Tube Amp Archive

This is my first cab build and I've learned a lot just reading through this forum. My goal with this build is to have a tight/focused low end (no boomy flabby bass) but with nice airy highs with good clarity. I mostly play clean with some crunch. Some fuzz, but almost never anything too gain-y.

My main cab is 2x12 JBL K120's. This 1x15 will have a Celestion Fullback. It will likely spend a lot of its time as a wet channel in a w/d/w rig, but I will rotate the cab into the dry channel.

I based initial cab dimensions on a Zilla Super Fatboy, but I wanted to angle the front and slightly taper front-to-back & side-to-side to help with standing waves, so I added a few inches vertically to compensate for the reduced volume.

I was already planning to make slots to the interior boards (also to help with standing waves), which is how I stumbled on the Forte design. I really liked their idea of using a closed-back cab with side vents so I'm stealing that idea along with their adjustable interior baffles for directing energy out of the side vents.

I'll likely use 3/4" baltic birch on most of the cab, especially anywhere it will be slotted on the interior.

I'd love any general feedback, but I do have a few specific questions...

1) Bracing... I was thinking of running two 1-2" braces from the front panel to the rear panel. One from top right of the Fullback and the other from the bottom left. Forte & Zilla don't seem to brace their cabs front to back, but I cannot really tell. The idea behind this is to put the front and rear panels in phase (see pic below). Any reason to NOT brace this as I'm planning?

2) Can the braces be round wood or would round vibrate more?

3) Given this kind of "art deco" inspired cab design, should I attach the speaker directly to the front panel or attach it to a baffle attached to the front panel?

4) If I use a baffle, should the front-to-rear bracing attach to the front panel or the baffle?

5) Thickness of front and rear panels?

http://imgur.com/ZK6rxSp

http://imgur.com/t63Wa9z

http://imgur.com/wBwTxrg

http://imgur.com/G7YCfkL

http://imgur.com/FK55XZh

http://imgur.com/ZtAMvQX

http://imgur.com/Y0hIvUq

Thanks in advance for your advice!

I would think with this design, 3/4 ply on the sides would be good with 1/2 ply on the front and back. If I could get away with it, I would use 1/2 ply overall, and forgo the routing efforts and focus more on bracing!

1. Bracing is good IMO (especially if you're going to be routing on the ply). I personally prefer a rigid cab vs. a resonant one.
2. Round is okay. Depends on how simple or complex you want to go with your bracing.
3. Like a speaker baffle ring? If yes, then yes. Love the old art-deco style cabs!!!
4. Front panel.

I like the way that Mesa went about bracing their Ultra-Lites (dual purpose brace/vent).
https://www.youtube.com/watch?v=lxojJXBWJmQ

echuta13 wrote: ↑Thu Apr 22, 2021 12:06 am I would think with this design, 3/4 ply on the sides would be good with 1/2 ply on the front and back. If I could get away with it, I would use 1/2 ply overall, and forgo the routing efforts and focus more on bracing!

1. Bracing is good IMO (especially if you're going to be routing on the ply). I personally prefer a rigid cab vs. a resonant one.
2. Round is okay. Depends on how simple or complex you want to go with your bracing.
3. Like a speaker baffle ring? If yes, then yes. Love the old art-deco style cabs!!!
4. Front panel.

I like the way that Mesa went about bracing their Ultra-Lites (dual purpose brace/vent).
https://www.youtube.com/watch?v=lxojJXBWJmQ

Just saw this video and its interesting to see a big company like this switching away from Birch baffles and walls and moving to Poplar!
Could pave the way for many others. I love the light weight of poplar.
Beautiful cabinet design Gr8fulPickr!

Just more food for thought would be Bareface's take on a cab: https://www.youtube.com/watch?v=jMp0GxTKSNQ&t=377s
Bracing info on their bass cabs as well: https://barefacedbass.com/technical-inf ... osures.htm

P.S. I have an Eminence Legend 1518 that I really like in one of my extension cabs. Would like to hear your opinion on the Celestion Fullback 15 when all is said and done.

echuta13 wrote: ↑Thu Apr 22, 2021 12:06 am I would think with this design, 3/4 ply on the sides would be good with 1/2 ply on the front and back. If I could get away with it, I would use 1/2 ply overall, and forgo the routing efforts and focus more on bracing!

1. Bracing is good IMO (especially if you're going to be routing on the ply). I personally prefer a rigid cab vs. a resonant one.
2. Round is okay. Depends on how simple or complex you want to go with your bracing.
3. Like a speaker baffle ring? If yes, then yes. Love the old art-deco style cabs!!!
4. Front panel.

I like the way that Mesa went about bracing their Ultra-Lites (dual purpose brace/vent).
https://www.youtube.com/watch?v=lxojJXBWJmQ

Thanks for the reply and feedback! I've gotten a bit of an unexpected curve ball. I live in Medellin, Colombia and apparently baltic birch is not available here. What's readily available is pine, oak, teak, cedar, sapan.

Of these, it seems pine is the only good option. I was trying to avoid a highly resonate cab, which is why I was going with birch rather than pine, but seems I'm not gonna have great alternatives. Hopefully doing the bracing as I've laid out will be sufficient. A little resonance is probably a good thing anyway.

You think I will need any side-to-side bracing?

Teak might be good. Not sure but I saw a few cabs in teak, whose users seem to be very happy with.

Pine is a pretty known quantity (1000's of Fender amps can't be wrong right?!?)

I think Teak would be really cool looking! Teak also has great anti-rot characteristics, but it is a known sensitizer so be conscious of that when you work with it (never had a splinter from Teak, and don't want one)!

I wouldn't overthink the bracing too much, the thinner the material you work with, the more important it will become though. Good example of cab resonance: https://www.youtube.com/watch?v=uJy3TscsL-U

Disclaimer, I know a lot more about woodworking than speaker cab design.

Teak is stupid heavy, very expensive and the silicate in it is murder on your tools (but still doable). It does look good though. I always come back to sapele (aka African mahogany) as pretty light strong and cheap(ish). It has interlocking ribbon grain that can make planing it with not sharp tools prone to tear out, but it's an order of magnitude easier to pick on than teak or, God help you, rosewood. Clear pine also absolutely works.

What's you main goal? Are you trying to reduce weight? Hit a certain size req? Make it look good? Yes, all of these? Usually you design a closed back to hit a certain volume and be acoustically dead. Pine is very resonant being ligth and fairly stiff, so it's usually not used in "dead" designs. Open backs, it's much more "whatever". Ported are trying to do something else entirely. In that case, it's just all about weight, so pine is fine and good choice.

For front baffle, the thickness is not really a thing, it's the effective stiffness. It needs to be stiff enough to resist bending so you don't deform the frame of the speaker. stiffness goes up as somethign like the third power of the thickness, so you can get away with 1/2" even in a 15" box if you braces the sides (go look at the fEarful designs, all 1/2" ply + bracing for high power handling) By brace the sides, I mean run a stiffener cleat along two edges of the baffle behind. I always cut the hole(s) in the baffle, then tack my speaker cloth to the back, the attach the speaker to the back of the baffle. Then I drive threaded inserts into the back of the baffle so I can screw from the edge of the cab into the back of the baffle without any screws showing.

You don't need bracing front to rear baffle. Put the brace along each side of the speaker mount instead (ie effective increasing the thickness of the baffle from behind).

For an art deco 20s radio look, I'd go bare, pretty wood, then grill cloth, then the speaker. I recommend upholstery fabric for guitar since you don't mind cutting out some super high freq. You're building a guitar cab, not "audiophile" unobtainium speakers.

https://photos.app.goo.gl/UtV6xmquRsJRu5iq7

Other dumb questions: what's you level of tooling skill and availability? Since you're in Colombia, If you really wanted something crazy, pernambuco (aka Brazilwood) would be insane, but I don't recommend picking on it unless you have insanely sharp tools or a cnc. Not sure how far north it grows.

Looking at the photos you posted, those are all basically "dead" cabs inside. They're trying to kill and vibration inside the cab itself. This makes for a more linear "neutral" cab sound, but that might not be what you want. Lots of Fender amps just hung the speaker off an open baffle and called it good. If you want a dead, closed back cab, you can do this more cheaply by just filling the cab with a bit of insulation (the regular fiberglass kind). 1920s Deco cab all would have been partially open back.