Peterson combo driver upgrade (and related plywood boxes)

[JohnDaBass]

On 25/06/2022 at 17:31, Phil Starr said:

I think that would be a great solution. Your problem is that the ports will then be quite small and you'll have problems with wind noise in the ports. If you can fit in two drainpipe ports that will help a lot or use a single 10cm port. Two ports 13.2cm or a 10cm port 14.4cm long.

I found that a single 10cm port worked best for me. Single hole to cut, easier to position on the the baffle and lots of vendor options. 

[Pea Turgh]

Well heck, this is taking a while to sort!

 

I’m going to combine a couple of projects here.  I need to make a sleeve for a Trace Elliot head, and I want another cab to pair with the Trace or the Peterson.

 

The Peterson amp has a fault, so will need to get that sorted.  Whilst it’s not operational, I might as well do the proper woodworking on the cab to optimize it.

 

Order of business;

1. Design the 2nd cab so it matches the Peterson dimensions (at least just the width so it sits nicely).

2. Go get some ply cut up

3. Build the Trace amp sleeve

4. Build the new extension cab using the Beyma from the Peterson.

 

Working amp & cab

 

5. Get the Peterson amp head fixed

6. Put the Peterson shell under the knife to optimise the tuning.

7. Acquire a 2nd Beyma (should have bought that 2nd one from you at the time @Chienmortbb!)

 

Will put pen to paper this evening when I’m in the house, also try WinISD to see if I can work out tunings myself.  Will then post my crayon drawings here for comedy value/feedback.

[Chienmortbb]

32 minutes ago, Pea Turgh said:

Well heck, this is taking a while to sort!

 

I’m going to combine a couple of projects here.  I need to make a sleeve for a Trace Elliot head, and I want another cab to 

7. Acquire a 2nd Beyma (should have bought that 2nd one from you at the time @Chienmortbb!)

 

Will put pen to paper this evening when I’m in the house, also try WinISD to see if I can work out tunings myself.  Will then post my crayon drawings here for comedy value/feedback.

Sadly that Beyma went dome time  ago. The 12CVM2 is a close alternative but not an exact replacement. 
 

I have a Faital Pro 12PR320 neo if it helps or @Phil Starrmight have a Beyma. 

[Phil Starr]

8 hours ago, Chienmortbb said:

if it helps or @Phil Starrmight have a Beyma.

 

I probably need to go up into the loft, I'm not sure what is up there any more.

[BassmanPaul]

That's a lofty ambition Phil!

 

[Pea Turgh]

9 hours ago, Chienmortbb said:

Sadly that Beyma went dome time  ago. The 12CVM2 is a close alternative but not an exact replacement. 
 

I have a Faital Pro 12PR320 neo if it helps or @Phil Starrmight have a Beyma. 

It was a 12CVM2 that I bought from you, so should be able to source a 2nd one as they appear to be current. 👍

[Pea Turgh]

Ooh, should be able to get the Peterson cab to 41 litres with woodwork.  Should help, I guess.  Will make sure by checking it out on WinISD before getting the tools out!

[Pea Turgh]

Bought some 12mm ply, some wood glue and a circular saw.  Sh*t’s getting real!

 

Found an app called Cut List, for optimising cuts on the ply - should help minimise waste.

 

Trying to see what colours Tuffcab do, but their site doesn’t appear to work very well on a mobile.  Will fire up the laptop to browse later on.  Half tempted to do the same domestic emulsion + protection coat like I used for the “BC house jam micro cab”.

[Downunderwonder]

1 hour ago, Pea Turgh said:

their site doesn’t appear to work very well on a mobile.

When that happens I select "desktop site" on the phone browser. It doesn't always work but usually I can zoom in on the good bits.

[Pea Turgh]

Measure, check, measure, check, measure, check, cut, check, measure.  It was all perfect right up until I glued & screwed it together.  Suddenly my 1mm extra all around disappeared and it’s 2mm too narrow!!!  Amp head no fit.

 

Stuff it.  I’ll crack on with the cab for now.  

[Chienmortbb]

53 minutes ago, Pea Turgh said:

Measure, check, measure, check, measure, check, cut, check, measure.  It was all perfect right up until I glued & screwed it together.  Suddenly my 1mm extra all around disappeared and it’s 2mm too narrow!!!  Amp head no fit.

 

Stuff it.  I’ll crack on with the cab for now.  

Put the amp head in the freezer, it will give all enough to fit. However, assuming it does not split the case as it expands, it will never come out. 

[Pea Turgh]

I also failed to take in to account the rivets holding the transformer to the chassis, so I’ll just have to make a fresh case.  No biggy, it’s all learning.  Mrs Turgh says I seem happiest when I’m cutting wood! 😂

 

Tip that I discovered (but is probably widely known):  the circular saw wasn’t flowing as I’d like, so I rubbed a candle on the bottom and side of the guide rail - now it glides along!

 

Wood cut for the cab.  Will pop to B&Q later for another sheet for the baffle and the 2nd anttempt amp sleeve.

Edited June 23 by Pea Turgh

[BassmanPaul]

Make sure that the amplifier sleeve doesn't block any ventilation holes in the amp's case. You don't want the amp to overheat in use.

 

[Pea Turgh]

The amp was pulled from a combo, so there isn’t really a case, as such!  The heat sink should sort it.  I don’t recall seeing a Trace combo with vent holes, and there’s no fan, so would assume it was designed to be fully enclosed.

Equally happy cutting more holes if the experts think it worthwhile!

 

[Pea Turgh]

Progress

 

 

[nekomatic]

On 23/06/2025 at 17:03, Pea Turgh said:

I also failed to take in to account the rivets holding the transformer to the chassis, so I’ll just have to make a fresh case.  No biggy, it’s all learning.  

 

1. Find an alternative use for the incorrect one
2. Insist it was meant to be that all along
3. Don't ask me why my printer stand is coated in Tuff Cab

[Pea Turgh]

Ooh, I wander if tuffcab is any good for cars?

 

Box 2 for the Trace is glued and screwed.  Will wait for it to dry then get busy with a flush bit first for nice square corners, then a round over bit for finished shape.  If I can get away with no mistakes, I might go for a stained finish to match the Peterson.

 

The new cab is ready for its baffle.  Will check exact volume then have another pop at WinISD.
 

Chrome corners and dark brown leather handles on order for both.  Will also need to get some better gain & volume knobs!

[stevie]

The wood looks nice. I'd expect a stained finish to look good.

[Pea Turgh]

Calculated the internal volume as 48.998 litres, taking in to account the battens, but not driver volume.

 

Found a Beyma 12CMV2 file online and loaded in to WinISD.  There endeth my knowledge on how to calculate port size! 

I watched some WinISD videos on YouTube, which only confirmed I am in over my head.

 

Might some kind soul with WinISD skills be able to confirm what port diameter and length would be suitable for my cab, please?

[Pea Turgh]

Roundover bits are a marvellous thing!  Tips for next time I do this;

1. outside on a windy day will blow dust in to your eyes and make you wobble.  Avoid if possible.

2. set the damn bit depth properly!

 

Nothing a bit of sanding won’t sort.  Next up, filler, sand, sand, sand, stain, protective coat, assemble, make noise!

 

Oh and the port calcs…

 

 

[Downunderwonder]

On 28/06/2025 at 05:07, Pea Turgh said:

 

Oh and the port calcs…

Plug in cab volume.

 

Plug in driver if your version supports the Beyma. If not, give it the T/S specs from the datasheet.

 

Tell it you have a tuning of 50hz and two 4" round ports. It will tell you the length, also the port velocity and response chart and displacement chart for whatever wattage you input.

 

It's a big enough box you might get away with a lower tuning.

[Balcro]

Hello P.T

winISD calculations:-

Using data from a 2021 spec 12 CMV2 (now replaced by 12 CMV3) your volume calculation of 49.98 for the box and allowing for the volume of the drive and port you should get a net volume of 47 litres.

The "fs" for the driver is 49.30Hz. With that you select one vent that is exactly 10cm internal diameter. The vent length will be 12.68cm. With a 100w input the winISD calculation is for an output of up to 116dBa at around 115HZ. Not a bad match at all.

If you decide upon two 8.20cm diameter ports (as per the options in winISD) vent length is 20.9cm.

It all depends upon the space you have for 1 or 2 ports on the front baffle and or what ports you can buy.