Cab building tips?

Amp tinkerers and people who aren't afraid of 700 volts or so in here....

Moderators: Slowy, Capt. Black

User avatar
Zaulkin
Vintage Post Junkie
Vintage Post Junkie
Posts: 5465
meble-kuchenne.warszawa.pl
Joined: Thu Nov 27, 2008 4:01 pm
Has liked: 763 times
Been liked: 532 times

Cab building tips?

Post by Zaulkin »

Hi all,

Thinking of making up two oversized 1x12 cabs. I bought those plastic bass reflex ports off Aliexpress, 2 per cab. Anyone tried these? I also bought my corners etc from the express of Ali, so I hope they don't rust quickly.

Borge has kindly donated me some grille cloth, just need to get some white piping and black tolex I think.

What things have you learnt to do and not do for the optimum result? Is 18mm ply the standard? I want light cabs hence the single speaker.

I was going to do finger joints, but is glue and nail just as good if I leave room for my round over bit?

Are most grilles just velcroed on at the front?

User avatar
rickenbackerkid
Vintage Post Junkie
Vintage Post Junkie
Posts: 6751
Joined: Thu Apr 28, 2005 1:52 pm
Has liked: 212 times
Been liked: 667 times

Re: Cab building tips?

Post by rickenbackerkid »

I wouldn't bother with finger joints, lot of work, hard to do well. Just glue and screw. 18mm ply should be fine. If you want lots of bass, I highly recommend sealing the thing really well, all joints etc. This made a substantial difference when I rebuilt a Marshall cab

User avatar
Jay
Vintage Post Junkie
Vintage Post Junkie
Posts: 7885
Joined: Sat Sep 25, 2010 9:35 pm
Has liked: 1669 times
Been liked: 1315 times

Re: Cab building tips?

Post by Jay »

I wouldn't glue and nail but glue and screw will work fine. Rebate the screws so the router won't hit them. After Rounding fill up the rebates with Wood filler

Finger joints are nicer. Especially for pine but 18mm ply, yeah, screw and glue
When faced with quality, I recognise it every time.

User avatar
Bg
Site Admin
Posts: 43464
Joined: Fri Sep 05, 2003 12:13 am
Location: Auckland
Has liked: 2281 times
Been liked: 4015 times

Re: Cab building tips?

Post by Bg »

If you don't have the tools for finger jointing or dovetails then there are two better options - you sound like you have a router for rounding over - so :

1. Double rebated corner joints
Sounds way harder than it is - its just two router cuts on each corner and gives way more glue area
Image

2. Edge joints with dowels
You're rounding over the edges - if you hit a screw you'll know about it, at best you'll chip your round over bit, at worse it will be way worse than a chip and you want to make sure you're wearing PPE.
I'd put at least 4 dowels in on each joint. Dowels also give you greater glue area than just glue/screw.

If you want light cabs - go with pine, 18mm ply is heavier, not mdf heavy but heavier.

You need to look up some baffle options, I wouldn't use velcro unless you're wanting to go half arsed :) Usually the baffle will be plywood with a frame glued to it ( 10 mm ) and the cloth stapled around it and inserted from the back. This is the usual method.

But you do you, as long as you're happy with the end result.
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

User avatar
Reg18
Vintage Post Junkie
Vintage Post Junkie
Posts: 3729
Joined: Thu Feb 06, 2014 1:57 pm
Has liked: 322 times
Been liked: 964 times

Re: Cab building tips?

Post by Reg18 »

My advise is copy someone else’s proven dimensions, going over size in my experience isn’t always best. The last 2x12 I built was oversized but it was too bloated. Not much attack, I ended up cutting it down in size and went from closed back, to half open to eventually cutting an oval shaped hole in the back before I was actually happy with the tone. There’s a happy middle ground between big ballsy sound but still keeping the note attack.

User avatar
Bg
Site Admin
Posts: 43464
Joined: Fri Sep 05, 2003 12:13 am
Location: Auckland
Has liked: 2281 times
Been liked: 4015 times

Re: Cab building tips?

Post by Bg »

I should also have mentioned - treat routers with respect, they can kick back and if they do you know about it.
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

User avatar
jeremyb
Chorus of Organs
Posts: 41946
Joined: Sat Dec 06, 2008 9:03 am
Has liked: 7945 times
Been liked: 4272 times

Re: Cab building tips?

Post by jeremyb »

Glue + brads + lots of clamps == job done!

For the grill cloth I just made a frame and stapled the cloth to it then yeah velcro on the back to attach it to the baffle :-)
Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.

User avatar
Zaulkin
Vintage Post Junkie
Vintage Post Junkie
Posts: 5465
Joined: Thu Nov 27, 2008 4:01 pm
Has liked: 763 times
Been liked: 532 times

Re: Cab building tips?

Post by Zaulkin »

Reg18 wrote: Thu May 23, 2024 6:08 pm My advise is copy someone else’s proven dimensions, going over size in my experience isn’t always best. The last 2x12 I built was oversized but it was too bloated. Not much attack, I ended up cutting it down in size and went from closed back, to half open to eventually cutting an oval shaped hole in the back before I was actually happy with the tone. There’s a happy middle ground between big ballsy sound but still keeping the note attack.
Good point. I already have a cab in the dimensions I'm thinking.

It also seems to be very similar to a Dr z best, which I had in the past. That was the best cab I had!

User avatar
Zaulkin
Vintage Post Junkie
Vintage Post Junkie
Posts: 5465
Joined: Thu Nov 27, 2008 4:01 pm
Has liked: 763 times
Been liked: 532 times

Re: Cab building tips?

Post by Zaulkin »

Bg wrote: Thu May 23, 2024 5:37 pm If you don't have the tools for finger jointing or dovetails then there are two better options - you sound like you have a router for rounding over - so :

1. Double rebated corner joints
Sounds way harder than it is - its just two router cuts on each corner and gives way more glue area
Image

2. Edge joints with dowels
You're rounding over the edges - if you hit a screw you'll know about it, at best you'll chip your round over bit, at worse it will be way worse than a chip and you want to make sure you're wearing PPE.
I'd put at least 4 dowels in on each joint. Dowels also give you greater glue area than just glue/screw.

If you want light cabs - go with pine, 18mm ply is heavier, not mdf heavy but heavier.

You need to look up some baffle options, I wouldn't use velcro unless you're wanting to go half arsed :) Usually the baffle will be plywood with a frame glued to it ( 10 mm ) and the cloth stapled around it and inserted from the back. This is the usual method.

But you do you, as long as you're happy with the end result.
Good advice, thank you sir!

borge
Fender
Fender
Posts: 528
Joined: Tue Apr 19, 2005 1:54 pm
Has liked: 9 times
Been liked: 15 times

Re: Cab building tips?

Post by borge »

I used 9mm ply with 2 x 18mm square pine ribs per panel. This ended up about 4% stiffer than 18mm ply alone and around 40% lighter. My key criteria was low weight so I spent a bit of time balancing stiffness against weight.
Baffle is 12mm, loaded from the front with 10x M5's from the rear into T nuts. There are strips of 12mm ply around the front so it doesn't look 9mm thick and the corners fit.
Screenshot 2024-05-24 101022.png
Screenshot 2024-05-24 101022.png (798.01 KiB) Viewed 977 times
IMG_20240412_070054.jpg
IMG_20240412_070054.jpg (1.35 MiB) Viewed 977 times

I couldn't find anything but anecdotes when trying to research guitar cab design, this video was about the only thing with some form of data. I'm a design engineer by day so averse by nature to thoughts and feelings as design inputs :D

User avatar
Miza
Vintage Post Junkie
Vintage Post Junkie
Posts: 2322
Joined: Mon Oct 29, 2007 1:07 pm
Location: Hamilton
Has liked: 778 times
Been liked: 261 times

Re: Cab building tips?

Post by Miza »

Agree about using a tried and true design/specs. Especially the Dr Z, they are supposed to be good, so trust the work has already been done figuring that out!

Also agree about using dowels instead of screws/nails, no risk to hitting them with your round-over bit.
I use 6mm dowels and 18mm ply (the general rule is dowel size should be about 1/3 the thickness of the material).

In terms of attaching the baffle, there's so many different designs, I reckon do what you want.
Lots of the fancy FR/FR cabs have velcro baffles, so why not?
Small fender combos just screw straight on from the face, leaving an exposed screw in each corner. Just make sure to use cup washers if you do this.
Big 4x12 cabs tend to have a lip built into the cab, and the baffle goes in from the back and screws in against the lip.
I went with the small Marshall (1974x) design of front mounting the baffle, but installing T-nuts in it, so you can screw it in from the inside.
I also added a valence on my baffle, which looks great, but is a bit more work in terms of an extra piece to tolex/vinyl, and more area to add piping. The trick is to make the valence from the same thickness material as the frame for the grill clothe (I used hardboard for this, the stuff you find at the bottom of drawers, and it actually was). That way, the depths match when you attached the valence.
Another part of the Marshall 18W design that works in your favour is the additional piping around the body. Means more faffing cutting the groove, but means you attach 4 separate pieces of vinyl/tolex with no visible seam.

Other advice:
Make a circle-cutting jig for your router to cut the speaker hole. Just cut the rough hole first with a jigsaw (lesson learnt hard way).
Corners are a bastard to tolex if you're not covering them.
You never have enough clamps.
Nothing to see here.

User avatar
Jay
Vintage Post Junkie
Vintage Post Junkie
Posts: 7885
Joined: Sat Sep 25, 2010 9:35 pm
Has liked: 1669 times
Been liked: 1315 times

Re: Cab building tips?

Post by Jay »

The article says Jim Marshall's 4x12" cab was a random 'design'.

https://www.mojotone.com/blog/speaker-c ... -your-tone
When faced with quality, I recognise it every time.

User avatar
Bg
Site Admin
Posts: 43464
Joined: Fri Sep 05, 2003 12:13 am
Location: Auckland
Has liked: 2281 times
Been liked: 4015 times

Re: Cab building tips?

Post by Bg »

Jay wrote: Fri May 24, 2024 4:13 pm The article says Jim Marshall's 4x12" cab was a random 'design'.

https://www.mojotone.com/blog/speaker-c ... -your-tone
Yep, important design feature was to get it out of one sheet of plywood :rofl:
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

User avatar
Bg
Site Admin
Posts: 43464
Joined: Fri Sep 05, 2003 12:13 am
Location: Auckland
Has liked: 2281 times
Been liked: 4015 times

Re: Cab building tips?

Post by Bg »

Miza wrote: Fri May 24, 2024 2:44 pm
Other advice:
Make a circle-cutting jig for your router to cut the speaker hole. Just cut the rough hole first with a jigsaw (lesson learnt hard way).
Corners are a bastard to tolex if you're not covering them.
You never have enough clamps.
Never had a problem with circle cutting, never bothered with a jigsaw. Just use a sharp 6mm bit.
Corners are only a bastard until you've done a few - black tolex is easiest as you can prespray the corners of the cab with black paint ;) and this is why you should use tolex and not 'vinyl' as its way more forgiving and has a bit of stretch in it.

You never have enough clamps - unless you use dovetails then you only need 4.

Having said which, I have about 32 clamps, just in case.

Jointed this today, AC15 cab I’ve been meaning to do for awhile.

IMG_1344.jpeg
IMG_1344.jpeg (3.25 MiB) Viewed 892 times
I will say, you can never have too many routers. I have 4 now :mental:
One in a table, one trim router, one setup for dovetails and a big 1/2" router I use for marshall style cab roundovers - 19mm radius. If that hit a screw I'd know about it!
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

User avatar
Zaulkin
Vintage Post Junkie
Vintage Post Junkie
Posts: 5465
Joined: Thu Nov 27, 2008 4:01 pm
Has liked: 763 times
Been liked: 532 times

Re: Cab building tips?

Post by Zaulkin »

Bg wrote: Thu May 23, 2024 5:37 pm 2. Edge joints with dowels
You're rounding over the edges - if you hit a screw you'll know about it, at best you'll chip your round over bit, at worse it will be way worse than a chip and you want to make sur
I'd put at least 4 dowels in on each joint. Dowels also give you greater glue area than just glue/screw.
What length dowels should I use for an 18mm ply cab?

Post Reply