Cab build (and refurb) projects

CHrisP86

I want to try building a 1x12 and a 4x12 at some point this year (4x12 subject to how the 1x12 goes).

What are the general thoughts on cab dimensions?  I was going to use the old Cornford specs for both but probably out of plywood rather than pine.  Any thoughts or recommendations for other dimensions?  I had also thought about using the rectifier or ubercab dimensions for the 4x12.

ecc83

there is little "science" behind guitar speaker cabs, they are pretty much cut and try for any particular drive unit.

I did a bit of research a couple of years ago and the box sizes varied from about 1/2cu ft to about 1.5cuft so there is no "right size". 

If you were really sneaky you could go to the music store with a Stanley Steelmaster secreted, find a cab you like the sound of and have a quick "rule"!

If there was any rule at all it would be to make it as big as you reasonably can. You can always cut it down by making it less deep or filling it with air displacing (as against sound absorbing) materials.

Dave.

midiglitch

I built an angled 1x15 plywood cab after someone gave me a 15" celestion driver. My experience might relate to a 112, probably less relevant to a 412 but here's What I learnt: 

An angled cab is disproportionately more work to do well than a straight cab!  Not just joints and corners but all the way through to covering it at the end.

When considering the dimensions the main factors in contributing to the sound are probably* baffle area (particularly if you go open back), and volume (if you go closed.). But...also consider if you might stack the cab or be putting a head on top of it - you'll want to make the width and depth of the top big/small enough to stack well.

I started out using 18mm ply I think and it was unnecessary - very heavy.  I'd go for 12mm or maybe even less for the box.  You might try a couple of different thicknesses for the baffle and see how they sound.

With regards to the baffle you have options as to how you fix it- fully fixed or floating.  Again it's suck it and see really!

When all was said and done and it was finished and tolexed, I reckon I could have bought a commercially made cab off the shelf for about what I spent on the materials.  If I factored in my own time at £30 per hour (the figure I generally use when I'm trying to decide between the trade off of doing something myself or buying it in) it was *way* cheaper to buy a ready made cab!

I'm no craftsman - merely an amateur with the basic tools and skills (grandad was a cabinet maker) so ymmv!

*see Dave's comment above.

digitalscream

Why not build something that's not readily-available instead? Something like one of these:

http://www.thomann.de/gb/jet_city_amplification_jetstream_iso12.htm

?

Misterg

There's an interesting discussion about designing a 1x12 cabinet over on AX84.com.

The archived version (pdf) is here

Plans from it (pdf) here

All I would say is: don't build it out of MDF like I did - heavy and dead!

CHrisP86

It is nagging me that I could get a second hand cab rather than building but I just want a project really. The AX84 discussion has a lot of useful stuff. Might give that one a go as the plan is all there. Was thinking of trying a neodymium speaker (maybe eminence tonkerlite) so hopefully that fits the design.

impmann

I just bought a home made isolation cab on ebay for £5, complete with a Fender speaker fitted!! 

Sometimes it pays just to keep an eye on Ebay for such stuff. ;-)

chillidoggy

What about getting one of the Montage cabs? I got one unloaded, stuck a speaker in, and it's very good. Saves all the pissing around trying to cut bits of wood in straight lines.

hywelg

Keep it simple. The practicalities are:-
Can you saw wood accurately and square? If not go to B&Q and have them saw the pieces for you. They keep 18mm birch ply but not much else unless your happy with cheap ply. If you want 15mm birch then you'll need to vist a woodyard and see if they'll cut to size for you. If you want pine, finding boards more than about 250mm wide is not easy. If at all possible look for 'unsorted red deal' which is usally a  type of fir, very straight grain and very few knots If possible hand pick it. Dont be tempted to take knotty pine or you'll just be making work for yourself.

Are you able to cut dovetail or fingerjoints? If not youre going to need to dowel or screw the corners with come bracing. Use stout  screws, not drywall screws. No12 or 14.

Do you want to cover it in tolex? If so you will need a hot air gun, trying to mould the corners neatly without is problematic, unless you are very very good with a stanley/moedlling knife. If you are going to fit metal corners you need to know the radius of the curve and you will need a router and appropriate rounding over cutter to shape the cabinet edges. Usually 12mm or 15mm radius. Using PVA glue will give you time when covering unlike contact adhesive which demands speed. PVA will respond well to a hot air gun, so if it is nearly dry , heat it and it will become tacky and stick just like contact adhesive.

Are you going for a cloth covered baffle? If yes you will need a staple gun (cheap manual one will do). You will need to decide before you start whether the grille cloth gets fixed to the speaker baffle or you will make a separate frame for it.

You will need M5 or M6 T-nuts for the speaker mountings. I would recommend always using 8 per speaker even though most speakers only have 4 holes. If you wreck one (with a baffle which has the grille cloth fixed to it) you just turn the speaker 45°. I think most eminence speakers have 8 holes though you only need to use 4.

I'm suer theres more to think about but I want to get this posted before the 11pm forum shutdown

CHrisP86

Am definately getting the feeling that half way through this project I am going to re-read the posts here and think 'they were right, I should have just bought one...'

Thanks for the info. 

Was going to go to a timber merchant so I could get a decent sheet of 18mm ply and probably 12mm for the baffle and back.  Will try to rebate the baffle for extra strength.  A bit confused on the bracing though.  The cornford 2 x 12 cab I have is meant to have the baffle rebated but it also has bracing around the back of it.  Is that for extra strength or some kind of clever internal volume reduction?

I have a router, nail gun and hot air gun so all set there.  Think I will try and do lock joints as don't look too bad to do with a router.

Seperate frame for the grill cloth.

Still can't decide on dimensions.  Think I need to go and try out a few more cabs.

ThePrettyDamned

Give us a good build thread with plenty of pics.

I'd love it to read (like @octatonic guitar builder thread, which is still my favourite thread on here) and if you encounter any difficulties, there are folks on here who will happily step in.

CHrisP86

Project is still on the cards but progress a bit slow, just been gathering up the bits i'll need.  So far got the tolex, bar handles, corners and speaker wire. 

Will add pics to this photo bucket album:  http://s1320.photobucket.com/user/CHrisP86/library/Cab Build?sort=3&page=1

Might be a bit of a delay before I get any more bits as just bought a new amp.  This might turn in to a new project though as I'm thinking about re-covering the amp to practice with the tolex.  Has anyone ever modded a JCM800 style head shell to a plexi head shell?  I'm not sure what size the piping channels need to be or what size piping to use.  Although I suppose I just get the piping and cut the channels to fit...

CHrisP86

Got the tolex off the amp.  Not looking forward to getting the old glue off though...

chillidoggy

How old is the glue? Mine came off pretty easily with a sander.

CHrisP86

It's fairly old and not too tacky. I had a quick go at it with a sheet sander yesterday and I think it will work with enough patience and maybe some coarser paper... What type of sander did you use?

Deadman

I always use thinners and abrasive pads to remove old adhesive. As this is a cab that'll be recovered anyway a sander will do the trick so long as you don't re-profile the edges too much in the process. I use an orbital air sander, use of a household sander will be a more laborious process as you don't get the cut you do with an professional automotive type. You need to be using 180 grade ideally or you'll be there forever

CHrisP86

Great, thanks!

chillidoggy

I used a Bosch Multi tool, with triangular coarse pads. It was a reasonably quick job, I didn't have to resort to using thinners as Deadman suggests, but as he says, watch the radii on the edges, even to the point of maybe hand finishing them. I did go to the trouble of filling every dent or depression I could find, so they didn't show through the Tolex, but I might have been a bit too pedantic about it.

CHrisP86

Finished my first re-tolexing job:

CHrisP86

Corners didn't turn out as well as i'd hoped though, pics here:

http://s1320.photobucket.com/user/CHrisP86/library/Cab Build

Any suggestions for how they might be salvageable?  Would be happy to put corners on it but seems as though only the genuine marshall corners have the right radius and I'm not sure whether black corners would look right.

Bod

Necro thread bump.  I'm about to start building a 2 x12 based on a Zilla Studio Pro dimensions.  The pics in this thread are missing - any chance you could repost along with an update @CHrisP86?