building a cabinet - tips?

I'm hoping to soon begin work on my own amp cabinet project. Comparing a home made amp cabinet (say, something like a simple 1X12 open back cab) to a manufactured or boutique made cabinet - what kind of sound quality difference will there be?

is there a lot of complicated acoustic science to building a cabinet?
or can you get a good sounding cabinet as long as its solidly built?

would you say its different for closed back cabinets?

what would be some good advice for a new builder to shoot for when building a cabinet?

Thanks,
Joel

P.S. I very much appreciate any and all advice - but i would ask that if all you have to say is "its not worth your while/its too complicated/don't do it" then please don't bother. I'm not doing this project to save a quick buck instead of buying a cab. I like being a hobbyist and want to give this a try - its a fun project. And I just want to put out the best end product that I can. If you can help me, i'd be very grateful. :smile:

I'm hoping to soon begin work on my own amp cabinet project. Comparing a home made amp cabinet (say, something like a simple 1X12 open back cab) to a manufactured or boutique made cabinet - what kind of sound quality difference will there be?

is there a lot of complicated acoustic science to building a cabinet?
or can you get a good sounding cabinet as long as its solidly built?

would you say its different for closed back cabinets?

what would be some good advice for a new builder to shoot for when building a cabinet?

Thanks,
Joel

P.S. I very much appreciate any and all advice - but i would ask that if all you have to say is "its not worth your while/its too complicated/don't do it" then please don't bother. I'm not doing this project to save a quick buck instead of buying a cab. I like being a hobbyist and want to give this a try - its a fun project. And I just want to put out the best end product that I can. If you can help me, i'd be very grateful. :smile:

Joel,

I'm not an expert... which probably means I have less of a strong opinion to push! :wink:

But I have put some time studying cabs, and gotten a lot of opinions, so here's my take...

Open Back Cabs. The size is not that crucial, and staying close to standard vintage cabinet dimensions for 1x8 Champs, 1X10 Princetons, 1X12 Deluxes, 4X10 Bassmen (?:neutral:) etc, is perfectly safe, as is adding an inch or two here and there. Seems like a basic formula is something like 0.6 X 1.0 X 1.6, but look around and you'll see people messing with that formula all the time.

Closed Back Cabs. Serious can of worms! I went through several different online calculators, included 'Speaker Cone Volume' and all the specs of the individual speaker and then chassis volume, tube volume, brace volume and speaker cable volume... Oops, I guess the last few were a bit exaggerated. :oops: But in the end, the cabinet was like the size of a small bathroom! Then I foud there are ways to 'fool' the volume into being bigger by adding insulation or blankets or whatever, allowing for a smaller enclosure. But then, everyone seemed to disagree about where and how much, and that it was a mystical thing anywho. So, in the end, it seems that speaker designers come up with a cool idea and then experiment until hey get it to work. Maybe that's not totally fair to speaker designers, but it's pretty close! :grin: I made two closed back cabinets, an 8" and a 10", and I just found a few models I liked, calculated their interior volumes, adjusted the dimensions to meet my needs and use the material at hand, and voila! Great sounding enclosures, honestly! I added a bit extra volume to the 8" and got a bit heftier bass response, just like you'd expect. The 10" I copied a boutique builder's volume, which was a bit bigger than most mass manufacturers, and boom! Nice sound.

Either I am a genius (I sincerely doubt that!), or very lucky (kind of doubt that, too), or it's not magic or rocket science, but common sense and elbow grease. A reasonably good speaker helps, too! :grin: (btw, I did make the baffle board adjustable to increase/decrease the volume about 10~20%, but never messed with that)

Have fun!!

charisjapan

Seems I read that Jim Marshall just more or less built a box four 12" speakers would fit in. Then angled the top back because he thought it looked better.

+1 .. study all the cab sizes from different makers online...all the old amps,etc...

and write down all the measurements..... compare...

I think the trick is no even sizes... to eliminate standing waves inside the cab messing with the sound.... not 24x24x12.... 23x19x11 sorta thing....

there's all sorts of formulas.. to get a Q number....or something?....

I found some hell stereo cabs at the dump, proper ply and miter corners... put a new 12" baffle in.. and cut the depth down to get them closer to "traditional" cab sizes....cut the trim off the front and the pedestal part... I'll cover them one day,,,

they were too deep and D's would resonate louder somehow?... cut down from 15" to 11" deep they cleaned up (the closed back one under the super210).... the open back one has a 10" atm...
I still use them ... :cool:

Studying existing cabs is a good idea. Closed-back are more critical than open-back. Match the speaker to the cab; some speakers work better with open back, some work better with closed back, some work with both. Here is a guide which might be useful to you:
http://www.tt-cabs.com/tt_tech/doc/TTC-Boxen_und_Lautsprecher_Leitfaden-english.pdf

My rules for open-back cabs are: make sure it's not a cube. Copy a known design. Nothing I'm interested in doing is new; it's all been done before.

As far as the woodwork goes, I enjoy it, and find it is its own reward. Picking the right wood is critical; if you use plywood, you have to make sure it is voidless, or you run the risk of mysterious noises (all unpleasant) coming out of your cab when it is under heavy load. Using solid wood for open-back cabs influences the sound.

The way you join the corners determines the strength of the cabinet. You can use (reinforced) butt joints, or do biscuit joins (stronger), but you can also learn to do finger joints or half-blind dovetails. I like half-blind dovetails, though it took practice to learn to do them (with a router). It gets covered up with tolex, but I know they are there.

You don't talk about tools - you will need, at least:

- a way to cut the wood (a saw, so to speak)
- a way to hold the wood in place while you glue the sides together (clamps of some sort) - this, by the way, is one reason I like half-blinds over finger or any other joint; they don't need to be held at right angles; the dovetails take care of it
- a way of cutting the speaker holes (again, I use a router for perfect, easy to do holes)
- a way of rounding over the corners (router again for me. You could sand them over, but the router gives me more consistent results
- a drill (holes for handles, corners, mounting the baffle and back panels ...)


Once you build the cab, you get to Tolex - oh boy.

anyway, I really enjoy building cabs. If you use good quality wood and take your time, you can build cabs that noone would know are home-made. Have fun with it.

steven

Building a cabinet is not too complicated and is worth your while. I started out building a solid pine cabinet to replace the chip board one for my Blues Jr. while I had it apart for repairs.
The sound difference between the two was amazing. I have now built several amps and build all my own cabinets. I would have to say that fabricating and covering my own cabinet is one of my favorite parts of the process.

Here's a cabinet I put together today... i'm just waiting overnight for the glue to cure so I can get it ready for tolex. It was easy getting to this stage. All you need is a router, the right router bit, a few DIY jigs and you can pretty much wing the rest.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5611-1.jpg

I have a few pics I can upload, but it's bedtime here - gimmie a night and i'll show you how I built it from scratch on the cheap.

Logging in

This is how I did mine.

I'd never done a scrap of woodwork in my life until last weekend, but a $100 investment and now I can build cabinets like this.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5515.jpg

You need a few basic things - a $50 router, a few clamps, very accurate rulers, a drill... saw horses are handy.... screws... blah blah blah.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5617.jpg

My home brand hardware store router bit went dull very quickly, so I got two of the bigger router bits seen here from Eagle America... one for backup, just in case.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5498.jpg

About $20 in parts, you need to make one of these table jigs to get the finger joints / box joints happening. It's the key to everything.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5625.jpg

It's basically a table with a hole for a router bit, and a 1/4"x1/4" running guide for your 'panel pusher'. This running guide needs to be 100% accurate or your joints will be shoddy. Of course the table also needs to stay thin or you'll have trouble finding long enough router bits. I used 12mm marine ply as anything thinner wasn't straight enough.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5626.jpg

Here's the panel pusher thing. It runs along the guide and you clamp your panel to cut on the front of the pusher (so it doesn't fly out of your hands with the router on).

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5627.jpg

A few braces on the underside of the table to stiffen up the ply... but 12mm is already pretty good. You can also see how the router is attached - via two stainless bolts... needless to say - the router must be on as tight as possible.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5621.jpg

It might start to make a little sense here. Here's the front of the panel pusher and where it meets the router bit. You set the router depth to the thickness of the panel or a little over if you're confident enough to trim it back flush.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5631.jpg

I only have scrap left to demonstrate, but here's how the jig works. As you can see, the scrap bit of wood is clamped to the pusher (and pushed firmly into the travel guide, where it can be pushed along to make the first box joint cut.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5633.jpg

This first slot can now be moved along to straddle the travel guide. This will then create the second (and subsequent thereafter) finger joint cuts.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5635.jpg

Of course, you'll have to do a bit of tweaking to get the jig accurate, so make sure to buy a few bits of scrap to practise... most important thing is the position of the jig travel guide in relation to the router bit. This determines if the joint will be tight or sloppy - sloppy is no good - when assembled, you want less than a playing card's width of space between each finger cut.

Take the time to get it right, and the results will speak for themselves.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5508.jpg

You also need to install your baffle board. In this pic the bottom is the baffle - you can see I cut a recess in the panels to secure in the baffle when the
top/bottom/sides are clamped. Work out where you want your speaker... make sure no tubes are in the way.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5569.jpg

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5557.jpg

Here's the radial jig I made for the router. The bar came with the router itself - I vice clamped a nail on the end and tightened in the thread so it will never budge again. The inner cut is just a practise run.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5573.jpg

Cut carefully. Plan a pattern to cut to otherwise the router will fall through the ply and tear it.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5580.jpg



Of course, then you need to clamp and glue it all together. As for the gluing process... well... I hope I get that right on the next build!

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5601.jpg

I cut circle holes with a jigsaw,,, with a radius wire twisted on the foot plate to a loop on a centre nail...

quick and easy.... once you get the radius right... you just keep the wire tight and go around in a circle....

Adding to my finger jointing jig above. Here's how I adjusted for accuracy... remember, accuracy is critical! You basically want your joint cuts so tight you can't even slip a playing card between the fingers of the cabinet when assembled.


Butt up a straight edge to the running guide and clamp.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5659.jpg


Undo your running guide.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5661.jpg


This metal ruler proved a perfect jig width adjustment when I switched from a 12mm router bit to a 1/2" router bit. You could use playing cards or anything equally thin to make micro-adjustments.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5662.jpg


This is my overall gap increase. I've now glued the running guide into position as I know this jig is 100% accurate.

http://i257.photobucket.com/albums/hh230/ravenhaller/IMG_5664.jpg

Works with 100% accuracy, and at a fraction of the cost of a pro jig.