wondering about baffle construcion

[Eugene Martone]

I'm building a 412 (with a carpenter friend) and I have a couple of questions about how a slant baffle is/should be constructed I'm (btw it's a 1960):

1.How are the two bords connected? Is it just the one bracing on the back holding them together? Or does the bracing for the grill cloth contribute anything to rigidness?

2.Are the boars just screwd onto the bracing (both grill and/or back) or also glued? Wouldn't a glued assembly be better? Are there any tried ways of assembly that provide a more rigid or durable result?

3.Does anyone have detailed drawrings of any slant baffle they could share? It would be greatly appreciated.

[Eugene Martone]

Bump
Just to explain a little: We are building this one cab just for me (so strictly non comercial). My friend the carpenter has not done a guitar cab before and is... well, baffled by some of the construction preferances of a guitar cab (birch ply being one). He seems to think the screwd on a board baffle construction (witch, as stated i my previous post, i believe to be the marshall way) will not have the same rigid or lasting quality of the dovetailed glued cab. I don't rightly know (not even shure about the way the marshalls are put together), so if anyone could shed any light on the theme of angled baffle construction i'd be very happy. thx

[908ssp]

Since Marshall wraps the grill cloth around the baffle board itself it has to be removable. Some companies make glued in baffle boards with removable grill frames just not Marshall. I think the boards between the upper and lower half's of the baffle are machined on an angle and glued together then the inner brace is machined with an angle on its face that duplicates the baffle and glued and screwed to the inside to strengthen the joint. If you want the cab to sound like a Marshall cab best not to think too much just copy the way the Marshall is built.

[somethin'else]

Dude, you gotta use the search function on this site!
The best info of cab design by the best makers around is here on MetroAmp.

Also, Google search on the WWW is pretty handy too.
This outta get yer carpenter bud goin'...

...and what taught me the bestest about recovering old cabs is this ultimate, bar none, restoration thread by Mr. Jim Seavall.

Get an old JCM800 or 900 cab, sand it down and have your carpenter re-build the front and rear MDF baffles by copying what's already in the cab, 'cept using birch ply.

Hope that helps.

[Eugene Martone]

thx guys . somethn', I did try the searchfunction, but I don't think I'm using it right, cuz the results are a little confusing (is there a way to search just topics?)... Google rendered some good links but not quite detailed/exact enough for my friend, witch takes this as a bit of a challenge and likes to have everything sorted before he starts building something. Thats why I was wondering about the glue/screw thing. So thx 908, since you've confirmed my theory about the marshalls I have a pretty good Idea of how we could go about this. I'll have my friend check out those links (they do look informative enough ). Also, I think I've seen some pics where the two boards were fingerjointed, was this ever the case with marshalls?

[somethin'else]

Cool, I was just razzin' ya bout the search. It can come up with general stuff that you just have to weed through and narrow in on. George (Metro) and Jim (Scumback) have it down for correct cabs.

Finger joining the front two pieces? I doubt Marshall did it that way, but if you're friend can or wants to, I'm sure it would be the bees knees of sturdy.

I think the biggest trick would be getting the angle right with a nice, clean, flush join. That can be made by replicating the profile, which would be copped from the side wall profile of the cab. It's the angle join that'll matter. The rear horizontal connecting board will have to be milled on a table saw for that same angle. Glue it, screw it, sell it to the butcher in the store...

Have fun.

[Eugene Martone]

Thanks somethin'. I think we'll do the marshall glued at an angle type construction (witch I think I've got a good idea how to do now). Now a bit off my own topic, but now my friend wants to know if he can do the box with angled jointery using biscuits (it's alot faster according to him). I find myself thinking this is an inferior way of doing it (compared to fingerjoints), but he claims the difference would only be cosmetic, though he leaves the decision to me because he's not really comfortable with the whole "audio" side of it. Am I right in my assumption that fingerjoints is the way to go, or is there no real difference?

[908ssp]

If he will do finger joints do finger joints. Biscuits are an inferior joint. Dove tail would be equal to finger joints but requires special tools he may not have and isn't what Marshall used.

I think Marshall used 1/4 inch finger joints mostly because the glue they used was crap. The 1/4 finger joint affords the most possible glue area. Modern urethane glues are so much stronger plus moisture resistant than the old glues. If you're not a stickler for accuracy I'd do larger fingers say 3/8 or even 1/2 inch save some work and use a modern urethane or epoxy glue.

[somethin'else]

If he will do finger joints do finger joints. Biscuits are an inferior joint. Dove tail would be equal to finger joints but requires special tools he may not have and isn't what Marshall used.

I think Marshall used 1/4 inch finger joints mostly because the glue they used was crap. The 1/4 finger joint affords the most possible glue area. Modern urethane glues are so much stronger plus moisture resistant than the old glues. If you're not a stickler for accuracy I'd do larger fingers say 3/8 or even 1/2 inch save some work and use a modern urethane or epoxy glue.

+1 908ssp

[Eugene Martone]

thx 908ssp. My friend has agreed to do the fingerjoints but wonders if he should do it by hand or with a machine. What do you guys think (keep in mind im gonna have to pay the guy something for this cus he'll be doing all the work ). Also he was wondering what the reasons are for fingerjoints being superior in this application? He says the glue should hold the same strengt eitherway (as long as the biscuited jont is angled). Could anyone elaborate on the reasons for this so I can satisfy his curiosity?

[908ssp]

"should hold" it isn't enough. All that work on wood and tolex and you're going to take a chance on "should hold". I am poking fun here but I know many cab makers who have done the testing and finger joints or dovetails is the way to go. They simply make stronger joints. Your goal I take it is that the cab sound as much like a Marshall cab as possible and the only way to assure that is to make it as much like a Marshall cab as possible.

[somethin'else]

My friend has agreed to do the fingerjoints but wonders if he should do it by hand or with a machine. What do you guys think (keep in mind im gonna have to pay the guy something for this cus he'll be doing all the work ). Also he was wondering what the reasons are for fingerjoints being superior in this application? He says the glue should hold the same strengt eitherway (as long as the biscuited jont is angled).

Man, I'm sorry, but if you're paying him, have him use a machine to make those finger joins. And I don't mean to sound rude, but if he's pondering doing finger joins by hand vs by machine, then he may need to acquire a router bit and a jig, 'cause I would never attempt to finger join a 4x12 by hand. I'm too busy whittling Cigar Store Indians with my chainsaw!

Also, if he's equating finger joins with biscuit joins, then... I just don't know. Finger joins or dovetail joins are the way to go. Home Depot has a $40 Dovetail jig that would do.

Definitely "join" the corners. As far as the front baffle, just straight cut the two pieces and make the joining brace correct and that should be perfect.

Do you plan to recover the cab yourself? Or would you leave it natural wood, stained or something? Reason I ask is it would STILL seem much easier to score a 1960A cab unloaded, even if the tolex was junk, and just restore it. A JCM900 or JCM800 would do the job. It might end up cheaper.

But if the process of the construction and building the cab together is more fun, and you're in no hurry, then disregard this message!

[Eugene Martone]

Thanks again guys. I'm pretty shure modern glue would give both these joints enough strength to hold, but if you say finger/dovtail is preferable I have no reason to disagree (there must be a reason why everyone makes cabs that way). It would take quite a bit of weight to break both of these joints, so i believe the real advantage would have to be in energy transfer, no? (It's not like I'll be standing a car on top of this box ) I would appreciate any physics regarding this subject (mostly because it's damn interesting).
Somethn', I'm not paying him full fee or anything, but I wouldn't be much of a friend if I didn't pay him a little for his labor (especially if he'd use weeks doing ti by hand). And it's fun making something "your self", and you know the structural integrity of all the joints etc. I believe the finished quality would be better than (or at least as good as) any comercially made cab. I'll start a thread with some pics as soon as we get going .

[somethin'else]

Awesome, Eugene, that will be cool to see your cab built from scratch. Will keep an eye out for it.