Building amp heads and guitar cabinets?

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audio_moksha

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Joined 2006
#1
Hi folks,

I'm in the process of building a tube amp head and I would also like to build the enclosure for the amp head, as well as a 2x12 cab. Could somebody kindly guide me to any well documented projects of this nature? Constructing the cabinets should be easy but what I really don't know is what would be the best way to put on the tolex covering as well as the piping and in what order (i.e tolex before gluing the panels or vice versa?)

Thanks.
 
#5
I sometimes build guitar amps and cabs, but I often farm out the cab construction. I also play bass, build bass rigs and am starting to build a new PA.

In all of this, I've learnt a few things that I apply to my designs, but others may not.

- use quality ply. Brace the corners of the cab as shown in some of the links, but I also add a couple of x-braces as more typically seen in hifi builds. "resonant' enclosures are a bit hit and miss so I prefer to concentrate on the amp and drivers.
-- If you don't have a lot of tools, go to a timber specialist to buy your ply and get them to gut it for you on their big table. It'll be more accurate, and (mine) usually go together perfectly.

- Use urethane glue, but you'll need good clamps. It also expands to fill any small gaps which is handy for sealed caps.

- When the cab is complete, I usually give the inside a coat of epoxy thinned down as a moisture sealant. Probably not neccessary, but it takes 10 min and 50c so why not.

- Flip out handles are useless, use recessed metal ones. Wherever you put them make sure they're actually useful, ie placed where you will actually be able to grab then and carry the box comfortably. A mate build a cab once with the recessed side handles at about 20*. Everyone gave him stick until they saw they were angled perfectly for him to pick it up and carry and keep his wrists straight.

- I don't like carpet. It's the easiest to apply but you'll have an olefactory memory of every gig. Tolex/vinyl scuff and tear easily, so I've settled on Rockard paint or spray on ute/truck bed liner. Indestructible and looks good for a long time. Most gear is painted or covered black anyway.

- if you use more than one driver, stack them vertically. No horizontal phasing and you'll hear yourself better on axis. Never understood having two drivers blasting at your ankles.

- Depending upon how high the cab ends up being, put a corner handle on the top rear corner and a pair of large castors on the bottom of the rear panel, and you have a built in tilt and roll. I hate carrying things. The handle may be better in the centre of the top; you'll need to sort out what's best for you. I don't do this on my gear as I always use a removalists handtruck.

- in higher power combos, I build the poweramp into the base and the preamp + controls on the top. Run the B+/filaments up one side in a conduit, and signal up the other. Batter balance and more stable.

- a hinged tiltback isn't hard to add to the rear. Hinge it at the top, and at the bottom glue a small piece of steel with a little neo magnet glued into a recess drilled in the back to old it when not in use. I usually puf some thin carpet (ratfur) between the hinged tilt panel and the back to make sure it doesn't resonate.

- use the best (tonally) drivers you can get. Lots of great neo's out there, but one of my faves is the EVM12L (ceramic).

I've got to run. If I think of anything else I'll add it later.
 
#6
Brett said:
- use quality ply. Brace the corners of the cab as shown in some of the links, but I also add a couple of x-braces as more typically seen in hifi builds. "resonant' enclosures are a bit hit and miss so I prefer to concentrate on the amp and drivers.
Click to expand...

My only comment would be to make your own choice on the cabinet material - good plywood is stronger and will take a lot more abuse than chipboard or MDF, plus it's usually lighter as well.

However, chipboard and MDF are more acoustically 'dead' so have that advantage, plus the much lower cost. As long as you're not planning abusing your cabinets?, then the lower cost option may be better?.

If you're planning lending or renting out your cabinets though?, make sure you go for very good quality plywood - as they are likely to get much more abuse than you would give them yourself.
 
#7
Thanks for that very informative reply Brett; some very useful pointers indeed. I'm still in the process of designing my amp head: a Fender bandmaster derived circuit with switchable 15W or 30W power. When I build the cab its going to be a 2x12 Celestion Greenback with black levant to match my amp head. Just one more thing; are there any real (acoustical) advantages to dove tailing? It seems like butt joints with internal bracing is every bit as sturdy than dove tailed joints...
 
#8
Nigel Goodwin said:
My only comment would be to make your own choice on the cabinet material - good plywood is stronger and will take a lot more abuse than chipboard or MDF, plus it's usually lighter as well.
Click to expand...
Ply is a lot tougher, taking the myriad knocks that come from an active gigging rig. Don't use MDF, . NONE of the Pro companies do.
 
#9
audio_moksha said:
Thanks for that very informative reply Brett; some very useful pointers indeed. I'm still in the process of designing my amp head: a Fender bandmaster derived circuit with switchable 15W or 30W power. When I build the cab its going to be a 2x12 Celestion Greenback with black levant to match my amp head. Just one more thing; are there any real (acoustical) advantages to dove tailing? It seems like butt joints with internal bracing is every bit as sturdy than dove tailed joints...
Click to expand...
Dovetialing joints is apparently stronger, but I've never had a failure with well amde and reinforced butt joints.
 
#10
Brett said:

Ply is a lot tougher, taking the myriad knocks that come from an active gigging rig. Don't use MDF, . NONE of the Pro companies do.
Click to expand...

Which is pretty well exactly what I said, except you're ignoring the fact chipboard/MDF is a lot cheaper and acoustically better!.

If you want idiots to throw your cabs about, out the back of trucks, and down steps etc. - then use good quality plywood. But many great sounding cabs use chipboard/MDF - sound just as good as plywood, and perhaps even better?, but obviously won't take the abuse of ply.
 
#11
Nigel Goodwin said:
Which is pretty well exactly what I said, except you're ignoring the fact chipboard/MDF is a lot cheaper and acoustically better!.
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I'm not ignoring anything. For the difference in cost between ply and MDF for a guitar cab, ply is by far the better option. It's tougher and lighter. After seeing how gear can be accidentally damaged in a heap of ways from doing a lot of gigs, mdf is simply not an option.

As for acoustically better, a guitar cab is a musical instrument, not a reproducer.
 
#12
Brett said:
I'm not ignoring anything. For the difference in cost between ply and MDF for a guitar cab, ply is by far the better option. It's tougher and lighter. After seeing how gear can be accidentally damaged in a heap of ways from doing a lot of gigs, mdf is simply not an option.

As for acoustically better, a guitar cab is a musical instrument, not a reproducer.
Click to expand...


Despite that, for a home practice or recording cabinet, it is by no means necessary to make it out of plywood and the lack of cabinet resonances could be beneficial.
 
#13
Borteep said:
Despite that, for a home practice or recording cabinet, it is by no means necessary to make it out of plywood and the lack of cabinet resonances could be beneficial.
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Where do you get hte idea that a properly made ply cab is resonant? It's stiffer than mdf. Did you bother to read my first post?
 
#14
Brett said:
Where do you get hte idea that a properly made ply cab is resonant? It's stiffer than mdf.
Click to expand...


Because it's not as acoustically dead as chipboard or MDF, this is well known, and it's normal to take extra precautions with plywood to try and avoid excessive colouration of the sound.

As suggested, for home practice, recording - or indeed with a modicum of care for gigging, chipboard or MDF is a more sensible option - and is only a small fraction of the cost of plywood.

If you want to give a cabinet serious abuse, and hope it will last for years, then you NEED good plywood. But for many (most?) applications chipboard is fine, and has better acoustic properties. You might notice HiFi speaker manufacturers don't use plywood? - for that very reason.

We knocked four Altec style bins together back in the 70's, just out of chipboard, and only painted matt black. They happily survived all the abuse they had, never had a problem with them - just a quick splash of new paint occasionally. They weren't my bins, and I would have taken more care with them - but they survived with no problems. This included an occasion where one fell off the top of the speaker stack on stage (outdoor gig), bounced off the back of a Volvo estate car, and landed on the disco decks we used between sets - the cab was completely undamaged, the Volvo was dented, and the deck it landed on had the pin for the centre of the record smashed (but was otherwise unharmed).
 
#16
Nigel Goodwin said:
Because it's not as acoustically dead as chipboard or MDF, this is well known, and it's normal to take extra precautions with plywood to try and avoid excessive colouration of the sound.

chipboard is fine, and has better acoustic properties. You might notice HiFi speaker manufacturers don't use plywood? - for that very reason.
Click to expand...
References please. Chipboard is c-r-a-p. Hifi is not pro audio.

MDF is used in hifi because it's cheaper and easier to machine.
 
#17
Hey guys,

I've never heard of people MDF for hi-fi applications. In fact I've heard of pro audio PA systems made of MDF. When I say hifi I mean horn systems like the Cain and Cain back loaded horns or the Avant Garde front loaded horns. Interestingly a lot of front loaded horns are made from fiberglass.
 
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