Easy 12" cab build

[Phil Starr]

 

On 05/01/2021 at 14:42, Beer of the Bass said:

I used a hole cutter similar to that. The blades as supplied are not very sharp at all, so I gave them a quick sharpen much like you would with a chisel. There's a bit of a knack to adjusting them, if the "kerf" between inner and outer edges of the two blades is even slightly too wide, it's much harder work for the drill than if you get it just right. The results were fine once I'd got those two things figured though.

Ha ha I should have said that the only time I've used these was with a hand brace, you need really slow speeds and decent torque to get a good cut and I've never used power tools to drive this sort of bit. I'd also cut the whole half way and turn the board round to cut the other face . I actually use a router to cut my own holes.

6 hours ago, stevie said:

I reckon there's some confusion here with port sizes here. The 118mm size you've mentioned is correct for the larger 50-litre cab. However, if you want to fit that tube to a 30-litre cab while maintaining the same tuning, it needs to be about 250mm long, which won't fit. I'd suggest you recalculate with a 100mm port, a size that's available everywhere.

Hi, I used a different and higher tuning to get the best out of the smaller cab and i was looking for a good hump around 100Hz rather than extending the lower end response. This emphasizes the second harmonic  of the lowest notes rather than the fundamental but gives a pleasant warmth. It was never conceived of as having an extended flat bass but as something usable in the small pub venues I regularly play in with my covers band. I checked your tuning on WinISD and it was very close to the tuning I intended. Old school bass rather than FRFR if you like.

[sergelebasse75]

So, my first calculation was right? The 30lt one is tuned to 56 Hz and has a bump around 100 hz. There was 3 versions if this, if im not mistaken, 50lt 1 speaker, 50lt speaker plus tweeter, and the 30/one speaker. It seems to me i read something about a 40 lt one, but this didnt go further, or am i wrong? Thank you

Edited January 8, 2021 by sergelebasse75

[Phil Starr]

UPDATE It looks like Beyma are about to pull the SM212. Coincidentally I've just been given a Beyma 12CMV2 (thanks to @Chienmortbb) to try in this cab, it has the same magnet but with a heavier cone, stiffer suspension and a new voice coil. It also has a pressed steel chassis and is considerably cheaper. The good news is that in this cab it actually sounds better. The bass  response is basically unchanged, but one of the frequency anomalies of the SM212 has gone and there is a broad boost in output in the upper mids which makes the sound lighter and more detailed. I'm still investigating and haven't tried it at a gig for COVID reasons but I'm happy to recommend this speaker if anyone is thinking of a build. If I get more information I'll put it here.

Edited January 30, 2021 by Phil Starr

[Phil Starr]

Just for interest these are the predicted responses of the two speakers at 320W, the thermal limit of the 12CMV2. You can see that the response below 100Hz is pretty nearly identical, above that the SM212 has about an extra db which is just about noticeable in A/B listening. Subjectively the volume levels are the same as the 12CMV2 has a broader midrange peak and of course that is where our hearing operates best. As i said above I think this is why it sounds more agile and detailed. The -10db point is around 50Hz which is quite good for a little cab like this and both speakers manage 120db levels across most of the range which was the original design target and should be enough to work for most bands.

 

[RG55]

Seeing this Easy 12"" cab build referred to as 30L puzzles me... since its internal dimensions give it a little over 37L... or are my calculations off?

[RichardH]

I suspect that the volume of the driver has been deducted...

[Phil Starr]

I allowed for the driver, the ports and a little left over for any bracing. you'll find that a similar amount is also allowed in the 50l enclosure

[RG55]

Ah, OK , thank you, chaps. But then whether it's 30L or 32L or something else, would depend on the driver....

Phil, have you considered the B&C 12CL64?
 

[Phil Starr]

10 hours ago, RG55 said:

Ah, OK , thank you, chaps. But then whether it's 30L or 32L or something else, would depend on the driver....

Phil, have you considered the B&C 12CL64?
 

The original cab was built just because I needed something I could build live for the bass bash. I used the Beyma SM212 because I had one laying around and because it is a decent driver.

The main reason I went for a 30l cab is because I'd been gigging the original BassChat Mk1 design for a while and the extended bass was proving a problem in a lot of small venues. Not a problem with my Hartke where I could use the graphic but not good with other amps. I was regularly dialing down the response 10db at 50Hz and then adding something extra at 120Hz. I already knew that by putting the SM212 in a 30l cab I could engineer that response and have a smaller lighter cab. It worked better than I expected and it was a bit of a 'wow' moment when I played it at the end of the demo. It's been my go to speaker for pub gigs ever since.

The B&C 12CL64 looks like an interesting speaker and I had considered it myself. It's engineered slightly differently from the Beymas with a lower excursion and higher efficiency. It has a lower thermal limit and that with the lower Xmax will mean less ability to handle deep bass. On the plus side it's a really affordable lightweight neo speaker.

If you wanted to build something with it and share your build here then I'd be happy to do some modelling and design a cab for you.

Welcome to BassChat

 

[RG55]

Thank you for the welcome Phil, this was indeed my first "delurking".

If looking for lightweight, well, the 12CL64 is only 1.9kg! B&C recommends 64Hz tuning and 40L volume. Without the baffle recessed, this cab may be appropriate.

I may take your offer sometime -- but my wife is not as pleased by sawdust as yours 😉

[stevie]

I think there are better options for bass guitar than that particular B&C driver, including the more expensive drivers in the B&C range. The main problem, as Phil mentioned, is the lack of excursion due to the short voice coil.

[RG55]

5 hours ago, stevie said:

I think there are better options for bass guitar than that particular B&C driver, including the more expensive drivers in the B&C range. The main problem, as Phil mentioned, is the lack of excursion due to the short voice coil.

Ah, yes -- more expensive. And heavier.
B&C 12CL76? Faital PR300? Which ones do you have in mind?
It's for the small 30ish cab...

[stevie]

I have in mind something with more excursion - like the 12CL76, but neither of those B&C drivers will have much bottom end in a 30-litre cab. If you model them, you'll see that they have less than the two Beymas - and Phil was specifically going for a bass-light cab.

It depends what your goals are (price, weight, size, output , bass extension), but a 10" system might make more sense in a 30-litre cab. There's also a wider choice of bass guitar drivers available in that size.

[RG55]

On 07/02/2021 at 19:56, stevie said:

I have in mind something with more excursion - like the 12CL76, but neither of those B&C drivers will have much bottom end in a 30-litre cab. If you model them, you'll see that they have less than the two Beymas - and Phil was specifically going for a bass-light cab.

It depends what your goals are (price, weight, size, output , bass extension), but a 10" system might make more sense in a 30-litre cab. There's also a wider choice of bass guitar drivers available in that size.

I kinda fancied the 12'' system -- but I'm now following the new 10'' system thread.

[Phil Starr]

On 07/02/2021 at 17:52, RG55 said:

Ah, yes -- more expensive. And heavier.
B&C 12CL76? Faital PR300? Which ones do you have in mind?
It's for the small 30ish cab...

I'd go for the Faital PR320 if you wanted a neo, lots of bang for your £££'s.

 

On 11/02/2021 at 12:06, RG55 said:

I kinda fancied the 12'' system -- but I'm now following the new 10'' system thread.

Traitor

We can put up the predicted bass responses later so you can compare. If you want a horn then obviously the top end is going to be determined by that and the crossover. Whatever choice you make you can always just screw the baffle down so you can replace the front panel if you decide to try the other option. 

[RG55]

21 hours ago, Phil Starr said:

Traitor

😁 No-no-no, I meant also, not instead of ;  I'd still prefer a 12" system. As simple as possible.

The PR320 is about 45% more expensive and less sensitive than the PR300...
The Beymas are heavy...
The B&Cs seem to be geared towards low mids, with weaker bass...

Getting Xmax, vent air velocity and full power to work together is a conundrum.

[Phil Starr]

I've got the PR300 at £111 and the 320 at £120 so not much in it. The sensitivity is quoted at 2db higher but the 300 has a broader mid range peak under cone break up, the sensitivity in the bass is similar. What you gain is extra excursion so less chance of over excursion and ultimately more deep bass. Having said that using either as a single speaker without a tweeter the choice would come down to the sound you prefer. The Beyma's are only around a kilo heavier. However the SM212 is about to be discontinued and has also become expensive.

However you are right, designing any cab is always a matter of making compromises and it is squeezing balloons. you squeeze down on one thing and something else pops up elsewhere.

We've tried the Faital 320 (with a horn) and it works well, we haven't tried it in the smaller cab yet though.

It'll be interesting to look at how the 10 and 12 model in the 30l cab. I'm trying to spend time actually doing the woodwork at the moment.

[RG55]

On 13/02/2021 at 13:18, Phil Starr said:

However you are right, designing any cab is always a matter of making compromises and it is squeezing balloons. you squeeze down on one thing and something else pops up elsewhere.

Hehe. Well put.

[sergelebasse75]

Hallo, I was wondering if using a little bigger size cab could help with bass response without being overwhelming, mantaining Hi mid emphasis. I was about to build the 30 lt one, but virus has being striking hard where i live and havent already started, if we used the 12cvm2 and an internal 40x25x47 (total 47lt) with the same building method, Port should be a little longer, but still being possible to mount? Thank you

[Phil Starr]

Hi Serge, I was considering doing something similar, I've been gigging with various prototypes up until last year when the pandemic put a stop to it. I decided in the break that I wanted to settle on something for the next few years that would look a little better and become my regular set up.  I allow around 7l for the ports and the speaker itself so a 40l cab is around 47l actual size The SM212 models very well in the 40l cab and does give a useful extra amount of bass. I haven't modeled the 12CMV2 yet but i've no reason to assume it would behave very differently. I'd probably make the cab slightly taller and less wide, square shapes are to be avoided to reduce resonances but i think a 40l cab would be an excellent compromise. 

[Beer of the Bass]

 

18 hours ago, sergelebasse75 said:

Hallo, I was wondering if using a little bigger size cab could help with bass response without being overwhelming, mantaining Hi mid emphasis. I was about to build the 30 lt one, but virus has being striking hard where i live and havent already started, if we used the 12cvm2 and an internal 40x25x47 (total 47lt) with the same building method, Port should be a little longer, but still being possible to mount? Thank you

A 40 litre model would be pretty close to the pair I built several years ago now, though the bracing and porting in mine drew heavily from the Mark I basschat 1x12", and I used Eminence Beta 12A drivers because I found a couple lightly used at good prices. Those cabs are still serving me well and I haven't found any compelling reason to change them. I think I went slightly deeper and less wide in my proportions though.

[Phil Starr]

4 hours ago, Beer of the Bass said:

 

A 40 litre model would be pretty close to the pair I built several years ago now, though the bracing and porting in mine drew heavily from the Mark I basschat 1x12", and I used Eminence Beta 12A drivers because I found a couple lightly used at good prices. Those cabs are still serving me well and I haven't found any compelling reason to change them. I think I went slightly deeper and less wide in my proportions though.

Great to see they are still in use

[StraightSix]

On 11/02/2021 at 12:06, RG55 said:

I kinda fancied the 12'' system -- but I'm now following the new 10'' system thread.

This thread is a very interesting read.

I have done a search but I can't find the 10" cab thread mentioned here by RG55 - can someone point me to it...?

[RichardH]

Here's the 10" cab build thread

 

Edited April 1, 2021 by RichardH

[StraightSix]

Many thanks Richard.