Easy 12" cab build

[Phil Starr]

Just a little update, I used the little cab on it's own for the first time in a while last night. Typical situation hereabouts, a small country pub with a low ceiling and they had changed the start time so no chance to soundcheck. I made a last minute decision to use the 30l cab on it's own backed against a wall but up on a bench seat to save space. It sounded fab with my J-bass/John East set up. Lot's of punch and bite and no need to roll off the bottom end, just a little tweak to the mids. It shouldn't have been a surprise as that's what it was designed to do but it's nice to have the theory backed by practical experience. There was another bass player, ex band member but now fully pro there. He made a point of complimenting the sound and seemed genuinely impressed. Maye it was just to avoid commenting upon my playing of course

[J Mac]

Hey everyone. I'm totally new to building cabs so I want to try to keep it as low budget as possible. Could anybody recommend a speaker suitable for this project that is below £70?
I was going to buy the Celestion b12 200x that Stevie recommended but I can't seem to find them for that price any more.
Cheers

[Phil Starr]

Hi John, just pm'd you. 

you might be better off bulding this cabs big brother, there's a link at the beginning of this thread. This little cab is less likely to work well with a cheaper speaker. I'll have a look when I get back from holiday.

[J Mac]

Just managed to source a Celestiob B12 200x from a kind member of this forum for a good price. Would the 30l suit that speaker Phil? 

Cheers

[Chienmortbb]

I am sure Phil would answer soon enough but there are few 12” speakers at a reasonable price that would work well in a 30 litre cabinet. However,  if you can wait a few hours I will model it for you. 

[Balcro]

Hello J Mac,

The short answer is yes; it will work. Bear in mind that you will have to change the port sizes from Phil's original, as that was specifically designed to suit the Beyma driver. Don't worry about that. I & several others can do the calcs needed.

In a 30 litre cab the Celestion will produce a slightly warm sounding bass, but with reduced bass output in the low bass below 100Hz. If your project is a get-you-going sort of idea and the special price is important then go for it.

Phil has said elsewhere that the cab dimensions result in a volume over 30 litres, to account for the space taken up by the Beyma and it's ports.
Going by his dimensions of 350 x 450 x 236mm internal, you get just over 37 litres. Once a 12" driver is installed and the ports fitted that will result in a net volume of about 33 litres.

If the Celestion from a fellow Basschatter doesn't work out, then there is an alternative in the Fane Sovereign 12 300 @ £70 from bluearan.co.uk.

Chienmortbb should be along later with some details.

 

 

 

[Phil Starr]

just off to jump on the Vaporetto

You are in safe hands with these two john

[J Mac]

6 hours ago, Chienmortbb said:

I am sure Phil would answer soon enough but there are few 12” speakers at a reasonable price that would work well in a 30 litre cabinet. However,  if you can wait a few hours I will model it for you. 

Thanks very much for your help. That would be much appreciated.

[Chienmortbb]

 Based on Phil's cabinet the BL-12-200X will work but it will be limited in output. I have modeled the following speakers

1. Celestion BL12-200X
2. Beyma SM212
3. Fane 12-300
4. Beyma 12CMV2

Of these the "league table" is as follows:

1. Beyma SM212
2. Beyma 12CMV
3. Fane Sovereign 12-300
4. Celestion BL12-200X

In terms of cost, lowest first as of  13th October 2019

1. BL12-200X (not sure what you paid for it)
2. Beyma 12CVM2. £44.34 (£50.40 inc delivery) - Blue Aran Jam Club £49.30 inc
3. Fane Sovereign 12-300 £69.88, free delivery - Blue Aran Jam Club £65.69 inc
4. Beyma SM212 £86.21 (£90.31 inc delivery) - Blue Aran JAM Club £88.15 inc

To sum up, if you had to buy a speaker for the cabinet, I would choose the Beyma 12CVM2. It is close to the performance of the SM212 but a lot cheaper. If anyone wants to see the plots, I will post them.

 

Edited October 13, 2019 by Chienmortbb

[J Mac]

51 minutes ago, Chienmortbb said:

 Based on Phil's cabinet the BL-12-200X will work but it will be limited in output. I have modeled the following speakers

1. Celestion BL12-200X
2. Beyma SM212
3. Fane 12-300
4. Beyma 12CMV2

 

Thanks so much for doing the math, Chienmortbb.  I paid £25 for the B12 200x. What are my options going forward? Should I write the Celestion off as a poorly thought out impulse purchase and look for something more suitable?

If I was to stick with the Celestion how would I go about calculating the dimensions for the cab and the size of the ports? Apologies if these questions are stupidly obvious or don't make sense. I'm totally new to this.

[Balcro]

The Celestion should not be written off, it's a perfectly adequate driver and you're questions are not stupid. If you're happy to go ahead and build a box and cut some holes in the panels then Chienmortbb and I can give you the dimensions for the box and the ports.

As has been said before elsewhere, designing a speaker is matter of endless compromise. For example, reduce the size/internal volume of the box will cause the sound response to increase in the low-mid bass, make the box too big and overall power handling suffers. Make the box too small and the optimum port size can change to something impractical, and on and on etc,.

In this case I would advise you to  make a box to Phil's basic dimensions but extend the top, bottom & side panels so that they are 25mm deeper, back to front. So the panel dimensions should be:

Top & bottom: - 374 x 315mm
Sides: -               450 x 315mm
Front & back:  - 450 x 350mm.
That will give you a gross internal volume of 41.1 litres. One 4" / 100mm port should suffice.

Chienmortbb will probably comment later.

 

[J Mac]

Cheers Balcro. Following that advice i'm going to go forward with the Celestion and see how it turns out. This project is more just to see how I get on with a simple design and have fun with it. I'm not expecting to achieve something amazing just something to get me started in the world of DIY cabs. I'll follow those dimensions you've kindly included and will report back once it's done.

[Phil Starr]

2 hours ago, Balcro said:

The Celestion should not be written off, it's a perfectly adequate driver and you're questions are not stupid. If you're happy to go ahead and build a box and cut some holes in the panels then Chienmortbb and I can give you the dimensions for the box and the ports.

As has been said before elsewhere, designing a speaker is matter of endless compromise. For example, reduce the size/internal volume of the box will cause the sound response to increase in the low-mid bass, make the box too big and overall power handling suffers. Make the box too small and the optimum port size can change to something impractical, and on and on etc,.

In this case I would advise you to  make a box to Phil's basic dimensions but extend the top, bottom & side panels so that they are 25mm deeper, back to front. So the panel dimensions should be:

Top & bottom: - 374 x 315mm
Sides: -               450 x 315mm
Front & back:  - 450 x 350mm.
That will give you a gross internal volume of 41.1 litres. One 4" / 100mm port should suffice.

Chienmortbb will probably comment later.

 

Footsore from 6 hours walking round Venice I thought a break in order. Basschat is the distraction I need. This looks like great advice. You will end up with a very usable cab and if you like it a second one will cover any need you are likely to have. If not you'll have invested only a little and learned a lot.

A cab this size is a nice easy carry.

[Chienmortbb]

You don’t have to write off the Celestion but  It will not go so loud as modelled and (unless I entered some parameters wrong) has more bass extension than the Beyma. This was the thing Phil was trying to design out. 

However it will not take as much power and will only get to about 113-114dB. The Beymas will get to 120dB+. 

So I would build with the Celestion as the others should slot straight in if you want to upgrade at a later date. 

Edited October 14, 2019 by Chienmortbb

[J Mac]

On 14/10/2019 at 15:20, Balcro said:

 

Top & bottom: - 374 x 315mm
Sides: -               450 x 315mm
Front & back:  - 450 x 350mm.
That will give you a gross internal volume of 41.1 litres. One 4" / 100mm port should suffice.

 

Is that the length of the port? What would the diameter be?

Edited October 15, 2019 by J Mac

[vinceom]

Hi. I’m thinkîng of building the 50 L cab. Is there someone who tried to load the Beyma 12CMV2? Specs are close to beyma SM212’s. (And 12CMV2 is 50€ cheaper).

Phil, do you recommand this one?

thanks !

Vinceom

[Phil Starr]

John, (Chienmortbb) has bought one and has been playing around with it. It looks like a better buy than the SM212 and it models well in the 50l cab. Coronavirus allowing I'm going to meet up with John fairly soon so we could try it in the Mk 1 cab if you want to wait for a listening test. However I'd have to say the 12CMV2 looks a real bargain and I'd have no reservations about using it other than the fact I haven't actually tried it. I gigged the SM212 fairly extensively and still do from time to time. Playing with a couple of the MK1's is to drown in a sea of bass.

If you decide to go ahead and are happy to do a build diary I can help you through the build and maybe tweak the cab a little.

 

[vinceom]

Thanks for answering quickly ! Can you send me your Winisd project for SM212 in your first cab (50 L), thank you. You are a reference in DIY bass cab !

Last question : What is the avantage to create 4 ports instead of 2 ?

VInceom

Edited March 14, 2020 by vinceom

[Phil Starr]

Hi, I haven't kept anything from the design process, everything should be in here 

The reason for four ports is the 'easy build' bit. I wanted something that could be cut without specialist tools and easy to source so drainpipe and a hole saw were chosen. I built one prototype with a slot port but couldn't build it without using lots of clamps that most people wouldn't have at home, so again that didn't fit the 'easy build' criterion.  A single port with the same area would be better in terms of port noise if you can cut a bigger hole accurately. The other thing is that this design was specified to match a 19" rack mount so the dimensions can be changed if you want to have something a little less blocky in shape.

[vinceom]

Ok. Thanks Phil!

[vinceom]

Phil, what are the dimensions of your box in the video page 1 ? The front panel is about 53 cm height. It's not the height of your 30L. Are there dimensions of your first cab (50L) but with only 2 ports ? And what are diameters and length of the 2 ports ?

Thanks, take care

Vinceom

Edited March 21, 2020 by vinceom

[Phil Starr]

One of us is confused, it may be me. The cab in the video is the 30l cab the one drawn three posts up from this is the 50l cab, are you wanting to build the 50l cab or the smaller cab?

The dimensions for the 30l cab are in the first post here but I've copied them here

the panels for the 30litre cab are 2x 374mmx290mm, 2 450mmx 290mm and 2 450mmx350mm (all 12mm ply) the front baffle is set back 30mm to allow for the grille so internally the cab is 350mmx450mmx236mm. the ports are made of drainpipe/downpipe which is 64mm internal diameter 160mm long

[vinceom]

Thanks Phill. I calculate height 53 cm with a cross multiplication on the video, not very accurate... The cab seems big for only 30L ! I don’t know yet if i build a 30L or 50L. What did you lose with your 30L cab? Loudness ? But you get more accuracy in sound ?

I will load the Beyma SM212 and i want to hear its 350W !(my bass amp head is TC BH250 250W)

Thanks !

 

[RichardH]

I think Phil described the differences  between the 30 and 50l cabs very well in his first post - quoted below with my bold highlighting.

 

On 01/05/2018 at 07:55, Phil Starr said:

The original cab was a 50l cab based upon the Beyma SM212 driver and designed to produce lot's of deep well controlled bass with a neutral uncoloured response, several people here have built versions of the cab and I've been gigging it for two years. My problem with the original cab has been that in rooms with poor acoustics there has been too much bass and I was tending to dial down the deep bass and boost the upper bass. It sounds great in non resonant rooms and out of doors but has way too much bass if you are shoved into the corner of a low ceilinged room. Since I had promised to demonstrate a cab build anyway I thought I'd squeeze the Beyma into a smaller cab which would reduce it's bass output but give it a 2dB boost in the lower mids/upper bass which I thought would help cut through in difficult spaces. 

[vinceom]

Oh yes ! I didn’t remember.

Thanks

Edited March 22, 2020 by vinceom