Why Use Finger Joints?

Seeing and hearing is believing

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rjgtr
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Post by rjgtr »

Some people have used bed liner for a covering. I think the foam idea might be too resonant, but who knows.
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Badfinger
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Post by Badfinger »

the rhino covering and foam core would be about as dead as you could make a cabinet. Which would be great if that's what you were after.

Just personal opinion, but I still havn't heard anything I liked better for a cab than plain ol pine. I think it adds a warmth to the overall tone of an amp that hardwoods or plywoods don't have.

YMMV
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Post by StarGeezers »

I think what you guys are hearing with pine is resonance... We did some testing long ago with a spectrum analyzer and found natural woods resonate more than the other materials ... MDF was the least resonant , ply was in the middle ... All whatever you like huh !!!
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Post by Badfinger »

Oh yeah, without a question, it is resonance added to the tone by the cabinet with pine.
Wouldn't want a cab without it.
:D
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Post by CurtissRobin »

That's not resonance it's sympathetic vibration. The difference is big. An example of resonance is a cab with boomy bass.

First, materials:
Cut a scrap of pine, plywood and MDF of about the same size. Hold each by the corner and rap it with a drumstick, a screwdriver handle or your knuckle. The pine THOKs like a Wittner metronome and rings a bit with a distinct pitch. The ply THOKs as well but doesn't ring. The MDF is more leaden in sound, crisp but dull with no ring at all. Plywood and MDF damp the vibration quite effectively. You can use these characteristics to advantage. A pine cab will color the sound of your amp, chipping in its own vibrations complementary to the speakers. Ply colors a lot less than pine and a bit more than MDF, depending on its thickness. If you want only the sound of the speaker then 3/4" ply or MDF is the way to go.

Next, joinery:
If you build with pine, box ("finger") joints are best, though many other joints including rabbet or butt joints with cleats, glue and screws are excellent as well. With plywood or MDF the box and dovetail joints should be avoided because at least 40% of the grain runs the wrong way. i.e. At least two of five plies (or five of eleven if you use baltic birch) are not end grain so the stress on a box or dovetail joint is working to split the wood in those plies. No strength there.

Finally, cost:
MDF is the lowest cost material, hands down. Plywood (of a good grade) is most expensive with #2 pine somewhere between. When I read posts about the cost of a cabinet I think about living in L.A. some years ago. On the street you'd see an astonishing multi-thousand dollar paint job that was applied on top of $300-$400 of body work. Do what's important to you.

KennyO
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Post by StarGeezers »

CR, makes good sense to me !!! Thanks !!! I stand corrected on the resonance thing , all the cabs we tested resonated on the lower freqs.
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Post by Badfinger »

Sure, I agree on all points as well CR.

I still like Pine cabs.

:D
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Post by Cknopp »

Badfinger wrote:the rhino covering and foam core would be about as dead as you could make a cabinet. Which would be great if that's what you were after.

Just personal opinion, but I still havn't heard anything I liked better for a cab than plain ol pine. I think it adds a warmth to the overall tone of an amp that hardwoods or plywoods don't have.

YMMV
Is this statement based in fact, or is it just a gut feeling?

I would really like to see evidence that leads you to that conclusion, because I have yet to find any of the sort in my time researching the idea (about 2 years).

Thanks!

Chris
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Post by Badfinger »

First, I'm not saying it would be a bad thing. Quite the opposite, depending.

I built cabinets pretty steadily for a time through the mid-nineties, mostly FOH and monitor cabinets, but some guitar and bass cabs as well.

One method I played with was 3/4 birch ply front baffles, 1/4 ply inner box, with industrial urethane-based foam around 1 inch thickness, and an early version of bedliner sprayed over that. There were some braces along the edges and bottom of 1.5 by.750 ply also.
I found those enclosures to be very "dry", at least in comparison to similar cabs built more traditionally, with ply mainly.
It was a bonus for sound-reinforcement speakers.
I didn't care for it with guitar/bass cabs, other did. In fairness, I did'nt make many guitar cabs with the method so I couldn't say they were as "dry" in that instance as I found them otherwise.

I think it might depend on the foam to a large degree. My first attempts were with styro and insulation foam board, and I didn't like those at all, personally. A lot of ringing in the upper mids in particular.

Anyway, that's what i found, YMMV.

Still think pine sounds way cool for guitar cabs.

:D
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