Trace Elliot 3x12 SC speaker Cabinet

[Invader Zim]

Does anyone have a link or know of a resource that has a diagram or blueprint of this cabinet?

( mods move if needed )

 

 

[curtisa]

Pretty oddball looking cab, I've never seen such an arrangement before. You wouldn't be tempted to improvise your own plans based on how it looks in the photos?

The boxy bit would be pretty straight forward. There must be dozens of rough plans floating around that show how a typical 4x12 guitar cab might be assembled. Looks like a simple square with equal length sides, top and bottom.

The speaker baffle is the tricky bit, but the lower section just looks like an equilateral triangle with each edge the same length as the bottom of the box. Tipping it backwards by, I dunno, 10-15 degrees maybe? The two side baffles are then just cut to fill in the remaining voids created by the equilateral triangle on either side. Getting the three pieces to meet in the middle and coming up with some kind of bracket to hold them all together is probably the hardest part.

[curtisa]

From a German auction site:

BxHxT(mm )= 675 x 640 ohne /745incl. Rollen ) x 370

Which I'd take to mean 675mm wide x 640mm high (or 745mm high including castors) x 370mm deep. That'd give you a starting point to guesstimate some of the other required dimensions.

[Prostheta]

I remember these! I only ever owned a huge 4x10 which ended up nicknamed The Paincube. Yep, it should be pretty simple to derive angles and dimensions. I see it the same as @curtisa; the lower speaker is in an equilateral triangle which forces the outer two speakers into a very specific angle based on how the tip meets the outer leaves. Quite a lot of these dimensions can likely be derived by measuring the number of perforations in the grille against a known value such as the speaker diameter.

Construction would be made easier with access to a good compound sliding table saw. I think however, that the purpose of the cabinet seems less than clear; the arrangement reduces internal reflections and standing waves whilst simultaneously reduced internal volume. I've never come across TE blueprints for cabs before, so you'd have to find an owner who was willing to pass along construction notes. A long shot, I've got to say.

This is the sort of product that I would be expected to produce manufacturing plans for as part of my job (albeit, not speaker cabs).

[Prostheta]

There's always the possibility that the speakers are isolated from each other internally similar to say, an Ampeg 8x10 being four pairs of spaces. That would reduce construction fragility since the whole thing would be three boxes connected by strong edges. TE did make monster heavy cabs, so this might be the case here also.

[Bizman62]

On https://en.audiofanzine.com/other-guitar-cabinet/trace-elliot/SC-312/user_reviews/  it reads that "the 3 Hps radiate sound 120 degrees,". Does that correlate with the angles of the front triangles is beyond my logic.

[Prostheta]

Imagine if we all designed things using marketing wank as a brief! Hahaha....Homer's car all over again.

[curtisa]

9 hours ago, Bizman62 said:

it reads that "the 3 Hps radiate sound 120 degrees,"

If in doubt do the math.

Imagine looking down on top of the cab. Draw an isosceles triangle with the apex opening at the top of the triangle at 120 degrees apart (the point where the two side baffles meet in the middle) and the longest edge opposite the opening at 675mm long (the width of the cab):

The cab is supposedly 370mm deep. All you need to do is solve the unknown height of the triangle using a bit of trigonometry and compare the two values:

Rearranging and solving for x you get:

Comparing with the photos, the amount the baffles 'sink back' into the box appears to be much less than 194mm (certainly not half of the overall depth of the cab), so I'd say the claim of 120 degrees of sound dispersion is bollocks. From the photos the angle that the two baffles meet has to be much wider so that the depth they sit back into the cab is much less. Maybe something like a third of the depth of the cab?

So if you do decide to make that assumption you can work backwards to find the angle the two baffles will meet at:

Who says maths is for nerds?

[Prostheta]

It always delivers!

[Bizman62]

8 hours ago, curtisa said:

If in doubt do the math.

Thanks, your drawing actually seems to match with the photos! When I first read the sentence about 120 deg I actually visualized something similar to that. What then confused me was re-reading it to notice that it says the sound is radiated to 120 degrees which made me think about the radiation patterns of the speakers. Knowing the directionality of sound is dependent on frequency the 120 deg angle could add yet another meaning... And the sentence was automatically translated from French!

Anyhow, if the idea of that speaker cabinet is to spread the relatively directional sound of the guitar, it's actually similar to a trick I once heard: Back in the day when the guitar amps weren't too powerful and the PA systems were mostly non-existent they put the amp facing the back corner of the stage and tilted it back. That spread the sound all over the hall even at moderate volumes.

 

[Prostheta]

Also, standing an amp perpendicular to the walls is asking for standing waves to occur but is the quickest way of getting sound from one end of the room to another. I'm wondering if there was a degree of novelty to that cab, however it should allows the musician to hear the cab directly rather than their ankles.

[Invader Zim]

On 7/22/2021 at 6:22 PM, curtisa said:

If in doubt do the math.

Who says maths is for nerds?

Math is for nerds it just depends on which nerditarium the nerd(s) are found.

Algebra II is as far as I got and that was a few moons ago.

 

Are you saying that where the 2 arrows are pointing that angle "should be 140 degrees?

 

 

[Bizman62]

1 hour ago, Invader Zim said:

Are you saying that where the 2 arrows are pointing that angle "should be 140 degrees?

No, we are saying it might be 120 degrees. Based on the pictures and the tiny pieces of information that may well be close.

 

 

[curtisa]

2 hours ago, Bizman62 said:

No, we are saying it might be 120 degrees.

No. I am saying it's probably not 120 degrees. If it were 120 degrees the math dictates that the point at which the two side baffles meet in the middle is more than half the depth of the cab, which in the second photo at the top of the page doesn't look right. What I am suggesting is that the angle is wider due to the point of intersection appearing to be less than half the depth of the cab. 140 degrees is based on the guesstimate from the photo that the point at which the two baffles meet is nearer to one third the depth. The intersection depth might be more, in which case the angle will be less.

But at the end of the day you really just need to decide how critical these dimensions are to you in order to create a cab with this novel baffle arrangement. The cab appears to be a rare item and no plans exist for it in the public domain, so the chances of you ever needing to square your own interpretation of the cab against the Trace Elliot original are slim, both physically and acoustically. If you work within the known parameters (the overall dimensions quoted above and the appearance of an equilateral triangle for the lower baffle) anything you do after that to make it appear close enough should be sufficient.

[Drak]

I found a ton of pics of them, apparently they were around for at least a few short years.

I wanted to verify they were closed back, which they are.

I saw at least two, maybe three different iterations of them.

The one above with the indented top and metal mesh screens.

Another with a squared front (just like a 4-12 straight) with flat cloth grille.

A third I couldn't see very well so not sure, maybe it was the difference between a top and a bottom stack model.

I would guess the squared front and cloth grille were made later, or were a lower-cost version.

Because (most likely) those design parameters reduced the cost of production by a reasonable sum.

Just a guess.

You go Ritchie.

[Drak]

Which leads me to wonder...

If the cabs used the metal mesh screens to match the heads they went with...

And there (obviously) were cloth screen flat front versions...

I'm guessing the heads would have had, at that point in time or level of cost, cloth grills too...

Metal grille with indented frame (top stack?)

 

Metal grille with flat face front frame (bottom stack?)

 

Cloth grille, BOTH flat fronts (both bottom stacks?)

[Bizman62]

8 hours ago, curtisa said:

No. I am saying it's probably not 120 degrees. --- 140 degrees is based on the guesstimate from the photo that the point at which the two baffles meet is nearer to one third the depth.

My bad, didn't reread your math, only looked at the quoted picture. Then again, looking at the Sambora gig photo the angle could well be 120 deg. But the one with a bent grille and straight top front definitely looks more like 140 deg.

All that said I fully agree with you regarding the accuracy as there's no specs available to build an exact copy. "In the spirit of" is usually much more interesting anyway.

 

[Invader Zim]

On 7/22/2021 at 8:02 AM, Prostheta said:

Quite a lot of these dimensions can likely be derived by measuring.............a known value such as the speaker diameter.

 

Outer diameter of an EVM-12L = 12.2".

I used that to infer the rest of the measurements against known dimensions.

Thus my first mockup. It needs some refinement but it is a close starting point.

 

[Prostheta]

Super cool. That's the way to do it. I can think of a number of ways to do the joinery between each panel, however there are caveats with each. If you want me to throw some numbers together, derived from a CAD sketch then let me know.

[Bizman62]

Cardboard to the rescue! That's the way to visualize objects you're unsure of!

[Prostheta]

It always reminds me of Bad Obsession Motorsports' fabricating on YouTube!

[Bizman62]

CAD - Cardboard Aided Design

[Prostheta]

Can't Actually Draw

[Drak]

If I were actually doing that (which I am certainly not)

I would do a 12" in the bottom and 10's on the sides.

Just me.

I used to experiment a lot with different size speakers in the same cab many years ago, most of which were duds and fails.

Tho it was a great learning experience and I enjoyed the hell out of doing it.

And different types of 10's in a 4-10 (Super) setup, which was a most profitable and rewarding experience with many payoffs.

But if it were this, I'd go 12" in the bottom and 10's in the sides, no question.

And I'd work my ass off on the weight reduction factor.

Anywhere in the construction where I could shed a pound here and a pound there in materials selection, I'd do it.

[Drak]

Just another observation looking at your cardboard mockup.

Chances are those cabs load from the front, not the back.

So you need to make sure you have all the room you need for a FULL 12" circumference.

With room for the 'tangs' (the speaker clips) if you're planning on using them.

If you're drilling straight in and just using screws for mounts, make sure you've got good wood meat there.

From the cardboard mockup, it looks a little tight and thin on the edges there for my blood.

I'm not sure what your holes represent, a full-on 12" cutout or the cone cutout.

 

If you wanted to go full-nuts-on custom with it...

If you add separators to each section to isolate them...

You could then add partial ports to either just the sides or all three sections.

So you could have any combination of closed back / open back / ported back.

Just depends on how you design it.

If I were going to all that trouble, I'd want options. I'd build it in.