about eminence discounts until after posting this, carry on.
 
#11
pie_man_25 said:
I don't know about bergantino, but my cabinet has b&c woofers, if you like lots of bottom and low mids those drivers are great, but not too clear on the high mids I don't think. I know there's a thread about a guy who made a 112 with a b&c woofer, and his results seemed promising, and apparently more midrange content than my cabinet - the link is right here: Another DIY cab thread. Loud, Small, and Cheap. 22 pounds that pounds. | TalkBass.com

It seems like a good cabinet, and you could easily just build one 212 by building two 112s as a vertical stack.

Edit: I didn't see the earlier posts about eminence discounts until after posting this, carry on.
Click to expand...


I did build a TL806, and a TL806"D" a decade and a half back. They have been put to good use with many different drivers. My favorite is the DeltaLite II. And the new Berg CN212 is VERY similar to the TL 2x12 design, with a few updates (upgrades). Which is where my starting point is.
 
#12
Thank you for the link, by the way. I did see it when it originally came up, and again just now. That cab appears similar to the Berg CN112, from what I can tell. Slightly bigger than the TL806, etc.

I will photograph my progress, and post when my new project is complete.
 
#15
Geez, give the guy a break. If the original cab uses an OEM based on the 2512, then how would starting with a model of the cab and tweaking from there be WORSE than starting completely from scratch? It's a proven design. I don't know, maybe the OEM really is completely different, but if that's the case, then modeling the retail version should show that.

And giving the guy port dimensions is not really doing anyone "a disservice". If he can't afford the original cab, they're not losing a customer anyway, and if he DID get an original cab he would probably buy used, so STILL not a customer. Any commercial enterprise that wanted to copy the cab could just buy one and do that, and either write it off as a business expense or resell it anyway.
 
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#16
Omega Monkey said:
Geez, give the guy a break. If the original cab uses an OEM based on the 2512, then how would starting with a model of the cab and tweaking from there be WORSE than starting completely from scratch? It's a proven design. I don't know, maybe the OEM really is completely different, but if that's the case, then modeling the retail version should show that.

And giving the guy port dimensions is not really doing anyone "a disservice". If he can't afford the original cab, they're not losing a customer anyway, and if he DID get an original cab he would probably buy used, so STILL not a customer. Any commercial enterprise that wanted to copy the cab could just buy one and do that, and either write it off as a business expense or resell it anyway.
Click to expand...

The reference to the Berg driver as 'an OEM based on the 2512' is itself misleading, as it suggests, even assumes, that the differences are 1) so small that the CN212 cab will provide the same alignment (bass response) as the Berg driver, and 2) that the differences do not significantly change the mids and highs. In other words, that the copy will be 'functionally' as good as the original. For those with an ear that appreciates the tone of the original, the copy will not fill the bill. For those who don't hear a significant difference, why bother?

Why start with a copy? Let's acknowledge that we are dealing with a 2512, and design a cab that delivers a tone that the OP is seeking. If the OEM and Eminence drivers are functionally identical with respect to TS parameters (highly unlikely IMO), and his target tone is like the CN212, he will end up with the same volume cab and tuning, and with the tone he is looking for. If not, he will end up with an optimally designed cab volume and tuning, and the tone he is looking for.

Triangular ports are difficult to adjust and offer no audible advantage (try it and see). They are however an efficient use of materials and space, once you know the target tuning frequency, as they function as both ports and bracing.

If the OP is as skilled and experienced as he says, he can easily find the tuning and box volume that meet his tone goals. There is simply no need to copy the berg box design. Starting from scratch really is a more efficient approach. And there is plenty of DIY build information on TB for 2512 builds. It's a win-win approach.
 
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#17
But you're making just as many assumptions that it WOULDN'T work as he would be that it would. And logically, it would be kind of silly for a cab company to commission an oem based on an existing speaker model and then completely change it. So yes, a pre-existing cab is as good a place to start as any.
 
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#18
I'm making assumptions based on experience. See my post above where I explicitly say that it WILL 'work', and it may even sound good to the OP. It just is not likely to be optimum, let alone sound like a Berg CN212. If that doesn't really matter, copying may be the best way to go.

What I am saying is that as long as the TS parameters of the Berg driver are not known, an optimum cab for them cannot be designed. The chances of them being the same as the 2512 are not 50/50 because more than two cases (states) are possible. Many more. While the frame, and magnetic structure are likely the same, the length of the voice coil, and cone are probably different. The VC length has likely been increased to increase Xmax, but that also decreases magnetic damping (Qes and Qts increase, while sensitivity goes down a little). A different cone may have been used to change the upper mids and highs. This would likely change the resonant frequency. If the surround has been changed, Vas would also be changed. These changes to the TS parameters could make this a rather different driver from the 2512. And these are typical OEM changes.

If the OP had scored a pair of Berg drivers, copying the CN212 cab would make some sense. The OP is using 2512's and does have the TS parameters for them, so an optimum design is possible, based on driver/cab modeling (the OP says he is familiar with winISD), and the desired bass quality. If the TS parameters of the Berg drivers are the same as the 2512, we will end up with a cab basically the same as the CN212. If they are different, we end up with a cab that's different. Doing it this way (by design), we end up with a cab that has the tone the OP is looking for (in so far as that is possible using 2512's). If we assume the drivers are the same, so he copies the CN212 cab, but they are not the same, the OP is stuck with a chance alignment, and those wood triangle ports are a pita to adjust. To adjust the design (cab tuning), the OP must either model (i.e., design) the Berg cab with different porting or adjust by trial and error.
 
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#19
He's not using the Berg driver so he doesn't HAVE to come up with an optimum cab for them. And it's already been designed anyway.

Starting with the volume and tuning of the original cab is just as good a starting point as any of the somewhat random choices WINISD gives you. Those have never given me anything close to what I was looking for, and I always have to do a lot of tweaking to get what I want. So why not load the 2512 parameters and start with a box with the volume and tuning of the original cab AS A STARTING POINT? It literally takes 5 seconds to do that once you have those numbers.

So why the intense opposition? It's just to get him in the ballpark, and if for some reason the retail driver doesn't make sense for that exact volume and tuning of the original cab, that will be obvious to him from the model pretty quickly and he can adjust as necessary. You're being like the dude in They Live who just wont put the damn glasses on and see for themselves. What's the big deal about putting on the glasses? It's completely harmless and takes about 5 seconds. No but instead youre going to fight Roddy Piper in the alley for 10 minutes straight.

Also, shouldn't 2 triangle ports model just like the equivalent rectangle/shelf port? WinISD just uses surface area and length to calculate tuning anyway.
 
#20
I'm using the Eminence Designer software - more accurate and helpful than WINISD, IMO/IME.

I began using the box dimensions available at Berg's website... And using a standard Eminence driver (2512 II) rather than the Berg Custom spec'ed Eminence driver, and a square port (one flush end), I've approximated my own version of this great little CN212 cab!

I've also utilized my TL cab experience (both building and design-wise) to compare with "my" version of Berg's cab.

I've cut the panels already. Now it's time to cut the baffle for speakers and vents. I'm doing what is called "measuring twice, cutting once." Best I can tell from photographs, the triangle vents are between 1/3 and 1/2 the width of the baffle! And what appears to be 2"-4" deep.

A bigger opening lowers vent velocity (did I already say that?). So far, I'm liking what I see with a larger vent opening (90* angle @ 6" x 6"), and a 6" depth.

Which brings me back to my question, what is the port size in the Berg cab? I don't need to copy, just fact check.

Thanks for the discussion anyway!
 

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