Details needed to build 2 x 12 cabinet

[fretting about]

Details needed to build 2 x 12 cabinet

 

Let me start out by saying that I am new to the forum and hope I am not trodden over previously covered topics. I searched for the info I needed and didn't receive anything really relevant so here goes ...

 

I am building a 2 x 12 cabinet for use with a Marshall Jubilee 2553 head (50 watts). So far I have comped the following info.

 

Build from 3/4" baltic birch (15 ply)using finger joints. The basic measurements of 30" x 24" x 12".

Using vintage 30 speakers possibly with stereo option in the wiring pattern (not convinced I need this option but am open to opinion.

 

Question 1 - I have seen some cabs that include ports but most without. I have assumed that without ports is the way to go to avoid a 'boomy sound'

 

Question 2 - do cabinets such as Marshall 1936 or Fender 2 x 12 typically have baffles or are they wide open inside

 

Question 3 - The design of the ENGL 2 x 12 is that the speakers are mounted vertically as opposed to all others mounting horizontally. Additionally the top speaker in this vertical style is angled slightly upward.

 

Please give me any input you can or if anyone knows of any web sites that will give me more then simple outside measurements, it would be greatly appreciated.

 

Cheers

[Guitarzan]

welcome to the forum Fretting about. funny you posted this, for i am thinking the same thing. i have a yamaha dg100 and i want to put the vintage 30's in a separate cab to get rid of the boominess of the combo. open back sounds good for low gain but when i turn it up i want the closed back tone.

good topic. hang around here dude. where are you in Canada?

[BillWelcome Home Studios]

Speaker manufacturers often provide cabinet designs for free, just ask them. You will need to tell them that you are building a guitar cabinet with what model of their speakers that you are using. Much better than guessing.

 

If you desire to design your own, get one of the basic speaker cab building books to guide you with proper diemnsions. It helps to have the free air resonance of the speaker.

 

Bill

[fretting about]

Thanks for the quick respose guys. If anyone has had the back of there 2 x 12 that could let me know if there are any baffles or insulation in the name brand stuff, that would be great.

 

Cheers

[mwestenberg]

Don't know about 2x12 but my Marshall 4x12 has no baffles whatsoever. I made a couple of 2x12's copying the Marshall cabinet silhouette(slant front) and making them several inches more than half of the 4x12 width, if that makes sense. If you start messing with insulation, ports, and free air resonance alculations, you're starting to get into bass response/PA territory; though maybe you're one o' them 7 string detuners?!? I think if you're going to wire and run stereo though, you probably should baffle them off to prevent unwanted phase cancellations. Oh yeah, Baltic birch ply is way overkill unless you're really into Mad Max durability

[Blue Strat]

I built my 2 x 12" speaker cabinet 30" x 18" x 11" with a straight front and back, not slanted. I used 1/2" pine ply for the speaker baffle (what the speakers bolt up to) and another 1/2" thick piece for the back. It's a sealed cabinet, no ports. The back is flush, and the speaker baffle is 1/2" below the edges of the face. I'm using Weber VST C12GB "Thames" speakers, capable of 80W each for a total power handling of 160W. I'm using a 50W homebrew JCM 800 2204 head into that cab, with sweet results.

 

Pictures:

http://www.geocities.com/teleman28056/mv_clone.html

[Guitarzan]

jeez chris that sounds very tasty!! i don't know how i missed the clip on your page before but that sounds sweet. have you ever had chance to try it with a 4x12?

[Blue Strat]

Originally posted by Guitarzan:

jeez chris that sounds very tasty!! i don't know how i missed the clip on your page before but that sounds sweet. have you ever had chance to try it with a 4x12?

It would have to be wired right - I'm using a tweed Bassman output transformer, which runs with a 2 ohm load. I've got two 4 ohm, 12" speakers in parallel. I would have originally built a 30" x 30" 4 x 12" cab, but I didn't have the $300 I'd need for the speakers.

 

I've got a second JCM 800 2204 head that I built, but it's running at lower voltage and has a 2, 4, and 8 ohm selectable output transformer in it. I'll have to give it a go with one of my uncle's 1972 basket-weave 4 x 12" cabs one of these days.

[BlueZet]

as far as I can tell, what guitar amp builders did in "the old days" was make a cabinet that fits the amount of spekers you want to put in, some of them closed the back some of them left it open - again as far as i can tell - for no specific reason at all

 

NOW we think we have to measure it up and be all scientific about it... that would be great if we had speakers with the EXACT same specifics and WOOD with the EXACT same specifics and...

 

so I suggest you measure the speaker(s) add some space for the cab itself and go... that's how I made two 1x12" cabs that sounded great

[fretting about]

Thanks for all the input guys. I didn't really think of it as a high fidelity project that required exacting standards in order to attain a perfect sound, I just wanted to get the basics in order to avoid building it twice. I like woodworking but I would much rather be playing!!

 

BTW, I am into the classic rock era and writing originals - not so much on the shredder stuff.

 

Cheers

[Chad Thorne]

Originally posted by badblues:

as far as I can tell, what guitar amp builders did in "the old days" was make a cabinet that fits the amount of spekers you want to put in, some of them closed the back some of them left it open - again as far as i can tell - for no specific reason at all

 

NOW we think we have to measure it up and be all scientific about it... that would be great if we had speakers with the EXACT same specifics and WOOD with the EXACT same specifics and...

 

so I suggest you measure the speaker(s) add some space for the cab itself and go... that's how I made two 1x12" cabs that sounded great

Hey, I thought we agreed "no sensible, practical advice here"... - Of course, in the old days they also used to get distortion by cutting the speaker cone with a razor blade. That's perhaps a little too lo-tech even for MY tastes..("Q: How many blues guitar players does it take to change a lightbulb? A: Two - one to change it and the other to mutter about how much better the old one was...")

 

Welcome, Fretting About! Good topic, I was thinking the same thing, because I've bought a JCM2000 head but 4 speakers (a la Marshall 4x12 cab) is just too much for me.

[BillWelcome Home Studios]

Originally posted by fretting about:

Thanks for all the input guys. I didn't really think of it as a high fidelity project that required exacting standards in order to attain a perfect sound, ...

 

Cheers

Ah, but it is, at least, with closed back designs. With too small of a cabinet, the back pressure changes the tone. With too much air flow (say, too big of a port) the speaker is not properly supported by enough back pressure, also changing the tone. Put in a port fo the right size, and you get more out of the cabinet as some of the rear excursion is routed out to the front. Do you need baffles between the speakers? Depends upon the cabinet design. Generally, no. But the SVT bass amp cabinet is basically 8 little 10 inch cabinets in one box.

 

Sure, you can hack a couple of holes in a sealed box of any size and call it a speaker cabinet. Hey, it even IS! But does it actually take advantage of the characteristics of the speakers and enhance the sound, or does it just keep the speakers from falling to the floor?

 

Bill

[DC]

First off, you don't need Baltic birch, just go to Lowe's and get the regular birch plywood, I think it's like 7 ply or something. Used to cost about $50.00 a sheet (4' x 8'). I've made loads of bass bins and guitar cabs out of this stuff with great results.

 

All speaker cabs have baffles, that's the board you cut the holes in to mount the speakers. Marshall cabs are usually closed back because Celestions won't take much abuse and a sealed cab (infinite baffle) lets the air inside act like a spring so the cones don't move as much. You might need this design if you play really loud.

 

An open back cab will give you more sound from the front and back (room filling/ less directional), but you're speakers will flop around more which could damage the coil or spider if you play loud. If you've got specific questions, send me a PM or post em here.

[BillWelcome Home Studios]

Originally posted by DC:

All speaker cabs have baffles, that's the board you cut the holes in to mount the speakers. ...

That would be the motor board. It could be the baffle board if it has baffles or ports.

 

Bill