Cabinet/head building advice

[dan_]

Hi all,

I stumbled upon your forum while looking information on cabinet and head building. I've seen a few good plans on here (namely the 5e3 plans and the marshall 4x12 slant plan), but I'm not convinced if those two are the best plans to use for my build.

I'm having an amp built by a close friend, however, I'm looking after building all the cabinetry for the head and cab. To that end...the head i'm getting built is modelled after an AC30...is there a specific cab design any of you would recommend for this style of amp (or does it make that much of a difference?)

As well, what materials should I use for this project? Any specific recommendations on wood for the cab/head (should I build both out of the same?)

Looking forward to your hints/tips. Thanks in advance!

[tubeswell]

Hi all,
As well, what materials should I use for this project? Any specific recommendations on wood for the cab/head (should I build both out of the same?)

I had good success with plain old 3/4" pinus radiata (white Pine) for the cabinet and 3/4" interior/marine grade plywood for the baffle.

Pine is a soft timber - easy to cut/sand/file/drill, and makes a light cabinet that really sings. The 3/4" thickness ensures that there is plenty of strength

[Casey4s]

Head cabs are pretty straight forward, its basically a box. You can either cover it in Tolex, paint it, Stain it, or make it from hardwood like Maple or Walnut and a natural finish.

These pics are in reverse order, but it is a basic head build.

http://s238.photobucket.com/albums/f...ead%20Cabinet/

[Paul P]

Casey4s, I'm in the middle of designing a head cabinet for my amp much like
the one you just showed. You may be able to answer a question that's
been giving me some trouble. Since your cabinet is solid wood and its grain
runs vertically on the sides and left to right on the top and bottom, the
maximum wood movement due to humidity changes will occur front to back,
across the grain.

Now, since the chassis isn't going to be moving any, how do you prevent a
gap appearing between the chassis front panel and the cabinet face during
the winter ? Or if a gap does appear, is it noticable ?

I've been thinking of using a rear wood frame much like on the front that
would push against the chassis (keeping it from falling out) and I'd mount
springs between this frame and the chassis so that the chassis could move
back and forth a bit when the cabinet expands and contracts with humidity
changes. Ie, the chassis' front panel would always be pushed forward
against the front frame.

If you have a simpler alternate method I'd like to hear about it.

Paul P

[Casey4s]

Casey4s, I'm in the middle of designing a head cabinet for my amp much like
the one you just showed. You may be able to answer a question that's
been giving me some trouble. Since your cabinet is solid wood and its grain
runs vertically on the sides and left to right on the top and bottom, the
maximum wood movement due to humidity changes will occur front to back,
across the grain.

Now, since the chassis isn't going to be moving any, how do you prevent a
gap appearing between the chassis front panel and the cabinet face during
the winter ? Or if a gap does appear, is it noticable ?

I've been thinking of using a rear wood frame much like on the front that
would push against the chassis (keeping it from falling out) and I'd mount
springs between this frame and the chassis so that the chassis could move
back and forth a bit when the cabinet expands and contracts with humidity
changes. Ie, the chassis' front panel would always be pushed forward
against the front frame.

If you have a simpler alternate method I'd like to hear about it.

Paul P

I never even thought about a gap there. If there is one it is negligable I guess. I use some sorta soft rubber feet under the chassis and ran some bolts up through the bottom to some wood cleats on the side of the chassis, and cranked em down till everything was aligned and that is what keeps the chassis in the box. If you make the holes in the wood just slightly oversized (use washers) it will give a bit of adjustment in all directions.

From the rear....




I also like to line the inside with Foil Tape and ground the chassis to it to help cancel any intruding Hummmmmmmmmm



I hope this answers your question, or did I misunderstand you....

[Paul P]

I hope this answers your question, or did I misunderstand you....

Yes it does, thanks. I see that you solve the problem of mounting the
chassis (independent of any wood movement issues) with strips of wood
on the sides. I hadn't thought of this. If I do this and only screw the
front of these strips to the cabinet from underneath it'll keep the front
panel in place and any movement would then occur at the back where it
doesn't matter. I think it would be possible to use longer screws through
the cabinet feet so that they wouldn't show (and cause a bit a head-
scratching to a tech somewhere down the road...).

The only problem in my particular case is that I'd have to remove these
strips from the chassis before mounting it in my chassis vise.

Cheers,

Paul P

[Casey4s]

You can sometimes mount the wood cleats inside the open side of the chassis. This one is for a Fender Style hanging chassis, but will work as well with the other style installation in many cases. Just some food for thought.

[dan_]

Thanks for the tips guys! So, it's looking like I'll use 3/4" white pine for the cabinetry. Any other tips before I start down this long and windy road?? (thanks for the replies to date)

[Bruce / Mission Amps]

Thanks for the tips guys! So, it's looking like I'll use 3/4" white pine for the cabinetry. Any other tips before I start down this long and windy road?? (thanks for the replies to date)

My advice is to not use pine boards (unless you have a jointer, maybe a biscuit jointer tool too, and then do glue ups with alternating {growth rings} 1x3 pine, followed by sending them through a 12"-15" planner and then sand it all smooth) ...but instead just use 19mm, furniture grade Baltic birch plywood, cut to size for the carcass and 13mm Baltic birch for the baffle board. It comes in sheets about 60"x60".
I've built many fabulous sounding amp and speaker cabinets using Baltic birch plywood.

[dan_]

what's the price point on the baltic birch plywood? I sourced pine at $2/board foot, and have all the appropriate tools to do what you discussed. If the price point on the birch is competitive, though, I'll definitely go check it out.

With regards to the baffle, specifically, how great an impact does the wood have on the sound?

[Bruce / Mission Amps]

what's the price point on the baltic birch plywood? I sourced pine at $2/board foot, and have all the appropriate tools to do what you discussed. If the price point on the birch is competitive, though, I'll definitely go check it out.

With regards to the baffle, specifically, how great an impact does the wood have on the sound?

I don't know what the price is now, I don't build any cabinets in our shop anymore. However, 19mm BB use to be around $45-$55 a 5'x'5 sheet.

Thicker 3/4" sized baffle boards sound tighter on the bottom end and a little more punchy with 25-100 watt amps.
Thinner 5/16"-3/8" baffle boards add a certain reediness to the tone and have less tight bass response but sound a bit woody and vocal with 5-20 watt amps.
How it is mounted is important as a cabinet with a loose floating baffle will never have the bass response of one where the baffle is clamped tightly to the carcass with cleats all around the outside edges of the baffle board.
The floating baffle board will also have a little more low midrange sound to it because the amp will be missing a little of the tight, punchy bass response.
The type of wood in the baffle board is not so critical to me but a very soft 3/8"-1/2" Doug Fir plywood sounds softer and a little thick "papery".
Harp players would probably like a thinner, 5/16"-3/8" thick Doug fir plywood over a 19mm Baltic birch one.
Metal players would probably like a very thick baffle board clamped in tight as a drum head.

[tubeswell]

No disrespect intended to the fine gentlemen giving you top knotch advice, but FWIW I didn't use jointed pine on my recent 5F2A, I just used one solid 8ft x 9 inch x 3/4 inch pine board, which cost $50NZ and did me for a tweed deluxe sized cab. I used 1" x 1" square cleating strips to reinforce the corners and polyurethane glue and pk screws to hold it all together. I didn't bother with finger jointing (because I didn't have the tools), so I just did butt joints. With the internal cleats it all worked out fine and they came in handy for getting perfect 90 degree angles on everything and getting it to hold really tightly together. Sanding to get nice corners and edges and surfaces was easy, as was the drilling, cutting etc etc. I covered it with Gingham tweed fabric to hide the external screwholes and it looks and sounds like a million bucks.

Anyway, having said that I probably would try a harder timber at some stage if I could get it, just to see how it compares.