Easy 12" cab build

[Obrienp]

2 hours ago, Phil Starr said:

It'll take me a while to model the response of some of the drivers available today but this looks very do-able. The thickness of the ply isn't going to add a lot to the weight, just remember it's the internal dimensions you need to worry about so you'll need to allow for that when you cut the panels. For example going from 12mm ply to 18mm would make the cab wider by 6mm each side and it would need to be 12mm wider overall. Thicher panels means less pracing so you can shave a bit there.

 

Think about the 4ohm driver a little more. You will gain at best 2db which is just noticeable and for acoustic gigs you won't need that much, I use a BC110T for open mics and it is really overkill. I do a lot now with my 6" design and we've recently put up a design for an 8 which works well, all this with a Warwick Gnome 130W into 8ohm. This cab is around the size of your Monza and roughly the same weight you could go smaller IMO. The 8" cab uses the same 'easy build' construction so is effectively the same cab with smaller panels.

Thank you for the advice @Phil Starr. I hadn’t thought about thicker ply changing the internal dimensions. I will have to do some calculations to make sure I am getting at least 30 litres internally. 
 

I have decided to go for @Chienmortbb’s 12PR320. It will save me quite a few quid over buying a new one and keep the overall cost down. I wanted to do a 12” simply because I have 10” well covered by my Monzas and BF Two10. I had a little Mark Bass 8” combo and that has somewhat put my off 8” drivers, even though the real limitations were in the EQ department. Illogical I know.

[Obrienp]

50 minutes ago, pete.young said:

 

Or just buy a Gnome/Elf and use that with the Monza.

I have a Gnome iPro and I really don’t like it with the Monza. It is possible to get a sound I like with that combination but the EQ settings have to be really radical and there is nowhere to go for variation once it is dialled in.

 

I already have the HB GPA-100 power amp, which I use occasionally for guitar with a multi effects pedal as preamp. I have also used it with a Monza and Bass Flyrig V2 for rehearsals and small gigs. The advantage of the Flyrig is that it has two preamp channels and all the effects I use built in, a tuner, plus a good DI (it’s raison d’etre). It just reduces the kit required in cramped conditions. An active cab would reduce it further but I really don’t like the affordable options available at the moment. I could use a 12” active PA cabinet but it doesn’t look right. Also I want the challenge of building a cab and the sense of achievement when it’s built.

[Obrienp]

33 minutes ago, basstone said:

Slightly off topic, but may be of interest - I have a 700RB for sale on this forum. They are great sounding versatile amps. Mine is a 2 x 10" combo which is reassuringly heavy but the head could be used very effectively in a project like this?

Thanks for the offer but I already have the GPA -100 power amp, plus I currently have 4 amp heads. I really need to cull the herd a bit rather than enlarge it.

[basstone]

Just now, Obrienp said:

Thanks for the offer but I already have the GPA -100 power amp, plus I currently have 4 amp heads. I really need to cull the herd a bit rather than enlarge it.

Understood, I thought it may be of interest to others considering a DIY bi-amped cab project 🙂

 Good luck with the project and keep us posted

[Obrienp]

1 minute ago, basstone said:

Understood, I thought it may be of interest to others considering a DIY bi-amped cab project 🙂

 Good luck with the project and keep us posted

Sounds like a good option for somebody. 👍

 

I’ll keep you posted. Probably in panicked calls for help when I mess up😏. Just collecting the parts at the moment.

[Obrienp]

On 20/10/2025 at 07:45, Phil Starr said:

It'll take me a while to model the response of some of the drivers available today but this looks very do-able. The thickness of the ply isn't going to add a lot to the weight, just remember it's the internal dimensions you need to worry about so you'll need to allow for that when you cut the panels. For example going from 12mm ply to 18mm would make the cab wider by 6mm each side and it would need to be 12mm wider overall. Thicher panels means less pracing so you can shave a bit there.

 

Think about the 4ohm driver a little more. You will gain at best 2db which is just noticeable and for acoustic gigs you won't need that much, I use a BC110T for open mics and it is really overkill. I do a lot now with my 6" design and we've recently put up a design for an 8 which works well, all this with a Warwick Gnome 130W into 8ohm. This cab is around the size of your Monza and roughly the same weight you could go smaller IMO. The 8" cab uses the same 'easy build' construction so is effectively the same cab with smaller panels.

Now I have decided to go for the Faital Pro 12PR320, has that already been modelled? 
 

I am fully bought into Apple these days and WinISD only runs on Windows. There is an app for iPadOS called Speaker Box but the pro version that gives you a cabinet design, cutting plan and parts list is £7 a month!! That’s a lot of money to spend on an unknown quantity. Has anybody tried it and is it worth the cash? Sub-question is it friendly to those with very little knowledge of acoustics and speaker design?

[Phil Starr]

45 minutes ago, Obrienp said:

Now I have decided to go for the Faital Pro 12PR320, has that already been modelled? 
 

I am fully bought into Apple these days and WinISD only runs on Windows. There is an app for iPadOS called Speaker Box but the pro version that gives you a cabinet design, cutting plan and parts list is £7 a month!! That’s a lot of money to spend on an unknown quantity. Has anybody tried it and is it worth the cash? Sub-question is it friendly to those with very little knowledge of acoustics and speaker design?

 

As it happens I had the details with the Faital saved from a previous project. With 130W which is the typical mini-amp output into 8 ohms it looks like this. Ideally the Faital would be better in a bigger cab (better in terms of more bass and a flatter response) There's a 2db peak at 120Hz which is typical of many commercial cabs, but that's not awful; it will sound quite warm and bass heavy without eq . My original driver did much the same and so did the Beyma 12CMV2 It's really quite a good match. The biggest problem is that you need quite a big port for a small box to avoid turbulence in the port but if you limit it to 150W that shouldn't be a big issue

 

[Obrienp]

15 minutes ago, Phil Starr said:

 

As it happens I had the details with the Faital saved from a previous project. With 130W which is the typical mini-amp output into 8 ohms it looks like this. Ideally the Faital would be better in a bigger cab (better in terms of more bass and a flatter response) There's a 2db peak at 120Hz which is typical of many commercial cabs, but that's not awful; it will sound quite warm and bass heavy without eq . My original driver did much the same and so did the Beyma 12CMV2 It's really quite a good match. The biggest problem is that you need quite a big port for a small box to avoid turbulence in the port but if you limit it to 150W that shouldn't be a big issue

 

Many thanks @Phil Starr. That sounds good.
 

Would the dimensions of that quite big port be given at the start of the thread? If not, how would I work out what they need to be and if one big port could be problematic, could two smaller ones do the same job? Apologies again for the idiot boy questions.

[Phil Starr]

The dimensions at the start would work but I'd tune slightly lower for this driver Two drainpipe ports of 18cm each would be a better tuning and what I was using in the computer model above. You can get a slighly better response with bigger ports but the port is then longer than the cab is deep and would need to be removed, probably bottom venting. At anything below 200W you wouldn't have problems anyway. 

 

In the end I used this cab for quite a while with one of my bands and had no problems with wind noise from the ports at gigs despite playing with one of my loudest drummers (David you know who you are  ). Like any ported cab using a highpass filter helps power handling and chuffing a lot as well as cleaning up your sound.

 

It might be worth having a quick look at this thread. Although this is designed as a 10" cab with a tweeter/horn the basic cab is the same except for the front panel and a bit of extra bracing. There are proper drawings in the first post

 

Edited 1 hour ago by Phil Starr